CD Switch

Intro: CD Switch

In the realm of assistive technology, a switch (aka "ability switch") can be anything from a plastic button to a muscle twitch sensor.  This album is a great look at the variety of switches that are available.  These switches are almost always wired to a 3.5mm (1/8") mono plug, and can be connected to anything with a matching jack. They are used with power wheelchairs, computers, speech devices, toys, remote controls, and so on.

The problem is that switches are expensive.  A basic Jellybean Switch or Buddy Button costs around $50-60 (USD), for just a plastic button.  While these are worth their weight in gold, the price is still a bit steep, especially in the low-budget/non-profit world of assistive technology.

Sometimes, it's handy to make your own.

Fortunately, a switch is a very simple thing.  It's just a circuit closing, just two wires touching.  We will use less than $10 (USD) worth of parts to let a person press a surface (in this case a CD), and touch two wires together.  R. J. Cooper also sells CD Switch Kits for about $10 (USD) each, in packs of five or ten.

Save the left over scraps from this project, as you can use them to build a No-Solder Battery Interrupter, which you can use to let this switch control toys and other devices.

STEP 1: Materials

Materials Needed:

- Adhesive backed copper foil sheet.  5"x10".
- Adhesive backed Velcro strip.  6" of each side.  
(I used 3/4", but nearly any width should work.  Foam mounting squares will also work.)
- 3.5mm mono cable with male jack.
(Buy a 3.5mm mono extension cable, cut it in half, and use the male end for this, and the female end to make a No-Solder Battery Interrupter.)
- CDs.  2.
(Old software, AOL trials, blanks, whatever you have laying around.)

Tools:

- Scissors
- Ruler
- Sharpie (or other fine point marker)

STEP 2: Trace CDs Onto Foil Sheet

Use the Sharpie to trace two CDs onto the foil sheet.  Flipping the sheet over and tracing onto the backing will help to avoid smearing ink on the copper itself.

(Place the CDs close to the edge, to preserve left over foil for use in more CD Switches or No-Solder Battery Interrupters.)

STEP 3: Cut Out Foil Pieces

Use the scissors to cut out two CD-shaped pieces of foil.  Cut slightly inside the lines, so that the pieces are slightly smalled than the CDs, and will not overlap their edges.

(Cutting out the center circles is optional, and will not affect the function of the switch.)

STEP 4: Apply Foil to CDs

Peel the backing from one CD-shaped foil piece and attach it to one of the CDs.  Repeat for the second piece of foil, attaching it to the second CD.  Attach the foil to the bottom, label free side of the CDs, or the labels may peel off and destroy the switch.

The result will be two foil lined CDs.

(It helps to peel only a small portion of the backing, stick it to a CD, and then slowly peel off the rest of the backing as you affix the foil.  This will also help to avoid causing bubbles under the foil.)

STEP 5: Measure and Cut Velcro

Using the ruler and scissors, measure and cut the Velcro into pieces of 1.5", 1.5", and 3".

STEP 6: Find Two Main Wires

Find the two main wires in the center of your cable. Some will only have two wires, while some will have a third wire, comprised of the strands that run through the outer insulator of the wire. If you cut and stripped the cable yourself, the outer insulator strands may be splayed out. If these are in the way, twist them together, fold them back, and tape them to the cable with electrical tape.

STEP 7: Attach First Wire to CD

Using one of the 1.5" pieces of Velcro (hook or loop doesn't matter), attach the tip of one of the main wires to the outer edge of the copper side of the first CD.  Make sure that the bare wire makes solid contact with the copper, and that the Velcro overlaps some of the wire's plastic insulation.  Press hard and make a firm connection.

STEP 8: Repeat With Second Wire and CD

Repeat the previous step, attaching the second main wire to the copper side of the second CD.  Use the opposite side (hooks or loops) of the same 1.5" piece of Velcro.  Again, make sure that the bare wire makes solid contact with the copper, and that the Velcro overlaps some of the wire's plastic insulation.

(Note that the two pieces of Velcro line up, so that they will stick to each other when the CDs are pressed together.)

STEP 9: Apply Velcro to Other End of CDs

Apply the other pair of 1.5" pieces of Velcro (one hooks, one loops) to the opposite edges of the CDs, as shown in the image.

(Once again, note that these pieces of Velcro line up so that they will stick together when the CDs are pressed together.)

STEP 10: Press Two CDs Together

Press the two CDs together, so that the Velcro lines up and sticks together, and the two wires line up at the edge of the CDs.

STEP 11: Apply Velcro to One Side of Switch for Mounting

Stick the pair of 3" pieces of Velcro (hooks and loops) together, and attach them to one side of the CD switch, as shown in the image.

This Velcro will be used for mounting the switch.  Peel the backing from the outer piece of Velcro and press it onto a solid surface to mount it.  Simply peel apart the Velcro to remove the switch.

(Use more Velcro to create mounting points on multiple surfaces, and move the switch between them freely.)

STEP 12: Test Your CD Switch

Test your new CD switch by plugging it into a switch adapted toy or device (anything controlled by a 3.5mm switch jack) and pressing the two CDs together.  When the two pieces of copper foil touch, the circuit is completed, allowing current to flow from one wire to the other.

(If you don't have a switch adapted device, use the scraps from this project to build a No-Solder Battery Interrupter, and use it to adapt a battery-powered toy or device yourself.)


Now experiment!  A switch is just a way of connecting two wires.  Find other ways to touch two wires together and complete a circuit.  Use some of the scrap pieces of foil from this project, along with tape, hot glue, super glue, solder, or whatever you have on hand.  You don't even have to use foil if you can find a way for the tips of the wires to touch directly.

- The fingertips of a glove?
- The end of a clothespin?
- Something spring loaded that holds the wire apart or together?
- Be creative!

Comments

[spark master]

stop wasting money, spray cd with 3M's delux rubber cement spray then invert onto a sheet of heavy duty aluminum foil , use the sticky velcro and wires as shown.

then if it wears out make more they are cheap. you could even take some finer stranded wire and place between cd and foil then press foil on then add the velcro and wire as shown for more areas of contact.

very nice instructable.

enjoy

[spark master]

Heck I swear my brain was in neutral when I wrote that use a disposable pie plate again put wire under the plate as the wires held down by the velcro, and slice them.

If you put say two perforations in the pie cut outs you can "weave the wire through then apply to the cd and the velcro ill make the top stick very nicely while the 3m stuff will keep the underside in place. contact will be longer and spread out.

do not waste time making circles put the cd and plate toghter press down , use tubber roller if you have one , then trim excess off the discs.

For a water resistant switch. snake leads through a tiny slit in a vacuum bag {stripped ends of wire are to be encapsulated with liquid rubber (RTV RUBBER GOO) allowed to cure before you do the bag part}. then you seal the hole with same goo, allow to cure. Put silica packet from pair of shoes whatever in bag, evacuate bag and seal with heat. Your switch is now in a vacuumed bag and is safe from moisture and simple spills and moisture

It is important to seal the wires to the insulator on the leads inside the bag, cause if you do not then it will draw air however slowly through the space betwixt the insulatied coating and the copper core.

walla insta Switch

it will last a good time I believe as I made similar ones in HS .

[spark master]

Help I 'm talking and I can't shut up.....

use a copper PC etching board, no need to make circles solder the leads right to the board (best connection) put tiny bead of rubber goo around the board to connect them. If you wish to make it more sensative drill a tiny hole and make a valve seal and evacute enough to pull board together, but not touch. back up that simple valve with foil patch and rubber cement.

see stuff like this

http://www.minute-man.com/acatalog/Printed_Circuit_Boards___Standard_Copper_Clad.html

they may even sell the sticky copper foil.

[gavin.philips]

Great idea, and spray adhesive like that may be easier to find than the sticky foil. Thanks!

[spark master]

Oh it is cheap to me as I have the stuff on work shelf, perhaps the sticky copper foil IS cheaper. You gotta do the numbers

none the less nice project

[patt39]

How much force does this need to be connected? I'd like to use this as a drum pad. (was just asking to make sure it does make contact at rapid rate and don't shatter on me)

[gavin.philips]

It doesn't take much force to connect, depending where you press on the disc. A person with some weakness (like with muscular dystrophy or ALS) might be able to use it.

I haven't tried hitting one with a drumstick or a mallet, but it would probably work.

If you want to change the amount of force needed, change the "buffer" material that holds the discs apart. If the velcro is too much, try gluing in some soft cloth, a few piece of a sponge, or whatever you have on hand. I find that foam mounting squares work well ( http://goo.gl/yfupg ).

[vittal]

pretty cool

[RDSawicki]

can u do this with tin foil ????

[mostly water]

You could use double sided tapes, like carpet tape, to attach tin foil.

[gavin.philips]

Good call! I wasn't sure if double sided Scotch tape would last very long, but carpet tape might be perfect.

[gavin.philips]

Sure, you would just have to find another way to solidly attach the foil to the CDs. Super glue or something might get the job done.

You just need a nice conductive surface on each CD, so that the circuit completes when they touch.

[Jodex]

Yes you can.

[mostly water]

Great job of showing how simple & affordable making a switch can be. Thank you Gavin.

[james waweru chege]

YES IT IS POSSIBLE

[dweb98]

In steps 2-4, I would do things a little differently my self. Instead of cutting out Circles and trying to then match them back to the CD's most likely ending up with miss matched pieces that are permanently stuck in place... If you've ever worked with Decals or Sticky Tape. You know how hard exact placement of something sticky and the object you want to stick it too can be! This should save you some time and frustration... I would just sit the CD's on the Sticky Foil to mark out squares slightly bigger than the CD's. Then cut out the Squares. Then, Peel the Backing off the Sticky Foil, with the Sticky Side up on your Work Bench - Table, what ever you have that it flat. Then just lay the CD's down on the Sticky Foil. Then flip them over and trim the Excess Foil with a Box Cutter or ExactO Knife, something with a thin sharp blade. Don't to this on your Wife or Mothers Kitchen Counter Top!:O She will whip your Butt if you do! And never let you forget how you completely ruined her Kitchen Counter Top! You've been warned!...;) You can use a flexible, straight edged plastic Squeegee to push the Air Bubbles out to the edge of the CD's, to get rid of them. Now a Days, I just use the ones that came in Some Auto Body Bondo that I bought a few years ago ( I keep them clean enough to reuse).They sell them all over for putting on Decals though. You can also use your fingers and thumb to Push the Air Bubbles to the Edges of the CD and eliminate them that way. An old trick for putting on Decals may help here. But, I'm not sure just how sticky the Sticky Foil is, since I've never actually worked with it. But, you may be able to use a wet sponge, dipped in water, squeezed out so that it does not drip, just leave it damp. Before you stick the CD's down on the Sticky Foil, just swipe them lightly withe the Wet Sponge. This will make it allot easier to wipe out the Air Bubbles after you stick them onto the Sticky Foil. I would just try one first and see how well this works, before doing them all this way... Ok, now you're ready to finish building your CD Switch and you didn't mess up any of your Foil and end up with stuck together forever pieces, good for nothing but the trash;)

Don

[lackofindian]

Thank you for realizing that my wife is worth just as much as my mother's kitchen counter.

[dweb98]

Oh! and I think I forgot to say... Nice Switch and a good idea!:)

Don

[dweb98]

Ha Ha! Well, I just didn't know if you or the readers, would have a wife or a mother... But I figured one of the two would apply:) Either way, I've been there and done both;)

Don

[RDSawicki]

this thing was actually pretty cool =]