Transistor Man

For Halloween of 2012, I went with a dead simple idea. I wanted to make something. I also wanted it to be interactive, something a little different for all to enjoy. What I came up with is “Transistor Man”.

Scroll down to see pictures of the shirt front, back and the electrical schematic.

The costume is a white t-shirt I purchased from [big-box store] in a 5 pack. Blue sharpie provided the “art”, and an old yogurt container lid provided the support for the one-transistor circuit. The two metal contacts I’m touching in the image below are bare metal buttons I purchased in a 10-pack from Michael’s (the craft store).

The circuit just lights up two blue LEDs inside the shirt whenever there is a very very small amount of current flowing between the two metal contacts, which is why it works when a person touches both metal contacts with their hands, elbows, cheeks… etc. It is most enjoyable when you get a whole room full of people to hold hands and the two end people each touch one of the contacts!

The back of the shirt. Just for fun!

R_HUMAN is the resistance between the two metal contacts. It is essentially infinite (or 'open circuit') when nobody is touching them.

R_limit is a resistor that limits the current through the two LEDs, or they might blow up…

The battery is a +9Volt type.

The “PN2222A” device is where all the magic happens. It amplifies the very small amount of current entering it to drive the two LEDs.

A few things I learned from putting this together:

• Elmer’s white glue is conductive, initially I wanted to cover the whole thing in glue to make it more robust, but it ended up turning on the circuit permanently…
• licking your fingers improves your conductivity greatly!
• 9 Volt batteries can last a loooong time if left unattended (it still works just fine, over a year later)
• Simple can be fun!