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unlv007 · 6th May 2008, 06:04 AM

I want to make a simple square pulse generator producing a +5V pulse for 5ms followed by off period=20ms. How do i synthesize it using readily available ICs, transistors etc? Any ideas?
Thank you very much.
Regards

mneary · 6th May 2008, 09:14 PM

Is 5% accuracy good enough? When you say 5V, do you really mean a logic "1" for 5V logic?

Sounds like a job for a 555.

KMoffett · 6th May 2008, 09:50 PM

http://home.cogeco.ca/~rpaisley4/LM555.html#4

The second or forth circuit.

Calculators are available on that site to select components for your on and off times.

Ken

unlv007 · 7th May 2008, 05:20 AM

How do you compare 7490 and 555? I guess 555 is a classic circuit, ,but how is its performance? please let me know.

yes 5% should be good enough, the pulse train should be 5V=on and 0V=off .
So logic 1=5V.
thank you very much.

unlv007 · 7th May 2008, 05:21 AM

Thanks once again for your help

KMoffett · 7th May 2008, 02:12 PM

I don't think the 7490 will give you the time periods you are looking for. Maybe a CMOS 4060 internal oscillator set to 200Hz and with a reset after the 5th count?
http://www.fairchildsemi.com/ds/CD%2FCD4060BC.pdf

Ken

unlv007 · 9th May 2008, 05:55 AM

Is it possible to build a pulse generator with controllable amplitude? The amplitude may vary from 0 to 5V? Can LM555 implement this?

KMoffett · 9th May 2008, 01:31 PM

Yes...a potentiometer as a variable voltage divider, from pin 3 of the 555 to ground...voltage from wiper to ground can be varied from 0 to 5v. Simple, but with cannot drive any significant load.

Ken

unlv007 · Yesterday, 11:04 PM

If i want to increase with voltage of the pulse to 40V and be in the same timescale,that is pulse time period in ms, how should i go about it? Should i build an amplifier or should i use a new IC?
Thanks.

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6th May 2008, 06:04 AM
unlv007 New Member	pulse train generator I want to make a simple square pulse generator producing a +5V pulse for 5ms followed by off period=20ms. How do i synthesize it using readily available ICs, transistors etc? Any ideas? Thank you very much. Regards

6th May 2008, 09:14 PM
mneary Experienced Member	Is 5% accuracy good enough? When you say 5V, do you really mean a logic "1" for 5V logic? Sounds like a job for a 555.

6th May 2008, 09:50 PM
KMoffett Experienced Member	http://home.cogeco.ca/~rpaisley4/LM555.html#4 The second or forth circuit. Calculators are available on that site to select components for your on and off times. Ken __________________ "To invent, you need a good imagination and a pile of junk." Thomas A. Edison (1847 - 1931)

7th May 2008, 05:20 AM
unlv007 New Member	How do you compare 7490 and 555? I guess 555 is a classic circuit, ,but how is its performance? please let me know. yes 5% should be good enough, the pulse train should be 5V=on and 0V=off . So logic 1=5V. thank you very much.

7th May 2008, 05:21 AM
unlv007 New Member	Thanks once again for your help

7th May 2008, 02:12 PM
KMoffett Experienced Member	I don't think the 7490 will give you the time periods you are looking for. Maybe a CMOS 4060 internal oscillator set to 200Hz and with a reset after the 5th count? http://www.fairchildsemi.com/ds/CD%2FCD4060BC.pdf Ken __________________ "To invent, you need a good imagination and a pile of junk." Thomas A. Edison (1847 - 1931)

9th May 2008, 05:55 AM
unlv007 New Member	Is it possible to build a pulse generator with controllable amplitude? The amplitude may vary from 0 to 5V? Can LM555 implement this?

9th May 2008, 01:31 PM
KMoffett Experienced Member	Yes...a potentiometer as a variable voltage divider, from pin 3 of the 555 to ground...voltage from wiper to ground can be varied from 0 to 5v. Simple, but with cannot drive any significant load. Ken __________________ "To invent, you need a good imagination and a pile of junk." Thomas A. Edison (1847 - 1931)

Yesterday, 11:04 PM
unlv007 New Member	If i want to increase with voltage of the pulse to 40V and be in the same timescale,that is pulse time period in ms, how should i go about it? Should i build an amplifier or should i use a new IC? Thanks.