Higher loads on triac light dimmer ???
CS
has a heating element rated at 1300W.
Rather than using a bulky & expensive step down transformer, I would prefer
to use a standard thyristor light dimmer to control the heating element
since it is just a resistive load, but every light dimmer I've seen is
limited to about 600W.
Is it possible to modify something to get this to work, like add a heatsink
to the 600W light dimmer ??
Thanks.
Jim Thompson
"CS" <clif...@yahoo.com>,
In Newsgroup: sci.electronics.design,
Article: <LdIh9.431$L35....@newsread2.prod.itd.earthlink.net>,
Entitled: "Higher loads on triac light dimmer ???",
Wrote the following:
You could use an auto-transformer with a substantial size reduction.
...Jim Thompson
--
| James E.Thompson, P.E. | mens |
| Analog Innovations, Inc. | et |
| Analog/Mixed-Signal ASIC's and Discrete Systems | manus |
| Phoenix, Arizona Voice:(480)460-2350 | |
| Jim-T@analog_innovations.com Fax:(480)460-2142 | Brass Rat |
| http://www.analog-innovations.com | 1962 |
For proper E-mail replies SWAP "-" and "_"
I love to cook with wine. Sometimes I even put it in the food.
Kevin Aylward
"CS" <clif...@yahoo.com> wrote in message
news:LdIh9.431$L35....@newsread2.prod.itd.earthlink.net...
> Hi, I'm moving a coffee machine from the USA 110V to Australia 220V
which
> has a heating element rated at 1300W.
>
Buy a new coffee machine.
Kevin Aylward
ke...@anasoft.co.uk
http://www.anasoft.co.uk
SuperSpice, a very affordable Mixed-Mode
Windows Simulator with Schematic Capture,
Waveform Display, FFT's and Filter Design.
Kevin McMurtrie
"CS" <clif...@yahoo.com> wrote:
A dimmer works by chopping up the AC wave. Choping up 220VAC and
feeding it into your coffee maker's 9.3 Ohm (1300W / 110V) load would
create terrible line noise. 220VAC peaks at 311V. 311V into 9.3 Ohms
is 33.4 Amps! It could fry electronics and heat up your house's
electrical wiring.
Get a new coffee maker.
The.Central.Scru...@invalid.pobox.com
I can't believe someone suggested using a light dimmer. Obviously not having
the *slightest* clue isn't enough to keep "CS" from posting his brand of
advice. Perhaps someday "CS" will burn his own house down to the ground and
that'll end his helpfull non-advice.
elektrode
Even if you found a dimmer with a high enough rating it would only reduce
the voltage, not increase it. Why don't you see if you can get a new element
rated at 220 volts for your machine? If not, scrap it and start again.
--
JohnS
CS
<The.Central.Scru...@invalid.pobox.com> wrote in message
news:slrnaoertk.an0.The.Cent...@localhost.localdomain..
.
Mike Poulton
What? Read it again, John. He has a heater for 110V, and he wants to
use it in 220. Therefore, he needs to divide the applied voltage by
two! A triac circuit will work fine for this, although it doesn't
really decrease the voltage. The best way to go is to use a "universal
control" designed for 220V stove elements. These are cheap, made for
220V (can't use a 120V dimmer on 220!), and will easily handle the
power. Check an appliance repair shop. Keep in mind that you will need
to measure the power somehow, and a regular volt meter won't cut it --
the waveform is totally funky. You could do it with a really good RMS
meter, or with an oscilloscope and some fun math.
--
Mike Poulton
MTP Technologies
Not only do I speak for my company, I AM my company!
Live free or die!
http://www.indefenseoffreedom.org/
The.Central.Scru...@invalid.pobox.com
>Thank you for redefining a new depth to the word JERK!
Yes, you certainly are a jerk of epic proportions for your wonderfull advice of
using a dimmer to get 120Vac from 240vac for the purpose of running a 1300W
heater.
John Fields
---
Unfortunately, it's not that simple.
First, you've got the dissipation of the TRIAC to consider. When it's
fully on, you've got what amounts to a diode drop from MT1 to MT2, so
with that diode in series with a 600 watt load you'll have about
600W/120V = 5A flowing through it. Assuming the drop across the TRIAC
is 1V means the TRIAC will be dissipating about 5W when the load is
dissipating 600W. If you try to use it with a fully-on 1300W load the
TRIAC will need to pass about 10A (and dissipate about 10W) which it's
surely not rated for if it's being sold with a 600W load limit. On top
of that, it's going to have to stand off 220V because you're going to
have to fire it on the far side of 90° and 270°. So, what you could do
would be to get a TRIAC capable of standing of 220V and handling 12A,
then phase control it so it fired at the right time. Or, put a 110V
1300W iron in series with the coffeemaker and (have your wife) iron your
clothes while the coffee's brewing. ;^)
---
John Fields
Professional circuit designer
http://www.austininstruments.com
CS
"Mike Poulton" <mpou...@mtptech.com> wrote in message
news:Xns928C9D96199C9m...@129.93.1.40...
scada
be all resistive, unless it has an electronic timer or such in it!
"John Fields" <jfi...@texas.net> wrote in message
news:3D879533...@texas.net...
Mike Poulton
> Why not put a rectifier diode in series with the load! The coffee pot
> should be all resistive, unless it has an electronic timer or such in
> it!
Well... Half voltage does not equal half power. If you do that, you
will still be running the element at double the rated power.
scada
> On 17 Sep 2002, "scada" <scada...@optonlinenospam.net> said:
>
> > Why not put a rectifier diode in series with the load! The coffee pot
> > should be all resistive, unless it has an electronic timer or such in
> > it!
>
> Well... Half voltage does not equal half power. If you do that, you
> will still be running the element at double the rated power.
>
If the pot is resistive there should not be a problem!
Mike Poulton
>
> "Mike Poulton" <mpou...@mtptech.com> wrote in message
> news:Xns928CD0C17E1D2m...@129.93.1.40...
>> On 17 Sep 2002, "scada" <scada...@optonlinenospam.net> said:
>>
>> > Why not put a rectifier diode in series with the load! The coffee
>> > pot should be all resistive, unless it has an electronic timer or
>> > such in it!
>>
>> Well... Half voltage does not equal half power. If you do that, you
>> will still be running the element at double the rated power.
>>
> Half of 220V is 110V! Is that not what the pot is designed for?
> If the pot is resistive there should not be a problem!
What I means is that by installing a series diode, you are running half
power, not half voltage. It is equivalent to 50% pulse width
modulation, not 50% voltage reduction.
Ian Stirling
<snip>
> What I means is that by installing a series diode, you are running half
> power, not half voltage. It is equivalent to 50% pulse width
> modulation, not 50% voltage reduction.
Yes, we know, and you'r wrong.
If you double the voltage, you quadruple the power.
What'd the average wattage be if you turned it on for a second, off for a
second?
--
http://inquisitor.i.am/ | mailto:inqui...@i.am | Ian Stirling.
---------------------------+-------------------------+--------------------------
Paranoia: A game for the whole family, and anyone else who might be watching.
Ian Stirling
>
> Thanks Mike. A universal control from a stove top makes great sense.
No it doesn't.
It'll burn out the heater when it first comes on.
The stove-top regulators cycle every 30 seconds or so.
Plus, you'd need to replace all the heater wiring with stuff rated for
20A, as well as the socket it plugs into.
You really need to either replace the element, or do something clever
electronically.
The circuit you'd need isn't real complex (bridge rectifier-cap-10Khz switch)
but it's not something you'd find easily available IMO.
--
http://inquisitor.i.am/ | mailto:inqui...@i.am | Ian Stirling.
---------------------------+-------------------------+--------------------------
"The device every conquerer, yes, every altruistic liberator should be required
to wear on his shield... is a little girl and her kitten, at ground zero"
- Sir Dominic Flandry in Poul Andersons 'A Knight of Ghosts and Shadows'
petrus bitbyter
"scada" <scada...@optonlinenospam.net> schreef in bericht
news:sbQh9.13016$X7.3...@news4.srv.hcvlny.cv.net...
> Why not put a rectifier diode in series with the load! The coffee pot
should
> be all resistive, unless it has an electronic timer or such in it!
>
Some simple calculations using Ohm's law show that its a wrong assumption.
A resistive load for 110V and 1300W will draw a current of 1300/110=11.8A.
So its resistance is 110/11.8=9.32Ohm.
Double the voltage will double the current 220/9.32=23.6A.
So the dissipated power will be 220*23.6=5192W (or about 4*1300=5200).
When you use a diode, voltage, current and power will remain unchanged for
half a period and be zero for the other half. So effectively the dissipated
power will still be double the rated 1300W.
pieter
John Fields
>
> "Mike Poulton" <mpou...@mtptech.com> wrote in message
> news:Xns928CD0C17E1D2m...@129.93.1.40...
> > On 17 Sep 2002, "scada" <scada...@optonlinenospam.net> said:
> >
> > > Why not put a rectifier diode in series with the load! The coffee pot
> > > should be all resistive, unless it has an electronic timer or such in
> > > it!
> >
> > Well... Half voltage does not equal half power. If you do that, you
> > will still be running the element at double the rated power.
> >
> Half of 220V is 110V! Is that not what the pot is designed for?
> If the pot is resistive there should not be a problem!
---
As some other posters have mentioned, a series diode is not a good idea.
Look at it this way:
If the coffee maker is rated for 1300W at 110V and it's resistive, then
it will have a resistance of E²/P = 12000/1300W ~ 9.3 ohms. Connected
across 220V mains it will dissipate E²/R = 48400/9.3ohms ~ 5200W !!!
With a diode in series between the mains and the heating element what
will happen is that one half of each mains cycle will be blocked, with
the result that the element will be dissipating one half of what it
would be if the diode was not there. That's 2600 watts, which the
element would not be happy with for long.
Mike Poulton
> Mike Poulton <mpou...@mtptech.com> wrote:
> <snip>
>> What I means is that by installing a series diode, you are running
>> half power, not half voltage. It is equivalent to 50% pulse width
>> modulation, not 50% voltage reduction.
>
> Yes, we know, and you'r wrong.
>
> If you double the voltage, you quadruple the power.
> What'd the average wattage be if you turned it on for a second, off
> for a second?
I don't know if you are misreading my post, or simply not thinking.
Double the voltage (120 to 240), quadruple the power -- we're up to
5200W.
Now turn if off half of the time, dividing the average power by two --
that's 2600W.
2600W is not 1300W. It is twice 1300W. Thus, using a series diode will
still double the power.
Unknown
Take a look at this ST appnote. On page 7 fig. 10 they show a triac
controlled 220v > 110v stepdown curcuit.
http://www.st.com/stonline/books/pdf/docs/3566.pdf
Fred Bloggs
Yes you can make any number of modifications but you will end up
building an entirely new coffee maker. The coffee maker is much more
than a resistive heater. For one thing you have thermal regulators and
safety cut-outs that are designed to operate at maximum duty cycles,
voltages, and interrupt current ratings. Every bit of this will be
operating beyond design and approval ratings at 220Vrms and the
resulting peak currents. The dimmer idea is out, the new coffee maker
idea is in.
Ian Stirling
>
> On 18 Sep 2002, Ian Stirling <ro...@mauve.demon.co.uk> said:
>
>> Mike Poulton <mpou...@mtptech.com> wrote:
>> <snip>
>>> What I means is that by installing a series diode, you are running
>>> half power, not half voltage. It is equivalent to 50% pulse width
>>> modulation, not 50% voltage reduction.
>>
>> Yes, we know, and you'r wrong.
>>
>> If you double the voltage, you quadruple the power.
>> What'd the average wattage be if you turned it on for a second, off
>> for a second?
>
> I don't know if you are misreading my post, or simply not thinking.
>
> Double the voltage (120 to 240), quadruple the power -- we're up to
> 5200W.
>
> Now turn if off half of the time, dividing the average power by two --
> that's 2600W.
>
> 2600W is not 1300W. It is twice 1300W. Thus, using a series diode will
> still double the power.
Oops, I got turned around, and thought you were arguing otherwise, when
in fact it was the person you were responding to.
You are of course correct, as am I :)
Sorry for any confusion.
--
http://inquisitor.i.am/ | mailto:inqui...@i.am | Ian Stirling.
---------------------------+-------------------------+--------------------------
Q: What do you call a train that doesn't stop at stations?
A: Thomas the Bastard. -- Ben
John Fields
> Yes you can make any number of modifications but you will end up
> building an entirely new coffee maker. The coffee maker is much more
> than a resistive heater. For one thing you have thermal regulators and
> safety cut-outs that are designed to operate at maximum duty cycles,
> voltages, and interrupt current ratings. Every bit of this will be
> operating beyond design and approval ratings at 220Vrms and the
> resulting peak currents. The dimmer idea is out, the new coffee maker
> idea is in.
---
Au contraire, Bloggsy!
The proper TRIAC, a DIAC, an R and a C will do it:
220>--------+---------------+
| |
| [MR.COFFEE]
[R] |
| MT2
+--[DIAC]----G
| MT1
[C] |
| |
| |
220>--------+---------------+
The choice of R and C for the proper firing angle is left as an exercise
for the interested!^)
Ian Stirling
<snip>
> The proper TRIAC, a DIAC, an R and a C will do it:
>
>
> 220>--------+---------------+
> | |
> | [MR.COFFEE]
> [R] |
> | MT2
> +--[DIAC]----G
> | MT1
> [C] |
> | |
> | |
> 220>--------+---------------+
>
> The choice of R and C for the proper firing angle is left as an exercise
> for the interested!^)
And will emit horrendus amounts of noise onto the supply, as well as causing
excessive heating in the wiring, and possibly blowing the fuse in the plug.
(?)
--
http://inquisitor.i.am/ | mailto:inqui...@i.am | Ian Stirling.
---------------------------+-------------------------+--------------------------
Among a mans many good possessions, A good command of speech has no equal.
John Fields
>
> John Fields <jfi...@texas.net> wrote:
> <snip>
> > The proper TRIAC, a DIAC, an R and a C will do it:
> >
> >
> > 220>--------+---------------+
> > | |
> > | [MR.COFFEE]
> > [R] |
> > | MT2
> > +--[DIAC]----G
> > | MT1
> > [C] |
> > | |
> > | |
> > 220>--------+---------------+
> >
> > The choice of R and C for the proper firing angle is left as an exercise
> > for the interested!^)
>
> And will emit horrendus amounts of noise onto the supply, as well as causing
> excessive heating in the wiring, and possibly blowing the fuse in the plug.
---
Depends on when you turn it on in the cycle.
Ian Stirling
>
> Ian Stirling wrote:
>>
>> John Fields <jfi...@texas.net> wrote:
>> <snip>
>> > The proper TRIAC, a DIAC, an R and a C will do it:
>> >
>> >
>> > 220>--------+---------------+
>> > | |
>> > | [MR.COFFEE]
>> > [R] |
>> > | MT2
>> > +--[DIAC]----G
>> > | MT1
>> > [C] |
>> > | |
>> > | |
>> > 220>--------+---------------+
>> >
>> > The choice of R and C for the proper firing angle is left as an exercise
>> > for the interested!^)
>>
>> And will emit horrendus amounts of noise onto the supply, as well as causing
>> excessive heating in the wiring, and possibly blowing the fuse in the plug.
>
> ---
> Depends on when you turn it on in the cycle.
There isn't really any choice.
--
http://inquisitor.i.am/ | mailto:inqui...@i.am | Ian Stirling.
---------------------------+-------------------------+--------------------------
What a wonderfull world it is that has girls in it! -- Robert A Heinlein.
John Fields
> There isn't really any choice.
---
Where would that be, then?
Ian Stirling
>
> Ian Stirling wrote:
>
>> There isn't really any choice.
>
> ---
> Where would that be, then?
If you want the power through the resistor to be a quarter of that it would
normally be, then you'r pretty much stuck with having it come on a bit after
the peak.
CS
"CS" <clif...@yahoo.com> wrote in message
news:LdIh9.431$L35....@newsread2.prod.itd.earthlink.net...
> Hi, I'm moving a coffee machine from the USA 110V to Australia 220V which
> has a heating element rated at 1300W.
>
> Rather than using a bulky & expensive step down transformer, I would
prefer
> to use a standard thyristor light dimmer to control the heating element
> since it is just a resistive load, but every light dimmer I've seen is
> limited to about 600W.
>
> Is it possible to modify something to get this to work, like add a
heatsink
> to the 600W light dimmer ??
>
> Thanks.
>
>
Phil Allison
> Hi, I'm moving a coffee machine from the USA 110V to Australia 220V which
> has a heating element rated at 1300W.
>
> Rather than using a bulky & expensive step down transformer, I would
prefer
> to use a standard thyristor light dimmer to control the heating element
> since it is just a resistive load, but every light dimmer I've seen is
> limited to about 600W.
>
> Is it possible to modify something to get this to work, like add a
heatsink
> to the 600W light dimmer ??
** A device called "Travellers Friend", or other similar title, has
been on sale for decades for just this purpose from places like Wal Mart and
large comsumer type hardware outlets. It has a 16 amp triac dimmer cct
inside adjusted and fixed to fire at about 62 degrees before each zero
crossing. This conduction angle produces the same rms current in a resistive
heater or lamp designed for 110 volt supply when used at 230 volts AC.
The one I saw on sale here in Australia carried a 1300 watt load
rating.
The exact same idea is also used when 110 volt PAR lamps must be
operated from 230 volts AC for professional stage lighting dimmers.
If the coffee maker has any electronics inside it (uP etc) then I
would not try it since the peak voltage is 300 volts using this trick as
against 160 volts for a sine wave supply of 115 volts AC.
BTW A standard AC meter (average responding but calibrated for rms
value on sine waves) has a large error with the chopped sine pulses from a
triac dimmer and in this case the reading would be only 63 volts. A true
rms meter would however read 110 volts, as expected.
Regards, Phil
Kevin McMurtrie
Ian Stirling <ro...@mauve.demon.co.uk> wrote:
>John Fields <jfi...@texas.net> wrote:
>>
>> Ian Stirling wrote:
>>
>>> There isn't really any choice.
>>
>> ---
>> Where would that be, then?
>
>If you want the power through the resistor to be a quarter of that it would
>normally be, then you'r pretty much stuck with having it come on a bit after
>the peak.
The problem is that having a small duty cycle means the peak voltage
must be higher. That also means the peak current is _much_ higher.
That's what's going to be a problem for the house wiring and nearby
appliances.
Jim (from Oz)
<ro...@mauve.demon.co.uk> wrote:
>John Fields <jfi...@texas.net> wrote:
>> The proper TRIAC, a DIAC, an R and a C will do it:
snip
>And will emit horrendus amounts of noise onto the supply, as well as causing
>excessive heating in the wiring, and possibly blowing the fuse in the plug.
Not in Oz it won't - 'cause we don't have fuses in the plugs :)
But of course; we should!
Sort of interesting thread - I'm not at all convinced you can
triac 240V down to 110V and nobody has mentioned the
matter of insulation. Diodes or phase control still mean
you're applying 240V to an item designed for 110V.
Jim (from Oz)
--
Speed doesn't kill - bad driving kills
Phil Allison
"Jim (from Oz)" <ji...@DELETEME.pobox.com> wrote in message
news:3d899ef0...@news.mel.ihug.com.au...
> On Wed, 18 Sep 2002 19:13:59 +0000 (UTC), Ian Stirling
> <ro...@mauve.demon.co.uk> wrote:
>
> >John Fields <jfi...@texas.net> wrote:
> >> The proper TRIAC, a DIAC, an R and a C will do it:
>
> snip
>
> >And will emit horrendus amounts of noise onto the supply, as well as
causing
> >excessive heating in the wiring, and possibly blowing the fuse in the
plug.
>
> Not in Oz it won't - 'cause we don't have fuses in the plugs :)
> But of course; we should!
** The rms current in the wiring , and so any heating effect caused,
will be about 12 amps, just as it would be if fed with 110/120 volts AC.
> Sort of interesting thread - I'm not at all convinced you can
> triac 240V down to 110V and nobody has mentioned the
> matter of insulation.
** 110/120 volt cables and switches etc generally seem to have the same
clearances and insulation thickness as 240 volt stuff - if not more.
There is also very widespread use of auto-transformer stepdowns for
240 to 120 volt conversion. This means that a simple missing neutral
connects 240 volts to both 120 volt lines. Also, if active and neutral are
simply reversed the 120 volt appliance will have 240 volts on one wire and
120 on the other.
No-none I have contacted at the relevant safety authorities in NSW,
Australia, thinks this particular issue is worth a pinch of salt . ( I did
use another word here and edited it for the sake of the many genteel folk
who read these pages)
They don't care so why should we??
Regards, Phil
John Woodgate
<mcmu...@sonic.net> wrote (in <mcmurtri-918ADD.01350219092002@typhoon.s
onic.net>) about 'Higher loads on triac light dimmer ???', on Thu, 19
Sep 2002:
>The problem is that having a small duty cycle means the peak voltage
>must be higher. That also means the peak current is _much_ higher.
>That's what's going to be a problem for the house wiring and nearby
>appliances.
What a curious notion! The idea is to reduce the power in a resistive
load by applying a sliced sine voltage waveform. To reduce the power,
the peak voltage has to be *reduced* and this *reduces* the current.
I can't draw sine waves in a small ASCII graphic, but imagine that the
triangular waveform is actually a sine wave (use Courier font):
/\
/ \
/ \ /
/ \/
Sine wave
_ __|\_
|/
Sliced sine wave
To get 1/4 power, you need to fire the triac at around 120 degrees from
the positive zero-crossing, IIRC.
--
Regards, John Woodgate, OOO - Own Opinions Only. http://www.jmwa.demon.co.uk
Interested in professional sound reinforcement and distribution? Then go to
http://www.isce.org.uk
PLEASE do NOT copy news posts to me by E-MAIL!
John Woodgate
wrote (in <LChi9.35822$g9.1...@newsfeeds.bigpond.com>) about 'Higher
loads on triac light dimmer ???', on Thu, 19 Sep 2002:
>Australia, thinks this particular issue is worth a pinch of salt . ( I did
>use another word here and edited it for the sake of the many genteel folk
>who read these pages)
I don't see much wrong with the expression 'dingo's kidney'. Or did you
have in mind a reference to part of a wallaby?
I should warn you that concern for the feelings of genteel folk is a
sure sign of the onset of maturity.
Ian Stirling
>
> I read in sci.electronics.design that Kevin McMurtrie
> <mcmu...@sonic.net> wrote (in <mcmurtri-918ADD.01350219092002@typhoon.s
> onic.net>) about 'Higher loads on triac light dimmer ???', on Thu, 19
> Sep 2002:
>>The problem is that having a small duty cycle means the peak voltage
>>must be higher. That also means the peak current is _much_ higher.
>>That's what's going to be a problem for the house wiring and nearby
>>appliances.
>
> What a curious notion! The idea is to reduce the power in a resistive
> load by applying a sliced sine voltage waveform. To reduce the power,
> the peak voltage has to be *reduced* and this *reduces* the current.
It reduces the current from the value it would have had if the heater
was connected to twice it's design voltage.
But it increases the peak current from that that would occur if
it was connected to it's design voltage of sine-wave.
Taking the above case.
1300W heater with 110V sine-wave.
RMS current = 11.8A
Resistance = 9.3 ohms
Peak current = 16.63A
Peak voltage = 155V
Now, if you chop a 220V sine wave so that the RMS power through the heater
is the same (at about 40 degrees after the peak):
1300W heater with chopped 220V sine-wave.
RMS current = 11.8A
Resistance = 9.3 ohms.
Peak current = 25.4A
Peak voltage 237V
--
http://inquisitor.i.am/ | mailto:inqui...@i.am | Ian Stirling.
---------------------------+-------------------------+--------------------------
Tad Williams has an interesting new fantasy: http://www.shadowmarch.com/
Rob Paisley
> Hi, I'm moving a coffee machine from the USA 110V to Australia 220V which
> has a heating element rated at 1300W.
>
> Rather than using a bulky & expensive step down transformer, I would prefer
> to use a standard thyristor light dimmer to control the heating element
> since it is just a resistive load, but every light dimmer I've seen is
> limited to about 600W.
>
> Is it possible to modify something to get this to work, like add a heatsink
> to the 600W light dimmer ??
>
----------
And the best suggestions are:
1- Buy an new machine.
Best.
2- Replace the element with one rated for 220 Volts.
Great idea but probably not be possible.
3- Use an autotransformer.
Best after #2 and probably most practical.
4- Place a 1300 Watt clothes iron in series with the load.
Idea #4 has some merit but it would be better if 1300 watts of
resistive lighting was placed in series with the coffee machine. Keep
in mind that these would need to be 220 Volt lamps running at 1/2
voltage for this solution. (If you don't mind basking in a 1300 watt
warm glow while you wait for a cup of mud.)
Seeing as how you are attached to this machine you could also by a
second machine and run them in series. Just kidding.
-----
There are some practical considerations with this problem and the
members of this news group would need to know more about the
particular coffee machine's actual electrics in order to give credible
answers to this problem.
The greatest of these considerations is: What type of brewing
controls does this machine have, is it an electronic control or a
bimetal thermostat.?
If the machine has anything except a simple bimetal thermostat that
controls the entire load you can forget about idea #4 and anything
that involves lamp dimmers, stove element controllers, diodes or
"something clever electronically". Not that these are practical
anyway.
If electronic control is used idea #2 would require that the
controls be adapted or replaced along with the element. A highly
unlikely event unless the Australians have the exact same machine
ratted for 220 Volts In which case just buy one of theirs.
The diode in the line method proposed will fail no matter how many
watts is evolved because the even though the current is applied for
only 1/2 of the cycle at 220 volts it will still be twice what the
heating element is designed for and will blow the internal fuse or
destroy the element.
Rob.
John Woodgate
<ro...@mauve.demon.co.uk> wrote (in <amcsvr$6rg$1$8302...@news.demon.co.
uk>) about 'Higher loads on triac light dimmer ???', on Thu, 19 Sep
2002:
>Now, if you chop a 220V sine wave so that the RMS power through the heater
>is the same (at about 40 degrees after the peak):
>
>1300W heater with chopped 220V sine-wave.
>RMS current = 11.8A
>Resistance = 9.3 ohms.
>Peak current = 25.4A
>Peak voltage 237V
>
I see what you mean, now. It wasn't clear before. I don't see that the
peak voltage is a serious problem, and the wiring is affected only by
the r.m.s current.
Ian Stirling
>
> I read in sci.electronics.design that Ian Stirling
> <ro...@mauve.demon.co.uk> wrote (in <amcsvr$6rg$1$8302...@news.demon.co.
> uk>) about 'Higher loads on triac light dimmer ???', on Thu, 19 Sep
> 2002:
>>Now, if you chop a 220V sine wave so that the RMS power through the heater
>>is the same (at about 40 degrees after the peak):
>>
>>1300W heater with chopped 220V sine-wave.
>>RMS current = 11.8A
>>Resistance = 9.3 ohms.
>>Peak current = 25.4A
>>Peak voltage 237V
> I see what you mean, now. It wasn't clear before. I don't see that the
> peak voltage is a serious problem, and the wiring is affected only by
> the r.m.s current.
The wiring needs sized to the RMS current though, which is quite a bit
higher than the power use would imply.
Fuses IME tend not to like spiky waveforms also.
It's going to do nasty things to the waveform too.
--
http://inquisitor.i.am/ | mailto:inqui...@i.am | Ian Stirling.
---------------------------+-------------------------+--------------------------
The fight between good and evil, an epic battle. Darth vader and Luke,
suddenly in the middle of the fight, Darth pulls Luke to him, and whispers
"I know what you'r getting for christmas!" Luke exclaims "But how ??!?"
"It's true Luke, I know what you'r getting for christmas" Luke tries to ignore
this, but wrenches himself free, yelling "How could you know this?",
Vader replies "I felt your presents" -- The Chris Evans breakfast show ca. 94
Phil Allison
"Ian Stirling" <ro...@mauve.demon.co.uk> wrote in message
news:amd95k$op9$1$830f...@news.demon.co.uk...
>
> The wiring needs sized to the RMS current though, which is quite a bit
> higher than the power use would imply.
** The rms current in the coffee maker's wiring is the SAME as for
normal opeartion on a 110/120 supply. The exact same current flows in the
230 volt wiring - about 11.5 amps in this case - slighlty above the nominal
10 amp limit but should be no problem because of that.
Regards, Phil
Phil Allison
"John Woodgate" <j...@jmwa.demon.contraspam.yuk> wrote in message
news:TPMh1IBs...@jmwa.demon.co.uk...
Phil wrote:
> >No-none I have contacted at the relevant safety authorities in NSW,
> >Australia, thinks this particular issue is worth a pinch of salt . ( I
did
> >use another word here and edited it for the sake of the many genteel folk
> >who read these pages)
>>
> > I should warn you that concern for the feelings of genteel folk is a
> sure sign of the onset of maturity.
** The remark was entirely sarcastic - what genteel folk ??
. . . . . . . . Love, Phil
Ian Stirling
The power used by the appliance is ~1.3Kw.
The wire dissapates the same as when used with a ~2.6Kw load.
--
http://inquisitor.i.am/ | mailto:inqui...@i.am | Ian Stirling.
---------------------------+-------------------------+--------------------------
<Squawk> Pieces of eight!
<Squawk> Pieces of eight!
<Squawk> Pieces of eight!
<Squawk> Pieces of eight!
<Squawk> Pieces of eight!
<Squawk> Pieces of nine!
<SYSTEM HALTED: parroty error!>
Phil Allison
> Phil Allison <bi...@bigpond.com> wrote:
> >
> >
> > "Ian Stirling" <ro...@mauve.demon.co.uk> wrote in message
> > news:amd95k$op9$1$830f...@news.demon.co.uk...
> >
> >>
> >> The wiring needs sized to the RMS current though, which is quite a bit
> >> higher than the power use would imply.
> >
> >
> > ** The rms current in the coffee maker's wiring is the SAME as for
> > normal opeartion on a 110/120 supply. The exact same current flows in
the
> > 230 volt wiring - about 11.5 amps in this case - slighlty above the
nominal
> > 10 amp limit but should be no problem because of that.
>
> The power used by the appliance is ~1.3Kw.
> The wire dissapates the same as when used with a ~2.6Kw load.
** Which wires?? Not the lead used on the coffee maker. The
"Traveller's Friend" was built in the form of a plug in box with USA style
outlet so has no external wires. There is no wire sizing issue to worry
about.
Regards, Phil
Rob Paisley
> Hi, I'm moving a coffee machine from the USA 110V to Australia 220V which
> has a heating element rated at 1300W.
>
> Rather than using a bulky & expensive step down transformer, I would prefer
> to use a standard thyristor light dimmer to control the heating element
> since it is just a resistive load, but every light dimmer I've seen is
> limited to about 600W.
>
> Is it possible to modify something to get this to work, like add a heatsink
> to the 600W light dimmer ??
>
> Thanks.
And the best suggestions are:
John Fields
---
here's suggestion #5, the series capacitor reactive voltage dropper:
220>----[C]-----+
|
[9R3]
|
220>------------+
With a voltage of 110VRMS across the 9.3 ohm coffemaker we'll have
110V/9.3ohms ~ 12A flowing through it, so if we interpose a capacitor
between the coffeemaker and the 220V mains which can limit the current
through the coffeemaker to 12A, that'll do the job. In order to do that
we'll need the impedance of the cicuit to look like 18.6 ohms, so since
Z = sqrt(R² + Xc²) we can solve for Xc by rearranging:
Xc = sqrt(Z²-R²) = sqrt(346 - 86.5) ~ 16 ohms.
Since Xc = 1/2pi*f*C, we can solve for the capacitance by rearranging:
C = 1/2pi*f*Xc = 1/6.28*60*16 = 165.9E-6F for 60Hz and 199.0E-6F for 50
Hz. (I forget if Oz is 50 or 60Hz...)
GE makes some nice oil-filled caps, Z97FXXXX (where the X's are a
numerical suffix describing the capacitance, voltage rating, etc.) which
would prob'ly work nicely. I don't know for sure, though, since I
haven't checked their ESR. The caps might cost more than the
coffeemaker but, hey, if there's an emotional attachment to the
coffeemaker... ;^)
Ian Stirling
>
>
> "Ian Stirling" <ro...@mauve.demon.co.uk> wrote in message
> news:ameec6$one$1$8300...@news.demon.co.uk...
>> Phil Allison <bi...@bigpond.com> wrote:
>> >
>> >
>> > "Ian Stirling" <ro...@mauve.demon.co.uk> wrote in message
>> > news:amd95k$op9$1$830f...@news.demon.co.uk...
>> >
>> >>
>> >> The wiring needs sized to the RMS current though, which is quite a bit
>> >> higher than the power use would imply.
>> >
>> >
>> > ** The rms current in the coffee maker's wiring is the SAME as for
>> > normal opeartion on a 110/120 supply. The exact same current flows in
> the
>> > 230 volt wiring - about 11.5 amps in this case - slighlty above the
> nominal
>> > 10 amp limit but should be no problem because of that.
>>
>> The power used by the appliance is ~1.3Kw.
>> The wire dissapates the same as when used with a ~2.6Kw load.
>
>
>
> ** Which wires?? Not the lead used on the coffee maker. The
> "Traveller's Friend" was built in the form of a plug in box with USA style
> outlet so has no external wires. There is no wire sizing issue to worry
> about.
The wires in the appliance will be sized for the current.
The wires in the plug/socket/... may not, even though the wattage of the
appliance might seem to indicate that they are.
Probably completely OK with one appliance.
Run a few of them this way, and you could run into problems.
--
http://inquisitor.i.am/ | mailto:inqui...@i.am | Ian Stirling.
---------------------------+-------------------------+--------------------------
Paranoia: A game for the whole family, and anyone else who might be watching.
John Fields
> The wires in the appliance will be sized for the current.
> The wires in the plug/socket/... may not, even though the wattage of the
> appliance might seem to indicate that they are.
> Probably completely OK with one appliance.
> Run a few of them this way, and you could run into problems.
---
If the wires _in_ the appliance are sized to carry 12A, then it's a
pretty safe bet that the appliance's plug and the wires leading from to
the plug to the appliance's heating element can also carry that current.
If the maufacturer has a UL label on the appliance then it's a no
brainer. Then all that's left is the receptacle in the wall, the mains
wiring itself, and the breaker. I don't know what the spec's are for
residential wiring in Oz, but if it's at least #14, which is common here
for 15A sevice, then no problem with overheating. Same for the
receptacle's spec's. I don't know what they are, but I'd be willing to
bet it's capable of carrying at least 15A. Then there's the breaker,
which needs to be able to shrug off the repetitive current peaks, and
that's going to depend on the breaker's switching characteristics since
it's going to be carrying 12A RMS. Of _course_ if he exceeds the
breaker's rating by plugging in more appliances than it can handle, it
will shut down, but that's the case anywhere.
Rob Paisley
> > heating element is designed for and will blow the internal fuse or
> > destroy the element.
>
> ---
> here's suggestion #5, the series capacitor reactive voltage dropper:
>
>
> 220>----[C]-----+
> |
> [9R3]
> |
> 220>------------+
>
>
> With a voltage of 110VRMS across the 9.3 ohm coffemaker we'll have
> 110V/9.3ohms ~ 12A flowing through it, so if we interpose a capacitor
> between the coffeemaker and the 220V mains which can limit the current
> through the coffeemaker to 12A, that'll do the job. In order to do that
> we'll need the impedance of the cicuit to look like 18.6 ohms, so since
>
> Xc = sqrt(Z2-R2) = sqrt(346 - 86.5) ~ 16 ohms.
>
> Since Xc = 1/2pi*f*C, we can solve for the capacitance by rearranging:
>
> C = 1/2pi*f*Xc = 1/6.28*60*16 = 165.9E-6F for 60Hz and 199.0E-6F for 50
> Hz. (I forget if Oz is 50 or 60Hz...)
>
> GE makes some nice oil-filled caps, Z97FXXXX (where the X's are a
> numerical suffix describing the capacitance, voltage rating, etc.) which
> would prob'ly work nicely. I don't know for sure, though, since I
> haven't checked their ESR. The caps might cost more than the
> coffeemaker but, hey, if there's an emotional attachment to the
> coffeemaker... ;^)
> ---
>
> John Fields
> Professional circuit designer
> http://www.austininstruments.com
---
The same argument could be made for a inductive reactance voltage
divider.
The count is now at 6, maybe.
But the problem of the brewing control system rears its ugly head
again.
If the control is electronic, when the element shuts off the balance
in the reactance / resistance circuit will shift so that the capacitor
or inductor is by far the lowest resistance in the circuit.
This will cause most of the voltage drop to occur across the
electronics of the machine and possibly destroy them with a pop and a
puff of smoke. It would provide for a unique indication that the
coffee is ready though.
If the control is strictly bimetalic then suggestions 5 and 6 could
be a workable but perhaps expensive option.
Perhaps the originator of this thread should just stop drinking
coffee altogether before someone gets hurt.
Rob Paisley
Completely unprofessional in every respect.
dmi...@spamblock.demon.co.uk
<Snip>
> Sort of interesting thread - I'm not at all convinced you can
> triac 240V down to 110V and nobody has mentioned the
> matter of insulation. Diodes or phase control still mean
> you're applying 240V to an item designed for 110V.
For a lovely variation on this trick, there is a theatrical lighting
manufacturer who sells a system capable of running two independently
controlled loads via one power cable). Not sold in europe, and seems
to me to be a nasty hack, but it is done by using 70 volt bulbs, with
the 'dimmer doubler' containing a pair of large diodes! The rack
control software controls the phase angle of the positive and negitive
half of the waveform independently.
I do not need to point out what happens when some twat plugs a
transformer driven load into the output side of a dimmer doubler do I....
These things must do wonders for the upstream power transformers as they
are probably not really designed to handle loads with large DC components.
Regards, Dan.
--
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