Updated 2018-12-02: More precise required material
I was looking for an Octopi case with extra space for a relay board but didn't find one which matched my needs.
Therefor I designed my own which houses a Raspberry-Pi 3, a self made Relay card and mounting material. The idea was to have to relais to control the power of the printer and the light as well as one DS18S20 for measuring the temperature.
What you will need on material:
1 x Raspberry-Pi 3
1 x simple Relay card (1 made one myself using 2 Relais, 2 x 1N4007, 2 x BC548 and 2 x 3k9 Resistors)
2 x Relay HJR1-2C-L-05VDC
1 x DS18S20
1 x 4mm socket terminal strip 5 units (PA12)
Kabel and power plugs , and sockets
3 x KSS AGR12L cable grommets for 4mm cabels
6 x M3x25 Screws
6 x M3 Nuts
Through the first grommet I mounted the main power cable
Through the second I mounted the light kable and the sensor cable
The third grommet is used for the printer power outlet.
I used connectors male and female to connect the printer and the light without cutting the cables.
The four bigger holes in the corners are used to screw the thing below the printer case using 4x35mm wood screws.
A SPECIAL NOTE AND WARNING!
The relay is able to hold 2A at 220V but not able to switch it. So never turn off the printer while printing or the relay might be damaged! Maybe look for another type which is equal size but able to switch the printer while printing.
Only assemble the electronic while all cables are disconnected or you may be hurt or your electronic equipment distroyed!
Please post your makes as "i made one"!
The cover (Deckel) needs to be printed 180° turned
A little bit of filing maybe
After printing you may have to file the upper edges of the openings for the lan and usb sockets if the Raspberry Pi keeps staying up on its back side.
Maybe you can avoid that when you print with supports everywhere.
I personally did the filing as its only a bit to do and the work to get out the supports and cleanup everything than is more work.