In making a project with conductive paint, I wasn't entirely happy about the paperfold switch I used. The paper fold switch is simple, robust, and easy to make, but it was a momentary switch. For some electronics projects I want a permanent switch.
To that end, I'm beginning to prototype some solutions. One possibility I've been exploring is the knob switch, like the knob on your stove top. Although not a potentiometer, but a simple on off switch. When turned 90 degrees the knob switch starts or stops current.
Step 1: Tools and Materials
Twist awl (not necessary, but useful)
Paperboard or cardstock
Copper tape — I used Rentokil "Slug and Snail Barrier Tape" found in home and garden supply stores. Be aware that the adhesive side is not as conductive as the top side.
Coin cell battery
Three brass fasteners (3/8" long preferred)
Step 2: Cut the Card
I cut out a 2" x 3 1/4" piece of cardstock for the platform and a 3/4" x 4" piece for the switch.
Step 3: Fold Switch
For the switch, fold paper into quarters.
Step 4: Attach Copper Tape
Fold the paper strip into a triangle and attach a 3/8" x 1" piece of copper tape to the bottom.
Using the twist awl or the craft knife make a small hole in the bottom of the switch.
Step 6: Layout the Circuit
Layout copper traces about 5/8" an inch apart and insert fasteners on the end (this is to insure good contacts with the switch). For aesthetic purposes, you can cover the fasteners with copper tape.
Step 7: Get It Together
Add the components:
Apply copper tapes to the tops of the battery and LED leads and fasten the switch to the middle of the gap.
Step 8: Mission: Accomplished
By twisting the switch, the copper makes contact with copper. You now have a complete circuit.
Step 9: Variations, Improvisations, and Meditations
I originally intended to make the knob switch with conductive paint, but ran out. As soon as I get more, I'll try making a switch with it. But I must say I'm happy with copper tape and think it would make an excellent medium for teaching electronics.
As you can tell from my sketches, I wanted to make a small plastic knob. If anyone knows of a good source of plastic bits in the UK, please let me know. I'm also exploring ways to make the switch more two-dimensional, maybe I'll make a switch that you can move with a pencil point.
A knob switch would also be useful for soft circuits. Elizabeth Perry, who helped me out in thinking this through, also suggested surface mount LEDs. She also told me not to miss plusea's Instructables. Don't you miss them either.
You can also check out this soft-circuit permanent switch.