UART connection between ATSAMD20 and ATtiny4313

[pozz]

I'd like to use async UART to let these MCUs communicate.
The protocol will be request-response with the request generated by the
SAM MCU. The baudrate will be 38400bps.

I'd like to use internal oscillator of ATtiny4313, while the SAM will
use an external 32.768kHz crystal (that is multiplied by internal PLL to
reach 48MHz).

I'm not sure if this scenario can work well. My concerns are related to
the internal oscillator of ATtiny4313 that hasn't a good accuracy over
temperature and life.

The tiny MCU will be supplied by 3.3V and its temperature will be in the
range 0-80°C.

[David Brown]

The rule of thumb is a maximum of 5% total mismatch in baud rates
between the two sides. One side has a crystal and PLL, so it will be
quite close - that means you can have most of the error margin on the
other side. If the internal oscillator is within 2%, you should be
fine. If it is 5% or more, you will want to do some automatic
measurement of the rate.

[Rick C]

I don't get what your question is. You seem to understand the concepts. You don't tell us the relevant data however. What does the data sheet say about the frequency variability of the internal clock over PVT (process, voltage and temperature)? I assume you are aware that the 3.3V supply will have an accuracy and an RC clock rate can be voltage dependent. It depends on how they designed the circuit. There are techniques for removing most of the voltage dependency, if they used them.

You can always use the bit times of the SAM to adjust the bit rate on the ATtiny. That used to be part of the protocol for low data rate modems. The first characters sent were AT if I recall, which give good edges to time to measure the bit rate. At 38400 bps this might be a bit tricker, it depends on your instruction rate. A bit time is just 26 us. Will this be a software UART, or a hardware unit?

--

Rick C.

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[pozz]

ATtiny4313 datasheet[1] says the internal oscillator is factory
calibrated with an accuracy of +/-10% at Vcc=3V and 25°C temperature.
This accuracy can be reduced to +/-2% at a fixed voltage and a fixed
temperature with a user calibration.

I could calibrate for a fixed voltage (3.3V), but I can't fix a
temperature, because it can vary in the real application.

I tried to heat the ATtiny4313 with a heat gun and the communication
between SAM and tiny didn't stopped, but I know this isn't an exaustive
test.


[1] https://ww1.microchip.com/downloads/en/DeviceDoc/doc8246.pdf

[pozz]

Il 26/04/2023 18:26, Rick C ha scritto:
> On Wednesday, April 26, 2023 at 10:57:01 AM UTC-4, pozz wrote:
>> I'd like to use async UART to let these MCUs communicate.
>> The protocol will be request-response with the request generated by the
>> SAM MCU. The baudrate will be 38400bps.
>>
>> I'd like to use internal oscillator of ATtiny4313, while the SAM will
>> use an external 32.768kHz crystal (that is multiplied by internal PLL to
>> reach 48MHz).
>>
>> I'm not sure if this scenario can work well. My concerns are related to
>> the internal oscillator of ATtiny4313 that hasn't a good accuracy over
>> temperature and life.
>>
>> The tiny MCU will be supplied by 3.3V and its temperature will be in the
>> range 0-80°C.
>
> I don't get what your question is. You seem to understand the concepts. You don't tell us the relevant data however. What does the data sheet say about the frequency variability of the internal clock over PVT (process, voltage and temperature)? I assume you are aware that the 3.3V supply will have an accuracy and an RC clock rate can be voltage dependent. It depends on how they designed the circuit. There are techniques for removing most of the voltage dependency, if they used them.

ATtiny4313 datasheet[1] says the internal oscillator is factory

calibrated with an accuracy of ±10% at Vcc=3V and 25°C temperature. This
accuracy can be reduced to ±2% at a fixed voltage and a fixed

temperature with a user calibration.

>

> You can always use the bit times of the SAM to adjust the bit rate on the ATtiny. That used to be part of the protocol for low data rate modems. The first characters sent were AT if I recall, which give good edges to time to measure the bit rate. At 38400 bps this might be a bit tricker, it depends on your instruction rate. A bit time is just 26 us. Will this be a software UART, or a hardware unit?
>

I will use the interal UART peripheral of ATtiny4313. I can't add too
much code, the Flash memory is almost full. I wanted to know if the
figures shown on the datasheet guarantee good communication between the
the MCUs. It seems this isn't the case.


[1] https://ww1.microchip.com/downloads/en/DeviceDoc/doc8246.pdf

[Grant Edwards]

On 2023-04-26, pozz <pozz...@gmail.com> wrote:

> ATtiny4313 datasheet[1] says the internal oscillator is factory
> calibrated with an accuracy of +/-10% at Vcc=3V and 25°C temperature.

10% total error (combination of both ends) is pretty much right at the
limit according to the usual rule of thumb for UART receivers that
sync only on the start bit. IIRC, there used to be UART receivers that
would sync on every edge within the data "word" as well, but I don't
think that was ever very common -- and to take advantage of it, you
had to make sure your data had edges. :)

Can you spare a line for a clock and go synchronous? (Or are they
really UARTs and not USARTs?).

> This accuracy can be reduced to +/-2% at a fixed voltage and a fixed
> temperature with a user calibration.

2% is no problem at all. With a crystal on the other end, you should
be able to easily tolerate +/-5%. The requirement for a fixed
temperature, OTOH, is usually a problem.

> I could calibrate for a fixed voltage (3.3V), but I can't fix a
> temperature, because it can vary in the real application.

Does the ATtiny have an on-die temp sensor? If yes, you could try
characterizing the oscillator over temperature at 3.3V and adjusting
the baud rate divisor as the temperature changes. That get's expensive
if you have to do it on every unit during production, but if the T/F
curve is consistent enough between units, then maybe...

[Rick C]

On Wednesday, April 26, 2023 at 4:44:20 PM UTC-4, pozz wrote:
> Il 26/04/2023 18:26, Rick C ha scritto:
> > On Wednesday, April 26, 2023 at 10:57:01 AM UTC-4, pozz wrote:
> >> I'd like to use async UART to let these MCUs communicate.
> >> The protocol will be request-response with the request generated by the
> >> SAM MCU. The baudrate will be 38400bps.
> >>
> >> I'd like to use internal oscillator of ATtiny4313, while the SAM will
> >> use an external 32.768kHz crystal (that is multiplied by internal PLL to
> >> reach 48MHz).
> >>
> >> I'm not sure if this scenario can work well. My concerns are related to
> >> the internal oscillator of ATtiny4313 that hasn't a good accuracy over
> >> temperature and life.
> >>
> >> The tiny MCU will be supplied by 3.3V and its temperature will be in the
> >> range 0-80°C.
> >
> > I don't get what your question is. You seem to understand the concepts. You don't tell us the relevant data however. What does the data sheet say about the frequency variability of the internal clock over PVT (process, voltage and temperature)? I assume you are aware that the 3.3V supply will have an accuracy and an RC clock rate can be voltage dependent. It depends on how they designed the circuit. There are techniques for removing most of the voltage dependency, if they used them.
> ATtiny4313 datasheet[1] says the internal oscillator is factory
> calibrated with an accuracy of ±10% at Vcc=3V and 25°C temperature. This
> accuracy can be reduced to ±2% at a fixed voltage and a fixed
> temperature with a user calibration.

Ok, that is information. Do you have a question?

> > You can always use the bit times of the SAM to adjust the bit rate on the ATtiny. That used to be part of the protocol for low data rate modems. The first characters sent were AT if I recall, which give good edges to time to measure the bit rate. At 38400 bps this might be a bit tricker, it depends on your instruction rate. A bit time is just 26 us. Will this be a software UART, or a hardware unit?
> >
> I will use the interal UART peripheral of ATtiny4313. I can't add too
> much code, the Flash memory is almost full. I wanted to know if the
> figures shown on the datasheet guarantee good communication between the
> the MCUs. It seems this isn't the case.
>
>
> [1] https://ww1.microchip.com/downloads/en/DeviceDoc/doc8246.pdf

You point me to a data sheet. I am not reading the data sheet to do your work for you. I'm happy to discuss the information and offer advice and opinion. The info you provide above with the 2% stability if temperature and voltage are maintained and the clock calibrated, is not enough to know if this will work.

When you write, "It seems this isn't the case.", what do you base this on? What is your reasoning?

I don't think the software UART is a lot of code, but you don't need that. You need to write a routine to measure a bit time on the input to calibrate your clock to the incoming bit times. That should not be a lot of code. Translating a loop count into a bit clock setting for the UART should be a simple linear relationship, although it may involve a divide. You only need to work over a small range, so a small table lookup should be pretty close to optimal solution.

I don't see where you have a choice, unless you want to add a crystal to the ATtiny. Can the SAM chip send a clock? You can use an SPI port instead of a UART, or just send a clock to use for the bit rate clock in the UART?

--

Rick C.

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[Rick C]

On Wednesday, April 26, 2023 at 5:00:22 PM UTC-4, Grant Edwards wrote:
> On 2023-04-26, pozz <pozz...@gmail.com> wrote:
>
> > ATtiny4313 datasheet[1] says the internal oscillator is factory
> > calibrated with an accuracy of +/-10% at Vcc=3V and 25°C temperature.
> 10% total error (combination of both ends) is pretty much right at the
> limit according to the usual rule of thumb for UART receivers that
> sync only on the start bit.

I think you are not doing the calculation right. The limit is based on the UART trying to sample in the middle of a bit. If it gets out by a half a bit time, either way, it will sample the wrong bit. With 10 bits in the character, including start and stop bits, that puts the total error limit at about 5%. This is actually closer to 5.5% (because while it is 10 bits, it's only 9 bit times between start and stop bits), but then you need to subtract a fraction of a bit for the internal Nx clock used to sample the bit stream. So round off to 5%. That's the total error allowed, including both ends. Then there's distortion in the pulse edges. With 26 us bit times, there may be issues with asymmetric edge distortion. There has been no mention of the electrical interface.

> IIRC, there used to be UART receivers that
> would sync on every edge within the data "word" as well, but I don't
> think that was ever very common -- and to take advantage of it, you
> had to make sure your data had edges. :)
>
> Can you spare a line for a clock and go synchronous? (Or are they
> really UARTs and not USARTs?).
> > This accuracy can be reduced to +/-2% at a fixed voltage and a fixed
> > temperature with a user calibration.
> 2% is no problem at all. With a crystal on the other end, you should
> be able to easily tolerate +/-5%. The requirement for a fixed
> temperature, OTOH, is usually a problem.
> > I could calibrate for a fixed voltage (3.3V), but I can't fix a
> > temperature, because it can vary in the real application.
> Does the ATtiny have an on-die temp sensor? If yes, you could try
> characterizing the oscillator over temperature at 3.3V and adjusting
> the baud rate divisor as the temperature changes. That get's expensive
> if you have to do it on every unit during production, but if the T/F
> curve is consistent enough between units, then maybe...

Calibration, in general is expensive. But yes, a calibration curve is worse, since you need to wait for temperature to adjust.

--

Rick C.

-- Get 1,000 miles of free Supercharging
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[David Brown]

On 27/04/2023 02:10, Rick C wrote:

> I don't think the software UART is a lot of code, but you don't need
> that. You need to write a routine to measure a bit time on the input
> to calibrate your clock to the incoming bit times. That should not
> be a lot of code. Translating a loop count into a bit clock setting
> for the UART should be a simple linear relationship, although it may
> involve a divide. You only need to work over a small range, so a
> small table lookup should be pretty close to optimal solution.
>

That's definitely one way to do it, yes.

Have the master side send a couple of 0x00 bytes before the data, and
use an interrupt on the Rx pin falling edge - when that comes in, count
the time until a rising edge is seen. If that time works out to within
10% of the nominal expected time, you are calibrated and can turn off
the interrupt. Alternatively, send 0x55 bytes first and measure
multiple short periods. There will be some details to work out,
depending on the what you are sending, the type of noise you expect, how
often you need to re-calibrate, etc. You are making a software
equivalent to a PLL.

There's no need for a lookup table here (unless I've got my calculations
upside down!). The more cycles you count for the incoming trainer
characters, the bigger the UART divider value you need. That means your
divisions will be done with constant values, and the compiler will turn
those into multiplies.



An alternative is trial and error. If your clock source is ±10%, and
you need to get within ±2%, start your UART at the nominally correct
baud rate. If you don't receive error-free telegrams within a timeout,
go 2% faster. Keep adding 2%, stepping from +10% to -10%, until you hit
a baud rate that works.

You can get even fancier here by figuring out the lowest and highest
rates that work, then picking their average to get the best value.

[pozz]

Il 26/04/2023 23:00, Grant Edwards ha scritto:
> On 2023-04-26, pozz <pozz...@gmail.com> wrote:
>
>> ATtiny4313 datasheet[1] says the internal oscillator is factory
>> calibrated with an accuracy of +/-10% at Vcc=3V and 25°C temperature.
>
> 10% total error (combination of both ends) is pretty much right at the
> limit according to the usual rule of thumb for UART receivers that
> sync only on the start bit. IIRC, there used to be UART receivers that
> would sync on every edge within the data "word" as well, but I don't
> think that was ever very common -- and to take advantage of it, you
> had to make sure your data had edges. :)
>
> Can you spare a line for a clock and go synchronous? (Or are they
> really UARTs and not USARTs?).

No, I can't. The MCUs are not on the same board and they are really
connected through RS485 half-duplex transceivers.

>> This accuracy can be reduced to +/-2% at a fixed voltage and a fixed
>> temperature with a user calibration.
>
> 2% is no problem at all. With a crystal on the other end, you should
> be able to easily tolerate +/-5%. The requirement for a fixed
> temperature, OTOH, is usually a problem.
>
>> I could calibrate for a fixed voltage (3.3V), but I can't fix a
>> temperature, because it can vary in the real application.
>
> Does the ATtiny have an on-die temp sensor? If yes, you could try
> characterizing the oscillator over temperature at 3.3V and adjusting
> the baud rate divisor as the temperature changes. That get's expensive
> if you have to do it on every unit during production, but if the T/F
> curve is consistent enough between units, then maybe...

Thank you for this suggestion, but I can't use this trick.

[pozz]

And I don't want you do it if you don't want. The datasheet link is
there if someone WANTS to look at it with a single click of the mouse.

> I'm happy to discuss the information and offer advice and opinion. The info you provide above with the 2% stability if temperature and voltage are maintained and the clock calibrated, is not enough to know if this will work.
>
> When you write, "It seems this isn't the case.", what do you base this on? What is your reasoning?

Because internal oscillator has an accuracy of 10% and I read that UART
receivers are usually able to decode the input signal with an error of
2-5% order.

However I tested one sample at high temperature, but the MCUs continued
communicating well.

> I don't think the software UART is a lot of code, but you don't need that. You need to write a routine to measure a bit time on the input to calibrate your clock to the incoming bit times. That should not be a lot of code. Translating a loop count into a bit clock setting for the UART should be a simple linear relationship, although it may involve a divide. You only need to work over a small range, so a small table lookup should be pretty close to optimal solution.

Ok, thanks for suggestion.

> I don't see where you have a choice, unless you want to add a crystal to the ATtiny. Can the SAM chip send a clock? You can use an SPI port instead of a UART, or just send a clock to use for the bit rate clock in the UART?

No, this isn't an option.

[Andrew Smallshaw]

The other option would be to adopt a Manchester-encoded (self
clocking) signal. Wouldn't be true RS485 but would pass through
transceivers and cabling at sensible baud rates. Manchester coding
is fine provided the clocks are within 2:1 of each other. You will
need to bit-bang the interface though, the UART won't handle it.

--
Andrew Smallshaw
and...@sdf.org

[Rick C]

I'm glad we are in agreement. My point is you could have pointed us to any useful info in the document, or better quoted it, if there was anything you had not already quoted. I find CPU data sheets to be rather onerous to read, as they have so much data in them these days, and they don't always put timing data in the timing section, for example.

> The datasheet link is
> there if someone WANTS to look at it with a single click of the mouse.
> > I'm happy to discuss the information and offer advice and opinion. The info you provide above with the 2% stability if temperature and voltage are maintained and the clock calibrated, is not enough to know if this will work.
> >
> > When you write, "It seems this isn't the case.", what do you base this on? What is your reasoning?
> Because internal oscillator has an accuracy of 10% and I read that UART
> receivers are usually able to decode the input signal with an error of
> 2-5% order.

The 10% was for a fixed voltage and temperature without calibration. I don't recall if you are adverse to calibration. But you do have a wide temperature range which is an issue.

> However I tested one sample at high temperature, but the MCUs continued
> communicating well.

That means pretty much nothing. While testing can prove that something doesn't work, it can't prove that it does.

Instead of simply testing pass/fail, it would have been more useful to measure the clock rate, by measuring the bit rate over temperature. Get some numbers for multiple units to see what sort of spread you get.

> > I don't think the software UART is a lot of code, but you don't need that. You need to write a routine to measure a bit time on the input to calibrate your clock to the incoming bit times. That should not be a lot of code. Translating a loop count into a bit clock setting for the UART should be a simple linear relationship, although it may involve a divide. You only need to work over a small range, so a small table lookup should be pretty close to optimal solution.
> Ok, thanks for suggestion.
> > I don't see where you have a choice, unless you want to add a crystal to the ATtiny. Can the SAM chip send a clock? You can use an SPI port instead of a UART, or just send a clock to use for the bit rate clock in the UART?
> No, this isn't an option.

You can't add a crystal? Then the two workable choices would appear to be calibration of each unit over temperature, or a real time calibration from the data rate of the incoming data. I can't think of any other solutions. Adding the crystal seems the simple route.

--

Rick C.

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[Rick C]

What about Manchester encoding is not RS-485? That's just an electrical interface standard, no?

But that is a great idea... if the hardware will accommodate it. Or this can be done in the UART using a faster clock and synchronous mode. Send characters with one data bit per character, the Manchester encoded bit, x0F or xF0. It would not be terribly hard to decode the data in software.. possibly. I believe you align to the transition that is always present mid-cell, then look for the presence/absence of the other transition. The OP talked about the "small" processor being program space constrained, but again, this is not a lot of code... maybe. So maybe this will be too much. But it would solve the clocking issue. Then again, so would a crystal.

--

Rick C.

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[Tauno Voipio]

I doubt that the ATTiny can handle Manchester coding at the requested
bit rate, and it may be difficult for the SAM.

In 2016, I made a processor unit using AT91SAM4E for IEC H1 Manchester
coded bus at 31.25 kbit/s. The trick was to innovatively use the timer
counter units of the chip. A timer used to measure the times between
pulse edges could be used to receive and decode the incoming data, and
a timer running at half of the bit rate (15.625 kbit/s) could be used
to send the data. The receiver needed to respond to interrupts at the
incoming edge rate, and the transmitter needed to respond at the
outgoing bit rate.

--

-TV

[Ulf Samuelsson]

Den 2023-04-27 kl. 19:18, skrev Tauno Voipio:
> On 27.4.2023 16.28, Andrew Smallshaw wrote:
>> On 2023-04-27, pozz <pozz...@gmail.com> wrote:
>>> Il 27/04/2023 02:10, Rick C ha scritto:
>>>
>>>> I don't see where you have a choice, unless you want to add a
>>>> crystal to the ATtiny. Can the SAM chip send a clock?  You can use
>>>> an SPI port instead of a UART, or just send a clock to use for the
>>>> bit rate clock in the UART?
>>>
>>> No, this isn't an option.
>>
>> The other option would be to adopt a Manchester-encoded (self
>> clocking) signal.  Wouldn't be true RS485 but would pass through
>> transceivers and cabling at sensible baud rates.  Manchester coding
>> is fine provided the clocks are within 2:1 of each other.  You will
>> need to bit-bang the interface though, the UART won't handle it.
>
>
> I doubt that the ATTiny can handle Manchester coding at the requested
> bit rate, and it may be difficult for the SAM.

Atmel implemented Manchester Coding in the SAM7 USART (My proposal)
but the SAMD20 has a "SERCOM" module without Manchester Coding.
I would look into the event system.


The tiny will have to do it in S/W.
/Ulf

>
> In 2016, I made a processor unit using AT91SAM4E for IEC H1 Manchester
> coded bus at 31.25 kbit/s. The trick was to innovatively use the timer
> counter units of the chip. A timer used to measure the times between
> pulse edges could be used to receive and decode the incoming data, and
> a timer running at half of the bit rate (15.625 kbit/s) could be used
> to send the data. The receiver needed to respond to interrupts at the
> incoming edge rate, and the transmitter needed to respond at the
> outgoing bit rate.
>

The SAM4E USART supports Manchester Coding in H/W.
The SAM4E UART does not.

/Ulf

[Rick C]

That's if the entire job is handled in software, perhaps. The USART can be used to send the bits as characters at the transmitter. A USART can be used to handle the reception with software seeking edges. I don't think that would be a huge burden at 38.4 kbps. But then, I'm more used to FPGA work.

--

Rick C.

++ Get 1,000 miles of free Supercharging
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[Tauno Voipio]

The problem with the USART Manchester coder was in address markers
(intentional mis-codings). It was not possible to conform with the
markers in the IEC coding.

--

-TV

[Tauno Voipio]

Had to bit-bang. The USART cannot create or detect IEC H1 standard
address marker octets.

--

-TV

[Rick C]

I did a Google search and this didn't return anything useful. So I don't know for certain what an IEC H1 standard address marker octet is, but if I'm specifying the waveform, rather than relying on the hardware to do the Manchester encoding, I can't see a reason why I could not transmit any given waveform. Can you point me to something that describes these marker octets?

--

Rick C.

--- Get 1,000 miles of free Supercharging
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[David Brown]

On 27/04/2023 18:22, Rick C wrote:
> On Thursday, April 27, 2023 at 9:28:33 AM UTC-4, Andrew Smallshaw wrote:
>> On 2023-04-27, pozz <pozz...@gmail.com> wrote:
>>> Il 27/04/2023 02:10, Rick C ha scritto:
>>>
>>>> I don't see where you have a choice, unless you want to add a crystal to the ATtiny. Can the SAM chip send a clock? You can use an SPI port instead of a UART, or just send a clock to use for the bit rate clock in the UART?
>>>
>>> No, this isn't an option.
>> The other option would be to adopt a Manchester-encoded (self
>> clocking) signal. Wouldn't be true RS485 but would pass through
>> transceivers and cabling at sensible baud rates. Manchester coding
>> is fine provided the clocks are within 2:1 of each other. You will
>> need to bit-bang the interface though, the UART won't handle it.
>
> What about Manchester encoding is not RS-485? That's just an electrical interface standard, no?
>

Technically, you are correct. In reality, the term "RS-485" is usually
used to mean "UART signalling on an RS-485 bus" - any other kind of
signalling (such as Manchester encoding) would be specified explicitly.
It's good to be technically accurate, but also good to consider less
accurate common usage of terms.

> But that is a great idea... if the hardware will accommodate it. Or
> this can be done in the UART using a faster clock and synchronous
> mode. Send characters with one data bit per character, the
> Manchester encoded bit, x0F or xF0. It would not be terribly hard to
> decode the data in software.. possibly. I believe you align to the
> transition that is always present mid-cell, then look for the
> presence/absence of the other transition. The OP talked about the
> "small" processor being program space constrained, but again, this is
> not a lot of code... maybe. So maybe this will be too much. But it
> would solve the clocking issue. Then again, so would a crystal.
>

Not all microcontroller UARTs have synchronous modes. Receiving or
sending Manchester encoded data with a UART is fiddly because of the
start and stop bits of UART, so it is often done by bit-banging.
Whether or not that suits the OP, only he can say.

[Tauno Voipio]

The H1 bus is an industrial fieldbus and technical information about
it has been notoriously difficult to access.

The Manchester coding in the H1 bus is sent as current variations,
which are converted into voltage variations for receiving.

I'll show the more positive voltage with a plus sign and the less
positive voltage with a minus sign.

A state pair takes one bit time (32 us) with the change at the middle.

A data bit of '1' is sent as +-
A data bit of '0' is sent as -+

There are two intentional miscodings for delimiters:

A coding N+ is sent as ++
A coding N- is sent as --

A frame starts with a preamble of alternating 0's and 1's:

1 0 1 0 1 0 1 0 1 0

After preamble a start delimiter is sent:

1 N+ N- 1 0 N- N+ 0

The packet content follows, with most significant bit first.

After last data octet an end delimiter is sent:

1 N+ N- N+ N- 1 0 1

After the packet the transmitter is switched off, so the line
will stay halfway between the + and - states.

The processor chip Manchester coders could not be twisted to
handle the start end end delimiters correctly.

--

-TV

[Rick C]

On Friday, April 28, 2023 at 3:48:32 AM UTC-4, David Brown wrote:
> On 27/04/2023 18:22, Rick C wrote:
> > On Thursday, April 27, 2023 at 9:28:33 AM UTC-4, Andrew Smallshaw wrote:
> >> On 2023-04-27, pozz <pozz...@gmail.com> wrote:
> >>> Il 27/04/2023 02:10, Rick C ha scritto:
> >>>
> >>>> I don't see where you have a choice, unless you want to add a crystal to the ATtiny. Can the SAM chip send a clock? You can use an SPI port instead of a UART, or just send a clock to use for the bit rate clock in the UART?
> >>>
> >>> No, this isn't an option.
> >> The other option would be to adopt a Manchester-encoded (self
> >> clocking) signal. Wouldn't be true RS485 but would pass through
> >> transceivers and cabling at sensible baud rates. Manchester coding
> >> is fine provided the clocks are within 2:1 of each other. You will
> >> need to bit-bang the interface though, the UART won't handle it.
> >
> > What about Manchester encoding is not RS-485? That's just an electrical interface standard, no?
> >
> Technically, you are correct. In reality, the term "RS-485" is usually
> used to mean "UART signalling on an RS-485 bus" - any other kind of
> signalling (such as Manchester encoding) would be specified explicitly.
> It's good to be technically accurate, but also good to consider less
> accurate common usage of terms.

Not technically, actually. "Wouldn't be true RS485" is a very clear statement, which happens to also be wrong, no matter how hands are waved.

> > But that is a great idea... if the hardware will accommodate it. Or
> > this can be done in the UART using a faster clock and synchronous
> > mode. Send characters with one data bit per character, the
> > Manchester encoded bit, x0F or xF0. It would not be terribly hard to
> > decode the data in software.. possibly. I believe you align to the
> > transition that is always present mid-cell, then look for the
> > presence/absence of the other transition. The OP talked about the
> > "small" processor being program space constrained, but again, this is
> > not a lot of code... maybe. So maybe this will be too much. But it
> > would solve the clocking issue. Then again, so would a crystal.
> >
> Not all microcontroller UARTs have synchronous modes.

I never said anything different.

> Receiving or
> sending Manchester encoded data with a UART is fiddly because of the
> start and stop bits of UART, so it is often done by bit-banging.
> Whether or not that suits the OP, only he can say.

It is simply not practical to send Manchester encoding with a UART... but Manchester is not the only encoding scheme that embeds a clock. Or you can roll your own. The point is, clock encoding with the data is a viable method of overcoming the lack of precision in the clock rate, which does not require bit banging an I/O pin. The encoding scheme of IRIG is a real possibility. The data bits are PWM encoded, with three values; 0.2, 0.5 and 0.8 widths for 0, 1 and a sync marker. This would fit a UART very nicely. With a distinction of symbols of 0.3 bit times, it can tolerate a lot more clock error than a typical async data stream with a start and stop bit on each character. It would also be pretty easy to decode. Align to the rising edge, and count the bits in the received data to find the falling edge. 0.1, 0.2 and 0.3 are all a zero bit. 0.4, 0.5 and 0.6 are all one bits. 0.7, 0.8 and 0.9 are all sync markers. To prevent the UART from missing anything important, set it for 7 data bits and no parity on receive. Then it always stops one bit early. Then if the timing is off by 10%, you still don't lose any data. This can be better than using a USART, actually. It does the alignment in the hardware, making the decoding simpler. It also includes a sync marker.

Yeah, I think this is a much better scheme than Manchester encoding.

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[Ulf Samuelsson]

If the bus speed is known, this packet seems overkill.
It can be used to detect the BAUD rate.

The Atmel USART is designed to use a 9-bit mode for packet data, with
the 9th bit set for addresses.

/Ulf.

[Rick C]

Yes, my point is you can run the USART at a higher rate and send data as x0F, xF0, x00 or xFF. You can use the hardware without a hardware Manchester encoder.

Actually, I think Manchester encoding is inferior to the scheme they use in the IRIG signal (also the WWVB time broadcast). I don't know if that PWM scheme has a particular name, but it is very robust and can be implemented with a UART, so no USART required. The UART aligns to the start of the bit frame, so less work in the software. It becomes a matter of recognizing which of the 7 bit patterns are received. You really only need to look at two bit positions to distinguish the three values.

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[Rick C]

Sorry, two points to distinguish the three values encoded in the eight possible received bit patterns using a 7 bit character.

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[David Brown]

You certainly /can/ do this kind of thing in software on a Tiny.
However, it might be a challenge depending on other factors. If the
device already has high-precision timing requirements for another task,
doing two of them can get complicated. If you need to deal with a lot
of noise on the lines, that too is messy.

[David Brown]

Perhaps he already has the boards produced - adding a crystal is then a
rather difficult task! Even if the design is not completed, the Tiny is
a very small, cheap and low power family. Adding a crystal makes the
design bigger, more expensive and uses more power - assuming there are
suitable pins free for connecting a crystal. Now, a small, cheap
crystal might be $0.50 and just a few square millimetres, but so is a
small AVR Tiny. I don't know why the OP is using a a Tiny, but if it is
for good technical or economic reasons, adding a crystal would work
against it.

Trial-and-error, as I suggested earlier, is another workable choice.

[Tauno Voipio]

The packet structure and coding is set in the standard. An USART cannot
create the bit patterns, even with fictive data, as there are fixed
start and stop bit patterns.

--

-TV

[Rick C]

I don't think you understand the issues. If there is a lot of noise, the project is dead in the water regardless. Fix your noise problems.

This does not impose "high-precision timing requirements" on the CPU. The only requirements are to handle the data without dropping. It's NOT bit banging, so there is lots of time to handle the data.

If the CPU is overloaded, then you picked the wrong CPU. Get a faster one.

Why are you bringing in all this silliness? It's almost as if you've never done design work.

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[Rick C]

Yes, trial and error. I believe that's the design process recommended by NASA.

WTF are you talking about? If he's designed the board without considering the requirements, that's a failure of the first order. If someone imposed new requirements on the design, that's a perfect justification to respin the board.

Once again, not rocket science.

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[David Brown]

Feel free to try /reading/ posts before making comments about them that
show you up your ignorance.

[David Brown]

Have you heard the saying that it is better to keep quite and be thought
a fool, rather than opening your mouth and proving it? Do you think the
OP would have started this discussion if "just use a better
microcontroller" were a viable option?

[Rick C]

David, that wasn't a reply to the OP, that was to your silly speculation.

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[pozz]

Il 26/04/2023 16:56, pozz ha scritto:
> I'd like to use async UART to let these MCUs communicate.
> The protocol will be request-response with the request generated by the
> SAM MCU. The baudrate will be 38400bps.
>
> I'd like to use internal oscillator of ATtiny4313, while the SAM will
> use an external 32.768kHz crystal (that is multiplied by internal PLL to
> reach 48MHz).
>
> I'm not sure if this scenario can work well. My concerns are related to
> the internal oscillator of ATtiny4313 that hasn't a good accuracy over
> temperature and life.
>
> The tiny MCU will be supplied by 3.3V and its temperature will be in the
> range 0-80°C.

I want to thank all the ones that spent some time to reply and give
suggestions. As usual, they are valuable for me.

I'm working on a board that is already in production. It was chosen a
tiny for its low cost.
The possibility to mount and use an external ceramic resonator is
available. Moreover it has been really mounted on around 1k boards that
are working now.

However a few customers reported a problem in a few installations: the
tiny blocks and only a power cycle is able to restart.

After some tests, we found that the problem is radiated noise on the
pins of the tiny oscillator. When power cables are near the board and
some specific load are connected to these cables, the noise generated is
capable to block the tiny.

We tried to replace the ceramic resonator with a quartz crystal without
success. We tried to strenghten the GND connection between the
resonator/quartz and the single GND pin of the SOIC20, without success.

The only change that seems effective in avoiding blocks is using the
internal oscillator.

This is the story.

[Rick C]

So I assume there is a reason why you can't route the power wires away from the ATtiny board?

I think you have been provided with all the possibilities for how to use the internal oscillator. It rather comes down to "pick one". Are any more appealing than the others? If you tell us what you don't like about it, maybe we can help refine the solution?

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[pozz]

It depends. In some cases it is possible, in other cases it isn't. The
installer isn't usually competent, so it routes cables as he wants. In
some cases, too near my board. After some weeks or months, he complains
the board has blocked. And he is my customer...

> I think you have been provided with all the possibilities for how to use the internal oscillator. It rather comes down to "pick one". Are any more appealing than the others? If you tell us what you don't like about it, maybe we can help refine the solution?

At the moment we are deciding what could be the best solution.

[David Brown]

Do you do EMC testing for radiation emission and susceptibility? I
don't know what the rules and regulations are like where you are, but
any finished product (as distinct from prototype or test systems) made
here in Europe should be EMC certified. If radiated noise from "normal"
power cables killed a card, that would be a failure in the certification.

Or is it the surrounding system that is bad? Maybe there is something
truly terrible connected to these power cables?

[Rick C]

Perhaps you can add an enclosure to your board so cables can not be so near? You could make it look like an EMI shield. Heck, a simple piece of plexiglass mounted a half inch from your board should do the job. Also, it is perfectly acceptable to specify that nothing be within some distance of your board. That is not an unusual thing for sensitive circuits.

BTW, do you get the same sort of hang condition if you bring other metal near the oscillators? It may not be an EMI issue at all, but rather a capacitive effect on the oscillator circuit. They often are sensitive to the details of the parasitic values. If you have a resistor in series with the crystal, this might need to be reduced in value, or increased. What circuit does the manufacturer recommend for the oscillator?

Can you provide more detail on the nature of the hang? Does the oscillator stop working? Does the frequency shift? Can you measure any of this? Just saying "without success" isn't much to go on.

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[pozz]

Yes, of course. This problem happens only on the field in a few
installations where cables are routed near my product, that is small and
in a plastic enclosure.

> Or is it the surrounding system that is bad?  Maybe there is something
> truly terrible connected to these power cables?

The critical installations often have cables that gives mains power
(230Vac) to coils, for example relays or door ring bell.

[pozz]

Yes, we are thinking about this solutions too.

> BTW, do you get the same sort of hang condition if you bring other metal near the oscillators? It may not be an EMI issue at all, but rather a capacitive effect on the oscillator circuit. They often are sensitive to the details of the parasitic values. If you have a resistor in series with the crystal, this might need to be reduced in value, or increased.

No problem with capacitive loads.

> What circuit does the manufacturer recommend for the oscillator?

Ceramic resonator has three pins, two that goes to the oscillator pins
of the MCU and one is GND.

> Can you provide more detail on the nature of the hang? Does the oscillator stop working? Does the frequency shift? Can you measure any of this? Just saying "without success" isn't much to go on.

The program seems stopped. Sincerely I didn't measure the oscilator
frequency after the noise, so I don't know if it stopped completely
and/or it is disturbed only during the noise.

Anyway, the total effect seems a stopped program. I noticed that in some
cases, this noise generates strange behaviours: GPIO connected to LED
toggle without a reason and so on.

[David Brown]

The current used for door bells - even modern monstrosities with cameras
- is tiny. I really think something must be wrong with the card if it
is susceptible to interference from such cables. Oscillators - crystal
or ceramic - usually need load capacitors and a damping resistor. These
are small loads (perhaps 15-20 pF and 10 MΩ), and are sometimes built
into the microcontroller. But if these are missing, your oscillator
could be unstable and easily affected by outside influence.

[pozz]

Il 05/05/2023 12:59, David Brown ha scritto:
[...]

>> The critical installations often have cables that gives mains power
>> (230Vac) to coils, for example relays or door ring bell.
>
> The current used for door bells - even modern monstrosities with cameras
> - is tiny.

In my installations they don't use that kind of door bells that are
digital circuits with digital audio output. I don't know what's their
exact name, similar to high power buzzers.

[Dimiter_Popoff]

On 5/5/2023 19:01, pozz wrote:
> Il 05/05/2023 12:59, David Brown ha scritto:
> [...]
>>> The critical installations often have cables that gives mains power
>>> (230Vac) to coils, for example relays or door ring bell.
>>
>> The current used for door bells - even modern monstrosities with
>> cameras - is tiny.
>
> In my installations they don't use that kind of door bells that are
> digital circuits with digital audio output. I don't know what's their
> exact name, similar to high power buzzers.

If it is some solenoid driven thing with a mechanical switch it may
cause all sorts of interference, depending also on luck - coincidence
between button being released, solenoid switch, sine wave peak etc.
Try to determine whether the interference which gets you is inductive
or capacitive, or if your board is powered off the same lines.
Things like that can be tricky to fix, you need to understand the nature
of what gets you first.

[Rick C]

You are talking about exactly like a buzzer, but with a clapper for the bell. A mechanical switch interrupts the current to the coil and very likely arcs on opening and closing, generating significant EMI. Perhaps you could convince them to add a capacitor like they used in automotive spark systems? The spark should be in the right place.

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[Grant Edwards]

On 2023-05-05, pozz <pozz...@gmail.com> wrote:

> The critical installations often have cables that gives mains power
> (230Vac) to coils, for example relays or door ring bell.

People use 230VAC for _doorbells_?!?! Are they trying to wake the dead?

Here in the US doorbells are usually 16VAC, though 24VAC is also used.
I've also seen 10VAC and 12VAC mentioned, but I think that's uncommon.

--
Grant

[pozz]

They are very common here (for example [1]). 230Vac is the common mains
voltage so the doorbells are connected to mains, through a momentary
switch out of the door.

[1] https://comenzielectrice.ro/pdf/Bticino%20-%20Matix%20Catalog.pdf
Search for AM5048

[pozz]

I saw it... very well.

> you need to understand the nature of what gets you first.

I will try. It's much more simple to avoid the problem at all disabling
internal oscillator.

[pozz]

Ok, thanks for suggestion.

[Rick C]

I don't know about where you live, but doorbells in the US are powered from low voltage, so they don't require all the safety precautions. A device on a high voltage circuit has to be mounted on a box or has to be a box rated for such wiring. A door bell uses much simpler wiring and needs no special boxes or precautions. I have seen no small number of doorbell buttons mounted directly in the door frame, having been drilled out to 1/2 inch for mounting the button.

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[David Brown]

Guessing from the URL, he could be in Romania, or a country near enough
to use Romanian webshops.

I have no idea about the regulations here in Norway, but I know our
doorbell has a transformer in the fuse cupboard, so it does not have
high voltage mains out to the bell. Driving mains to the doorbell
sounds like a safety nightmare. (Mind you, it's one way to deal with
annoying kids that ring the bell and run away...)

[David Brown]

Another thing to check is exactly where the noise gets into your system.
Maybe it is actually coming in through wires (such as power supply
wires) connected to your box, rather than directly from the bell wire to
the PCB traces. Do you have any connecting wires that might be run
parallel to the bell wire, acting as antenna? If so, try a capacitor on
those lines as a simple EMC filter.

[pozz]

My board is not so sensitive. You need to put the cables near my plastic
enclosure, exactly over the resonator. If you route the cables far from
the resonator/oscillator pins, the problem disappears, even if I tie all
the cables together (ring cables and 12Vdc power supply cables of my board).

[pozz]

Il 07/05/2023 23:27, Rick C ha scritto:
> On Sunday, May 7, 2023 at 5:17:55 PM UTC-4, pozz wrote:
>> Il 05/05/2023 22:16, Grant Edwards ha scritto:
>>> On 2023-05-05, pozz <pozz...@gmail.com> wrote:
>>>
>>>> The critical installations often have cables that gives mains power
>>>> (230Vac) to coils, for example relays or door ring bell.
>>>
>>> People use 230VAC for _doorbells_?!?! Are they trying to wake the dead?
>>>
>>> Here in the US doorbells are usually 16VAC, though 24VAC is also used.
>>> I've also seen 10VAC and 12VAC mentioned, but I think that's uncommon.
>> They are very common here (for example [1]). 230Vac is the common mains
>> voltage so the doorbells are connected to mains, through a momentary
>> switch out of the door.
>>
>> [1] https://comenzielectrice.ro/pdf/Bticino%20-%20Matix%20Catalog.pdf
>> Search for AM5048
>
> I don't know about where you live, but doorbells in the US are powered from low voltage, so they don't require all the safety precautions.

So you have a dedicated power supply for doorbells? Here 99% of house
doorbells are 230Vac. The installation is much more easy, because you
use directly the mains cables without additional hw.

The pushbutton that activates the doorbells are a normal button (but
momentary) that could be used to activate lights in the room.

> A device on a high voltage circuit has to be mounted on a box or has to be a box rated for such wiring. A door bell uses much simpler wiring and needs no special boxes or precautions. I have seen no small number of doorbell buttons mounted directly in the door frame, having been drilled out to 1/2 inch for mounting the button.
>

In the past, the doorbells were dedicated box mounted on the wall, near
the door, inside the apartment.

Now they tend to install as a module inside push-button frames that are
"inside" the wall ([1] just as an example).

Anyway my board is not near the buzzer, but could be near the pushbutton
that activates the buzzer.

[1]
https://www.rmelectric.it/3054-large_default/ronzatore-vimar-plana-230v-bianco-suoneria-campanello-segnalatore-acustico-14378.jpg

[Dimiter_Popoff]

Similar here (Bulgaria). When I was a kid starting to try to put
together this or that a "doorbell transformer" was a popular
option to make some sort of power supply. I think they had a few
outputs at the secondary, starting at 6V or something.
But even so if the buzzer has nasty solenoids and switches it
can cause plenty of interference, who knows.

[Grant Edwards]

On 2023-05-08, pozz <pozz...@gmail.com> wrote:
> Il 07/05/2023 23:27, Rick C ha scritto:
>
>> I don't know about where you live, but doorbells in the US are
>> powered from low voltage, so they don't require all the safety
>> precautions.
>
> So you have a dedicated power supply for doorbells?

Yes. A small transformer that costs a couple dollars. It allows use of
far cheaper wiring and switches than would be required for 120V and
avoids requirements for approved junction boxes, etc.

[Rick C]

On Monday, May 8, 2023 at 3:38:15 AM UTC-4, pozz wrote:
> Il 07/05/2023 23:27, Rick C ha scritto:
> > On Sunday, May 7, 2023 at 5:17:55 PM UTC-4, pozz wrote:
> >> Il 05/05/2023 22:16, Grant Edwards ha scritto:
> >>> On 2023-05-05, pozz <pozz...@gmail.com> wrote:
> >>>
> >>>> The critical installations often have cables that gives mains power
> >>>> (230Vac) to coils, for example relays or door ring bell.
> >>>
> >>> People use 230VAC for _doorbells_?!?! Are they trying to wake the dead?
> >>>
> >>> Here in the US doorbells are usually 16VAC, though 24VAC is also used.
> >>> I've also seen 10VAC and 12VAC mentioned, but I think that's uncommon.
> >> They are very common here (for example [1]). 230Vac is the common mains
> >> voltage so the doorbells are connected to mains, through a momentary
> >> switch out of the door.
> >>
> >> [1] https://comenzielectrice.ro/pdf/Bticino%20-%20Matix%20Catalog.pdf
> >> Search for AM5048
> >
> > I don't know about where you live, but doorbells in the US are powered from low voltage, so they don't require all the safety precautions.
> So you have a dedicated power supply for doorbells?

LOL, when you say "dedicated power supply", you mean this.

https://www.amazon.com/HQRP-Transformer-Compatible-8v-16v-24v-Replacement/dp/B094DKV9NQ

The high voltage side of the transformer is mounted on a proper high voltage box. The rest of the wiring is low voltage, so requires no particular safety precautions. The power is low, so even at the low voltage the wire is not heavy, typically 20 or 22 gauge.

> Here 99% of house
> doorbells are 230Vac. The installation is much more easy, because you
> use directly the mains cables without additional hw.

Doesn't the button require a much more substantial mounting, as well as the bell itself? That's what the low voltage is avoiding. I think my transformer is mounted in the pantry ceiling not unlike a lightbulb (which is also in the pantry ceiling).

> The pushbutton that activates the doorbells are a normal button (but
> momentary) that could be used to activate lights in the room.

I don't know what that means "normal". Here, all wiring junctions or terminations must be done in an approved box.

https://www.youtube.com/watch?v=6GUODvOVz10

The wire junctions shown here are valid, but not common in the US. Mostly people are used to "wire nuts", which are like this, and work well.

https://www.cableorganizer.com/categories/electrical-supplies/cable-termination/tan-wire-connector/

The mistake that is often made when using them, is to not twist the wires together before twisting the nut on. The nut is not intended to be a mechanical connection, just electrical. So the insulated portion of the wire should be twisted together first.

> > A device on a high voltage circuit has to be mounted on a box or has to be a box rated for such wiring. A door bell uses much simpler wiring and needs no special boxes or precautions. I have seen no small number of doorbell buttons mounted directly in the door frame, having been drilled out to 1/2 inch for mounting the button.
> >
> In the past, the doorbells were dedicated box mounted on the wall, near
> the door, inside the apartment.
>
> Now they tend to install as a module inside push-button frames that are
> "inside" the wall ([1] just as an example).
>
> Anyway my board is not near the buzzer, but could be near the pushbutton
> that activates the buzzer.
>
> [1]
> https://www.rmelectric.it/3054-large_default/ronzatore-vimar-plana-230v-bianco-suoneria-campanello-segnalatore-acustico-14378.jpg

The bell itself is not an issue. The PITA is the button.

https://www.amazon.com/doorbell-push-button/s?k=doorbell+push+button

These are much easier to mount where they are most convenient. See the small button with the screw terminals? Below is a crude video of a similar button showing the minimal requirements for installation. This guy is upgrading to a video doorbell.

https://www.google.com/search?q=round+doorbell+button+mounting&client=firefox-b-1-d&sxsrf=APwXEdfIYgYKthf4KothWTYEIfsvEMSPHg:1683555901893&source=lnms&tbm=vid&sa=X&ved=2ahUKEwj2l_e79uX-AhXaMVkFHVUuBuUQ0pQJegQIMBAG&biw=923&bih=497&dpr=1.94#fpstate=ive&vld=cid:1132e9ee,vid:N0H1jSUySH0

Much simpler and less expensive than running high voltage wiring to the button.

I'm wondering if your doorbell has the low voltage transformer inside and the wire to your doorbell is also low voltage? It just makes zero sense to run high voltage to the button.

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[pozz]

I understand a small transformer is cheap, but anyway it's cheaper and
simpler not having it at all.

Here cables for doorbells are routed together with other cables, for
example for lightning, so they uses the same junction boxes.
Moreover the push-button for the doorbell is identical to the one used
to switch on a lamp. It's not uncommon to have a 230Vac frame with
push-button for doorbell, push-button to activate outdoor lamps and a
RFID reader to disable the anti-burglar system. All these three elements
in a frame like this.

[1] https://i.ebayimg.com/images/g/1q0AAOSw7Wtd4lsd/s-l1600.png

[pozz]

Il 08/05/2023 16:32, Rick C ha scritto:
> On Monday, May 8, 2023 at 3:38:15 AM UTC-4, pozz wrote:
>> Il 07/05/2023 23:27, Rick C ha scritto:
>>> On Sunday, May 7, 2023 at 5:17:55 PM UTC-4, pozz wrote:
>>>> Il 05/05/2023 22:16, Grant Edwards ha scritto:
>>>>> On 2023-05-05, pozz <pozz...@gmail.com> wrote:
>>>>>
>>>>>> The critical installations often have cables that gives mains power
>>>>>> (230Vac) to coils, for example relays or door ring bell.
>>>>>
>>>>> People use 230VAC for _doorbells_?!?! Are they trying to wake the dead?
>>>>>
>>>>> Here in the US doorbells are usually 16VAC, though 24VAC is also used.
>>>>> I've also seen 10VAC and 12VAC mentioned, but I think that's uncommon.
>>>> They are very common here (for example [1]). 230Vac is the common mains
>>>> voltage so the doorbells are connected to mains, through a momentary
>>>> switch out of the door.
>>>>
>>>> [1] https://comenzielectrice.ro/pdf/Bticino%20-%20Matix%20Catalog.pdf
>>>> Search for AM5048
>>>
>>> I don't know about where you live, but doorbells in the US are powered from low voltage, so they don't require all the safety precautions.
>> So you have a dedicated power supply for doorbells?
>
> LOL, when you say "dedicated power supply", you mean this.
>
> https://www.amazon.com/HQRP-Transformer-Compatible-8v-16v-24v-Replacement/dp/B094DKV9NQ

The price on this link is 23 euros, I think a 230Vac doorbell costs less.

> The high voltage side of the transformer is mounted on a proper high voltage box. The rest of the wiring is low voltage, so requires no particular safety precautions. The power is low, so even at the low voltage the wire is not heavy, typically 20 or 22 gauge.

Here they usually route the doorbell 230Vac cables together with other
cable of electrical system (lightning...) using the same junction boxes.

>> Here 99% of house
>> doorbells are 230Vac. The installation is much more easy, because you
>> use directly the mains cables without additional hw.
>
> Doesn't the button require a much more substantial mounting, as well as the bell itself? That's what the low voltage is avoiding. I think my transformer is mounted in the pantry ceiling not unlike a lightbulb (which is also in the pantry ceiling).

See [1]. That is a 3-modules frame that can be installed in the wall.
It's already compatible with 230Vac push-buttons. With one of this you
can have the push-button for an outdoor lamp, a push-button for the
doorbell and a keytag reader for anti-burglar system (for example).

You don't need an additional substantial mounting dedicated for doorbell
pushbutton.

>> The pushbutton that activates the doorbells are a normal button (but
>> momentary) that could be used to activate lights in the room.
>
> I don't know what that means "normal". Here, all wiring junctions or terminations must be done in an approved box.

Yes, of course. The same box used for a switch that turns on a light.
There's no need to add a dedicated box for doorbell.

> https://www.youtube.com/watch?v=6GUODvOVz10
>
> The wire junctions shown here are valid, but not common in the US. Mostly people are used to "wire nuts", which are like this, and work well.
>
> https://www.cableorganizer.com/categories/electrical-supplies/cable-termination/tan-wire-connector/
>
> The mistake that is often made when using them, is to not twist the wires together before twisting the nut on. The nut is not intended to be a mechanical connection, just electrical. So the insulated portion of the wire should be twisted together first.
>
>
>>> A device on a high voltage circuit has to be mounted on a box or has to be a box rated for such wiring. A door bell uses much simpler wiring and needs no special boxes or precautions. I have seen no small number of doorbell buttons mounted directly in the door frame, having been drilled out to 1/2 inch for mounting the button.
>>>
>> In the past, the doorbells were dedicated box mounted on the wall, near
>> the door, inside the apartment.
>>
>> Now they tend to install as a module inside push-button frames that are
>> "inside" the wall ([1] just as an example).
>>
>> Anyway my board is not near the buzzer, but could be near the pushbutton
>> that activates the buzzer.
>>
>> [1]
>> https://www.rmelectric.it/3054-large_default/ronzatore-vimar-plana-230v-bianco-suoneria-campanello-segnalatore-acustico-14378.jpg
>
> The bell itself is not an issue. The PITA is the button.
>
> https://www.amazon.com/doorbell-push-button/s?k=doorbell+push+button
>
> These are much easier to mount where they are most convenient. See the small button with the screw terminals? Below is a crude video of a similar button showing the minimal requirements for installation. This guy is upgrading to a video doorbell.
>
> https://www.google.com/search?q=round+doorbell+button+mounting&client=firefox-b-1-d&sxsrf=APwXEdfIYgYKthf4KothWTYEIfsvEMSPHg:1683555901893&source=lnms&tbm=vid&sa=X&ved=2ahUKEwj2l_e79uX-AhXaMVkFHVUuBuUQ0pQJegQIMBAG&biw=923&bih=497&dpr=1.94#fpstate=ive&vld=cid:1132e9ee,vid:N0H1jSUySH0
>
> Much simpler and less expensive than running high voltage wiring to the button.

If you have only a doorbell pushbutton outdoor, yes it could be simpler.
However here usually installs a "normal" in-the-wall 3-modules box, so
you can have multiples commodities: doorbell push-button, button for a
light and so on. This box is already compatible for 230Vac signals.

> I'm wondering if your doorbell has the low voltage transformer inside and the wire to your doorbell is also low voltage? It just makes zero sense to run high voltage to the button.
>

[1] https://i.ebayimg.com/images/g/1q0AAOSw7Wtd4lsd/s-l1600.png

[Rick C]

On Monday, May 8, 2023 at 12:15:19 PM UTC-4, pozz wrote:
> Il 08/05/2023 16:12, Grant Edwards ha scritto:
> > On 2023-05-08, pozz <pozz...@gmail.com> wrote:
> >> Il 07/05/2023 23:27, Rick C ha scritto:
> >>
> >>> I don't know about where you live, but doorbells in the US are
> >>> powered from low voltage, so they don't require all the safety
> >>> precautions.
> >>
> >> So you have a dedicated power supply for doorbells?
> >
> > Yes. A small transformer that costs a couple dollars. It allows use of
> > far cheaper wiring and switches than would be required for 120V and
> > avoids requirements for approved junction boxes, etc.
> I understand a small transformer is cheap, but anyway it's cheaper and
> simpler not having it at all.

LOL You don't seem to understand. You either have the transformer as a separate entity, or its functionality is incorporated in something more expensive, because it is rated for 240V.

> Here cables for doorbells are routed together with other cables, for
> example for lightning, so they uses the same junction boxes.

I think you mean "lighting". But you can't lump the doorbell with anything else. At least not in existing construction. It is all irrelevant. Do what you wish. Spend the money on 240V wiring at a dollar a foot and high voltage boxes. That's your choice. But the fact is, the low voltage doorbell is much cheaper to install.

> Moreover the push-button for the doorbell is identical to the one used
> to switch on a lamp. It's not uncommon to have a 230Vac frame with
> push-button for doorbell, push-button to activate outdoor lamps and a
> RFID reader to disable the anti-burglar system. All these three elements
> in a frame like this.

You put your outside lights on an outside switch? Doesn't happen here, at least not at the front door.


> [1] https://i.ebayimg.com/images/g/1q0AAOSw7Wtd4lsd/s-l1600.png

Your photo looks like an indoor switch. Outdoor switches are typically much more robust and sealed from the elements. Which one is the doorbell switch? Or is all this inside the front door and a visitor opens the door to ring the bell?

--

Rick C.

-+-- Get 1,000 miles of free Supercharging
-+-- Tesla referral code - https://ts.la/richard11209

[Rick C]

On Monday, May 8, 2023 at 12:29:21 PM UTC-4, pozz wrote:
> Il 08/05/2023 16:32, Rick C ha scritto:
> > On Monday, May 8, 2023 at 3:38:15 AM UTC-4, pozz wrote:
> >> Il 07/05/2023 23:27, Rick C ha scritto:
> >>> On Sunday, May 7, 2023 at 5:17:55 PM UTC-4, pozz wrote:
> >>>> Il 05/05/2023 22:16, Grant Edwards ha scritto:
> >>>>> On 2023-05-05, pozz <pozz...@gmail.com> wrote:
> >>>>>
> >>>>>> The critical installations often have cables that gives mains power
> >>>>>> (230Vac) to coils, for example relays or door ring bell.
> >>>>>
> >>>>> People use 230VAC for _doorbells_?!?! Are they trying to wake the dead?
> >>>>>
> >>>>> Here in the US doorbells are usually 16VAC, though 24VAC is also used.
> >>>>> I've also seen 10VAC and 12VAC mentioned, but I think that's uncommon.
> >>>> They are very common here (for example [1]). 230Vac is the common mains
> >>>> voltage so the doorbells are connected to mains, through a momentary
> >>>> switch out of the door.
> >>>>
> >>>> [1] https://comenzielectrice.ro/pdf/Bticino%20-%20Matix%20Catalog.pdf
> >>>> Search for AM5048
> >>>
> >>> I don't know about where you live, but doorbells in the US are powered from low voltage, so they don't require all the safety precautions.
> >> So you have a dedicated power supply for doorbells?
> >
> > LOL, when you say "dedicated power supply", you mean this.
> >
> > https://www.amazon.com/HQRP-Transformer-Compatible-8v-16v-24v-Replacement/dp/B094DKV9NQ
> The price on this link is 23 euros, I think a 230Vac doorbell costs less.

Yeah, Amazon is often the highest price for various items. The transformer is as little as $8 in local stores.

> > The high voltage side of the transformer is mounted on a proper high voltage box. The rest of the wiring is low voltage, so requires no particular safety precautions. The power is low, so even at the low voltage the wire is not heavy, typically 20 or 22 gauge.
> Here they usually route the doorbell 230Vac cables together with other
> cable of electrical system (lightning...) using the same junction boxes.

"Routing" typically needs no boxes. You still need a box for the button and for the bell. I'm sure you are not grasping the simplicity of a low voltage doorbell.

> >> Here 99% of house
> >> doorbells are 230Vac. The installation is much more easy, because you
> >> use directly the mains cables without additional hw.
> >
> > Doesn't the button require a much more substantial mounting, as well as the bell itself? That's what the low voltage is avoiding. I think my transformer is mounted in the pantry ceiling not unlike a lightbulb (which is also in the pantry ceiling).
> See [1]. That is a 3-modules frame that can be installed in the wall.
> It's already compatible with 230Vac push-buttons. With one of this you
> can have the push-button for an outdoor lamp, a push-button for the
> doorbell and a keytag reader for anti-burglar system (for example).

Is it for outdoor use??? The only items I found were the 12V power supply.

> You don't need an additional substantial mounting dedicated for doorbell
> pushbutton.

I have no idea what you are describing. No one I've ever known has high voltage light switches mounted next to the front door with or without a bell button. In fact, it's not allowed to mix low voltage and high voltage in the same box.

> >> The pushbutton that activates the doorbells are a normal button (but
> >> momentary) that could be used to activate lights in the room.
> >
> > I don't know what that means "normal". Here, all wiring junctions or terminations must be done in an approved box.
> Yes, of course. The same box used for a switch that turns on a light.
> There's no need to add a dedicated box for doorbell.

You keep saying that, but you have to put in an unsightly and obtrusive high voltage box, next to your front door. If you want to put other high voltage switches in that, fine, but it doesn't change the need for the high voltage box for the doorbell button.

> > https://www.youtube.com/watch?v=6GUODvOVz10
> >
> > The wire junctions shown here are valid, but not common in the US. Mostly people are used to "wire nuts", which are like this, and work well.
> >
> > https://www.cableorganizer.com/categories/electrical-supplies/cable-termination/tan-wire-connector/
> >
> > The mistake that is often made when using them, is to not twist the wires together before twisting the nut on. The nut is not intended to be a mechanical connection, just electrical. So the insulated portion of the wire should be twisted together first.
> >
> >
> >>> A device on a high voltage circuit has to be mounted on a box or has to be a box rated for such wiring. A door bell uses much simpler wiring and needs no special boxes or precautions. I have seen no small number of doorbell buttons mounted directly in the door frame, having been drilled out to 1/2 inch for mounting the button.
> >>>
> >> In the past, the doorbells were dedicated box mounted on the wall, near
> >> the door, inside the apartment.
> >>
> >> Now they tend to install as a module inside push-button frames that are
> >> "inside" the wall ([1] just as an example).
> >>
> >> Anyway my board is not near the buzzer, but could be near the pushbutton
> >> that activates the buzzer.
> >>
> >> [1]
> >> https://www.rmelectric.it/3054-large_default/ronzatore-vimar-plana-230v-bianco-suoneria-campanello-segnalatore-acustico-14378.jpg
> >
> > The bell itself is not an issue. The PITA is the button.
> >
> > https://www.amazon.com/doorbell-push-button/s?k=doorbell+push+button
> >
> > These are much easier to mount where they are most convenient. See the small button with the screw terminals? Below is a crude video of a similar button showing the minimal requirements for installation. This guy is upgrading to a video doorbell.
> >
> > https://www.google.com/search?q=round+doorbell+button+mounting&client=firefox-b-1-d&sxsrf=APwXEdfIYgYKthf4KothWTYEIfsvEMSPHg:1683555901893&source=lnms&tbm=vid&sa=X&ved=2ahUKEwj2l_e79uX-AhXaMVkFHVUuBuUQ0pQJegQIMBAG&biw=923&bih=497&dpr=1.94#fpstate=ive&vld=cid:1132e9ee,vid:N0H1jSUySH0
> >
> > Much simpler and less expensive than running high voltage wiring to the button.
> If you have only a doorbell pushbutton outdoor, yes it could be simpler.
> However here usually installs a "normal" in-the-wall 3-modules box, so
> you can have multiples commodities: doorbell push-button, button for a
> light and so on. This box is already compatible for 230Vac signals.
> > I'm wondering if your doorbell has the low voltage transformer inside and the wire to your doorbell is also low voltage? It just makes zero sense to run high voltage to the button.
> >
> [1] https://i.ebayimg.com/images/g/1q0AAOSw7Wtd4lsd/s-l1600.png

Why do you keep showing pictures of indoor switches? This has nothing to do with the outside doorbell button.

I did find this in your catalog.

bronze bell 12 Va.c. - 5 VA - 80 dB

--

Rick C.

-+-+ Get 1,000 miles of free Supercharging
-+-+ Tesla referral code - https://ts.la/richard11209

[Grant Edwards]

On 2023-05-08, pozz <pozz...@gmail.com> wrote:
> Il 08/05/2023 16:12, Grant Edwards ha scritto:
>> On 2023-05-08, pozz <pozz...@gmail.com> wrote:
>>> Il 07/05/2023 23:27, Rick C ha scritto:
>>>
>>>> I don't know about where you live, but doorbells in the US are
>>>> powered from low voltage, so they don't require all the safety
>>>> precautions.
>>>
>>> So you have a dedicated power supply for doorbells?
>>
>> Yes. A small transformer that costs a couple dollars. It allows use of
>> far cheaper wiring and switches than would be required for 120V and
>> avoids requirements for approved junction boxes, etc.
>
> I understand a small transformer is cheap, but anyway it's cheaper and
> simpler not having it at all.

It's hard to see how the installed cost could cheaper. Using 16V
allows use of much cheaper wire, you don't need to install junction
boxes or conduit, the routing requirements for mains voltages don't
apply, and you don't need a certified electrician to do the work.

> Here cables for doorbells are routed together with other cables, for
> example for lightning, so they uses the same junction boxes.

There's a junction box on the outside of the house for light switches?

> Moreover the push-button for the doorbell is identical to the one used
> to switch on a lamp. It's not uncommon to have a 230Vac frame with
> push-button for doorbell, push-button to activate outdoor lamps and a
> RFID reader to disable the anti-burglar system. All these three elements
> in a frame like this.
>
> [1] https://i.ebayimg.com/images/g/1q0AAOSw7Wtd4lsd/s-l1600.png

Those switches are on the outside of the house and one of them is the
doorbell button?

[pozz]

I don't want to defend installations that THEY do here where I live. I'm
just describing what usually happens.

In the apartment there are already "in-wall" tubes and junction boxes
for mains distribution and frames for lights switches. In this case, I
think it's worth it to "waste" one module to install a 230Vac buzzer
inside and one module to install a 230Vac pushbutton to activate the
buzzer outside. During installation of mains circuits you already have
230Vac cables and you can use them for doorbell too.

The prices of 230Vac and 12Vac doorbells are similar (see [1] and [2]),
with the plus you can avoid an additional power supply/transformer, even
if it is cheap.

>>>> Here 99% of house
>>>> doorbells are 230Vac. The installation is much more easy, because you
>>>> use directly the mains cables without additional hw.
>>>
>>> Doesn't the button require a much more substantial mounting, as well as the bell itself? That's what the low voltage is avoiding. I think my transformer is mounted in the pantry ceiling not unlike a lightbulb (which is also in the pantry ceiling).
>> See [1]. That is a 3-modules frame that can be installed in the wall.
>> It's already compatible with 230Vac push-buttons. With one of this you
>> can have the push-button for an outdoor lamp, a push-button for the
>> doorbell and a keytag reader for anti-burglar system (for example).
>
> Is it for outdoor use??? The only items I found were the 12V power supply.

Sorry for misunderstanding. It isn't for outdoor use, it is usually
installed "out of the door" of the apartment, but inside a
multi-apartment building.
Of course, in isolated building where the doorbell switch is really
outdoor, you can't use that.

>> You don't need an additional substantial mounting dedicated for doorbell
>> pushbutton.
>
> I have no idea what you are describing. No one I've ever known has high voltage light switches mounted next to the front door with or without a bell button. In fact, it's not allowed to mix low voltage and high voltage in the same box.

When the apartment is one of many in a building (condominium), there's
usually a public light on the common part of the floor (balcony?
landing?) inside the building. And you could want to switch on when you
are outside your apartment. Both the light button and doorbell button
are 230Vac, so no mixing.

>>>> The pushbutton that activates the doorbells are a normal button (but
>>>> momentary) that could be used to activate lights in the room.
>>>
>>> I don't know what that means "normal". Here, all wiring junctions or terminations must be done in an approved box.
>> Yes, of course. The same box used for a switch that turns on a light.
>> There's no need to add a dedicated box for doorbell.
>
> You keep saying that, but you have to put in an unsightly and obtrusive high voltage box, next to your front door. If you want to put other high voltage switches in that, fine, but it doesn't change the need for the high voltage box for the doorbell button.

I don't think this[3] is worse than this[4]. Of course, it depends on
personal taste.

See above for the misunderstanding.

> I did find this in your catalog.
>
> bronze bell 12 Va.c. - 5 VA - 80 dB

Yes, I never said there aren't low voltage buzzers, but they aren't
frequently used here.


[1] https://amzn.eu/d/8iPOXgt
[2] https://amzn.eu/d/b31Lcre
[3] https://i.ebayimg.com/images/g/1q0AAOSw7Wtd4lsd/s-l1600.png
[4] https://m.media-amazon.com/images/I/71hYNep5oaL._AC_SL1200_.jpg

[pozz]

Il 08/05/2023 20:39, Rick C ha scritto:
> On Monday, May 8, 2023 at 12:15:19 PM UTC-4, pozz wrote:
>> Il 08/05/2023 16:12, Grant Edwards ha scritto:
>>> On 2023-05-08, pozz <pozz...@gmail.com> wrote:
>>>> Il 07/05/2023 23:27, Rick C ha scritto:
>>>>
>>>>> I don't know about where you live, but doorbells in the US are
>>>>> powered from low voltage, so they don't require all the safety
>>>>> precautions.
>>>>
>>>> So you have a dedicated power supply for doorbells?
>>>
>>> Yes. A small transformer that costs a couple dollars. It allows use of
>>> far cheaper wiring and switches than would be required for 120V and
>>> avoids requirements for approved junction boxes, etc.
>> I understand a small transformer is cheap, but anyway it's cheaper and
>> simpler not having it at all.
>
> LOL You don't seem to understand. You either have the transformer as a separate entity, or its functionality is incorporated in something more expensive, because it is rated for 240V.

See [1] and [2]. The prices are the same.

>> Here cables for doorbells are routed together with other cables, for
>> example for lightning, so they uses the same junction boxes.
>
> I think you mean "lighting".

Yes, sorry.

> But you can't lump the doorbell with anything else. At least not in existing construction. It is all irrelevant. Do what you wish. Spend the money on 240V wiring at a dollar a foot and high voltage boxes. That's your choice. But the fact is, the low voltage doorbell is much cheaper to install.

I don't want to spend any money for any doorbells ;-)
This is what I see, I'm not an expert of mains distribution in buildings
and apartments.

I'm only supposing that in a new house, where you already have 230Vac
tubes and junction boxes and you need one or more light push-buttons out
of the door (not outdoor), you can share everything and possibly share
some money, considering that 230Vac and 12Vac buzzers are similar in price.

>> Moreover the push-button for the doorbell is identical to the one used
>> to switch on a lamp. It's not uncommon to have a 230Vac frame with
>> push-button for doorbell, push-button to activate outdoor lamps and a
>> RFID reader to disable the anti-burglar system. All these three elements
>> in a frame like this.
>
> You put your outside lights on an outside switch? Doesn't happen here, at least not at the front door.
>
>
>> [1] https://i.ebayimg.com/images/g/1q0AAOSw7Wtd4lsd/s-l1600.png
>
> Your photo looks like an indoor switch. Outdoor switches are typically much more robust and sealed from the elements. Which one is the doorbell switch? Or is all this inside the front door and a visitor opens the door to ring the bell?

I was thinking to a typical situation here, an apartment in a
condominium, a bigger multi-houses building. Your doorbell pushbutton is
inside the building and you often need to switch on a lamp.

[pozz]

Il 08/05/2023 21:09, Grant Edwards ha scritto:
> On 2023-05-08, pozz <pozz...@gmail.com> wrote:
>> Il 08/05/2023 16:12, Grant Edwards ha scritto:
>>> On 2023-05-08, pozz <pozz...@gmail.com> wrote:
>>>> Il 07/05/2023 23:27, Rick C ha scritto:
>>>>
>>>>> I don't know about where you live, but doorbells in the US are
>>>>> powered from low voltage, so they don't require all the safety
>>>>> precautions.
>>>>
>>>> So you have a dedicated power supply for doorbells?
>>>
>>> Yes. A small transformer that costs a couple dollars. It allows use of
>>> far cheaper wiring and switches than would be required for 120V and
>>> avoids requirements for approved junction boxes, etc.
>>
>> I understand a small transformer is cheap, but anyway it's cheaper and
>> simpler not having it at all.
>
> It's hard to see how the installed cost could cheaper. Using 16V
> allows use of much cheaper wire, you don't need to install junction
> boxes or conduit, the routing requirements for mains voltages don't
> apply, and you don't need a certified electrician to do the work.

Yes, of course. Anyway, most of the time the doorbell is installed by
the certified electrician during a renovation or during construction of
a new building. In this case, you already have a lot of cables and you
can share already present conduits and junction boxes.

>> Here cables for doorbells are routed together with other cables, for
>> example for lightning, so they uses the same junction boxes.
>
> There's a junction box on the outside of the house for light switches?

Only the frame for push-buttons. Junction boxes are inside the house. On
the floor of 2-3 apartments, it could be a junction box for common
assets, such as common lights, antennas, elevator and so on.

>> Moreover the push-button for the doorbell is identical to the one used
>> to switch on a lamp. It's not uncommon to have a 230Vac frame with
>> push-button for doorbell, push-button to activate outdoor lamps and a
>> RFID reader to disable the anti-burglar system. All these three elements
>> in a frame like this.
>>
>> [1] https://i.ebayimg.com/images/g/1q0AAOSw7Wtd4lsd/s-l1600.png
>
> Those switches are on the outside of the house and one of them is the
> doorbell button?

Outside, not outdoor. Yes, one of this is the pushbutton of the doorbell.

[Grant Edwards]

On 2023-05-09, pozz <pozz...@gmail.com> wrote:

>> Is it for outdoor use??? The only items I found were the 12V power
>> supply.
>
> Sorry for misunderstanding. It isn't for outdoor use, it is usually
> installed "out of the door" of the apartment, but inside a
> multi-apartment building. Of course, in isolated building where the
> doorbell switch is really outdoor, you can't use that.

Ah, OK. we're talking about doorbells for single-family, detached
houses. There's typically a chime mounted on a wall in a central
location and one or more buttons (two is very common) wired to that
chime.

You're talking about apartment buildings. Here in the US, apartment
buildings don't use the 16V doorbells we've been describing. They
usually have buzzer/intercom/remote-door-lock systems that are
completely different than a "doorbell".

--
Grant

[Rick C]

I haven't seen you post anything that would be used outside. Worse, you have not explained why there would be a gang switch box outside where the doorbell button would be. Others have asked the same thing, and as far as I can tell, you ignore them as well.

> The prices of 230Vac and 12Vac doorbells are similar (see [1] and [2]),

You are picking one line item from a single catalog. Price out all the parts required.

> with the plus you can avoid an additional power supply/transformer, even
> if it is cheap.

I don't know what you are talking about. Sorry. You seem to be addressing doorbells with buttons inside your house. We just don't have much of that in the US.

> >>>> Here 99% of house
> >>>> doorbells are 230Vac. The installation is much more easy, because you
> >>>> use directly the mains cables without additional hw.
> >>>
> >>> Doesn't the button require a much more substantial mounting, as well as the bell itself? That's what the low voltage is avoiding. I think my transformer is mounted in the pantry ceiling not unlike a lightbulb (which is also in the pantry ceiling).
> >> See [1]. That is a 3-modules frame that can be installed in the wall.
> >> It's already compatible with 230Vac push-buttons. With one of this you
> >> can have the push-button for an outdoor lamp, a push-button for the
> >> doorbell and a keytag reader for anti-burglar system (for example).
> >
> > Is it for outdoor use??? The only items I found were the 12V power supply.
> Sorry for misunderstanding. It isn't for outdoor use, it is usually
> installed "out of the door" of the apartment, but inside a
> multi-apartment building.
> Of course, in isolated building where the doorbell switch is really
> outdoor, you can't use that.

Yeah, that makes more sense. In the US, older apartments that were made from a single family dwelling, have a number of low voltage buttons on the outside of the main door, or just inside in a foyer. More modern apartments have no doorbells.
You just knock on the doors. Works pretty well. We have these things called, "knockers".

> >> You don't need an additional substantial mounting dedicated for doorbell
> >> pushbutton.
> >
> > I have no idea what you are describing. No one I've ever known has high voltage light switches mounted next to the front door with or without a bell button. In fact, it's not allowed to mix low voltage and high voltage in the same box.
> When the apartment is one of many in a building (condominium), there's
> usually a public light on the common part of the floor (balcony?
> landing?) inside the building. And you could want to switch on when you
> are outside your apartment. Both the light button and doorbell button
> are 230Vac, so no mixing.

Even in such apartments, we just use low voltage doorbells for all the reasons that have been explained to you. Every part of the system is a lower cost than a 240V bell system. It requires no special consideration for the wiring and can be done by the kid next door, rather than under supervision of a licensed electrician. I don't know why you can't understand this simple matter.

> >>>> The pushbutton that activates the doorbells are a normal button (but
> >>>> momentary) that could be used to activate lights in the room.
> >>>
> >>> I don't know what that means "normal". Here, all wiring junctions or terminations must be done in an approved box.
> >> Yes, of course. The same box used for a switch that turns on a light.
> >> There's no need to add a dedicated box for doorbell.
> >
> > You keep saying that, but you have to put in an unsightly and obtrusive high voltage box, next to your front door. If you want to put other high voltage switches in that, fine, but it doesn't change the need for the high voltage box for the doorbell button.
> I don't think this[3] is worse than this[4]. Of course, it depends on
> personal taste.

Sorry, I don't know what 3 and 4 are.

Apparently where you live, no one goes outside. All front doors are inside. Nice world.

--

Rick C.

-++- Get 1,000 miles of free Supercharging
-++- Tesla referral code - https://ts.la/richard11209

[Rick C]

You literally know nothing of the issues of wiring high voltage vs. low voltage. You keep talking about the buttons in a catalog, without understanding how they are used. I can't spend any more time trying to explain it to you. So, you may hold your ideas dear.

> >> Moreover the push-button for the doorbell is identical to the one used
> >> to switch on a lamp. It's not uncommon to have a 230Vac frame with
> >> push-button for doorbell, push-button to activate outdoor lamps and a
> >> RFID reader to disable the anti-burglar system. All these three elements
> >> in a frame like this.
> >
> > You put your outside lights on an outside switch? Doesn't happen here, at least not at the front door.
> >
> >
> >> [1] https://i.ebayimg.com/images/g/1q0AAOSw7Wtd4lsd/s-l1600.png
> >
> > Your photo looks like an indoor switch. Outdoor switches are typically much more robust and sealed from the elements. Which one is the doorbell switch? Or is all this inside the front door and a visitor opens the door to ring the bell?
> I was thinking to a typical situation here, an apartment in a
> condominium, a bigger multi-houses building. Your doorbell pushbutton is
> inside the building and you often need to switch on a lamp.
> [1] https://amzn.eu/d/8iPOXgt
> [2] https://amzn.eu/d/b31Lcre

Ok, Enjoy.

--

Rick C.

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[pozz]

I don't know how we are fighting for this kind of arguments. I don't
want to convince you, I'm not a professinal electrician and for me is
good what you write. Keep on with embedded things.