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Potnom not rising above 15%
Posted: Sun Jan 18, 2026 2:32 pm
by MoonUnit
Hi, I am bench testing an SDU drop in board. It is v9, running 5.35 R sine release.
I am using an i3 pedal, single channel mode. I can see 'pot' varying between about 450 and 2480, I have set potmin and potmax accordingly but potnum never gets over about 15%. I have no DC attached to the motor and have set udcmin to zero. I suspect some derating is happening in the software but I can't find it.
Can anyone offer advice? Params used and a plot attached.
Re: Potnom not rising above 15%
Posted: Sun Jan 18, 2026 3:24 pm
by Bratitude
MoonUnit wrote: ↑Sun Jan 18, 2026 2:32 pm
Hi, I am bench testing an SDU drop in board. It is v9, running 5.35 R sine release.
I am using an i3 pedal, single channel mode. I can see 'pot' varying between about 450 and 2480, I have set potmin and potmax accordingly but potnum never gets over about 15%. I have no DC attached to the motor and have set udcmin to zero. I suspect some derating is happening in the software but I can't find it.
Can anyone offer advice? Params used and a plot attached.
params_20260118.json
Quite strange looking pot plot. is that smoothly pushing the throttle to 100%?
What power source are you running? Voltage sag?
Re: Potnom not rising above 15%
Posted: Sun Jan 18, 2026 3:54 pm
by MoonUnit
I was using a 12V bench power supply to power the board. No DC to the motor. It was me 'smoothly' pushing throttle with my hand.
Re: Potnom not rising above 15%
Posted: Sun Jan 18, 2026 5:54 pm
by manny
is it in reverse?
maybe post a screenshot of the spotvalues.
Re: Potnom not rising above 15%
Posted: Sun Jan 18, 2026 8:31 pm
by MoonUnit
I get the same behaviour whether the direction is set to forward, reverse, or neutral (not sure if potnum should vary whilst in neutral). I post the spot values here (throttle not pressed):
and this snippet when throttle fully pressed:
Re: Potnom not rising above 15%
Posted: Sun Jan 18, 2026 9:12 pm
by johu
I wonder if it gets caught on udcmin. It is set to 0 and udc is 2, quite close to the derating point. Can you try applying a small DC voltage, like 12V or so?
Re: Potnom not rising above 15%
Posted: Mon Jan 19, 2026 8:45 am
by MoonUnit
johu wrote: ↑Sun Jan 18, 2026 9:12 pm
I wonder if it gets caught on udcmin. It is set to 0 and udc is 2, quite close to the derating point. Can you try applying a small DC voltage, like 12V or so?
That appears to be the fix. I tried 12V, potnum now does range much better (but only up to 70%). I will experiment with potmax, it's probably not set correctly. Many thanks for this, I didn't fully understand the derating.