Post by keurslagerkurt on Mar 24, 2021 8:27:34 GMT
Hey all!
Was in search for a small & simple LFO to make on the breadboard/Braedboard for some extra modulation. Found this super-simple oscillator circuit based on the CD4069 hex inverter chip. The circuit uses 3 inverters and the CD4069 has 6 of them, so you can make two LFO's with one IC, some resistors and two caps. (source: scott.joviansynth.com/fatman/4069_lfo.html )
With the exact values mentioned on the circuit, the LFO stopped oscillating when turning the pot to higher values (making the LFO slower). When it went low it stopped oscillating until I plugged the 1K resistor in and out..
In the end I managed to make it work conistently with a 50k pot, a 10uF cap (instead of 1.33) and a 200k resistor instead of the top 110k one. I'm not sure why my values have to be so different to make it work (I mean, the bigger cap makes sense, but I dont get why the circuit wasn't stable with the 110k resistor). However, when it works, it is quite a fun circuit for being so simple! LFO is not really triangle shaped but more S-curved, which has some cool musical uses too. However with this values it can't go in the really low cycles/frequencies
In order to get a more of a grip on the circuit, I tried to simulated it in Falstad circuitjs, but it doesn't seem to work there, or at least, it oscillates very quickly.. Don't know why the simulation can't handle the circuit? (simulation txt file is added if you want to try it out yourself)
If anyone could share some experience or extra understanding, I'd be very interested!
CMOS_LFO_Fatman.txt (571 B)
Was in search for a small & simple LFO to make on the breadboard/Braedboard for some extra modulation. Found this super-simple oscillator circuit based on the CD4069 hex inverter chip. The circuit uses 3 inverters and the CD4069 has 6 of them, so you can make two LFO's with one IC, some resistors and two caps. (source: scott.joviansynth.com/fatman/4069_lfo.html )
With the exact values mentioned on the circuit, the LFO stopped oscillating when turning the pot to higher values (making the LFO slower). When it went low it stopped oscillating until I plugged the 1K resistor in and out..
In the end I managed to make it work conistently with a 50k pot, a 10uF cap (instead of 1.33) and a 200k resistor instead of the top 110k one. I'm not sure why my values have to be so different to make it work (I mean, the bigger cap makes sense, but I dont get why the circuit wasn't stable with the 110k resistor). However, when it works, it is quite a fun circuit for being so simple! LFO is not really triangle shaped but more S-curved, which has some cool musical uses too. However with this values it can't go in the really low cycles/frequencies
In order to get a more of a grip on the circuit, I tried to simulated it in Falstad circuitjs, but it doesn't seem to work there, or at least, it oscillates very quickly.. Don't know why the simulation can't handle the circuit? (simulation txt file is added if you want to try it out yourself)
If anyone could share some experience or extra understanding, I'd be very interested!
CMOS_LFO_Fatman.txt (571 B)
And actually, that would be the 'long term' dream pretty much, but first lets see how my module kits fare in the dangerous outside world.
