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Axiom with SIN/COS encoder and Motoenergy ME1304

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Boben
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Axiom with SIN/COS encoder and Motoenergy ME1304

First off, I need to mention that I do not have a genuine Axiom HW. Out of pure curiosity, I flashed the FW to a general purpose STM32F405 board which I've made.

I worked my way around the few fault codes that the VESC was spitting out and hooked up the SIN/COS signals from the ME1304. As the encoder of the motor uses a 5V supply, the voltage levels are not compatible and need some level shifting. For this, I used a differential amplifier build around an OPAMP. With the circuit, the SIN and COS signals have a DC offset of 1,65V and an amplitude of about 2Vpp.

When I rotate the motor, I can see the angle position changing in the real time data as expected, although the refresh rate of the graph is very slow.

The VESC seems to read the angle correct, but still there is a fault: FAULT_CODE_ENCODER_SINCOS_BELOW_MIN_AMPLITUDE

What might be causing this fault?

skyline1970
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Joined: 2017-09-07 22:28
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You could try decreasing amplitude to 1Vpp or 0.5Vpp .

Boben
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Last seen: 1 year 9 months ago
Joined: 2019-11-24 17:05
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Based on the description of the pull request, 1,65V DC-offset and 2Vpp should be spot on. What puzzles me the most is the fact that this fault is active right at startup when the motor is not turning. In this state, the signals from the encoder are static DC values with voltage between 650mV and 2650mV depending on the position of the rotor. How can the VESC diagnose that the amplitude is too low, when there is no amplitude yet to detect when the motor is at stand still?

Here is the signal format that should be compatible: