The picture above is of the safety circuit, it is mandatory according to the regulations of the Shell Ecomarathon. In the vehicle it will be plugged into safety buttons and a Hydrogen sensor. Should any of these trip then three things will happen:
- Power to the fuel cell will be cut
- The motor controller will be turned off
- The safety valve connected to the hydrogen tank will be shut off
The circuit is relatively simple: three switches (hydrogen sensor functions as a switch) are connected in series to each other. This then connects to a relay which provides power to the solenoid, fuel cell and MMS systems.
The eight pronged chip (inverter) and MOSFET on the top left are to regulate current and power the hydrogen sensor.
When I started on the project this year the safety circuit was not working. After doing some measurements with my trusty multimeter I found out that one of the diodes was cracked. We did not have the part in our stocks so I ordered several of them for the fix and as future backups. I soldered out the old part and soldered a new one in.
After mucking around with which ports were actual switches (poor documentation) I finally got it functioning again for use with the fuel cell.
