A raspberry Pi that will stand the most intense electromagnetic and electro static environments and cope with EMP (Electro Magnetic Pulse). The sort of environment around tesla coils.
I started with a Pi and a Adafruit Pi-Plate. My first job was to create a optic-fibre link (115Kb/s) for comms to my tesla coils and it also doubles up as a remote and insulated tty console for the PI. The chips I used for the fibre are the Avago 1524/2524 1Mb/s fibre transmitter/receiver.
The transmitter is driven from a Microchip TC4428 which takes the 3.3v TX to 5V and gives the current drive for the TX LED .The RX is level shifted and inverted using a BC337 (update – a speed up cap was added to the base as at 115kb Rx errors were seen)
I realised that the Pi would have to run on its own power supply, so 6 rechargeable AA cells giving 7.2V were added, along with a 7805 regulator to give 5V for the Pi and a couple of diodes to allow the batteries to smoothly take over when the external power was removed.
As the power connector is open to the EM noise on the out side of the case, there is a diode , a cap and a 30V TVS across the power input.
It also became apparent that there was no way of cleanly switching off the Pi without connecting a network or terminal. So I added a button and a script to shutdown the Pi (although not cut the power).
A Pi Cam was attached and bolted to the case, A small hole lets it see the outside world without letting in too much radiation. I also added in a sedcond button which allows the camera to be turned on and off. The script makes the camera take photos every 10 seconds. (I hope to add video too)
I added a removable panel that cover’s the USB, Ethernet and Fibre ports. This is not ideal as I can’t close it fully when I’m running on fibre.
I also added a shutter that goes across the external power/charging connector to further protect the circuits.
A quick test proved that the Pi can run when sat on top of a small tesla coil.
The camera also worked, but the breakout was too close for the camera to give good photos.
A monocle (50mm lens with 50mm focal length) was added
Giving a couple of goodish photos of the discharge from under the breakout point. (breakout is the wiggly black line to the LHS)