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Convert a keypad into a large single switch? Answered

Hi Guys,

I need a simple switch with a large footprint to light up an LED bulb. I was thinking to use a 12 or 16 key membrane keypad or maybe an old keyboard keypad and rig it for this purpose but I've never used either of them for anything like this.

My switch will be DC momentary switch with probably not more than 3.5V maybe 6V running through it off a battery. To make the entire keypad a sort of big single switch, would it be a simple matter of gathering all the positive wires from each of the keys together into one common wire and do the same with the negative wires or, maybe they have one ground wire? Then if any of the individual switches get pressed, will the switch activate ok?  If so, if two or more of the keys are pressed at the same time, will that cause a problem, like a short or over heating?

Please let me know. Thank you so much!!!

Bretina

Tags:keypad

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caitlinsdad
caitlinsdad

6 years ago

https://www.instructables.com/id/DDR-metal-dance-pad-PS2/ , you can even make do with aluminum foil, some foam, and cardboard. You shouldn't need to factor in the complexity of digital switching and pulses from a keyboard if all you need is an on/off switch.

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Bretina
Bretina

Reply 6 years ago

That's a great tutorial and definitely in the right direction for all I need. It clears up some questions - Thanks! However, mine needs to conform to a curved surface, I'm putting it on the outside surface of a ball about the size between a volleyball and a basketball and the switch will be circular with about a 6" diameter. Here's how I see it now:

1- Aluminum foil over the surface of the ball and secured to it along the edges.

2- A foam or rubber sheet 6" OD flat ring with 5.75" ID, secured over the aluminum layer.

3- A 6" OD metallic disc over and secured to the flat ring.

4- Connect one wire to the aluminum and another to the metallic disc.

So the remaining question is the material of the metallic disc. It will need to allow itself to be evenly laid over the curved surface and also be resilient so it will immediately open the circuit after it's released and be uniform. If spring steel is available in thin sheets I could hammer a slight dome shape into it. Do you think this is a good idea or something else?

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caitlinsdad
caitlinsdad

Reply 6 years ago

https://www.instructables.com/id/Flexible-Fabric-Pr...

https://www.instructables.com/id/Flexible-Fabric-Pressure-Sensor/ You can also do that so it looks like a giant softball. I don't know what your budget is or if you want to overengineer this thing. You can have a tinfoil wrapped core. Cover it with thin sheet foam that has large holes perforated throughout. Using a template for a globe, cut strips of the metal to place over it, you can rivet, tape, nylon tie-wrap all the pieces together or use copper for the steampunk soldered together with wire bits. You can also try to glue aluminum foil on the back of fabric to use for your outer covering and sew that together. The outer surface can be pieced together and joined by wires to be one electrically. Basic principle is to have a floating layer that connects when the foam support is squished around the open spots. Try just striping your inner sphere with foam mounting tape strips(longitude/latitude) and apply the outer shell. You can even make a fancy quaffle shaped thing if needed.

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Bretina
Bretina

Reply 6 years ago

Great suggestions! I think the easiest them would be the foam mounting tape, if I can get it in a sheet, then cut out two rings and have it be both the bonding adhesive and floating layer between the metals. If the open area is too big and the curve creates and physical arch making them touch at rest, I can add some more small pieces of the foam.

I think I've got it now. If I get stuck I'll be back. Thanks so much for your help! :)