circuit wanted-SQUARE PULSE GENERATOR
GEORGE BASILIOU
any circuit/page to find a square pulse generator,variable from 1 to 1000
Hz,with 1 Hz step?
I prefer not using 555.I want the circuit to be accurate.
Thanks in Advance
GEORGE BASILIOU
Uwe Zimmermann
You would need to be at least experienced in electronics in order to
achieve this goal. You will not find a ready made, single chip
solution, perhaps the easiest way would be to use the sound card in
your computer!
Every digital approach would ask for at least some of the following:
-quartz oszillator
-frequency divider
-PLL
-control electronics
-display electronics
-output stage
You would be amazed what high stability you could actually achieve
with an analog RC oszillator. If you combine it with a frequency
counter with >1s gate time you would get 1Hz resolution on the
display... Instead of a NE555 you would probably go for a MAX038 or
XR2206 as central part of your design.
For some more infos:
http://www.epanorama.net/links/oscillator.html
Uwe.
Leon Heller
"GEORGE BASILIOU" <basi...@rocketmail.com> wrote in message
news:1038145129.59721@athprx02...
This is a good way to do it:
http://www.myplace.nu/avr/minidds/
Leon
--
Leon Heller, G1HSM
leon_...@hotmail.com
http://www.geocities.com/leon_heller
John Fields
<le...@heller123.freeserve.co.uk> wrote:
>This is a good way to do it:
>
>http://www.myplace.nu/avr/minidds/
>
---
Excellent!!!
---
John Fields
Professional circuit designer
http://www.austininstruments.com
Kijoma
a minium brain power solution as far as hardware goes is a DDS (direct
digital synthesiser) which requires a clock oscillator and possibly a PIC
micro (damn.. software...thats blown it :( )
ho hum
Bill
"GEORGE BASILIOU" <basi...@rocketmail.com> wrote in message
news:1038145129.59721@athprx02...
Kijoma
"John Fields" <jfi...@texas.net> wrote in message
news:3de32923...@news.texas.net...
i second that.. neat use of a micro
bill
Leon Heller
> <le...@heller123.freeserve.co.uk> wrote:
>
> >This is a good way to do it:
> >
> >http://www.myplace.nu/avr/minidds/
> >
>
> ---
> Excellent!!!
I've designed a simple PCB for Jesper's Mini DDS, using a 'real' DAC
(buffered output) instead of the R-2R ladder network - details on my web
site.
Winfield Hill
>
> Unfortunately i'm not good in designing Circuits. Has anyone to
> suggest me any circuit/page to find a square pulse generator,
> I prefer not using 555. I want the circuit to be accurate.
The poor 555 gets so much abuse. What a great little chip, two
precision comparators, a flip-flop, a large discharge transistor,
serious output driving capability, a trimmable voltage divider.
These pieces are an excellent starting point for simple accurate
oscillators like George wants. If we choose a CMOS 555 version,
like Intersil's ICM7555, we can use low charging currents, like
0.33uA, and get accurate operation even down to 1Hz and below
with a 0.1uF film capacitor.
While Jesper Hansen's design for the AT90S2313 is appealing, see
if the simplicity of a few analog parts can't also be appealing.
Here's my design that uses a common 10k-ohm 10-turn pot with a
turns-counting dial for precision frequencies from 0 to 1000Hz.
The IC1 Q1 circuit creates a charging current I = Vr R2 / (R1 R3),
used by the 555 to make a frequency f = I / C Vth = I Vr / 2/3 C
Note, we can adjust the 2/3 term to eliminate the capacitor's 5%
tolerance error, the resistor values, and Q1's beta error. The
7555's DISCHARGE pin current limits at 40mA and then 20 ohms of
internal resistance below 1V, so R4 and C2 provide a fixed 25us
time for thoroughly discharging C each cycle.
After calibration the frequency is proportional to the setting of
the 10-turn pot with its counting-dial indicator from 0 to 1 kHz.
10k 10T pot
,--- R2 --+-------, +5 -- 1.65k -,
| __ | | |
,---+--|- \ | R1 1k calibrate
| | >--' 15.0k pot <------,
R3 ,--|+_/ | | |
10.0k | ,----------+ 4.02k |
| | | __ | | 2/3 Vr
gnd | '-|- \ |/V Q1 +5 gnd +/-5%
| | >--| 2n3906 ___|___________ |
+--------|+_/ |\ | | |
| IC1 | | CONTROL |--' Vth
Vr +5 LT1013 | 6 | |
+-----------| THRESHOLD |
| 2 | OUT |-----
0 to 1kHz precision +-- R4 -+---| TRIGGER |
555-type oscillator |\ | | |
| \____ |_7_| DISCHARGE |
3 R2 C _|_ | |_______________|
f = --------- ___ C2_|_ |
2 C R1 R3 film | ___ gnd IC2
0.1uF | 0.001 | ICL7555
| |
gnd gnd
IC1 is powered from +15V, and must be a low-offset-voltage opamp
because at 1Hz the current-programming voltage is only 5mV.
There's lots more to say about this circuit, but it's that time of
the year again; I have to go finish burying the fig tree.
Fred Bloggs
Hmmm- those turns-counting 10T are a bit on the pricey side. Instead of
the total-digital vs total-analog approach, maybe the new DAC-pots hold
promise for an accessible and economical hybrid solution, a circuit that
does not require a PC to operate and low cost all the way. Some of the
DAC pots have very simple one-button interfaces, some roll over -some do
not, some auto-store on power down- some reset to mid-range on power up
etc, some are 8-bit and some are >10bit, the flexibility seems infinite.
Jonathan Kirwan
<nos...@nospam.com> wrote:
><snip of Win Hill's suggestion to save space>
>Hmmm- those turns-counting 10T are a bit on the pricey side. Instead of
>the total-digital vs total-analog approach, maybe the new DAC-pots hold
>promise for an accessible and economical hybrid solution, a circuit that
>does not require a PC to operate and low cost all the way. Some of the
>DAC pots have very simple one-button interfaces, some roll over -some do
>not, some auto-store on power down- some reset to mid-range on power up
>etc, some are 8-bit and some are >10bit, the flexibility seems infinite.
The Jesper et al DDS solution doesn't need a PC to operate, if a
simple, mechanical quadrature panel mount dial is added, using
two input pins to the micro and writing a little more code.
(Optical ones are nice, too -- I just picked up a few Agilent
ones at $7 ea for hobby use.) With just a little bit more code,
a nice digital LED display could be added.
Jon
Fred Stevens
Perhaps take a look at the PIC12XX range of 8 pin micros if you insist
on avoiding 555s!
> >
> >
> >
> >
dan michaels
> "GEORGE BASILIOU" <basi...@rocketmail.com> wrote in message
> news:1038145129.59721@athprx02...
> > Unfortunately i'm not good in designing Circuits.Has anyone to suggest me
> > any circuit/page to find a square pulse generator,variable from 1 to 1000
> > Hz,with 1 Hz step?
> > I prefer not using 555.I want the circuit to be accurate.
>
> This is a good way to do it:
>
> http://www.myplace.nu/avr/minidds/
>
>
> Leon
Why won't that link work for me?
Most of us could russle up such a ckt with a microcontroller and a
countdown routine.
Of course, one thing not specified was how to control the freq. A pot
would not be accurate, so now you need either RS232 comms or a
not-too-complicated-yet-not-too-simple h.w. interface.
- dan michaels
www.oricomtech.com
===========================
Winfield Hill
>
> Fred Bloggs wrote:
>
>> <snip of Win Hill's suggestion to save space>
>
>> Hmmm- those turns-counting 10T are a bit on the pricey side.
>
> simple, mechanical quadrature panel mount dial is added, using
> two input pins to the micro and writing a little more code.
> (Optical ones are nice, too -- I just picked up a few Agilent
> ones at $7 ea for hobby use.) With just a little bit more code,
> a nice digital LED display could be added.
Indeed, just a little more code... and a little more hardware.
Sometimes one simply wants to get the job done... :>)
Here are two turns-counting dials available for $10.99 for both.
http://cgi.ebay.com/ws/eBayISAPI.dll?ViewItem&item=1790787842
Thanks,
- Win
Jonathan Kirwan
<wh...@picovolt.com> wrote:
>Jonathan wrote...
>>
>> Fred Bloggs wrote:
>>
>>> <snip of Win Hill's suggestion to save space>
>>
>>> Hmmm- those turns-counting 10T are a bit on the pricey side.
>>
>> The Jesper et al DDS solution doesn't need a PC to operate, if a
>> simple, mechanical quadrature panel mount dial is added, using
>> two input pins to the micro and writing a little more code.
>> (Optical ones are nice, too -- I just picked up a few Agilent
>> ones at $7 ea for hobby use.) With just a little bit more code,
>> a nice digital LED display could be added.
>
> Indeed, just a little more code... and a little more hardware.
> Sometimes one simply wants to get the job done... :>)
Hehe. I wasn't making a comparison, just noting that the
digital arrangement doesn't need a PC and can be set up as a
stand-alone system. The choice about which is better, depends.
Of course.
> Here are two turns-counting dials available for $10.99 for both.
> http://cgi.ebay.com/ws/eBayISAPI.dll?ViewItem&item=1790787842
The mechanical versions are a lot cheaper than the opticals I
mentioned, something in the $1-$2 range or so, new. No ebay to
contend with.
Jon
Tony Williams
Winfield Hill <wh...@picovolt.com> wrote:
> internal resistance below 1V, so R4 and C2 provide a fixed 25us
> time for thoroughly discharging C each cycle.
I'm still trying to see why that 25uS discharge time
doesn't result in a 2.5% non-linearity in the control.
Knowing you, you have it covered somewhere, but I just
can't see where. Must be going thick...........
--
Tony Williams.
Keith Wootten
<nos...@nospam.com> writes
<snipped>
>Hmmm- those turns-counting 10T are a bit on the pricey side. Instead of
>the total-digital vs total-analog approach, maybe the new DAC-pots hold
>promise for an accessible and economical hybrid solution, a circuit
>that does not require a PC to operate and low cost all the way.
I was thinking of using 1024 tap digital pots instead of ten-turn pots
for something I'm building. There are to be four of them, and it's not
the cost that matters, rather the front panel space.
My feeling is that 1024 steps, should give an adequate simulation of a
ten-turn pot, being 102 per revolution. Any gotchas?
Cheers
--
Keith Wootten
Tony Williams
Keith Wootten <kei...@ntlworld.Xcom> wrote:
> My feeling is that 1024 steps, should give an adequate simulation of a
> ten-turn pot, being 102 per revolution. Any gotchas?
I have done measurements on high-quality 10-T
pots and 35mm dials (the biggest in the RS cat).
When used as a potentiometer, the control linearity
is about 0.05% of full scale, and the tightest
setting resolution is about 0.025% of full scale.
When the dial mechanics/scale is added in, then
0.1% overall setting accuracy is on, but only just.
There is something pleasing about using a big 10-T
dial though. I still remember the best ever made....
on the old 555? oscilloscope.
--
Tony Williams.
Winfield Hill
>
> Winfield Hill wh...@picovolt.com wrote:
>
>> ... internal resistance below 1V, so R4 and C2 provide a
>> fixed 25us time for thoroughly discharging C each cycle.
>
> I'm still trying to see why that 25uS discharge time
> doesn't result in a 2.5% non-linearity in the control.
> Knowing you, you have it covered somewhere, but I just
> can't see where. Must be going thick...........
No, Tony, you have found me out! It's unavoidably there, a
[1/(1 + 2.5% Vin/Vmax)] term in the frequency formula. :>)
The discharge could be shortened to 5 or 10us, but it'd still
be there. Fixing the issue would require a switched negative
tracking current sink. And the added complexity (two opamp-
controlled current sources, two steering diodes) would likely
force one to abandon the cmos 555 approach entirely, choosing
instead a opamp triangle integrator / comparator scheme, etc.
There's another fault to my circuit. The O.P. specified a
"square wave." If we assume he meant 50% duty cycle, rather
than simply rectangular logic pulses, the 25us negative-going
pulses my circuit puts out are not acceptable. On the other
hand, modifying the circuit with the above-mentioned tracking
current sink would also solve this issue.
Thanks,
- Win
Keith Wootten
<to...@ledelec.demon.co.uk> writes
>In article <EpK$sPMIb0...@ntlworld.com>,
> Keith Wootten <kei...@ntlworld.Xcom> wrote:
>
>> My feeling is that 1024 steps, should give an adequate simulation of a
>> ten-turn pot, being 102 per revolution. Any gotchas?
>
> I have done measurements on high-quality 10-T
> pots and 35mm dials (the biggest in the RS cat).
>
> When used as a potentiometer, the control linearity
> is about 0.05% of full scale, and the tightest
> setting resolution is about 0.025% of full scale.
> When the dial mechanics/scale is added in, then
> 0.1% overall setting accuracy is on, but only just.
Thanks for that, Tony, looks like 1024 steps is in the right cricket
ground. Linearity isn't much of an issue for my application.
If I were to go with real pots, I'd use a dial mech, but really only for
the locking capability - these are bridge zeroing pots and the actual
pot position don't make no never-mind. A lockable 'ordinary' knob would
do just as well, but I can't recall ever having seen such a thing, only
the collet lock things for screwdriver slot adjustments.
Cheers
--
Keith Wootten
Leon Heller
"Jonathan Kirwan" <jki...@easystreet.com> wrote in message
news:f3n4uugbkh45ba5p5...@4ax.com...
[deleted]
> The Jesper et al DDS solution doesn't need a PC to operate, if a
> simple, mechanical quadrature panel mount dial is added, using
> two input pins to the micro and writing a little more code.
> (Optical ones are nice, too -- I just picked up a few Agilent
> ones at $7 ea for hobby use.) With just a little bit more code,
> a nice digital LED display could be added.
It could just use a couple of push-buttons, one for up and one for down.
Tony Williams
Keith Wootten <kei...@ntlworld.Xcom> wrote:
> .................... A lockable 'ordinary' knob would
> do just as well, but I can't recall ever having seen such a thing,
> only the collet lock things for screwdriver slot adjustments.
Yes there used to be. It was a knob with about
a 2" disk attached, backed by a square panel-
-mounted escutcheon. Up in the top right-hand
corner of the escutcheon was a knurled screw
assembly that could clamp the rotating disk.
--
Tony Williams.
Bob Masta
If front panel space is the problem, then wouldn't the 10-turn
pots take up a lot less space than up/down buttons plus
a display? Or do you already have a display that can do
double-duty? Actually, I've seen some pretty nice 10-turn
dials that take no more space than two pushbuttons.
Bob Masta
tech(AT)daqarta(DOT)com
D A Q A R T A
Data AcQuisition And Real-Time Analysis
Shareware from Interstellar Research
www.daqarta.com
Winfield Hill
>
> Tony Williams wrote...
>>
>> Winfield Hill wh...@picovolt.com wrote:
>>
>>> ... internal resistance below 1V, so R4 and C2 provide a
>>> fixed 25us time for thoroughly discharging C each cycle.
>>
>> I'm still trying to see why that 25uS discharge time
>> doesn't result in a 2.5% non-linearity in the control.
>> Knowing you, you have it covered somewhere, but I just
>> can't see where. Must be going thick...........
>
> No, Tony, you have found me out! It's unavoidably there, a
> [1/(1 + 2.5% Vin/Vmax)] term in the frequency formula. :>)
>
> The discharge could be shortened to 5 or 10us, but it'd still
> be there. Fixing the issue would require a switched negative
> tracking current sink. And the added complexity (two opamp-
> controlled current sources, two steering diodes) would likely
> force one to abandon the cmos 555 approach entirely, choosing
> instead a opamp triangle integrator / comparator scheme, etc.
>
> There's another fault to my circuit. The O.P. specified a
OK, just to complete the record, here's my corrected 7555
circuit, with a precise formula and 50% duty cycle. I've
added an EEpot feature. One EEpot issue is their high wiper
resistance, so I added a follower to solve that problem.
.....................................................................
. 2Vr _______ ========================= .
. 10.0k +10 | __ | = 0 to 1kHz precision = .
. ,- R2 --+--, '-|- \ | = 555-type oscillator = .
. | __ | X | >-+---, ========================= .
. ,-+-|- \ | X<---|+_/ | +5 -- 1.65k -, .
. | | >-' X EEpot ,----+ | .
. |+5-|+_/ | 10T pot | | 1k calibrate .
. | +5 15.0k R1 pot <---, .
. R3 | 15.0k | | .
. 10.0k ,-----------+ | matched 4.02k | .
. | | __ | V\| pair | | 2/3 Vr .
. gnd '-|- \ |/V |-- +5 gnd | +/-5% .
. | >---| /| _______________ | .
. IC1 +5 --|+_/ |\ | | | | .
. LT1014 | | 6 | CONTROL |--' .
. ,---------------------' +------| THRESHOLD | .
. | ,--+--|<|---+ 2 | OUT |--+-----o .
. | __ | | +------| TRIGGER | | 50% .
. +-----|+ \ |/ | C _|_ | | | duty .
. | | >--| | 0.1uF ___ |_______________| | .
. | ,--|-_/ |\V | film | | .
. | | | | 5% | IC2 ICL7555 | .
. | '-----------+ | gnd | .
. | | '--|<|-----------------------------' .
. 15.0k 7.50k 3 R2 k .
. | | f = --------- where k is the EEpot .
. gnd gnd 2 C R1 R3 or 10T pot fraction .
. .
.....................................................................
One issue, should anyone want to make one of these with a 5V EEpot,
power it from between the +10V and +5V points.
Hmm, doesn't look so bad!
Thanks,
- Win
John Jardine
Winfield Hill <wh...@picovolt.com> wrote in message
news:arvmf...@drn.newsguy.com...
Or just use a charge balancing V/F setup, eg, if in I.C. form, the
exceedingly good, Telcom TC9400.
(10T pots c/w counters can of course be replaced by decade/bcd
switches/thumbwheels using fixed resistors).
regards
john
Winfield Hill
>
> OK, just to complete the record, here's my corrected 7555
> circuit, with a precise formula and 50% duty cycle. I've
> added an EEpot feature. One EEpot issue is their high wiper
> resistance, so I added a follower to solve that problem.
>
>.....................................................................
>. 2Vr _______ ========================= .
>. 10.0k +10 | __ | = 0 to 1kHz precision = .
>. ,- R2 --+--, '-|- \ | = 555-type oscillator = .
>. | __ | X | >-+---, ========================= .
>. ,-+-|- \ | X<---|+_/ | +5 -- 1.65k -, .
>. | | >-' X EEpot ,----+ | .
>. |+5-|+_/ | 10T pot | | 1k calibrate .
>. | +5 15.0k R1 pot <---, .
>. R3 | 15.0k | | .
>. 10.0k ,-----------+ | matched 4.02k | .
>. | | __ | V\| pair | | 2/3 Vr .
>. gnd '-|- \ |/V |-- +5 gnd | +/-5% .
>. | >---| /| _______________ | .
>. IC1 +5 --|+_/ |\ | | | | .
>. LT1014 | | 6 | CONTROL |--' .
>
>
> power it from between the +10V and +5V points.
>
> Hmm, doesn't look so bad!
Oops! Blast! I copied an incomplete version of my drawing from the
text editor. Here's the right one. :)
....................................................................
. 2Vr _______ ========================= .
. 10.0k +10 | __ | = 0 to 1kHz precision = .
. ,- R2 --+--, '-|- \ | = 555-type oscillator = .
. | __ | X | >-+---, ========================= .
. ,-+-|- \ | X<---|+_/ | +5 -- 1.65k -, .
. | | >-' X EEpot ,----+ | .
. |+5-|+_/ | 10T pot | | 1k calibrate .
. | +5 any 15.0k R1 pot <----, .
. R3 value | 15.0k | | .
. 10.0k ,-----------+ | 4.02k | .
. | | __ | | PNP | | 2/3 Vr .
. gnd '-|- \ |/V |/V matched gnd | +/-5% .
. | >---|----| pair _______________ | .
. IC1 +5 --|+_/ |\ |\ | | 5 | .
. LT1014 | | 6 | CONTROL |---' .
. ,---------------------' +-----| THRESHOLD | 3 .
. | ,--+--|<|---+ 2 | OUT |---+-----o .
. | __ | | +-----| TRIGGER | | 50% .
. +-----|+ \ |/ | C _|_ | | | duty .
. | | >--| | 0.1uF ___ |_______________| | .
. | ,--|-_/ |\V | film | | .
. | | NPN | | 5% | IC2 ICL7555 | .
. | '-----------+ | gnd | .
. | | '--|<|-----------------------------' .
. 15.0k 7.50k 3 R2 k .
. | | f = --------- where k is the EEpot .
. gnd gnd 2 C R1 R3 or 10T pot fraction .
. .
....................................................................
Thanks,
- Win
Jonathan Kirwan
<le...@heller123.freeserve.co.uk> wrote:
>"Jonathan Kirwan" <jki...@easystreet.com> wrote in message
>news:f3n4uugbkh45ba5p5...@4ax.com...
>
>[deleted]
>
>> The Jesper et al DDS solution doesn't need a PC to operate, if a
>> simple, mechanical quadrature panel mount dial is added, using
>> two input pins to the micro and writing a little more code.
>> (Optical ones are nice, too -- I just picked up a few Agilent
>> ones at $7 ea for hobby use.) With just a little bit more code,
>> a nice digital LED display could be added.
>
>It could just use a couple of push-buttons, one for up and one for down.
And maybe one for coarse/fine shift mode?
Jon
Tony Williams
Winfield Hill <wh...@picovolt.com> wrote:
Ah! That's a nice solution, a discharge current
of 2x the charging current, steered on/off by
simple diodes. [*] And the pot is now a pot.
[*] I've seen that (1x charge, 2x gated discharge)
circuit somewhere before, complete in one chip.
Vague memories of someone's dual slope ADC?
--
Tony Williams.
Jim Thompson
Tony Williams <to...@ledelec.demon.co.uk>,
In Newsgroup: sci.electronics.design,
Article: <4b9b804...@ledelec.demon.co.uk>,
Entitled: "Re: circuit wanted-SQUARE PULSE GENERATOR",
Wrote the following:
I've been using the 1X/2X approach for at least 35 years in on-chip
VCM's (voltage-contolled multivibrators).
If you need exactly 50% I'd just use a DIV2.
Here's a question for all you lurkers:
Delay in the comparators (in a 555 or otherwise) affect the linearity
of the control curve, particularly at high frequencies (I've built
these at frequencies as high as 50MHz).
Can anyone here mathematically describe the effect as a function of
delay and operating frequency?
And then offer a solution?
(I can ;-)
...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.
John Jardine
Tony Williams <to...@ledelec.demon.co.uk> wrote in message
news:4b9b804...@ledelec.demon.co.uk...
[clip funtional but complex cct ;-)
>
> [*] I've seen that (1x charge, 2x gated discharge)
> circuit somewhere before, complete in one chip.
> Vague memories of someone's dual slope ADC?
>
> --
> Tony Williams.
'ICL8038' Function generator chip.
regards
john
John Jardine
Jim Thompson <Jim-T@analog_innovations.com> wrote in message
news:f1a7uu8r25ivdvbsj...@4ax.com...
Treading in *deep* water here but the solution is to stick a resistor in
series with that timing cap'. The effect is to add sufficient 'pre-act' to
balance the accruing switch losses
Jim Thompson
"John Jardine" <jo...@jjdesigns.fsnet.co.uk>,
In Newsgroup: sci.electronics.design,
Article: <as0aqj$9io$1...@news5.svr.pol.co.uk>,
Entitled: "Re: circuit wanted-SQUARE PULSE GENERATOR",
Wrote the following:
|
|Jim Thompson <Jim-T@analog_innovations.com> wrote in message
[snip]
|> Here's a question for all you lurkers:
|>
|> Delay in the comparators (in a 555 or otherwise) affect the linearity
|> of the control curve, particularly at high frequencies (I've built
|> these at frequencies as high as 50MHz).
|>
|> Can anyone here mathematically describe the effect as a function of
|> delay and operating frequency?
|>
|> And then offer a solution?
|>
|> (I can ;-)
|>
|> ...Jim Thompson
|
|Treading in *deep* water here but the solution is to stick a resistor in
|series with that timing cap'. The effect is to add sufficient 'pre-act' to
|balance the accruing switch losses
|
Congratulations, John, that *is* the solution. I didn't expect such a
quick answer !-)
I can't remember the application now, but I first came upon this while
doing a PLL at 20MHz back in the days of TTL.
John Jardine
Jim, You've just made my day ;-)
First used in a 1MHz function gen I was playing with. Used LM301's and a
I/2I triangle generator. Never pursued it as it disfigured my neat triangle.
regards
john
Winfield Hill
>
> I've been using the 1X/2X approach for at least 35 years in on-chip
> VCM's (voltage-contolled multivibrators).
>
>
> Delay in the comparators (in a 555 or otherwise) affect the linearity
> of the control curve, particularly at high frequencies (I've built
> these at frequencies as high as 50MHz).
>
> Can anyone here mathematically describe the effect as a function of
Well let's see, there's a delay in the integrator dV/dt output
(if one is implemented as an opamp integrator) and there's a
delay in the comparator and current-switching circuitry, let's
call all these delays td. If I is the charge/discharge current
and V is the low-frequency charging-voltage excursion, then we
get f = I / 2C V (1 + 2td f), which equivalent to the comparator
threshold voltage growing by the fraction 2td/T where T = 1/f is
the output period. So it would seem a correction that slightly
reduces the threshold voltage as a function of I would do the job.
Thanks,
- Win
Jim Thompson
Entitled: "Re: circuit wanted-SQUARE PULSE GENERATOR",
Wrote the following:
|
|Jim Thompson <Jim-T@analog_innovations.com> wrote in message
|news:6fc7uu052kr2cviij...@4ax.com...
|> On Tue, 26 Nov 2002 17:37:26 -0000,
|> "John Jardine" <jo...@jjdesigns.fsnet.co.uk>,
|> In Newsgroup: sci.electronics.design,
|> Article: <as0aqj$9io$1...@news5.svr.pol.co.uk>,
|> Entitled: "Re: circuit wanted-SQUARE PULSE GENERATOR",
|> Wrote the following:
[snip]
|> |Treading in *deep* water here but the solution is to stick a resistor in
|> |series with that timing cap'. The effect is to add sufficient 'pre-act'
|to
|> |balance the accruing switch losses
|> |
|>
|> Congratulations, John, that *is* the solution. I didn't expect such a
|> quick answer !-)
|>
|> I can't remember the application now, but I first came upon this while
|> doing a PLL at 20MHz back in the days of TTL.
|>
|> ...Jim Thompson
|
|Jim, You've just made my day ;-)
|First used in a 1MHz function gen I was playing with. Used LM301's and a
|I/2I triangle generator. Never pursued it as it disfigured my neat triangle.
|regards
|john
|
Yep, it does put an ugly "hickey" in the triangle shape, but for clock
restorers, etc., where loop gain in the PLL shouldn't be wandering,
it's a godsend.
Leon Heller
pressed the other button toggles between coarse/fine modes.
I keep meaning to see how far one can take a two button interface. We used
to joke about using just two buttons to control a copier when I worked on
interface design at Xerox Research (UK).
A lot can be done with one button, if it's used to send Morse code to the
system. 8-)
Jonathan Kirwan
<le...@heller123.freeserve.co.uk> wrote:
>"Jonathan Kirwan" <jki...@easystreet.com> wrote in message
>news:en67uuo881qn4gr9i...@4ax.com...
>> On Mon, 25 Nov 2002 18:41:31 -0000, "Leon Heller"
>> <le...@heller123.freeserve.co.uk> wrote:
>>
>> >It could just use a couple of push-buttons, one for up and one for down.
>>
>> And maybe one for coarse/fine shift mode?
>>
>One could do that with just two buttons. For instance, while one button is
>pressed the other button toggles between coarse/fine modes.
>
>I keep meaning to see how far one can take a two button interface. We used
>to joke about using just two buttons to control a copier when I worked on
>interface design at Xerox Research (UK).
>
>A lot can be done with one button, if it's used to send Morse code to the
>system. 8-)
Well, in keeping with this minimalist kick, let's work on what
can be done with only 1/2 a switch.
Jon
Jim Thompson
In Newsgroup: sci.electronics.design,
Article: <as0kks$l29$1...@newsg2.svr.pol.co.uk>,
Entitled: "Re: circuit wanted-SQUARE PULSE GENERATOR",
Wrote the following:
[snip]
|I keep meaning to see how far one can take a two button interface. We used
|to joke about using just two buttons to control a copier when I worked on
|interface design at Xerox Research (UK).
|
|A lot can be done with one button, if it's used to send Morse code to the
|system. 8-)
|
|Leon
I think two buttons, plus a display, can give you an *infinite* number
of functions...
Think Button one as scroll up and down a menu listing.
Button two scroll right/left.
Both buttons pressed equals "execute".
This not original with me... I have a 3-button remote for my spa (uses
third button for "execute"; of course it's a real pain-in-the-ass to
use.
Winfield Hill
Ah, a resistor in series with the capacitor! Does the same job as
lowering the threshold voltage as a function of current, nice!!!
Thanks,
- Win
Keith Wootten
<le...@heller123.freeserve.co.uk> writes
<snipped>
>One could do that with just two buttons. For instance, while one button is
>pressed the other button toggles between coarse/fine modes.
I used something similar for manual hydraulic ram positioning - one
button for up, one for down. The ram may be a long way off position
initially, but you need very fine control for the final positioning.
Initial pressing and holding in of one button goes at the slowest rate,
and subsequent momentary pressing of the other button increases the rate
by 2x up to some sensible maximum. Reset to slowest when both released.
It may sound tricky, but it actually works very well, and the users like
it. Better than separate coarse/fine buttons, single hand operation is
easy without looking.
>
>I keep meaning to see how far one can take a two button interface. We used
>to joke about using just two buttons to control a copier when I worked on
>interface design at Xerox Research (UK).
It can be hell. Eurotherm temperature controllers worked on some fairly
minimal button arrangement and were notoriously difficult to use unless
you were practised.
I once designed a system which replaced two 19" bays of knobs and
switches with five buttons, an encoder and a 64x240 pixel graphics LCD.
Lots of menus with icons, but you couldn't see at a glance what all the
settings were. Some of the top level menus were simply there to 'expand
the tree' to access the functional multiple lower levels. Not so good,
although the encoder was well received.
>
>A lot can be done with one button, if it's used to send Morse code to the
>system. 8-)
Cheers
--
Keith Wootten
John Fields
<Jim-T@analog_innovations.com> wrote:
>I think two buttons, plus a display, can give you an *infinite* number
>of functions...
---
I'm pretty sure you're right.
I've currently got a project where I'm using a telco formatted 3X4
keypad which, instead of presenting * and #, presents "N" and "Y".
The display is a 2X16 LCD display used to communicate with the
machine.
On power-up the LCD displays "PRESS N TO SCROLL MENU" and when you
do, the various options available are presented, with successive "N"
pressings, one at a time, in a circular array. When you get to a
selection you like you are prompted to press "Y", and then there are
various questions you are asked which you must answer with either
the "Y"(yes) or "N"(no) keys which further define what you want the
machine to do.
I'm using a 3X4 keypad because some of the menu choices require
numerical input and it would be a huge PITA to have to do it with
just the "N" and "Y" switches, but it _could_ be done, for sure.
I had a project, years ago, where I had to scroll a menu and do
numerical _and_ alpha input from a 4X4 keypad, and if you're
interested I'll post a picture of the keypad overlay to abse.
There _is_ another interesting way to do it, and that's to use a
quadrature encoder with an integral pushbutton switch as the input
device. The only real estate that's required to do it this way is a
1/4"(?) hole in the front panel, the front panel area the knob
needs, and the volume needed behind the panel for the device itself
(and the wiring, if the PCB is remote from the encoder). The
penalty is the extra code which has to be written, but once that's
done and amortized over a couple of million units it's almost like
it wasn't there at all, huh?
John Fields
Professional circuit designer
http://www.austininstruments.com
John Woodgate
<jki...@easystreet.com> wrote (in <5cm7uu8h4m9qk2hon9c8sirehk78jgi65f@4
ax.com>) about 'circuit wanted-SQUARE PULSE GENERATOR', on Tue, 26 Nov
2002:
>Well, in keeping with this minimalist kick, let's work on what
>can be done with only 1/2 a switch.
Which half? The SWI or the TCH?
--
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!
Jonathan Kirwan
<j...@jmwa.demon.contraspam.yuk> wrote:
>I read in sci.electronics.design that Jonathan Kirwan
><jki...@easystreet.com> wrote (in <5cm7uu8h4m9qk2hon9c8sirehk78jgi65f@4
>ax.com>) about 'circuit wanted-SQUARE PULSE GENERATOR', on Tue, 26 Nov
>2002:
>>Well, in keeping with this minimalist kick, let's work on what
>>can be done with only 1/2 a switch.
>
>Which half? The SWI or the TCH?
I was thinking perhaps either the SP or the ST.
Jon
Tony Williams
John Jardine <jo...@jjdesigns.fsnet.co.uk> wrote:
> Tony Williams <to...@ledelec.demon.co.uk> wrote
> > [*] I've seen that (1x charge, 2x gated discharge)
> > circuit somewhere before, complete in one chip.
> > Vague memories of someone's dual slope ADC?
> 'ICL8038' Function generator chip.
Good lord yes, I'd forgotten that one.
--
Tony Williams.
Keith Wootten
<jfi...@texas.net> writes
<snipped>
>I had a project, years ago, where I had to scroll a menu and do
>numerical _and_ alpha input from a 4X4 keypad, and if you're
>interested I'll post a picture of the keypad overlay to abse.
>
I did this recently for a project where there was only an occasional
need for text entry. I emulated a cellphone text message editor, which
seem to be fairly standard. The keys were legended appropriately.
>There _is_ another interesting way to do it, and that's to use a
>quadrature encoder with an integral pushbutton switch as the input
>device.
I did this a few years ago, but it wasn't really very good. It worked
ok, but the cellphone emulator (cellphones weren't ubiquitous at the
time) is much, much easier to use.
Cheers
--
Keith Wootten
Tony Williams
Winfield Hill <wh...@picovolt.com> wrote:
> [1/(1 + 2.5% Vin/Vmax)] term in the frequency formula. :>)
> The discharge could be shortened to 5 or 10us, but it'd still
> be there. Fixing the issue would require a switched negative
> tracking current sink. And the added complexity (two opamp-
> controlled current sources, two steering diodes) would likely
> force one to abandon the cmos 555 approach entirely, choosing
> instead a opamp triangle integrator / comparator scheme, etc.
Getting rid of the non-linearity might turn out far easier.
A few scribbles say that if the stimulus across the control
pot is increased in proportion to the Vout from the pot,
then the control non-linearity from the 555's fixed discharge
time can be cancelled completely.
Might have to re-arrange your original circuit slightly,
but the mod itself is relatively trivial.
--
Tony Williams.
Fred Bloggs
Winfield Hill wrote:
> Tony Williams wrote...
>
>>Winfield Hill wh...@picovolt.com wrote:
>>
>>
>>>... internal resistance below 1V, so R4 and C2 provide a
>>>fixed 25us time for thoroughly discharging C each cycle.
>>
>>I'm still trying to see why that 25uS discharge time
>>doesn't result in a 2.5% non-linearity in the control.
>>Knowing you, you have it covered somewhere, but I just
>>can't see where. Must be going thick...........
>
>
> No, Tony, you have found me out! It's unavoidably there, a
> [1/(1 + 2.5% Vin/Vmax)] term in the frequency formula. :>)
>
> The discharge could be shortened to 5 or 10us, but it'd still
> be there. Fixing the issue would require a switched negative
> tracking current sink. And the added complexity (two opamp-
> controlled current sources, two steering diodes) would likely
> force one to abandon the cmos 555 approach entirely, choosing
> instead a opamp triangle integrator / comparator scheme, etc.
>
> There's another fault to my circuit. The O.P. specified a
> "square wave." If we assume he meant 50% duty cycle, rather
> than simply rectangular logic pulses, the 25us negative-going
> pulses my circuit puts out are not acceptable. On the other
> hand, modifying the circuit with the above-mentioned tracking
> current sink would also solve this issue.
>
> Thanks,
> - Win
>
You still have the comparator tpd's which approach 1us or more at small
overdrives like 5mV at threshold crossings. Your circuit is basically
open-loop, and, although clever, will not compete with a 4046 wherein
the operator closes the loop with a stable output frequency display. The
tolerance on the threshold resistor divider chain is something like 25%
and your calibration pot can only get at one of two nodes.
ro...@mauve.demon.co.uk
> On Tue, 26 Nov 2002 18:48:01 -0000, "Leon Heller"
> <le...@heller123.freeserve.co.uk> wrote:
>
>>"Jonathan Kirwan" <jki...@easystreet.com> wrote in message
>>news:en67uuo881qn4gr9i...@4ax.com...
>>> On Mon, 25 Nov 2002 18:41:31 -0000, "Leon Heller"
>>> <le...@heller123.freeserve.co.uk> wrote:
>>>
>>> >It could just use a couple of push-buttons, one for up and one for down.
>>>
>>> And maybe one for coarse/fine shift mode?
>>>
>>One could do that with just two buttons. For instance, while one button is
>>pressed the other button toggles between coarse/fine modes.
>>
> Well, in keeping with this minimalist kick, let's work on what
> can be done with only 1/2 a switch.
Well, you could call an electrostatic touch plate 1/2 a switch.
--
http://inquisitor.i.am/ | mailto:inqui...@i.am | Ian Stirling.
---------------------------+-------------------------+--------------------------
"The theory of everything falls out trivially." -- Etherman, sci.physics kook.
Winfield Hill
>
> You still have the comparator tpd's which approach 1us or more at
> small overdrives like 5mV at threshold crossings.
That's a small effect, in the 0.05 to 0.1% level, which is roughly
what we're talking about for a 10-turn pot, etc. BTW, using what
we learned recently from Jim, even that small non-linearity can be
largely removed with one resistor in series with the capacitor. :)
> Your circuit is basically open-loop, and, although clever, will not
> compete with a 4046 wherein the operator closes the loop with a
> stable output frequency display.
Hey, I'm not claiming the world for this simple circuit, competing
with a crystal osc + PLL + dividers, a uP DDS, etc., but neither is
it a piece of #### as you would seem to be implying.
> The tolerance on the threshold resistor divider chain is something
> like 25% and your calibration pot can only get at one of two nodes.
You're overly pessimistic, Fred.
The worst-case 7555 divider-ratio tolerance is under 5%, the typical
value is probably closer to 1%. However, it really doesn't matter
so much. The CAL pot may control only the upper threshold, but the
lower threshold merely sets a charging dV as a fraction of the total.
The final result is a CAL operation that accounts for ALL the various
parameters affecting frequency... capacitor value, resistor ratios
(whether inside the chip or not), etc. We also know that after the
CAL the resistors track well with temperature, etc., from the chip's
typical 50ppm/C drift quoted on the data-sheet's cover. So while an
improvement would be gained if the 7555 were replaced with discrete
IC equivalents, the ciruit can serve well for a simple 0.1% bench-use
room-temp. oscillator.
Thanks,
- Win
Winfield Hill
> ,--- R2 --+-------, +5 -- 1.65k -,
> | __ | | |
> ,---+--|- \ | R1 1k calibrate
> | | >--' 15.0k pot <------,
> R3 ,--|+_/ | | |
> 10.0k | ,----------+ 4.02k |
> | | | __ | | 2/3 Vr
> gnd | '-|- \ |/V Q1 +5 gnd +/-5%
> | | >--| 2n3906 ___|___________ |
> +--------|+_/ |\ | | |
> | IC1 | | CONTROL |--' Vth
> Vr +5 LT1013 | 6 | |
> +-----------| THRESHOLD |
> | 2 | OUT |-----
> 0 to 1kHz precision +-- R4 -+---| TRIGGER |
> 555-type oscillator |\ | | |
> | \____ |_7_| DISCHARGE |
> 3 R2 C _|_ | |_______________|
> f = --------- film ___ C2_|_ |
> 2 C R1 R3 0.1uF | ___ gnd IC2
> R5 | 1nF ICL7555
> linearize |
> | gnd
> gnd
> ---
>>
>> [1/(1 + 2.5% Vin/Vmax)] term in the frequency formula. :>)
>
>> The discharge could be shortened to 5 or 10us, but it'd still
>
> Getting rid of the non-linearity might turn out far easier.
>
> A few scribbles say that if the stimulus across the control
> pot is increased in proportion to the Vout from the pot,
> then the control non-linearity from the 555's fixed discharge
> time can be cancelled completely.
>
> Might have to re-arrange your original circuit slightly,
> but the mod itself is relatively trivial.
Right. Even better, Tony, as we just saw in a recent thread
by Jim Thompson, et. al., just one resistor does the same job,
by instantly increasing the capacitor's voltage to effectively
provide the additional ramping necessary to cancel the time
delay. Cute! See the new R5 added to the drawing above. :>)
Thanks,
- Win
Winfield Hill
>
>Tony Williams wrote...
>>
>> Winfield Hill <wh...@picovolt.com> wrote:
>>
>> 10k 10T pot
>> ,--- R2 --+-------, +5 -- 1.65k -,
>> | __ | | |
>> ,---+--|- \ | R1 1k calibrate
>> | | >--' 15.0k pot <------,
>> R3 ,--|+_/ | | |
>> 10.0k | ,----------+ 4.02k |
>> | | | __ | | 2/3 Vr
>> gnd | '-|- \ |/V Q1 +5 gnd +/-5%
>> | | >--| 2n3906 ___|___________ |
>> +--------|+_/ |\ | | |
>> Vr +5 LT1013 +-----------| THRESHOLD |
>> | | |
>> R5 2 | OUT |-----
>> 0 to 1kHz precision 250 ,- R4-+---| TRIGGER |
>> 555-type oscillator | | | 7 | |
>> +-+---- | --| DISCHARGE |
>> 3 R2 C1 _|_ C2_|_ |_______________|
>> f = --------- film ___ ___ |
>> 2 C R1 R3 0.1uF | 1nF | gnd IC2
>> | gnd ICL7555
>> R5 is linearizer gnd
>>
>> ---
>>>
>>> [1/(1 + 2.5% Vin/Vmax)] term in the frequency formula. :>)
>>
>>> The discharge could be shortened to 5 or 10us, but it'd still
>>> be there. Fixing the issue would require ...
>>
>> Getting rid of the non-linearity might turn out far easier.
>>
>> A few scribbles say that if the stimulus across the control
>> pot is increased in proportion to the Vout from the pot,
>> then the control non-linearity from the 555's fixed discharge
>> time can be cancelled completely.
>>
>> Might have to re-arrange your original circuit slightly,
>> but the mod itself is relatively trivial.
>
> Right. Even better, Tony, as we just saw in a recent thread
> by Jim Thompson, et. al., just one resistor does the same job,
> by instantly increasing the capacitor's voltage to effectively
> provide the additional ramping necessary to cancel the time
> delay. Cute! See the new R5 added to the drawing above. :>)
An email crossing on the net arrived from Tony, he suggested a
better spot, see above, correcting for both capacitors at once.
R5 = 250 ohms drops 25us/1ms = 2.5% of 3.33V = 83mV at the 333uA
full-scale-frequency current. BTW, note that C in the frequency
formula is C1 + C2.
Thanks,
- Win
GEORGE BASILIOU
The problem is that i cannot cleary see the circuit.
The best way to cleary see the circuit is to be drawn on an other design
program and sent to me by email basi...@rocketmail.com.
At this time,that you drawn the circuit into the message,i see a mass of
numbers and lines,random arranged and appeared in my pc's screen.....
Anyway,thank you very much for your help.....
Regards
? "Winfield Hill" <wh...@picovolt.com> ?????? ??? ??????
news:3e852f41.02112...@posting.google.com...
> GEORGE BASILIOU wrote...
> >
> > Unfortunately i'm not good in designing Circuits. Has anyone to
> > suggest me any circuit/page to find a square pulse generator,
> > variable from 1 to 1000 Hz, with 1 Hz step?
> > I prefer not using 555. I want the circuit to be accurate.
>
> The poor 555 gets so much abuse. What a great little chip, two
> precision comparators, a flip-flop, a large discharge transistor,
> serious output driving capability, a trimmable voltage divider.
> These pieces are an excellent starting point for simple accurate
> oscillators like George wants. If we choose a CMOS 555 version,
> like Intersil's ICM7555, we can use low charging currents, like
> 0.33uA, and get accurate operation even down to 1Hz and below
> with a 0.1uF film capacitor.
>
> While Jesper Hansen's design for the AT90S2313 is appealing, see
> if the simplicity of a few analog parts can't also be appealing.
>
> Here's my design that uses a common 10k-ohm 10-turn pot with a
> turns-counting dial for precision frequencies from 0 to 1000Hz.
>
> The IC1 Q1 circuit creates a charging current I = Vr R2 / (R1 R3),
> used by the 555 to make a frequency f = I / C Vth = I Vr / 2/3 C
> Note, we can adjust the 2/3 term to eliminate the capacitor's 5%
> tolerance error, the resistor values, and Q1's beta error. The
> 7555's DISCHARGE pin current limits at 40mA and then 20 ohms of
> internal resistance below 1V, so R4 and C2 provide a fixed 25us
> time for thoroughly discharging C each cycle.
>
> After calibration the frequency is proportional to the setting of
> the 10-turn pot with its counting-dial indicator from 0 to 1 kHz.
>
> 10k 10T pot
> ,--- R2 --+-------, +5 -- 1.65k -,
> | __ | | |
> ,---+--|- \ | R1 1k calibrate
> | | >--' 15.0k pot <------,
> R3 ,--|+_/ | | |
> 10.0k | ,----------+ 4.02k |
> | | | __ | | 2/3 Vr
> gnd | '-|- \ |/V Q1 +5 gnd +/-5%
> | | >--| 2n3906 ___|___________ |
> +--------|+_/ |\ | | |
> | IC1 | | CONTROL |--' Vth
> Vr +5 LT1013 | 6 | |
> +-----------| THRESHOLD |
> | 2 | OUT |-----
> 0 to 1kHz precision +-- R4 -+---| TRIGGER |
> 555-type oscillator |\ | | |
> | \____ |_7_| DISCHARGE |
> 3 R2 C _|_ | |_______________|
> f = --------- ___ C2_|_ |
> 2 C R1 R3 film | ___ gnd IC2
> 0.1uF | 0.001 | ICL7555
> | |
> gnd gnd
>
> IC1 is powered from +15V, and must be a low-offset-voltage opamp
> because at 1Hz the current-programming voltage is only 5mV.
>
> There's lots more to say about this circuit, but it's that time of
> the year again; I have to go finish burying the fig tree.
Michael A. Terrell
You have to view the message with a fixed width font, like Courier.
--
Michael A. Terrell
Central Florida
Jim Thompson
|> ? "Winfield Hill" <wh...@picovolt.com> ?????? ??? ??????
|> news:3e852f41.02112...@posting.google.com...
|> > There's lots more to say about this circuit, but it's that time of
|> > the year again; I have to go finish burying the fig tree.
|
Win, I was fascinated when you mentioned "burying the fig tree" last
year.
Please take some pictures so we can see how it's done.
Thanks!
(I just had my citrus trimmed today for the *winter* fruit season ;-)
Rich Grise
> I would like to have a closer look to that circuit.
> The problem is that i cannot cleary see the circuit.
> The best way to cleary see the circuit is to be drawn on an other design
> program and sent to me by email basi...@rocketmail.com.
> At this time,that you drawn the circuit into the message,i see a mass of
> numbers and lines,random arranged and appeared in my pc's screen.....
>
> Anyway,thank you very much for your help.....
>
> Regards
>
as courier. I see the diagram perfectly. If you have your newsreader
set to display "proportional" fonts (like Times or Arial) then a
well-drawn ASCIImatic will look like crap. And this one was a well-
drawn ASCIImatic.
<well-drawn ASCIImatic snipped>
BTW who was it who gave me, a number of months ago, a circuit to
make a 555 put out a 50% square wave, with some unconventional
feedback loop? I was impressed!
Cheers!
Rich