Triple Function Generator project


4.2k is hard to find, so anything that comes close is usable

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Question on switch wiring - can someone indicate which numbers on the DPDT pinout diagram on
correspond with A B C D on the pcb? Thanks!

the dpdt switch has 2 rows of 3 pins.
1 2 3
4 5 6

connect A & B to row 1 (2 & 3)
connect B & C to row 2 (5 & 6)

the switch makes or breaks a single connection between A & B and C & D
So two of the pins are not used, they are ‘open connections’

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Just finished one channel of my build. My video setup is still a work in progress but this makes a fun waveshaper/folder(?)/rectifier for audio, especially when gradually adjusting audio input level before going into the TFG :star_struck:


The buildguide is almost done, sorry for the delay!

and here it is: (as PDF downloadable)

direct link:


Hi Martijn,
Could you comment on the intended function of the toggle switch?
By my reckoning it looks like when in the A-B position it increases the bias of the first op-amp’s negative input (i.e. moves the virtual ground slightly higher) and when in the C-D position it adds in a little bit of negative bias to the input of the summing last op-amp.
So I think the two switch positions shift the output voltage level, and change the position of the three adjustable bands slightly, which is essentially confirmed by what I see on my scope. Is that right or have I missed something?

EDIT: Never mind, I’ve worked out that it’s a bipolar/unipolar selector, switching the midpoint between 0V and 0.5V. It all made sense when I scoped it with a +/-1V ramp wave input rather than a +/-12V sine :slight_smile:

the switch sets the range of the lights-mid or mid-darks
just plug in a video camera source and you will get it :slight_smile: -> by adjusting the pots I mean

fixed the buildguide, thanks @GijsvO
the R4 / 100r resistor was not in the guide, now it is :relaxed:

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Are there any videos of this module in action yet?

Just open this up in three tabs:

In all seriousness though, the Sandin IP Function Generator module in that clip is what the Triple Function Generator is based on. The Triple Func Gen just has 3 of them in one module. I can’t remember if there’s any normalling or not. Still, I’d definitely like to see someone using a Triple Func Gen on R, G, and B channels, so hopefully someone posts something!

Yeah, that’s kinda what I was getting at, using all three in parallel or series for colorization or feedback. Need to see that :slight_smile:

I’ll try to make a video of this tonight
uploading to video right now. but internet is slow here …

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here it is:

patch info:
Camera -> sync generator -> video input -> TFG -> RGB encoder

I play with the brighness and contrast levels in the beginning of this movie, this has a lot of effect on the color shades and ranges.

For the rest I play with all the knob settings and switches to explore the different color values and inversions.

note: the scrolling color if the result of my crappy CCD camera, not the module.


Thanks again for making this project a reality, Martijn–really digging mine in a very similar patch as above and looking forward to the matrix mixer!

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Hello! I have a question about the pin connection on the switch. My reading of the build doc makes me believe that I have to crisscross the leads coming from 1 & 2 and 4 & 5 (see my drawings pictured below please).

Based on your comments above, I think I really just need to match up A & B with 1, 2, or 3 and C & D with 4, 5, or 6.

Am I understanding this correctly?

Thank you in advance for the help! Trying to get this project done before I have to go back to work. Great build project!

Those two drawings are electrically equivalent, but i think you may be trying to mount the switch the wrong way around. This would reverse the direction of the switch paddle,

Since the panel is unlabeled this is not all that problematic, but if you’re worried using coated wire of sufficient length would allow you to turn the switch around later.

switch copy

you can look at A and B as an on/off connection.
The switch makes a connection with 1&2 or 2&3 + 4&5 or 5&6
So you can solder it as shown in the picture.

The build doc says this:
Mount the DPDT switch to the panel. Use resistor leads to solder PADS A, B, C, D.
The switch looks like this: six pins, in rows of three.
1 2 3
4 5 6
Solder pad A to ‘1’ , pad B to ‘2’ , pad C to ‘4’ , pad D to ‘5’.

So both drawings are correct.
But the switch does not have a direction, so you could also connect A to ‘3’ and B to ‘2’,
or A to ‘2’ and B to ‘3’

Thank you very much for your response. I used coated wire that I had on hand. That worked for me. Plus the coated wire is more bendy than the leads, which made it easier for me. Thanks!

Thank you for adding the drawings. I love it! And it is very helpful!

I was making this more complicated than I needed to (probably “as usual”). I have finished up the first TFG and am starting on the second one now.

Thank you for your response and the help!