Continuing work on the Oversized RC Car Project, we last left off after the sprint day. Theoretically the code should be all working, except that we couldn’t get the MOSFET H-bridge working. We needed this working because the relay board used before this couldn’t handle the motor stall current.

Relays Relay bottom

Rather than keeping on with the MOSFET design (for now), I went out and ordered some higher current relays. Using the HRM-S-DC5V relays instead of the old M4-5H relays takes the current capacity from 0.5A to 5A, enough for the stall current of 5V. The issue with the newer relays however is a different footprint.

I chose the new relays to have a similar footprint, indeed the NC and NO output pins are the same. The only difference is the relay coil pins are spaced further apart. I was able to deal with this by raising the relays using header strips, then use wires to connect the coil.

Removing pins Removing pins to fit the header

New headers The board with new headers attached

Adding wires Adding wires

Now that this is working, hopefully we can test the code for the cars soon and have them running for the upcoming open day.

Final: side

Final: top