I’m really stuck. I used a super simple design. It worked on breadboard, so I put it on strip board and finished a module that worked with my simple opamp LFO clocking it. I played with it and jammed it for a couple days and then it just stopped working. Breadboarded it again and it still won’t work with the LFO. So my design worked on breadboard then on strip board and then it didn’t work on either one I’m so confused…
I used inverting opamps for the clock and reset. I couldn’t get the inputs to work as drawn. But when I bredboarded it with the inverting op amps for the inputs everything worked. I built the module and everything worked. Now nothing works. I’ve now completely eliminated any opamps at the inputs, and I can get it to work with a 555 pulse clocking it. I can sync my LFO to the control pin on the 555 and get that to work… somehow. I just need to understand why…
What’s the LFO voltage amplitude? Does the momentary step button work? Do you have an oscilloscope? Have you tried different TL072 and 555 chips? Have you tried a smaller value for R2? Smaller/larger values for C1 and R9?
The step and reset push buttons probably should move to the other side of C1/C2. C1/R9 and C2/R10 are pulse shaping networks, you want to inject your pulse upstream of them.
I couldn’t get that part of the circuit to work at all. At first I just changed the configuration of the op-amps to inverting amplifiers and left the switches out. I just use 100K resistors between the inverting and the output. I grounded the noninverting and had a 100k into the inverting. With that set up for the clock input and the reset input I had a working breadboard and a finished module that worked for a couple days and then while I was designing another circuit and using my LFO to test the modulation, I noticed when I plugged the LFO back in to my clock divider it was no longer working. That’s when I decided to breadboard it again and the same result. It no longer worked with my LFO. I completely redesigned the circuit and now I have it somewhat working with the 555 setup. I’m just totally confused as to why? The amplitude on the LFO hits around +6 to -6v, to answer question 1. I don’t have a scope. I have used a couple different 4024s as well as interchanged the TL 072 with an lm358 as well as other 72s. It’s as if the circuit should not have worked at all as I built it…but It did…I swear!
It’s hard to know for sure with just a word description, but if you didn’t have the protection diode in that circuit, you might have damaged your CD4024 with negative voltage on its input.
Are you using a rectangular wave output from the LFO? The pulse shaping circuit needs a sharp rising edge.
As @analogoutput mentions, you could try a lower threshold for the comparators.
Note that the CD4024 input has a Schmitt trigger so the pulse shaping circuit is not necessary. (That’s why the circuit worked with the opamp set up just as an inverting amplifier.) The pulse shaping circuit is actually detrimental as it requires a sharp edge and thus prevents usage with sine and triangle waves or random audio inputs.
I wouldn’t recommend that, as it would short the previous module’s output to VCC.
Problem with the schematic: one side of R12 is not connected.
I was actually using the triangle and a square from the lfo. Either one was working the triangle was actually working better. Was. As I stated everything just stopped working with the lfo. I don’t even use the buffer inputs now. I’m just curious as to why a circuit that was working which suddenly stop when none of the conditions have changed. I cannot recreate the experiment either. The circuit I built that worked seemingly does not work at all. I’m just confused.
So the schematic you posted isn’t the circuit that isn’t working? It’d be more helpful if you showed the actual non-working circuit.
If you don’t have a comparator, if you’re just feeding the LFO through an inverting op amp to the 4024, then its amplitude needs to be large enough to fire the 4024. For a 12 V supply it’d have to be above about 8 V. What’s the gain of your inverting op amp?
The CD4024 has an internal protection diode network, but relying on that may not be a good idea.
Good point, needs some protection there.
Another point is that the pulse shaping as shown will determine the width of the /1 output making it around 1 ms long. (The other outputs’ widths will be determined by the timing between input pulses.) You’d more likely want the /1 output to be the same width as the input, without any pulse shaping.
Ok. I’m sorry to confuse. Only posted the picture to somewhat illustrate part of the circuit I actually used. the only part of the diagram I used is the 4024. Just the outputs. I built the circuit on the diagram and I couldn’t get it to work at all that’s not my concern anymore. I got a circuit to work. I just used inverting op amps to feed the inputs. The breadboard circuit work so I built it on a strip board. I put the module together with knobs and Jack sockets. I jammed it out. After 2 days it stopped taking any inputs. I had to completely redesign the inputs. My only question is hypothetical. Can anyone think of a reason a seemingly functional module would just stop working? I have tried to recreate it on breadboard and get nothing. I had to completely redesign the circuit to get it to work I just don’t understand. I currently have it working on breadboard as driven by a 555 timer that I can sync up to my lfo. I’m not having any problems getting that to work at the moment I’m just curious as to why the other circuit just doesn’t work anymore. Theoretical. It’s eating my sanity away…lol. I don’t need a solution so much as an understanding of the malfunction…if that makes sense… It seems that it should not have worked in the first place. That’s what is confusing me the most. Lol. I can accept that it should not have worked but it did. That’s what’s difficult for me to get around. I’m just stubborn.
You kind of keep asking that question but without knowing exactly what the circuit is, without seeing your build, it’s pretty hard to answer. Advice is draw a schematic of what you built, or (less preferably) a stripboard layout, post that (clearly marked NOT WORKING) along with photos of the stripboard top and bottom.
I read you. A schematic is on the way. I just have to sit down and draw it up. I appreciate the commitment to this query, sincerely. Theoretical as it is at this point, it is important for me to understand the malfunction going forward with another redesign that is currently working. I anticipate unforseen problems and I need to understand the failure of my previous build. So I will draw up a schematic for the previous attempt as well as the one I now have working on breadboard. Once again, thank you. It’s on the way.
I’m using 12volts. 5 volts doesn’t seem to work as well. Haven’t tried anything in between. I’m using the 1M resistor between pins 6 and 7 of the 555 so my LFO will have time to complete it’s longest cycle ( abt 6 secs) before the 555 retriggers itself (10secs plus…). It is working (not very stable yet) on all outs as high and as low a frequency as my LFO will go…so far…
On the top, the inverting amps have gain -1, so if the LFO is ±6 V then you’re sending ±6 V to the 4024. The -6 V isn’t too good, though might not be damaging. The +6 V is too little to trigger the 4024.
You should not be sending the LFO signal to the reset pin.
It shouldn’t work, so if it did at one time, something must have been different.
A comparator followed by a series diode, as in the original circuit, but maybe omitting the pulse shaping stuff, would send 0 V / +10.5(ish) V, which is high enough to trigger. As is the output of the 555. Inverting amp (with series diode) replacing the 100k feedback with ~180k probably would work too, but I like the comparator without shaping, because that gives you a full-width pulse you can send to the /1 output.
So you think it’s worth trying the originally posted circuit with just a comparator driving the input and without the pulse shaping components? Any thoughts on the currently working schematic? Worth putting it on a strip board? I’m not planning to use the /1 out, btw. I hadn’t wired it up in either build. I’m gonna try what you’ve suggested with the comparator on breadboard…
6V is too little to reliably trigger the 4024.
But is is not impossible that it could work, in fact it is very possible that that is exactly what was happening, with the correct conditions of temperature, star alignment etc, the circuit worked, but something changed and 6V was no longer enough to trigger the 4024 and it stopped working.
The -6V may also have damaged the circuit just enough not to work anymore under those conditions.
So with more amplification and some negative voltage protection the circuit should work reliably.
Yes, that should work. Replace C1 by a short and remove R9.
If you want to use SW1 for manual stepping, add a 100K resistor in series with SW1 to avoid shorting out the previous module’s output. You may also need to add a small capacitor to ground on the comparator + input to debounce the switch.
A revelation. Thank you. I needed to know that it was theoretically possible, but that it probably shouldn’t have worked to begin with. Star alignment for sure. Righteous. I will give the original build another shot with your suggestions. Any thoughts on the 555 design? Is it worth exploring farther?
I think using an opamp gives you more control over signal conditioning and the resulting circuit will be easier to understand for others looking at it.
Well, then maybe also change the transistor configuration into something more conventional? Putting the LED and resistor between the emitter and GND looks odd to me. I’ve not seen that unless the transistor is a PNP type. In my experience it would look more recognizable as a driver when you put the LED and resistor between the V+ and the collector and connect the emitter to GND using an NPN transistor. Also, then use a series resistor (e.g. 10k or more) to control the base.
But that may be just my preference.
The outputs are configured as emitter follower buffers, that’s a pretty conventional circuit.
One advantage here is that a single transistor is used to drive both the LED and the module output.
Another advantage is that it doesn’t require the base resistor that you suggest adding.
The redesign you suggested worked! Thank you so much. I took out the pulse shaping components and the switch and it works like it should. I think I may not have been using as much resistance between pin 3 and 1 on the op-amp in addition to other things.
It seems that it should not have worked in the first place. That’s what is confusing me the most. Lol. I can accept that it should not have worked but it did. That’s what’s difficult for me to get around. I’m just stubborn.
Star alignment for sure. Righteous. I will give the original build another shot with your suggestions. Any thoughts on the 555 design? Is it worth exploring farther?