Scaling filter capacity for stepper driver

Thread Starter

bludin

Joined Oct 24, 2013
8
In the datasheet of the TMC5130 (and that of other driver ICs), Trinamic recommends to use a low ESR filter capacitor of 100uF for filtering the power supply in order to cope with the current ripple caused by chopper operation. Can the capacity be scaled down (when space is limited) when using a small stepper motor with a small driving current (e.g. 300mA instead the 2A the TMC5130 is capable of)?
 

LowQCab

Joined Nov 6, 2012
2,315
The Current that the Chip is ultimately capable of is largely irrelevant.
The expected performance of your Motor is, to some degree or another,
dependent on a stout Power-Supply,
which You will not have if You scrimp on the Capacitor.
Of course You may not even notice the difference,
but then again,
You may create an obscure problem that is hard to diagnose.
Bigger is better.
.
.
.
 

Thread Starter

bludin

Joined Oct 24, 2013
8
Thanks for your reply.
The Current that the Chip is ultimately capable of is largely irrelevant...
Yes. And no. If the datasheet gives a general recommendation for the capacitance w/o any reference to the current rating of the motor, I would expect that either the required capacitance is independent of the driving current or that it is adequate for the maximum current the driver is designed for. So my question really boils down to: does the adequate capacitance scale with the driving current or not?
I agree the bigger would be better - if space wasn't limited. Unfortunately, it is in my specific case.
 

MisterBill2

Joined Jan 23, 2018
12,690
That capacitor is probably there to absorb the inductive spikes from the chopping of the PWM function. I have accidentally destroyed a couple of stepper drive modules by not having an adequate capacitor in place. The damage happens within a few seconds of power on, before the motor even moves.
SO I suggest discussing it with the driver manufacturer. OR research some physically smaller capacitors.
 
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