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Tesla Small Drive Unit (SDU) pot tolerance

Posted: Sun Oct 01, 2023 1:00 am
by alexbeatle
Hello folks.
What is the acceptable tolerance on the pot input? I have a V6 board (fmw: 4.90.R-sine) with the bmw e45 throttle pedal. Below are my measurements of the fully released pedal on the multimeter (signal-to-ground) vs. on the web interface. When I fully press the pedal the value stays steady - 4095.
As you see the meter is pretty steady on the pedal released, but the values are jumpy on the web....Trying to figure out if it's a problem or not...

Multimeter:


Web interface:


Wiring: I use just vcc1, gnd1, sig1
e45_bmw_pedal_wiring.jpg
e45_bmw_pedal_wiring.jpg (10.38 KiB) Viewed 1621 times
Throttle parameters:
image.png

Re: Tesla Small Drive Unit (SDU) pot tolerance

Posted: Sun Oct 01, 2023 8:06 am
by johu
Seems like 50 digits jitter - a bit too much for my taste as well. With the pedal disconnected do you still see the jitter? I wonder whether the onboard low pass filter has the wrong capacitor or resistor value

Re: Tesla Small Drive Unit (SDU) pot tolerance

Posted: Sun Oct 01, 2023 10:46 pm
by alexbeatle
I think this can be marked as "solved" for now.
I have the pedal connected to the SDU via a terminal block. I re-seated the wires of the pedal on the TB and this made the values more steady.
I also connected the ch2 of the pedal to the pot2 input, 'cause I was thinking that when unconnected it maybe inducing noise onto ch1, but it had no improvement effect. I turned of the coolant pump, which dropped the inverter temp from about 24C to 20C - no imprevement effect. I will leave it like this for now and will work with the dualchannel throttle.
Perhaps I should bypass the terminal blocks altogether and solder the wires together directly.
Thanks for helping.

New throttle params:
potmin's and potmax's are now taking into account broken wire or short wire.
potmin's = min value +10%, potmax's = max value - 10%.
image.png
web interface live values: initially showing the pretty steady values when the throttle is released, then randomly pressing (and trying to hold in place) the throttle and finally throttle all the way down.