The diagnostic port for collecting data from
the EV1 while driving is under the driver's side dash. It
is an OBD II connector. This type of connector is commonly
used in the automotive industry and is based on SAE standard
J1850. Its difficult if not impossible to find the connector
hardware unless its at the end of an $80 cable. The connector
looks like the following illustration.
Only pins 4 or 5, 9, and 16 are needed to gather
data from the port. On the EV1 only pins 2, 4, 5, 9, and 16 have
metal contacts (This should help you orient the pins correctly).
You should be able to see these contacts from under the dash. The
pinout is standard (or a subset of) OBD II; pins 4 and 5 are ground,
pin 9 is the signal, and pin 16 is 12 volt power (really around
13 or 13.5 volts). The signal is 8192 baud at 5 volts with a base
voltage low. That means it needs to be inverted first to look like
a standard RS232 signal. Pin 9 is used at the factory to diagnose
and reprogram the car. The interface is known as the Assembly Line
Diagnostic Link or ALDL.
The easiest way to invert the signal on pin
9 and make it look more like an RS232 interface is to use
two 4.7K ohm resistors and one 2N3904 transistor. Mike Schwabe
came up with this circuit and is now making the small boards
that are inside the connectors.
The parts should be connected as in the illustration.
I decided to make a the adaptors with my homemade computer controlled milling machine (Robots
are one of my other hobbies.)
The connectors are no longer available.
Here's a picture of the first version of the housing
for the connector being milled from some polyethylene.
The connector consists of two halves plus the internal
PC board. Here is a picture of both sides of each half plus the
Heres a view from under the dash with the connector
plugged in. The older units had the DB9 facing toward the rear of
the car. The new ones face forward to give more room for gender
changers and null modems when hooking up a PC. The new connector
also fits more snugly against the sides of the ODB II connector
on the EV1 so there is not longer a need to wire tie the connector
to the car.
Next the PalmPilot needs to be mounted somewhere in
the car. Some people just set a cradle on the center console and leave
it at that. Others like to mount the Palm handheld somewhere where
it is easier to see while driving. If you want to make your own mounting
bracket its pretty easy to do. Here's what
For the real technical types that want to write
their own software to decode the data coming from the EV1 I've set
up a page about
the data stream.
Check out the sample graphs to see what
can be collected.