Help, triangle generator

The LM324 datasheet shows the amplifier slewing at about 0.5 V/uS. The first stage in your circuit, used as a comparator (U1A), appears to slew at 10V/50uS, or 0.2 V/uS if your article regarding pin numbers is to be believed. So that makes me suspect something differs between what you've built/probed and what you've shown.

Also, the (alleged) waveform at pin 3 does not look like the weighted sum of waveforms at pins 7 and 1, as can be expected of a resistor summer. This too makes me suspect a difference between what you did and what you claim.

Looking at the schematic, it appears to have been designed to keep both U1B and U1C out of saturation, but without enough margin to account for switching delays due to the LM324's slowness. I would reduce R7 to keep U1C from hitting its limits.

As for the waveforms you get not matching what you see at

At 5 KHz, I expect you will hear that circuit's effect upon the fan motor. Be prepared in case you dislike that noise. If you want a higher frequency, you will need a faster part. The LM324 is one of the slowest normal-power op-amps around. That circuit is not specifically designed for that op-amp, so you should be able to switch as long as the pot trim range is matched to the op-amp's swing. (And that is mainly a nicety, not a hard requirement.)

HTH.

I have posted waveforms and a schematic of a triangle generator I have put together, it is not working properly. Please see them at abse under- Help, triangle generator.

Mike

capability.

Thanks all, I noted one of the posts said it was running about 5Khz and it was supposed to be running about 125 hz. So I found I had installed a 1n where it the schematic called for a100n.. So who uses (n) anyway I put in a .1uf and it works fine.

Thanks again.

The circuit is fundamentally flawed in that the slew rate required for the integrator U1B- which is dV7/dt= +/- (Vcc/2)/(47K*C) or +/- 1.3V/us which is about 2.5x the typical LM324 performance ( and even that is theoretical because V7 will not hit the rails), so it will not keep up in other words. Then throw in the 12/0.5V/us= 24us for U1A to slew between the rails and storage time effects for coming out of saturation, and you have similarly substantial errors relative to your ~4KHz there. The TL084 will overcome these problems ( better) and should work with the values shown, except get rid of U1C and replace R8+VR1 with an adjustment that goes from (1/4-3/4)*Vcc (that would be an R8A+VR1+R8B type thing), and switch the input polarity of U1D to get the same sense-might try adding a smidgen of hysteresis there to make things a little more snappy. Have fun.

My error- the S.R. is 1.3mV/us and this is well within the LM324 capability.

Your period should be on the order of 7.5ms or 130Hz.

You obviously have used a component that is wildly off the schematic value. You do know that C=100n is 0.1u or 104, and 47K is yellow-violet-orange?