pulse generator - Electronic Circuits Projects Diagrams Free

patroclus · 20th February 2007, 10:22 AM

I built a simple pulse generator with a 4MHz crystal and a 4060 counter, to get several output frequencies. I checked them in my scope, and I get quite good pulses, with less than 200ns rise and fall times.

But there're other ways to do it, without crystals.

http://www.interq.or.jp/japan/se-inoue/e_ckt13.htm

or

http://www.interq.or.jp/japan/se-inoue/e_ckt29.htm

Do they have any advantage?
Maybe you can change frequency more easily with a potenciometer, while the crystals only lets you some power of 2 divided frequencies. But the crystal is more accurate, isn't it?

Thank you

**Nigel Goodwin** · 20th February 2007, 11:01 AM

Yes, the crystal is FAR more accurate. The best solution though is a PLL using a crystal as the reference, so you can switch frequencies easily and accurately.

audioguru · 20th February 2007, 02:41 PM

The simple oscillators have a different frequency with each IC and the frequency changes when the supply voltage changes.

patroclus · 20th February 2007, 03:30 PM

The links I posted, show 2 approaches with IC that do not depend on supply voltage, only R and C.

Yes, PLL is good, but seem much more complex.

audioguru · 20th February 2007, 04:22 PM

Quote:

Originally Posted by patroclus

The links I posted, show 2 approaches with IC that do not depend on supply voltage, only R and C.

No.
The links (performance) show a big change in frequency when the supply voltage is changed.
The datasheets for the ICs show that each one is very different (threshold voltage) which affects the frequency.

**Nigel Goodwin** · 20th February 2007, 05:00 PM

Quote:

Originally Posted by patroclus

Yes, PLL is good, but seem much more complex.

Yes, much more complex, but much more useful as well!.

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20th February 2007, 10:22 AM	#1
patroclus	pulse generator I built a simple pulse generator with a 4MHz crystal and a 4060 counter, to get several output frequencies. I checked them in my scope, and I get quite good pulses, with less than 200ns rise and fall times. But there're other ways to do it, without crystals. http://www.interq.or.jp/japan/se-inoue/e_ckt13.htm or http://www.interq.or.jp/japan/se-inoue/e_ckt29.htm Do they have any advantage? Maybe you can change frequency more easily with a potenciometer, while the crystals only lets you some power of 2 divided frequencies. But the crystal is more accurate, isn't it? Thank you

20th February 2007, 11:01 AM	#2
Nigel Goodwin	Yes, the crystal is FAR more accurate. The best solution though is a PLL using a crystal as the reference, so you can switch frequencies easily and accurately. __________________ PIC programmer software, and PIC Tutorials at: http://www.winpicprog.co.uk

20th February 2007, 02:41 PM	#3
audioguru	The simple oscillators have a different frequency with each IC and the frequency changes when the supply voltage changes. __________________ Uncle $crooge

20th February 2007, 03:30 PM	#4
patroclus	The links I posted, show 2 approaches with IC that do not depend on supply voltage, only R and C. Yes, PLL is good, but seem much more complex.