Pulse detector

On Thursday, April 23, 2020 at 5:26:23 PM UTC-7, Ricky C wrote:

On Thursday, April 23, 2020 at 7:06:38 PM UTC-4, whit3rd wrote:
On Thursday, April 23, 2020 at 3:55:42 PM UTC-7, whit3rd wrote:
On Thursday, April 23, 2020 at 10:48:11 AM UTC-7, edward...@gmail.com wrote:

I want to measure the peak DC voltage of a 10% duty cycle signal.

The simplest approach for that (used with proportional counter pulses) is
a peak detect/hold/convert-to-time-delay-and-count circuit
called a Wilkinson A to D converter.

Basic circuit is an op amp follower on the input voltage, feeding a diode and capacitor
(output through diode to capacitor, feedback from the capacitor). When a peak
passes, the diode reverse-biases, and the op amp output goes to the negative rail.
Then you disconnect the op amp (it's done its job) and either directly
voltage-measure the capacitor, OR connect an accurate current-sink to
the capacitor and count clock pulses as it discharges to zero volts.

Or you use a $0.60 MCU to digitize the 100 uS wide pulses at 100 kSPS, let software find the valid pulse measurements and you are done.

Why is everyone making this so hard? He didn't initially say he was measuring the pulses, but still, not sure what that implies. Does he want data to be sent to another computer? Does this need to drive a display? Is he looking for real time updates of each pulse? An average of some sort? Is the pulse height varying? Sounds like he wants window comparisons to produce a decision of some sort? All of the above is very easy to do in the same $0.60 MCU that is taking the measurement. It can send an output via RS-232, TTL signals, RF pulses or an amplitude modulated audio tone. It can even provide the universally hated output, a blinking LED.

This is a classic case of, "No, tell me the problem you are really trying to solve".

Don't need to count pulses. I know there will be 1000 pulses per second. just need to know the signal voltage level, in order to drive some switches.. The ideal diode (driven by op-amp) should be good enough. Too much trouble to program micro, if a few passive parts can do the job.

 

[boB]

On Thu, 23 Apr 2020 14:26:27 -0700 (PDT), Ricky C
<gnuarm.deletethisbit@gmail.com> wrote:

On Thursday, April 23, 2020 at 5:15:56 PM UTC-4, edward...@gmail.com wrote:
On Thursday, April 23, 2020 at 2:10:43 PM UTC-7, boB wrote:
On Thu, 23 Apr 2020 12:05:26 -0700 (PDT), edward.ming.lee@gmail.com
wrote:

On Thursday, April 23, 2020 at 12:01:32 PM UTC-7, Ricky C wrote:
On Thursday, April 23, 2020 at 2:44:35 PM UTC-4, edward...@gmail.com wrote:
On Thursday, April 23, 2020 at 11:40:39 AM UTC-7, Tauno Voipio wrote:
On 23.4.20 20:48, edward.ming.lee@gmail.com wrote:
On Thursday, April 23, 2020 at 10:43:52 AM UTC-7, whit3rd wrote:
On Thursday, April 23, 2020 at 10:13:00 AM UTC-7, edward...@gmail.com wrote:
I am looking for a voltage detector of a 10% duty cycle waveform.

This is close to what i need, best if it works with 12V:

https://www.simplecircuitdiagram.com/2150-peak-pulse-voltmeter/

The -20V at the top seems strange. Could it be a typo?

Wondering if i can scale it down to 12V.

Any other IC or circuit to do this?

What, exactly, is "this"? Do you really want to hold the peak DC voltage of an
incoming signal for a few milliseconds, or until you reset, or do you want to
measure that peak height?

Waveforms don't have 'a' voltage, and 'detector' is not very descriptive.

I want to measure the peak DC voltage of a 10% duty cycle signal.


How fast?

1Khz

Is it repetitive?

Yes.

At one kHz definitely use an op amp.

You could Google "op amp peak detector circuit" or here are a couple of examples.

https://www.circuitlab.com/circuit/y453h7/precision-active-peak-detector/

OK, that might work.


Yeah, that's a peak voltage detector.

Next for when to capture that voltage (DutyCycle = 10%), maybe an R-C
LPF and a window comparator circuit... Use two copmareators to
trigger the peak V capture (whatever you need to do with it) when the
duty cycle is 10% of the full range voltage ?

Yes, that's what i need. Should have search on "peak detector" instead of "pulse detector". It's just a simple sample and hold of the input, then using several comparators to trigger on the voltage level.

A 10% duty cycle, 1 kHz pulse can be measured quite well using a single chip, as small as 8 pins.

Yes. Like a simple 8 bit 8 pin micro to detect both at once if size
is an issue. Capture-Compare and A/D if the part has that capability

Then some way to output that information.

 

On Thursday, April 23, 2020 at 6:56:06 PM UTC-7, boB wrote:

On Thu, 23 Apr 2020 14:26:27 -0700 (PDT), Ricky C
gnuarm.deletethisbit@gmail.com> wrote:

On Thursday, April 23, 2020 at 5:15:56 PM UTC-4, edward...@gmail.com wrote:
On Thursday, April 23, 2020 at 2:10:43 PM UTC-7, boB wrote:
On Thu, 23 Apr 2020 12:05:26 -0700 (PDT), edward.ming.lee@gmail.com
wrote:

On Thursday, April 23, 2020 at 12:01:32 PM UTC-7, Ricky C wrote:
On Thursday, April 23, 2020 at 2:44:35 PM UTC-4, edward...@gmail.com wrote:
On Thursday, April 23, 2020 at 11:40:39 AM UTC-7, Tauno Voipio wrote:
On 23.4.20 20:48, edward.ming.lee@gmail.com wrote:
On Thursday, April 23, 2020 at 10:43:52 AM UTC-7, whit3rd wrote:
On Thursday, April 23, 2020 at 10:13:00 AM UTC-7, edward...@gmail.com wrote:
I am looking for a voltage detector of a 10% duty cycle waveform.

This is close to what i need, best if it works with 12V:

https://www.simplecircuitdiagram.com/2150-peak-pulse-voltmeter/

The -20V at the top seems strange. Could it be a typo?

Wondering if i can scale it down to 12V.

Any other IC or circuit to do this?

What, exactly, is "this"? Do you really want to hold the peak DC voltage of an
incoming signal for a few milliseconds, or until you reset, or do you want to
measure that peak height?

Waveforms don't have 'a' voltage, and 'detector' is not very descriptive.

I want to measure the peak DC voltage of a 10% duty cycle signal.


How fast?

1Khz

Is it repetitive?

Yes.

At one kHz definitely use an op amp.

You could Google "op amp peak detector circuit" or here are a couple of examples.

https://www.circuitlab.com/circuit/y453h7/precision-active-peak-detector/

OK, that might work.


Yeah, that's a peak voltage detector.

Next for when to capture that voltage (DutyCycle = 10%), maybe an R-C
LPF and a window comparator circuit... Use two copmareators to
trigger the peak V capture (whatever you need to do with it) when the
duty cycle is 10% of the full range voltage ?

Yes, that's what i need. Should have search on "peak detector" instead of "pulse detector". It's just a simple sample and hold of the input, then using several comparators to trigger on the voltage level.

A 10% duty cycle, 1 kHz pulse can be measured quite well using a single chip, as small as 8 pins.


Yes. Like a simple 8 bit 8 pin micro to detect both at once if size
is an issue. Capture-Compare and A/D if the part has that capability

Then some way to output that information.

Using micro, there are software programming effort and production programming effort. Furthermore, there are voltage level shifting from/to 12V. Running 12V passive and/or op-amp might be easier.

 

[Ricky C]

On Thursday, April 23, 2020 at 8:46:22 PM UTC-4, edward...@gmail.com wrote:

On Thursday, April 23, 2020 at 5:26:23 PM UTC-7, Ricky C wrote:
On Thursday, April 23, 2020 at 7:06:38 PM UTC-4, whit3rd wrote:
On Thursday, April 23, 2020 at 3:55:42 PM UTC-7, whit3rd wrote:
On Thursday, April 23, 2020 at 10:48:11 AM UTC-7, edward...@gmail.com wrote:

I want to measure the peak DC voltage of a 10% duty cycle signal.

The simplest approach for that (used with proportional counter pulses) is
a peak detect/hold/convert-to-time-delay-and-count circuit
called a Wilkinson A to D converter.

Basic circuit is an op amp follower on the input voltage, feeding a diode and capacitor
(output through diode to capacitor, feedback from the capacitor). When a peak
passes, the diode reverse-biases, and the op amp output goes to the negative rail.
Then you disconnect the op amp (it's done its job) and either directly
voltage-measure the capacitor, OR connect an accurate current-sink to
the capacitor and count clock pulses as it discharges to zero volts.

Or you use a $0.60 MCU to digitize the 100 uS wide pulses at 100 kSPS, let software find the valid pulse measurements and you are done.

Why is everyone making this so hard? He didn't initially say he was measuring the pulses, but still, not sure what that implies. Does he want data to be sent to another computer? Does this need to drive a display? Is he looking for real time updates of each pulse? An average of some sort? Is the pulse height varying? Sounds like he wants window comparisons to produce a decision of some sort? All of the above is very easy to do in the same $0.60 MCU that is taking the measurement. It can send an output via RS-232, TTL signals, RF pulses or an amplitude modulated audio tone. It can even provide the universally hated output, a blinking LED.

This is a classic case of, "No, tell me the problem you are really trying to solve".

Don't need to count pulses. I know there will be 1000 pulses per second. just need to know the signal voltage level, in order to drive some switches. The ideal diode (driven by op-amp) should be good enough. Too much trouble to program micro, if a few passive parts can do the job.

I'm the other way. I would never use so many passive parts when a single MCU and a bit of simple programming could do the job. If there is any volume to the job you can buy the parts preprogrammed.

BTW, I wasn't thinking of any pulse counting. The passive solution will use some six to ten times the board space and might cost two or three times as much and potentially be sensitive to manufacturing variations or other factors. There's more than one reason why so much analog has been replaced by digital.

Some years ago (maybe 20) I was talking with a girl friend about potential stocks to buy (who was no dummy at all, but not familiar with electronics). I mentioned Analog Devices might be a good pick for that time (might have been the post .com bubble recovery). Her response was, wouldn't they be going out of business...? analog you know. I had to explain to her that in some ways analog would never go away, just more and more encroached upon. Besides, they do a lot of digital too, they've been in business a long time (for electronics).

This is one of those "encroachments" that I think the digital solution is prime for. You already spent significant time putzing around looking for a proper circuit. The program could have been written by now. Let's see if I remember my C, I program in Forth and VHDL these days.


#include <stdio.h>
#include <stdlib.h>
#include <math.h>
// include your device specific libraries

void init_adc( int value )
{
--lib_func--( value ); // lib code
}

unsigned int read_sample( void )
{
return ADC_Sample( AD12_CH0 ); // lib code
}

void init_timer( int value )
{
--lib_func--( value ); // lib code
}

void wait_timer( ) {
--lib_func--( ); // lib code
}

unsigned sample_input (unsigned maxval, minval,
*maxval_new, *minval_new ) {
unsigned sample;

wait_timer( );
sample = read_sample( void );
if ( sample > maxval ) {
maxval_new = sample;
}
else if ( sample < minval ) {
minval_new = sample;
}
return (sample);
}

// stuff to control outputs based on the pulse amplitude.
void cntl_outputs ( unsigned maxval, minval ) {
user code goes here!
};

const unsigned mid_adc = 2048; // 12 bit ADC
const unsigned 90pct_cnt = 90; // 100 smpls/pulse per
const unsigned 110pct_cnt = 110; // 100 smpls/pulse per

int main () {
int time;
unsigned sample;
unsigned threshold = mid_adc;
unsigned maxval = mid_adc;
unsigned minval = mid_adc;
unsigned maxval_new = mid_adc;
unsigned minval_new = mid_adc;

init_adc( 1 );

init_timer( 10 ); // 10 us, 10 per pulse time, 100 per cycle

while ( 1 ) {
// Measure the pulse peak
for ( time = 0; time < 90pct_cnt; time++ ) {
sample = sample_input (maxval, minval,
&maxval_new, &minval_new );
}

do { // Sync to the falling edge of the pulse
time++;
sample = sample_input (maxval, minval,
&maxval_new, &minval_new );
}
while ( (sample > threshold) and (time < 110pct_cnt) );

// update data from prior pulse
threshold = ((maxval - minval) / 2);
maxval = maxval_new;
minval = minval_new;
maxval_new = threshold;
minval_new = threshold;

cntl_outputs ( maxval, minval );
}
}

This algorithm may take a few cycles to get aligned to the pulse high and low levels. You can add a bit of logic at the end to keep the output controls safe until the threshold is not defining either level and it is aligned to the pulse. I have no info on what the output controls will need to do.

I'm not sure this took me an hour to write and most of that was trying to remember the details of C.

--

Rick C.

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

 

[boB]

On Thu, 23 Apr 2020 19:29:33 -0700 (PDT), edward.ming.lee@gmail.com
wrote:

On Thursday, April 23, 2020 at 6:56:06 PM UTC-7, boB wrote:
On Thu, 23 Apr 2020 14:26:27 -0700 (PDT), Ricky C
gnuarm.deletethisbit@gmail.com> wrote:

On Thursday, April 23, 2020 at 5:15:56 PM UTC-4, edward...@gmail.com wrote:
On Thursday, April 23, 2020 at 2:10:43 PM UTC-7, boB wrote:
On Thu, 23 Apr 2020 12:05:26 -0700 (PDT), edward.ming.lee@gmail.com
wrote:

On Thursday, April 23, 2020 at 12:01:32 PM UTC-7, Ricky C wrote:
On Thursday, April 23, 2020 at 2:44:35 PM UTC-4, edward...@gmail.com wrote:
On Thursday, April 23, 2020 at 11:40:39 AM UTC-7, Tauno Voipio wrote:
On 23.4.20 20:48, edward.ming.lee@gmail.com wrote:
On Thursday, April 23, 2020 at 10:43:52 AM UTC-7, whit3rd wrote:
On Thursday, April 23, 2020 at 10:13:00 AM UTC-7, edward...@gmail.com wrote:
I am looking for a voltage detector of a 10% duty cycle waveform.

This is close to what i need, best if it works with 12V:

https://www.simplecircuitdiagram.com/2150-peak-pulse-voltmeter/

The -20V at the top seems strange. Could it be a typo?

Wondering if i can scale it down to 12V.

Any other IC or circuit to do this?

What, exactly, is "this"? Do you really want to hold the peak DC voltage of an
incoming signal for a few milliseconds, or until you reset, or do you want to
measure that peak height?

Waveforms don't have 'a' voltage, and 'detector' is not very descriptive.

I want to measure the peak DC voltage of a 10% duty cycle signal.


How fast?

1Khz

Is it repetitive?

Yes.

At one kHz definitely use an op amp.

You could Google "op amp peak detector circuit" or here are a couple of examples.

https://www.circuitlab.com/circuit/y453h7/precision-active-peak-detector/

OK, that might work.


Yeah, that's a peak voltage detector.

Next for when to capture that voltage (DutyCycle = 10%), maybe an R-C
LPF and a window comparator circuit... Use two copmareators to
trigger the peak V capture (whatever you need to do with it) when the
duty cycle is 10% of the full range voltage ?

Yes, that's what i need. Should have search on "peak detector" instead of "pulse detector". It's just a simple sample and hold of the input, then using several comparators to trigger on the voltage level.

A 10% duty cycle, 1 kHz pulse can be measured quite well using a single chip, as small as 8 pins.


Yes. Like a simple 8 bit 8 pin micro to detect both at once if size
is an issue. Capture-Compare and A/D if the part has that capability

Then some way to output that information.

Using micro, there are software programming effort and production programming effort. Furthermore, there are voltage level shifting from/to 12V. Running 12V passive and/or op-amp might be easier.

Yes, all true...

How you get this done also depends on time to get it done, which even
with a micro could be quick AND space requirements.

Also, is it for production ? A few or a lot ? You can get micros
programmed from the distributer as well. Getting 12V down to 3.3V or
5.0V is pretty easy and cheap.

How about repeatability ? A bunch of analog circuitry can be harder
to debug if you don't havve good techs. Using zeners and comparators
will not always be perfect. Maybe use a TL431 or two to get the
compare levels.

All compromises. You know which ones are important for your
application of course.

Good luck and we'll be waiting to see what you end up with and if it
works well.

 

[Ricky C]

On Thursday, April 23, 2020 at 10:29:38 PM UTC-4, edward...@gmail.com wrote:

On Thursday, April 23, 2020 at 6:56:06 PM UTC-7, boB wrote:
On Thu, 23 Apr 2020 14:26:27 -0700 (PDT), Ricky C
gnuarm.deletethisbit@gmail.com> wrote:

On Thursday, April 23, 2020 at 5:15:56 PM UTC-4, edward...@gmail.com wrote:
On Thursday, April 23, 2020 at 2:10:43 PM UTC-7, boB wrote:
On Thu, 23 Apr 2020 12:05:26 -0700 (PDT), edward.ming.lee@gmail.com
wrote:

On Thursday, April 23, 2020 at 12:01:32 PM UTC-7, Ricky C wrote:
On Thursday, April 23, 2020 at 2:44:35 PM UTC-4, edward...@gmail.com wrote:
On Thursday, April 23, 2020 at 11:40:39 AM UTC-7, Tauno Voipio wrote:
On 23.4.20 20:48, edward.ming.lee@gmail.com wrote:
On Thursday, April 23, 2020 at 10:43:52 AM UTC-7, whit3rd wrote:
On Thursday, April 23, 2020 at 10:13:00 AM UTC-7, edward....@gmail.com wrote:
I am looking for a voltage detector of a 10% duty cycle waveform.

This is close to what i need, best if it works with 12V:

https://www.simplecircuitdiagram.com/2150-peak-pulse-voltmeter/

The -20V at the top seems strange. Could it be a typo?

Wondering if i can scale it down to 12V.

Any other IC or circuit to do this?

What, exactly, is "this"? Do you really want to hold the peak DC voltage of an
incoming signal for a few milliseconds, or until you reset, or do you want to
measure that peak height?

Waveforms don't have 'a' voltage, and 'detector' is not very descriptive.

I want to measure the peak DC voltage of a 10% duty cycle signal.


How fast?

1Khz

Is it repetitive?

Yes.

At one kHz definitely use an op amp.

You could Google "op amp peak detector circuit" or here are a couple of examples.

https://www.circuitlab.com/circuit/y453h7/precision-active-peak-detector/

OK, that might work.


Yeah, that's a peak voltage detector.

Next for when to capture that voltage (DutyCycle = 10%), maybe an R-C
LPF and a window comparator circuit... Use two copmareators to
trigger the peak V capture (whatever you need to do with it) when the
duty cycle is 10% of the full range voltage ?

Yes, that's what i need. Should have search on "peak detector" instead of "pulse detector". It's just a simple sample and hold of the input, then using several comparators to trigger on the voltage level.

A 10% duty cycle, 1 kHz pulse can be measured quite well using a single chip, as small as 8 pins.


Yes. Like a simple 8 bit 8 pin micro to detect both at once if size
is an issue. Capture-Compare and A/D if the part has that capability

Then some way to output that information.

Using micro, there are software programming effort and production programming effort. Furthermore, there are voltage level shifting from/to 12V. Running 12V passive and/or op-amp might be easier.

You mean the pulse is 12 volts??? Isn't that completely trivial? Two resistors and you are done. If you mean the power supply, a simple three terminal regulator in a SOT-23 gives you the voltage you need, there's another $0.40.

I've already given you the code and the "production programming" is trivial.. If you have a low volume production run it takes a very simple connection which can be done without a connector even. Or program the chip before assembly. For higher volumes you can buy the chips with your program in them. The maker will do the programming.

If you think any of this is hard or complicated or expensive, I just don't think you are really trying.

--

Rick C.

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

 

Yes. Like a simple 8 bit 8 pin micro to detect both at once if size
is an issue. Capture-Compare and A/D if the part has that capability

Then some way to output that information.

Using micro, there are software programming effort and production programming effort. Furthermore, there are voltage level shifting from/to 12V. Running 12V passive and/or op-amp might be easier.

You mean the pulse is 12 volts???

Input is 6V to 12V. Also need to drive upto 12V output.

Isn't that completely trivial? Two resistors and you are done. If you mean the power supply, a simple three terminal regulator in a SOT-23 gives you the voltage you need, there's another $0.40.

I've already given you the code and the "production programming" is trivial. If you have a low volume production run it takes a very simple connection which can be done without a connector even. Or program the chip before assembly. For higher volumes you can buy the chips with your program in them. The maker will do the programming.

Volume not big enough for pre-programming.

> If you think any of this is hard or complicated or expensive, I just don't think you are really trying.

It's not difficult for me, but lots of hand holding for a small factory making them. I have done it before, for more complicated device. But this device is simple enough for discrete and passive.

 

[Ricky C]

On Friday, April 24, 2020 at 11:21:15 AM UTC-4, edward...@gmail.com wrote:

Yes. Like a simple 8 bit 8 pin micro to detect both at once if size
is an issue. Capture-Compare and A/D if the part has that capability

Then some way to output that information.

Using micro, there are software programming effort and production programming effort. Furthermore, there are voltage level shifting from/to 12V.. Running 12V passive and/or op-amp might be easier.

You mean the pulse is 12 volts???

Input is 6V to 12V. Also need to drive upto 12V output.

Isn't that completely trivial? Two resistors and you are done. If you mean the power supply, a simple three terminal regulator in a SOT-23 gives you the voltage you need, there's another $0.40.

I've already given you the code and the "production programming" is trivial. If you have a low volume production run it takes a very simple connection which can be done without a connector even. Or program the chip before assembly. For higher volumes you can buy the chips with your program in them. The maker will do the programming.

Volume not big enough for pre-programming.

Then self programming can't be that big a deal. I looked into pre-assembly programming an FPGA and found it was practical even at lower volumes. But I didn't want to commit to a firmware design and we have no problem programming as part of board test. My device takes up to 30 seconds for the programming and verification. That's time the worker spends on adding the serial number. The total test time is around 3 minutes when there are no failures. We have a semi-automated test fixture, the user has to press a key to say OK and touch a test point with a jumper wire for a test that wasn't designed in.

If you think any of this is hard or complicated or expensive, I just don't think you are really trying.

It's not difficult for me, but lots of hand holding for a small factory making them. I have done it before, for more complicated device. But this device is simple enough for discrete and passive.

Ok. Factories shouldn't have any trouble programming a device these days. Even if you don't buy the parts pre-programmed, you should be able to pre-program them yourself. Are you using surface mount or DIPs?

--

Rick C.

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

 

On Thursday, April 23, 2020 at 11:05:28 PM UTC-7, boB wrote:

On Thu, 23 Apr 2020 19:29:33 -0700 (PDT), edward.ming.lee@gmail.com
wrote:

On Thursday, April 23, 2020 at 6:56:06 PM UTC-7, boB wrote:
On Thu, 23 Apr 2020 14:26:27 -0700 (PDT), Ricky C
gnuarm.deletethisbit@gmail.com> wrote:

On Thursday, April 23, 2020 at 5:15:56 PM UTC-4, edward...@gmail.com wrote:
On Thursday, April 23, 2020 at 2:10:43 PM UTC-7, boB wrote:
On Thu, 23 Apr 2020 12:05:26 -0700 (PDT), edward.ming.lee@gmail.com
wrote:

On Thursday, April 23, 2020 at 12:01:32 PM UTC-7, Ricky C wrote:
On Thursday, April 23, 2020 at 2:44:35 PM UTC-4, edward...@gmail.com wrote:
On Thursday, April 23, 2020 at 11:40:39 AM UTC-7, Tauno Voipio wrote:
On 23.4.20 20:48, edward.ming.lee@gmail.com wrote:
On Thursday, April 23, 2020 at 10:43:52 AM UTC-7, whit3rd wrote:
On Thursday, April 23, 2020 at 10:13:00 AM UTC-7, edward...@gmail.com wrote:
I am looking for a voltage detector of a 10% duty cycle waveform.

This is close to what i need, best if it works with 12V:

https://www.simplecircuitdiagram.com/2150-peak-pulse-voltmeter/

The -20V at the top seems strange. Could it be a typo?

Wondering if i can scale it down to 12V.

Any other IC or circuit to do this?

What, exactly, is "this"? Do you really want to hold the peak DC voltage of an
incoming signal for a few milliseconds, or until you reset, or do you want to
measure that peak height?

Waveforms don't have 'a' voltage, and 'detector' is not very descriptive.

I want to measure the peak DC voltage of a 10% duty cycle signal.


How fast?

1Khz

Is it repetitive?

Yes.

At one kHz definitely use an op amp.

You could Google "op amp peak detector circuit" or here are a couple of examples.

https://www.circuitlab.com/circuit/y453h7/precision-active-peak-detector/

OK, that might work.


Yeah, that's a peak voltage detector.

Next for when to capture that voltage (DutyCycle = 10%), maybe an R-C
LPF and a window comparator circuit... Use two copmareators to
trigger the peak V capture (whatever you need to do with it) when the
duty cycle is 10% of the full range voltage ?

Yes, that's what i need. Should have search on "peak detector" instead of "pulse detector". It's just a simple sample and hold of the input, then using several comparators to trigger on the voltage level.

A 10% duty cycle, 1 kHz pulse can be measured quite well using a single chip, as small as 8 pins.


Yes. Like a simple 8 bit 8 pin micro to detect both at once if size
is an issue. Capture-Compare and A/D if the part has that capability

Then some way to output that information.

Using micro, there are software programming effort and production programming effort. Furthermore, there are voltage level shifting from/to 12V. Running 12V passive and/or op-amp might be easier.


Yes, all true...

How you get this done also depends on time to get it done, which even
with a micro could be quick AND space requirements.

Also, is it for production ? A few or a lot ? You can get micros
programmed from the distributer as well. Getting 12V down to 3.3V or
5.0V is pretty easy and cheap.

How about repeatability ? A bunch of analog circuitry can be harder
to debug if you don't havve good techs. Using zeners and comparators
will not always be perfect. Maybe use a TL431 or two to get the
compare levels.

I will have to double check, but the accuracy might not be too important. Perhaps +/- 5% at 6V and 9V. I might not even need the op amp, but a Darington pair buffer to isolate the input. None of the RC values are too critical either. So, perhaps: QQDRC-CC-RRRR. Namely, two transistors feeding a diode than RC, then compare with four resistor voltage divider (9V, 6V and 3V).

All compromises. You know which ones are important for your
application of course.

Good luck and we'll be waiting to see what you end up with and if it
works well.

 

On Friday, April 24, 2020 at 2:31:48 PM UTC-7, Ricky C wrote:

On Friday, April 24, 2020 at 4:05:17 PM UTC-4, edward...@gmail.com wrote:
On Thursday, April 23, 2020 at 11:05:28 PM UTC-7, boB wrote:
On Thu, 23 Apr 2020 19:29:33 -0700 (PDT), edward.ming.lee@gmail.com
wrote:

On Thursday, April 23, 2020 at 6:56:06 PM UTC-7, boB wrote:
On Thu, 23 Apr 2020 14:26:27 -0700 (PDT), Ricky C
gnuarm.deletethisbit@gmail.com> wrote:

On Thursday, April 23, 2020 at 5:15:56 PM UTC-4, edward...@gmail.com wrote:
On Thursday, April 23, 2020 at 2:10:43 PM UTC-7, boB wrote:
On Thu, 23 Apr 2020 12:05:26 -0700 (PDT), edward.ming.lee@gmail.com
wrote:

On Thursday, April 23, 2020 at 12:01:32 PM UTC-7, Ricky C wrote:
On Thursday, April 23, 2020 at 2:44:35 PM UTC-4, edward...@gmail.com wrote:
On Thursday, April 23, 2020 at 11:40:39 AM UTC-7, Tauno Voipio wrote:
On 23.4.20 20:48, edward.ming.lee@gmail.com wrote:
On Thursday, April 23, 2020 at 10:43:52 AM UTC-7, whit3rd wrote:
On Thursday, April 23, 2020 at 10:13:00 AM UTC-7, edward...@gmail.com wrote:
I am looking for a voltage detector of a 10% duty cycle waveform.

This is close to what i need, best if it works with 12V:

https://www.simplecircuitdiagram.com/2150-peak-pulse-voltmeter/

The -20V at the top seems strange. Could it be a typo?

Wondering if i can scale it down to 12V.

Any other IC or circuit to do this?

What, exactly, is "this"? Do you really want to hold the peak DC voltage of an
incoming signal for a few milliseconds, or until you reset, or do you want to
measure that peak height?

Waveforms don't have 'a' voltage, and 'detector' is not very descriptive.

I want to measure the peak DC voltage of a 10% duty cycle signal.


How fast?

1Khz

Is it repetitive?

Yes.

At one kHz definitely use an op amp.

You could Google "op amp peak detector circuit" or here are a couple of examples.

https://www.circuitlab.com/circuit/y453h7/precision-active-peak-detector/

OK, that might work.


Yeah, that's a peak voltage detector.

Next for when to capture that voltage (DutyCycle = 10%), maybe an R-C
LPF and a window comparator circuit... Use two copmareators to
trigger the peak V capture (whatever you need to do with it) when the
duty cycle is 10% of the full range voltage ?

Yes, that's what i need. Should have search on "peak detector" instead of "pulse detector". It's just a simple sample and hold of the input, then using several comparators to trigger on the voltage level.

A 10% duty cycle, 1 kHz pulse can be measured quite well using a single chip, as small as 8 pins.


Yes. Like a simple 8 bit 8 pin micro to detect both at once if size
is an issue. Capture-Compare and A/D if the part has that capability

Then some way to output that information.

Using micro, there are software programming effort and production programming effort. Furthermore, there are voltage level shifting from/to 12V. Running 12V passive and/or op-amp might be easier.


Yes, all true...

How you get this done also depends on time to get it done, which even
with a micro could be quick AND space requirements.

Also, is it for production ? A few or a lot ? You can get micros
programmed from the distributer as well. Getting 12V down to 3.3V or
5.0V is pretty easy and cheap.

How about repeatability ? A bunch of analog circuitry can be harder
to debug if you don't havve good techs. Using zeners and comparators
will not always be perfect. Maybe use a TL431 or two to get the
compare levels.

I will have to double check, but the accuracy might not be too important. Perhaps +/- 5% at 6V and 9V. I might not even need the op amp, but a Darington pair buffer to isolate the input. None of the RC values are too critical either. So, perhaps: QQDRC-CC-RRRR. Namely, two transistors feeding a diode than RC, then compare with four resistor voltage divider (9V, 6V and 3V).

So you need to distinguish four voltage levels with some number of outputs? That will require at least three comparators and some amount of logic unless it happens that your outputs match thermometer outputs.

Yes, mostly just 9V and 6V.

 

[Ricky C]

On Friday, April 24, 2020 at 4:05:17 PM UTC-4, edward...@gmail.com wrote:

On Thursday, April 23, 2020 at 11:05:28 PM UTC-7, boB wrote:
On Thu, 23 Apr 2020 19:29:33 -0700 (PDT), edward.ming.lee@gmail.com
wrote:

On Thursday, April 23, 2020 at 6:56:06 PM UTC-7, boB wrote:
On Thu, 23 Apr 2020 14:26:27 -0700 (PDT), Ricky C
gnuarm.deletethisbit@gmail.com> wrote:

On Thursday, April 23, 2020 at 5:15:56 PM UTC-4, edward...@gmail.com wrote:
On Thursday, April 23, 2020 at 2:10:43 PM UTC-7, boB wrote:
On Thu, 23 Apr 2020 12:05:26 -0700 (PDT), edward.ming.lee@gmail..com
wrote:

On Thursday, April 23, 2020 at 12:01:32 PM UTC-7, Ricky C wrote:
On Thursday, April 23, 2020 at 2:44:35 PM UTC-4, edward...@gmail.com wrote:
On Thursday, April 23, 2020 at 11:40:39 AM UTC-7, Tauno Voipio wrote:
On 23.4.20 20:48, edward.ming.lee@gmail.com wrote:
On Thursday, April 23, 2020 at 10:43:52 AM UTC-7, whit3rd wrote:
On Thursday, April 23, 2020 at 10:13:00 AM UTC-7, edward...@gmail.com wrote:
I am looking for a voltage detector of a 10% duty cycle waveform.

This is close to what i need, best if it works with 12V:

https://www.simplecircuitdiagram.com/2150-peak-pulse-voltmeter/

The -20V at the top seems strange. Could it be a typo?

Wondering if i can scale it down to 12V.

Any other IC or circuit to do this?

What, exactly, is "this"? Do you really want to hold the peak DC voltage of an
incoming signal for a few milliseconds, or until you reset, or do you want to
measure that peak height?

Waveforms don't have 'a' voltage, and 'detector' is not very descriptive.

I want to measure the peak DC voltage of a 10% duty cycle signal.


How fast?

1Khz

Is it repetitive?

Yes.

At one kHz definitely use an op amp.

You could Google "op amp peak detector circuit" or here are a couple of examples.

https://www.circuitlab.com/circuit/y453h7/precision-active-peak-detector/

OK, that might work.


Yeah, that's a peak voltage detector.

Next for when to capture that voltage (DutyCycle = 10%), maybe an R-C
LPF and a window comparator circuit... Use two copmareators to
trigger the peak V capture (whatever you need to do with it) when the
duty cycle is 10% of the full range voltage ?

Yes, that's what i need. Should have search on "peak detector" instead of "pulse detector". It's just a simple sample and hold of the input, then using several comparators to trigger on the voltage level.

A 10% duty cycle, 1 kHz pulse can be measured quite well using a single chip, as small as 8 pins.


Yes. Like a simple 8 bit 8 pin micro to detect both at once if size
is an issue. Capture-Compare and A/D if the part has that capability

Then some way to output that information.

Using micro, there are software programming effort and production programming effort. Furthermore, there are voltage level shifting from/to 12V. Running 12V passive and/or op-amp might be easier.


Yes, all true...

How you get this done also depends on time to get it done, which even
with a micro could be quick AND space requirements.

Also, is it for production ? A few or a lot ? You can get micros
programmed from the distributer as well. Getting 12V down to 3.3V or
5.0V is pretty easy and cheap.

How about repeatability ? A bunch of analog circuitry can be harder
to debug if you don't havve good techs. Using zeners and comparators
will not always be perfect. Maybe use a TL431 or two to get the
compare levels.

I will have to double check, but the accuracy might not be too important. Perhaps +/- 5% at 6V and 9V. I might not even need the op amp, but a Darington pair buffer to isolate the input. None of the RC values are too critical either. So, perhaps: QQDRC-CC-RRRR. Namely, two transistors feeding a diode than RC, then compare with four resistor voltage divider (9V, 6V and 3V).

So you need to distinguish four voltage levels with some number of outputs? That will require at least three comparators and some amount of logic unless it happens that your outputs match thermometer outputs.

You say the volume is low so the design costs would trump the unit costs. The MCU still seems like the cheap road, but if you don't have any MCU familiarity then not so much.

Do I misunderstand your outputs?

--

Rick C.

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

 

[Bill Sloman]

On Friday, April 24, 2020 at 3:13:00 AM UTC+10, edward...@gmail.com wrote:

I am looking for a voltage detector of a 10% duty cycle waveform.

This is close to what i need, best if it works with 12V:

https://www.simplecircuitdiagram.com/2150-peak-pulse-voltmeter/

The -20V at the top seems strange. Could it be a typo?

Wondering if i can scale it down to 12V.

Any other IC or circuit to do this?

What you have shown is a peak-grabber. It's simple and may do what you want, but it isn't a particularly good or safe solution.

You probably ought to reformulate your problem as a sampling question - you need to think about sampling your 1kHz 10% duty cycle waveform during the time when it is high.

Shannon says this means sampling at at least 20kHz. This would guarantee that at least one in twenty of your samples was squarely in the high period of the waveform. Mostly you'd get two, but there would be occasions where you'd sample in the rising edge and the falling edge and only get one good sample in between.

The fact that you are sampling means that you have to synchronise your sampling process to the waveform.

Twenty samples per cycle would give you enough information to set up a phase-locked loop to do that.

At 20kHz you could do all the processing in a cheap single chip microprocessor, which will usually offer a built-in A/D converter to do the sampling.

If you wanted to avoid using a microprocessor, and can live with a bulkier and more expensive solution, you could use a CD4046 to set up the 20kHz clock, which you'd have to divide down by 20 in some digital logic to get the 1kHz signal that you'd lock to your 1kHz waveform.

You can then decode the counter to generate a 1kHz sampling pulse (50 usec wide) which you could use to drive a sample and hold amplifier. The LF398 would do the job

http://mdc.custhelp.com/euf/assets/images/KB_856_NatSemi_SampleHold_circuit..pdf

but you could also set up a CD4066 transmission gate to do the sampling, and pretty much any op amp to buffer the output and hold it between samples.

Hope this helps.

--
Bill Sloman, Sydney

 

[Jasen Betts]

On 2020-04-23, edward.ming.lee@gmail.com <edward.ming.lee@gmail.com> wrote:

I am looking for a voltage detector of a 10% duty cycle waveform.

This is close to what i need, best if it works with 12V:

https://www.simplecircuitdiagram.com/2150-peak-pulse-voltmeter/

The -20V at the top seems strange. Could it be a typo?

old germainium transistors... ick.

Wondering if i can scale it down to 12V.

Any other IC or circuit to do this?

do you want peak to peak, or peak to ground?

--
Jasen.

 

[Jasen Betts]

On 2020-04-24, edward.ming.lee@gmail.com <edward.ming.lee@gmail.com> wrote:

On Thursday, April 23, 2020 at 5:26:23 PM UTC-7, Ricky C wrote:
On Thursday, April 23, 2020 at 7:06:38 PM UTC-4, whit3rd wrote:
On Thursday, April 23, 2020 at 3:55:42 PM UTC-7, whit3rd wrote:
On Thursday, April 23, 2020 at 10:48:11 AM UTC-7, edward...@gmail.com wrote:

I want to measure the peak DC voltage of a 10% duty cycle signal.

The simplest approach for that (used with proportional counter pulses) is
a peak detect/hold/convert-to-time-delay-and-count circuit
called a Wilkinson A to D converter.

Basic circuit is an op amp follower on the input voltage, feeding a diode and capacitor
(output through diode to capacitor, feedback from the capacitor). When a peak
passes, the diode reverse-biases, and the op amp output goes to the negative rail.
Then you disconnect the op amp (it's done its job) and either directly
voltage-measure the capacitor, OR connect an accurate current-sink to
the capacitor and count clock pulses as it discharges to zero volts.

Or you use a $0.60 MCU to digitize the 100 uS wide pulses at 100 kSPS, let software find the valid pulse measurements and you are done.

Why is everyone making this so hard? He didn't initially say he was measuring the pulses, but still, not sure what that implies. Does he want data to be sent to another computer? Does this need to drive a display? Is he looking for real time updates of each pulse? An average of some sort? Is the pulse height varying? Sounds like he wants window comparisons to produce a decision of some sort? All of the above is very easy to do in the same $0.60 MCU that is taking the measurement. It can send an output via RS-232, TTL signals, RF pulses or an amplitude modulated audio tone. It can even provide the universally hated output, a blinking LED.

This is a classic case of, "No, tell me the problem you are really trying to solve".

Don't need to count pulses. I know there will be 1000 pulses per second. just need to know the signal voltage level, in order to drive some switches. The ideal diode (driven by op-amp) should be good enough. Too much trouble to program micro, if a few passive parts can do the job.

maybe just feed the pulses to a voltage doubling rectifier with an offset ground
and use the scaled output to drive an amitter follower.
-+-- +12
|/
in -||----. +------10K---------+----|
| | | |e
+12---10K----+-->|-+-->|--+--||--+--10K---|<-+ ---- out
| |
0V--|<--|<--|<--+---||--------------+-- 0V

might need more diodes


--
Jasen.

 

[piglet]

On 24/04/2020 10:43 pm, edward.ming.lee@gmail.com wrote:

On Friday, April 24, 2020 at 2:31:48 PM UTC-7, Ricky C wrote:

So you need to distinguish four voltage levels with some number of outputs? That will require at least three comparators and some amount of logic unless it happens that your outputs match thermometer outputs.

Yes, mostly just 9V and 6V.

Rather than analog peak hold followed by comparators have you considered
having the comparators first and then latching their outputs?

piglet

 

[Bill Sloman]

On Sunday, April 26, 2020 at 12:48:21 AM UTC+10, jla...@highlandsniptechnology.com wrote:

On Thu, 23 Apr 2020 10:48:05 -0700 (PDT), edward.ming.lee@gmail.com
wrote:

On Thursday, April 23, 2020 at 10:43:52 AM UTC-7, whit3rd wrote:
On Thursday, April 23, 2020 at 10:13:00 AM UTC-7, edward...@gmail.com wrote:
I am looking for a voltage detector of a 10% duty cycle waveform.

This is close to what i need, best if it works with 12V:

https://www.simplecircuitdiagram.com/2150-peak-pulse-voltmeter/

The -20V at the top seems strange. Could it be a typo?

Wondering if i can scale it down to 12V.

Any other IC or circuit to do this?

What, exactly, is "this"? Do you really want to hold the peak DC voltage of an incoming signal for a few milliseconds, or until you reset, or do you want to measure that peak height?

Waveforms don't have 'a' voltage, and 'detector' is not very descriptive.

I want to measure the peak DC voltage of a 10% duty cycle signal.

Measure the average and multiply by 10.

The average what? This isn't specific enough to be in any way helpful.

--
Bill Sloman, Sydney

 

On Thu, 23 Apr 2020 10:48:05 -0700 (PDT), edward.ming.lee@gmail.com
wrote:

On Thursday, April 23, 2020 at 10:43:52 AM UTC-7, whit3rd wrote:
On Thursday, April 23, 2020 at 10:13:00 AM UTC-7, edward...@gmail.com wrote:
I am looking for a voltage detector of a 10% duty cycle waveform.

This is close to what i need, best if it works with 12V:

https://www.simplecircuitdiagram.com/2150-peak-pulse-voltmeter/

The -20V at the top seems strange. Could it be a typo?

Wondering if i can scale it down to 12V.

Any other IC or circuit to do this?

What, exactly, is "this"? Do you really want to hold the peak DC voltage of an
incoming signal for a few milliseconds, or until you reset, or do you want to
measure that peak height?

Waveforms don't have 'a' voltage, and 'detector' is not very descriptive.

I want to measure the peak DC voltage of a 10% duty cycle signal.

Measure the average and multiply by 10.



--

John Larkin Highland Technology, Inc

Science teaches us to doubt.

Claude Bernard

 

On Saturday, April 25, 2020 at 2:42:40 AM UTC-7, piglet wrote:

On 24/04/2020 10:43 pm, edward.ming.lee@gmail.com wrote:
On Friday, April 24, 2020 at 2:31:48 PM UTC-7, Ricky C wrote:

So you need to distinguish four voltage levels with some number of outputs? That will require at least three comparators and some amount of logic unless it happens that your outputs match thermometer outputs.

Yes, mostly just 9V and 6V.


Rather than analog peak hold followed by comparators have you considered
having the comparators first and then latching their outputs?

piglet

What is the benefit of such arrangement? Instead of:

OpAmp(D),RC -> Comp-(10V),Comp+(8V) -> OpenCollectorDriver

 

On Saturday, April 25, 2020 at 7:48:21 AM UTC-7, jla...@highlandsniptechnology.com wrote:

On Thu, 23 Apr 2020 10:48:05 -0700 (PDT), edward.ming.lee@gmail.com
wrote:

On Thursday, April 23, 2020 at 10:43:52 AM UTC-7, whit3rd wrote:
On Thursday, April 23, 2020 at 10:13:00 AM UTC-7, edward...@gmail.com wrote:
I am looking for a voltage detector of a 10% duty cycle waveform.

This is close to what i need, best if it works with 12V:

https://www.simplecircuitdiagram.com/2150-peak-pulse-voltmeter/

The -20V at the top seems strange. Could it be a typo?

Wondering if i can scale it down to 12V.

Any other IC or circuit to do this?

What, exactly, is "this"? Do you really want to hold the peak DC voltage of an
incoming signal for a few milliseconds, or until you reset, or do you want to
measure that peak height?

Waveforms don't have 'a' voltage, and 'detector' is not very descriptive.

I want to measure the peak DC voltage of a 10% duty cycle signal.

Measure the average and multiply by 10.

It's not likely, but possible to have different duty cycles. So, it would get confused with 10% 9V and 15% 6v.

 

[Ricky C]

On Saturday, April 25, 2020 at 12:47:51 PM UTC-4, edward...@gmail.com wrote:

On Saturday, April 25, 2020 at 7:48:21 AM UTC-7, jla...@highlandsniptechnology.com wrote:
On Thu, 23 Apr 2020 10:48:05 -0700 (PDT), edward.ming.lee@gmail.com
wrote:

On Thursday, April 23, 2020 at 10:43:52 AM UTC-7, whit3rd wrote:
On Thursday, April 23, 2020 at 10:13:00 AM UTC-7, edward...@gmail.com wrote:
I am looking for a voltage detector of a 10% duty cycle waveform.

This is close to what i need, best if it works with 12V:

https://www.simplecircuitdiagram.com/2150-peak-pulse-voltmeter/

The -20V at the top seems strange. Could it be a typo?

Wondering if i can scale it down to 12V.

Any other IC or circuit to do this?

What, exactly, is "this"? Do you really want to hold the peak DC voltage of an
incoming signal for a few milliseconds, or until you reset, or do you want to
measure that peak height?

Waveforms don't have 'a' voltage, and 'detector' is not very descriptive.

I want to measure the peak DC voltage of a 10% duty cycle signal.

Measure the average and multiply by 10.

It's not likely, but possible to have different duty cycles. So, it would get confused with 10% 9V and 15% 6v.

An analog approach could also get confused by small spikes in the signal unless you include filtering of the input signal. Or you can implement this in a digital approach with very little work and still a <$1.00 BOM.

--

Rick C.

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