simple oscillator formula - Electronic Circuits Projects Diagrams Free

soadrage7654 · 23rd May 2009, 11:29 PM

Hello, I am working on a simple oscillator that uses two inverter gates, a resistor and a capacitor. I planned this out a while back, but I cannot find the formula I used to calculate the frequency. I also can't find anything online that resembles the circuit that I am using and also gives a formula for it. Can someone help me out here? I attached the schematic.

Thanks,
Josh Clark

Sceadwian · 24th May 2009, 01:06 AM

http://www.musicfromouterspace.com/a...h/mmlogic.html

You may want to add one more inverter as a buffer to the LED separately from the feedback or the LED loading will effect the oscillator frequency, how much I don't know.

dougy83 · 24th May 2009, 03:28 AM

I would assume that the following would be correct:

Code:

F = x/(RC)

Just build the circuit and measure the frequency. Then you can calculate x. Then you can calculate the rough frequency for any RC.

soadrage7654 · 25th May 2009, 05:52 AM

Ok thanks for the suggestion. I was going to use that as a last resort, but I guess it's the only choice now.

I just thought it was weird that I had a formula for the frequency when I first planned it out, but I couldn't find it later so I wanted to check to see if anyone else happened to know it.

dougy83 · 25th May 2009, 06:14 AM

Actually, before you give up, have a look at
Square wave oscillator (2)

You will note that there is an extra resistor used, Rp, to 'protect' the CMOS input. It also has the added function of preventing the capacitor from being discharged through the CMOS input diodes (this affects the duty cycle & frequency, so the above f=x/r/c is no good due to the diodes affecting the timing)

Hero999 · 30th May 2009, 12:20 AM

Rp is just a high value resistor 100k to 1M is normally good enough.

MrAl · 30th May 2009, 07:19 AM

Hi,

Someone else asked about this and we talked about it can came up with
very good formulas. If someone could find it, it is here on this site somewhere.

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23rd May 2009, 11:29 PM	#1
soadrage7654	simple oscillator formula Hello, I am working on a simple oscillator that uses two inverter gates, a resistor and a capacitor. I planned this out a while back, but I cannot find the formula I used to calculate the frequency. I also can't find anything online that resembles the circuit that I am using and also gives a formula for it. Can someone help me out here? I attached the schematic. Thanks, Josh Clark Attached Thumbnails Last edited by soadrage7654; 23rd May 2009 at 11:31 PM. Reason: error in schematic

24th May 2009, 01:06 AM	#2
Sceadwian	http://www.musicfromouterspace.com/a...h/mmlogic.html You may want to add one more inverter as a buffer to the LED separately from the feedback or the LED loading will effect the oscillator frequency, how much I don't know. __________________ "Because I be what I be. I would tell you what you want to know if I could, mum, but I be a cat, and no cat anywhere ever gave anyone a straight answer, har har."

24th May 2009, 03:28 AM	#3
dougy83	I would assume that the following would be correct: Code: F = x/(RC) Just build the circuit and measure the frequency. Then you can calculate x. Then you can calculate the rough frequency for any RC.

25th May 2009, 05:52 AM	#4
soadrage7654	Ok thanks for the suggestion. I was going to use that as a last resort, but I guess it's the only choice now. I just thought it was weird that I had a formula for the frequency when I first planned it out, but I couldn't find it later so I wanted to check to see if anyone else happened to know it.

25th May 2009, 06:14 AM	#5
dougy83	Actually, before you give up, have a look at Square wave oscillator (2) You will note that there is an extra resistor used, Rp, to 'protect' the CMOS input. It also has the added function of preventing the capacitor from being discharged through the CMOS input diodes (this affects the duty cycle & frequency, so the above f=x/r/c is no good due to the diodes affecting the timing)

30th May 2009, 12:20 AM	#6
Hero999	Rp is just a high value resistor 100k to 1M is normally good enough. __________________ I do not answer private messages asking for help because no one else can: benefit from advice I may give or correct me if I'm wrong. Please ask on the open forum if you have a question and I'll be happy to help, if I know the answer.

30th May 2009, 07:19 AM	#7
MrAl	Hi, Someone else asked about this and we talked about it can came up with very good formulas. If someone could find it, it is here on this site somewhere.