Tuesday, July 31, 2007

Hacked Serial Cable Details and Bad Relay

A few people asked me about how I hacked together a serial port since AC kit people will need this in order to configure the controller correctly.

I basically took three 16 gauge wires (smaller would be fine) and soldered on crimp sockets at the end of each one. I also added heatshrink tubing so that adjacent signals wouldn't short out. The picture above shows the three wires plugged into the top three pins on the 8-pin connector on the controller. Yellow is Txd(controller to PC), blue is Rxd (PC to controller) and brown is ground.

Here's a view of the heat-shrunk ends with the sockets crimped and soldered on.

To connect to the PC, I got a female DB9 connector with solder cups. The solder cups were designed to handle 20 or 22 gauge wire, so I had to trim down the 16 gauge wire to fit into the cups. Txd to the PC goes on pin 2, Rxd goes on pin 3 and ground goes on pin 5. All connections were soldered to solder cups in the top row.

From there, I just used a long male-female 9-pin serial cable to connect to the male DB9 on the back of the PC. Again, if you use HyperTerm, the settings are 19200baud,N,8,1, no handshake.

Remember the flakey relay I found yesterday. Here it is, removed from the car. One set of contacts was highly resistive. I replaced this relay with the charger interlock relay from the front relay mounting board to get the car working. Afterwards, I pried off the clear plastic cover (off to the left in the picture) and used an extremely thin file to break through any corrosion on the bad contacts. The contacts on the common swing arm were actually slightly bent so only a tiny corner of the common contact touched the normally-open contact when the relay activated.

I'll keep this relay around as a spare since I replaced the front charger interlock relay with a normally-closed SPST relay from the auto parts store.

The car seems to start much more reliably now.

Next up: getting more performance and acceleration..... maybe.

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