Triple Function Generator project

Some earlier discussion on PCB cleaning:

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I do nothing cleaning-wise, and i’ve never had any problems.
YMMW wrt. flux use, of course.

Two pictures from the TFG:


My PCB kit arrived last week, still trying to track down a couple of components though.

With the 4.2k resistor, 4.32k is listed as an alternative; I have 4.3k resistors on hand, would they work as well?


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!