MINI Cooper speedometer cluster
Absoloutly DO NOT do this to your insturment cluster.
I'm warning you. If you break it, it'll be PLENTY to repair.
So don't blame me.
We don't actually have an analog speedometer even though it looks like it.
The center console listens to commands over the CAN bus and drives the needles digitally.
I took mine apart to see what's in there, and if the speedometer can be calibrated with pots or something. The quick anser os NO, it can't be calibrated with the turn of a screwdriver.
First off, they don't want to to get in here. They fill the phillips-head screws up with solder.
So you need to grab the screw with a pair of pliers to remove them. Then, use a soldering iron and solder-wick to remove the solder so you can get back in if you need to in the future.
On the back of the board, there are a bunch of ICs (of course)
A pair of
gauge driver ICs from Melexis are for driving the gauges
It's not clear why they need two driver chips. One chip can drive one 360-degree "logometer" and three 90-degree logometers. (I'm not sure why they call them logometers, but that's the terminology they use.) so they could drive the speedo, temp and fuel gauges with one driver.
Oh, there's this thing
which is a speaker, but I don't think I've ever heard sounds coming from the center console.
The whole console talks to the CAN bus to get information.
I was worried that the needles would get messed up, so I moved the speedo-needle
to 20 MPH, and it stays there, but when you plug the console back into the car, it zeroes itself against a hard-stop. Kind on like it tries to move counterclockwise 360 degrees, and bangs on the hard-stop, so there are no worries.
When the cluster is pluged in, the needle is stuck to 0 MPH, and if you push it, it bounces up to 10, then 20, then 30 (or so. Those are not the exact numbers it stops at) like it is being driven like a stepper-motor, not an analog gauge.
So I wonder if they are using the MLX10407 as a sin/cos stepper driver with a
very coarse stepper motor as the speedometer movement.