Electronics > Beginners
Basic Function Generator help
rstofer:
--- Quote from: dcbrown73 on August 06, 2019, 06:57:31 pm ---As suggested above. I will remove the 3rd pin from being connected to the gnd rail (which is sitting at -9v)
--- End quote ---
I missed what you said.
There are 3 wires to deal with: +9, -9 and Gnd. If you are talking about using one of the 'blue' rails for Gnd, well, that's pretty much what you have to do. You need 3 rails running down the side; 2 on one side of the board and 1 on the other. It makes sense to have the + and - on the same strip with Gnd on another strip.
rstofer:
It may not be obvious on the schematic that the output pin of the first op amp is connected to one end of the pot and one end of the 100k resistor. The 'dot' is a little small. I didn't try to trace the wiring...
Also, the wiper on the pot is not shown as connecting to one end of the pot. It is shown just dangling in space. I think this was discussed above.
dcbrown73:
Okay, I rewired the board with short 22 gauge wire, a smaller pot, and I obtained a film cap. Hopefully it's more clear how it's connected now.
The cap I've had both connected to -9v and not connected (as you see in the picture)
Here is how the power supply is wired.
Now, I actually got it to produce a square wave (once) at close to the supplied voltage, but it was operating at 1hz. I was expecting much higher.
Most of the time, I'm just seeing a terrible looking sine wave in the mV range sitting right around 60hz which I'm guessing is just AC ripple.
What is weird is I had the square wave. I turned the output off on the power supply and when I turned it back on. I started getting the 60hz, mV sine wave. Without changing anything.
A majority of the time, I'm just getting the sine wave. (you can see the counter) I generally have to turn the PSU completely off and come back later before I see the square wave again.
Clearly something is wrong. :(
bjbb:
Missing a 'ground' equipotential that would be the return reference.
dcbrown73:
--- Quote from: bjbb on August 10, 2019, 02:55:59 pm ---Missing a 'ground' equipotential that would be the return reference.
--- End quote ---
Are you referencing the cap not being connected to ground in the first picture?
The second picture shows I did connected, it just wasn't connected in the first image.
That begs the next question. Since the rails are +9v / -9v. Do I actually require a GND (0v) potential also?
For instance, when I measure the waveform with my scope. Do I connect the gnd connection to the -9v rail?
It's a bit maddening. Earlier someone said you need to ensure my rails are +9v / -9v for this to work, but I saw a video of someone powering the entire thing with a 9v battery which didn't produce a -9v rail.
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