Solid State Relays for Door Lock

Lately I've been working on a solid state module to replace the relays used for the door locks in the GM5. Finally the prototypes are done and ready for some testing.

Update 2009-06-03: I had the solid state relays in my car for a couple weeks and at first everything was fine, but, the driver's door lock would sometimes not lock or unlock all the way. I've been noticing for a while (even before the solid state relays) that that door seemed to operate more slowly than the rest. I believe that the actuator is starting to go bad. I put back my original GM5 with the good ole mechanical relays and it works again. One of these days I want to put a current probe on the actuators for each door and measure the current profile to see if that driver door actuator consumes more current. I have not put the solid state relays back in my car because I'm going to try a new set of MOSFETs with lower On resistance. The ones I originally chose where cheap and decently good. This time I bought some really good ones that cost over twice as much. I also have new boards coming. The new ones are 4 layer with power and ground plane, silkscreened, soldermasked and slightly relaidout with thicker traces everywhere.

This is a picture below if of my original solid state relay module. Four of these modules are required to replace the two V23084-C2001-A303 relays since each relay contains two independant relays. And each module contains 2 MOSFETs so that's a total of 8 MOSFETs per system.

The next two pictures show the four solid state relay modules installed on my spare GM5 module.

I currently don't have plans to offer these up for sale as they would be approximately 2-3x (with the new low On resistance MOSFETs the cost would be 3-4x) the cost of the original mechanical relays or about $15-20 per module. Remember 4 modules are required. This was mostly done for fun. This is not anything new. BMW uses solid state switching on their higher end cars like the 5 and 7 series. If you're really interested and aren't put off by the cost then let me know via email at scott@bmwgm5.com. If testing goes well and there is enough people interested I will make a batch of production boards (soldermasked and silkscreened).

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