Wan't to know how to test for trapezoidal wave in TMC9660 using osclloscope

manojroy123 10 months ago

Can someone please share me detail on how to see trapezoidal wave in TMC9660 driver board using osciloscope.

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0 manojroy123 10 months ago

Still no output even after executing command from direct mode.
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0 Jan Cumps 10 months ago in reply to manojroy123

Is that mounting point grounded?
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0 manojroy123 10 months ago in reply to Jan Cumps

Yes
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0 Jan Cumps 10 months ago in reply to Jan Cumps

Ow, just remembered that the road test is for a brushless DC motor ...
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0 Jan Cumps 10 months ago in reply to jc2048

jc2048 said:
You aren't going to see a trapezoidal waveform, whatever you do, because it's a velocity profile you're looking at in the diagram, not a voltage waveform (as Doug helpfully pointed out)

Yes, This is a capture of a trapezoidal I did for a stepper motor project,

Velocity profile is visible because the frequency at the begin ramps up, then stable in the middle, then ramps down.
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0 jc2048 10 months ago in reply to jc2048

I've just returned from walking to the shops to buy some groceries. On the way I realised that, of course, it only takes two half-bridges to make a full bridge so, with three outputs, at any instant one will be undriven and after settling will presumably end up at the half level (the motor Y configuration connecting it to the midpoint of two equal inductors connected between the rails), so suggesting 12V for the trigger level wasn't very inspired. Go higher or lower.

So, if I'm now understanding it correctly, the PWM is there to control the current, so it can adapt to different motors and circumstances, not the velocity which comes from the rate of sequencing round the phases.

Sorry for any confusion - I did say I didn't know a lot about motors and their controllers.
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0 jc2048 10 months ago in reply to jc2048

I've just returned from walking to the shops to buy some groceries. On the way I realised that, of course, it only takes two half-bridges to make a full bridge so, with three outputs, at any instant one will be undriven and after settling will presumably end up at the half level (the motor Y configuration connecting it to the midpoint of two equal inductors connected between the rails), so suggesting 12V for the trigger level wasn't very inspired. Go higher or lower.

So, if I'm now understanding it correctly, the PWM is there to control the current, so it can adapt to different motors and circumstances, not the velocity which comes from the rate of sequencing round the phases.

Sorry for any confusion - I did say I didn't know a lot about motors and their controllers.
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