How would YOU go about....?

How would YOU go about making a button pad circuit without PCBs.

You have a calculator button pad with the little conductive circles on the other side. How would you make the circuit for it… without a pcb.

Aluminum foil?
Pencil lines?

I was thinking about this when I searched through my junk box and found my button pads :slight_smile:

Looking for:
Clean result

I wouldn’t be so crazy as to do this unless I had no choice, but something that could be tried:

  1. Get a 2 or 3 liter bottle, remove the label and any glue residue, cut the top and bottom off, and a slit down one side of the resulting tube.

  2. Use an oven to heat up 2 pieces of 1/4" sheet steel to around 246 C (250 C is the melting point of PET - we just want to soften it).

  3. Carefully unroll and place the piece (you might have to cut it into smaller pieces) of the 2 liter bottle between the two pieces of steel, and continue to heat in the oven for a few minutes (this would require some experimentation, and I am not sure you would want to use your home oven for this!).

  4. Remove the “steel/PET sandwitch” from the oven, and let cool. You should end up with a pretty flat sheet of PET material.

  5. Cut three squares (or whatever shape) of the PET material out; they should all be roughly the same size and shape.

  6. Take one piece, and use a hole punch (or other tool - a tarp grommet punch will work; you ultimately want clean edges to the holes) to punch holes where you want your buttons.

  7. Take another piece, and lay out strips of alluminum or copper foil where the button will be; do the same for the other piece, but run it perpendicular (this is important if doing a grid of buttons - also, remember that one side with the foil will face up and the other down).

  8. Attach wires as needed.

  9. Make a sandwitch of one of the foil sided/trace PET pieces, then the punched hole PET piece, then the other foil sided/trace PET piece, aligning the pieces properly.

  10. You could glue the pieces together, or use an old soldering iron or other heat source to melt the sandwitch together, or use nuts and bolts, or screw it down to a backing material (wood, metal, plastic), or rivet it together (there’s even plastic rivets!).

  11. You would probably want to paint or otherwise indicate where the “buttons” are on the upper PET piece. In theory, if you used some form of resistive contacts, you could make a “touch” variable resistor, or a variable resistance “button”, etc.




cr0sh is good at that

its simple really, people make similar out of double sided sticky foam

If I were doing it I’d ignore “clean” and go with wire and tape. I’d tape bits of wire so there’s two ends under the button, and I’d do that for each button. I’d have a common positive wire for each button, and the other wire (one for each button) would have a different resistor on (not a mutliple of any other resistor either). I’d connect all the ends of those wires to one analog pin and ground, so it’d give me a different analog reading not only for every button pressed but for every combination of buttons pressed. In theory.

In theory.

This actually works well for a certain number of buttons, if you can find the right resistors. The problem is finding the right values of fixed resistors to handle the number of buttons to give you unique numbers (well - “ranges” - since resistors aren’t perfect) for each button press (or combo).

If you could set it up so that the resistances were calibrated in powers of 2 (perhaps using trimmers?) - or something close (fixed or adjustable, you would want ones with tight tolerances)…

After going thru that much trouble, though, it might be easier to do with some kind of multi-bit BCD encoder chip or something like that…

Well I did say I was ignoring the ‘clean’ bit :wink:

@cr0sh LOL! We live in AZ… You could just take it outside and melt it!

You could just take it outside and melt it!

In this heat, you better believe it!

A few years ago I built a solar oven that I managed to make “cornbread” in - unfortunately, I overcooked it and it was like a brick!

I still find it amazing that there is so little solar tech and such here in the valley; what does exist is a tenth of what should be here.

@cr0sh Yepp! You can noly do that here! And yes! Seattle has more solar than AZ!

Sorry for the thread jack BTW.