Intro: DIY Jelly Bean-style Single Switch
This is an inexpensive alternative to the AbleNet Jelly Bean Twist.
Single-switch devices are important for individuals with a wide range of disabilities. One of the most popular models is the "Jelly Bean Twist" switch, which can be used to trigger a host of different things, from toys, to augmentative communication devices.
It's a very nice product, but I think it's a little outrageous to charge $65 for some blown plastic, a momentary SPST switch, and a mono 3.5mm cable.
Thanks to ThatGuyBud on YouTube, I was able to make 4 switches for my niece for less than $25.
I'm putting together this guide because there were a few things I learned while making the switches that I didn't get from Bud's video, and I wanted to share.
Step 1: Supplies
To make this you will need:
- Learning Resources Answer Buzzers - $15
- 2x Mono (or stereo) 3.5mm Audio Cables (I bought these for $4 each)
- Cable Zip ties
- Soldering iron
- #1 Phillips head screwdriver
- X-Acto knife
- Hot glue gun
- Wire Cutters/Strippers
The answer buzzers pack comes with 4 switches, and if you use male-male 3.5mm cables, each one will provide a cable for two switches.
Step 2: Disassemble & Inspect
On the bottom of the switch are 4 rubber feet. Under those feet are four screws. I used my knife to pop the feet off.
Once unscrewed, you can see that there's plenty of room inside to work with.
The switch under here is a very simple, not ultra-high-quality dome switch. The top dome is literally held on with scotch-type tape. This is a far cry from the industrial spst momentary reed switch in the Ablenet device, but the thing is, you could buy 16 of these switches for every one JellyBean. And the way this switch is constructed, it will still be fairly durable. The potential tradeoff in longevity is well worth the affordability.
Step 3: Drill for Cable
You need to make a hole in the black ring for the audio cable.
If you notice on the bottom, there is a registration notch for the bottom so that it only fits into the ring one way. Pick a spot in your ring between the speaker and the battery compartment, on the side where the black/red wires attach to the battery contacts.
I simply twisted my X-acto knife while applying pressure to drill a small hole. You could use a drill if you want to but this was just as easy, and the results were good.
Step 4: Strip and Prep Cable
If you bought Male-Male 3.5mm cables, you can cut each cable in half and use it for two switches.
Feed the cut end of the cable through the hole.
Strip about 2" of the wire, and separate and twist the shield. On my first two switches, I tinned the shield wire as the video recommended, but this made the wire too stiff to route well.
Cut the shield wire down to about an inch
Step 5: Cut Trace
This PCB trace needs to be cut, disconnected from the circuit in order for the switch to work.
Using your knife, apply pressure and a sawing motion to make a break in the circuit board's contact.
It wasn't clear from the video, but the switch won't work both as a standalone noise maker and as an ability switch. Cutting this trace was how I chose to disconnect the switch from the rest of the electronics.
Step 6: "Drill" PCB
Again, I used my hacky spinning-knife trick to drill these holes. I tried this with my thinnest drill bit, but the hole was too large and the drill bit tended to pull the traces off the cheap pcb. Using my sharp knife allowed me to make smaller, neater holes.
Holes are not technically necessary, though I like the mechanical stability they offer. Also, I have a 40-watt weller soldering iron, and i was melting/burning the PCB trying to just tack the wires on in the proper spot. I didn't want to risk damaging the relatively fragile switch.
I found on some of the switches that the switch's tape covered the spot I needed to solder the positive lead to. I used my knife to push the tape back and scrape the PCB trace to make sure it had a good place to contact.
Step 7: Solder Wires
Attach the wires to the two places on the PCB you drilled
Step 8: Strain Relief!
To keep the wires from moving around against their fragile and hacky solder joints, I applied liberal amounts of hot glue between the wire and the PCB, the case, and even at the point where I had stripped and twisted the shield of the cable.
Once the glue hardened, I added a cable zip tie (about 1/8" beyond the edge of the bottom base) to provide strain relief. This will prevent normal pulling on the cable from straining the hot glue joints. Cinch it down tight.
Step 9: Reassemble
Reassembly is easy, just reverse the first step.
Now you have an AbleNet jelly bean for 1/10th the cost!