You've probably seen the Most Useless Machine before, but I thought it would be fun to build a temporary one with littleBits modules. For those of you who haven't seen it, this is the machine that does nothing except turn itself off as soon as you turn it on. littleBits provides all the electronics you need to build a Most Useless Machine, so I borrowed my nephew's Premium Kit, added the "Double OR" and toggle switch modules, and I was ready to go.
This Instructable is mostly about the electronics (there are plenty of write-ups on building the enclosure) so I'm just describing a basic setup here. You can add your own enclosure once you understand how this machine works.
The theory behind this setup is straightforward due to the functions of the littleBits modules.
- Power is split by the Branch module to both the toggle switch and the roller switch. At first, both switches are off.
- Then, both switches feed into the "Double OR" module. This means that if either switch is on, then power is supplied to the rest of the circuit.
- The servo motor is configured to swing, so when the toggle switch is turned on, the servo swings the shutoff arm to turn off the toggle switch.
- At the same time, the servo triggers the roller switch, so the servo continues to run. When the servo swings back to its original position, the roller switch is turned off, thus turning the entire machine off.