> On 14 Jul 2019, at 00:06, justin White <[email protected]> wrote:
>
> How’s the dc motor driven? Straight dc, or a dc drive of some type?
The former, just to move a gripper to a position. No need to have position
control, no need to be fast, just running into a product making physical
contact. I prefer to have a signal in my program logic as opposed to working
with timers to make sure I’m at the right position.
> Assuming it’s just a brushed dc motor you can install a current sensing
> device like a shunt resistor and feed it back to an analog input. A stalled
> dc motor will draw high current.
Yes, and I’d like to prevent burning the motor so I’d like to switch off the
motor when stalled. I’d hoped there was some protocol board, but I guess that I
need to do some calculations depending on supplies voltage (24 or 12V) and
motor resistance. I’ll start digging.
> You can use a comparator in Hal to trigger a fault output when the analog
> input voltage is higher to the setpoint on the other comparator input. Better
> idea is to use an h-bridge driver that has its own current fault output. Dc
> motors do a number on relay contacts used for reversing anyway so a simple
> drive is a better bet.
>
> I didn’t see good documentation on those step drivers on the website but the
> only one I see with stall detection is the spi model. There are 1 or 2
> diagnostic pins, find out how they work. If they output high or low level on
> a current fault you can use them on a gpio input. Otherwise maybe they do
> something over spi? If you find out more I could probably help you better.
Yes, I need to dig into spi for those drives. I’m getting a few to test.
Thanks!
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