Making two of these while using a single TL074 was my hope! I still wonder if it is a transistor issue.
I built this one using the same power set up lower down on the breadboard and it seems to work perfectly. I would just have to have another entire TL074 to build a second one which seems crazy if I can get the first one to work.
is it not a too big voltage for a 12V utilisation ? i know that not good to use a too big difference, which under exploits the capacitor and can damages it more quickly, but i don’t know where is the limit .
I have been bouncing back and forth with this and I think I’ll use the David Haillant’s LFO and mash it together with @juggle 's clock divider. Somehow. I wonder if I could squeeze it on the board somewhere…
" Condensateur de 63V pour montage alimenté en 9V ?
A de rares exceptions près, vous pouvez utiliser un condensateur dont la tension de service est très supérieure à la tension qu’il se verra réellement appliquée, par exemple tension de service de 40 V dans un montage alimenté en 12 V. La tension de service indiquée par le fabricant est en effet une indication de valeur maximale. A noter toutefois que pour certains condensateurs, il n’est pas conseillé de choisir une marge trop grande (par exemple prendre un condensateur 100 V pour réguler une tension de 5 V), sous peine de les “sous-utiliser” et de les vieillir plus vite. "
63V capacitor for assembly supplied with 9V?
With rare exceptions, you can use a capacitor whose operating voltage is much greater than the voltage that it will actually be applied, for example 40 V operating voltage in an assembly supplied with 12 V. The operating voltage indicated by the manufacturer is indeed an indication of maximum value. Note however that for some capacitors, it is not advisable to choose too large a margin (for example take a 100 V capacitor to regulate a voltage of 5 V), under penalty of “under-using” and aging them. faster.
It’s quite a desperate move but maybe someone has an idea, here is my breadboard (some legs are long I know, but they are not touching). +12V and -12V are stable but I get only some DC values on the outputs.
I am sure that the circuit works since @Dud has three of them demonstrating in a video but I don’t understand it
I also noticed that in the stripboard version the LEDs are backwards connected. I thought that the electrolytic caps might be wrong as well so I checked and reversed them. Then I see only a very slow raise or drop on Pin 7 (second output - TRI) which then saturates at the maximum level. If I adjust the shape or rate, the signal starts to move but again, stays after many seconds at some saturation voltage.
Any ideas? Has someone maybe successfully simulated that in CircuitJS or so? I am currently clueless… usually I do not give up that quickly and ask for help but this is now bugging me since yesterday evening
Here is my breadboard (notice that I replaced the trimpot with two 27k, so it’s basically in the middle position (the two tiny carbon resistors joining Pin 1 and 7).
They’re seeing bipolar voltages, so I’d be wary of polarized electrolytics there. In the oscillator mentioned below I use 220 nF for fairly low frequencies, but if you need much lower (22 µF), bipolar electrolytics might be a good idea. Anyway, I would not think reversing these caps would do much, since the voltage isn’t polarized. Or at least, it isn’t if it’s oscillating, which it isn’t… Yeah, if it’s not oscillating, and there’s a large enough DC voltage on them, then polarized electrolytics definitely are at risk!
I’D SUGGEST IMMEDIATELY SWAPPING IN THE BIGGEST FILM OR CERAMIC CAP YOU’VE GOT FOR NOW, TO AVOID A LOUD AND POTENTIALLY DAMAGING INCIDENT. Once it’s working you can go back to the electrolytics, though, again, I’d use bipolar ones.
It’s fairly similar to this one
which has some description of how it works. (And I’ve built that one, it does work — simulated it too, in CircuitLab.)
There the feedback and input resistors on the comparator are 220k and 100k, so the comparator flips when the triangle wave reaches about ±6 V. In the schematic you’ve used there’s instead a pot which would allow changing that amplitude, but if it’s centered then the comparator would not flip until the waveform is at about ±10.4 V, i.e. the maximum output of the TL072, and if it’s slightly beyond centered so the feedback resistance is smaller than the input, it seems to me it would not oscillate at all. If so then half the range of the trim pot is useless. And in your build you’ve used two resistors to sit somewhere close to, maybe just the wrong side of, the centered value. Maybe try something like a 20k for the input and 30k for the feedback instead.
Disclaimer: I haven’t had breakfast yet. My ability to think is suspect. The above paragraph may be dead wrong.