Firstly, I noticed that setting the number of poles not only has an effect on the measured cadence but also how smoothly the torque sensor controls. A higher count smooths out the operation but gives an incorrect cadence reading. I am a bit confused why this setting even has an effect on a torque sensor. I thought it would be a fixed number.
That is correct. What the CA does is average the torque signal over the previous complete pedal rotation. Or more precisely, it time averages the torque between each PAS sensor pulse, and then does a spacial average of these to cover one full pedal turn based on the #poles setting. That way in theory the averaging is perfectly aliased to your pedal cadence, and you don't get any undulations in the power output. However, there is enough variation between one pedal stroke to the next that I agree it's not as smooth as ideal, and I often end up using the ramp rate settings to keep it steadier still. If you have it set to say 16 poles, but use an 8 pole sensor (like the THUN), then it would be averaging the last two complete pedal strokes and that would help the smoothness a lot. But if say you set it to 12 poles, then your average signal would be much worse than with 8 because you could be alternating between two down strokes and one up stroke, then two up strokes and one down stroke etc.
If you simply time average the torque signal, then there would always be pulsations in power at your cadence frequency.
Other issue is voltage. I run 18S LiPo (75V hot off the charger.) No good for running a Thun and have dropped down to 12S which is still on the edge. I need a easy solution to use my 18S and Thun Setup. Something that is nice and compact that I can hopefully fit inside the CA.
It's quite possible to make a tiny DC-DC that fits in the casing, but most off-the-shelf ones are too tall in their form factor to fit in the box OK. For the simplist and most compact approach that would fit in the casing, one possibility is to use a resistor inline with the V+ signal to drop the voltage going into the CA's power mosfet. With the THUN sensor and throttle plugged in, you would have a total draw of about 32 mA, so if you have a 1K resistor, of at least a 1 or 2 watt rating, then that would drop 32V between your pack and the CA's power input.
Then in order to sense the correct voltage on the CA you'd wire up a pack voltage divider to the Vex input. There are a few circuitboard hacks you could do to decouple the onboard voltage divider from the V+ power input so that you don't even need to hook up a pack voltage sense to Vex, but I'd need to go over the layout a bit to see what would be easiest.
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