Automotive Isolation Box

2012-09-03 01:47 by Ian

This is a brief construction log of the barrier that sits between the computer and the hostile electrical environment found in a car.

Design goals


We're going to build this one vertically off of the inside surface of the lid. Here is the terminal stack (other side of the perf board), the solid-state relays, and the supply wires to the alarm.
The inside surface of the lid.

Second layer is a re-purposed DC/DC ATX PSU. I have removed the ATX connector.
Lid after wiring the relays and mounting the DC-DC board.

This is the trick I'm using to mount PCBs that do not have mounting holes.
Mounting PCBs without mounting holes.

I went three layers deep to get as much circuit into this box as possible.
This one has three layers.

Inside of completed box. The top perf board contains a digital audio switch, 4 optocouplers, and a voltage monitor circuit to ensure the PSU comes up in the correct state. Since this board also has the header for the external connectors, the relay header (with inline resistors) connects here as well.
Completed box: Opened

Completed box with computer interface cable attached. The three audio jacks will run to the radio (input), a non-committed input, and the stereo (as the common output). There is a third possible input, but it is connected internally via the DB15HD cable.
Completed Box: Closed

An abbreviated test configuration, to make sure everything plays nice.
Box in test setup.