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DRV8801 - ID#2136 Current sense feedback issue


#1

Hi,

I have the DRV8801 brushed dc motor driver up and running. Everything is working well!.. with the exception of the Current Sense Pin (CS). I’m getting ~0 on this through analogRead.

Has anyone gotten this to work?

I’ve tried to remove R3, and jump the Mode1 pin high as well… still no luck.


#2

Hello.

It sounds like you are leaving the Mode1 pin high (putting the driver in slow-decay mode). As noted in the Pinout table on the DRV8801 carrier’s product page, the CS pin will output 0V whenever the driver is in slow-decay mode. Do you get a reading if you pull the Mode1 pin low?

Brandon


#3

Hi Brandon,

I meant to say that i jumped it LOW*

Yes, i tried pulling BRK to low as well on a new driver. The highest reading i can get ( during a manual stall - hold the motor) is ~15 (raw).

(Currently im using a micromotor @ a 250:1 reduction - https://www.pololu.com/product/3055 )

The stall current on this is supposed to be around 0.75 Amps @ 12v. So i should be getting a reading of around 75 on the raw analog input (arduino).

500 mv/ amp = 0.5 v/amp (from CS)
1023 raw/5v = 204 raw/volt
(204 raw/volt)*(.5 v/amp) * .75amps = 76.5 raw

Im not sure why this reading is so low… any ideas?


#4

Are you really stalling those motors at 12V? As noted on the #3055 gearmotor’s product page, those gearmotors are strong enough to damage the gearboxes if stalled, so we strongly advise keeping applied loads well under the instantaneous torque limit of 25 oz-in (which is around 60% of the stall torque for that gearmotor). Can you describe what your test procedure was (e.g. what signals were you sending the driver, how were you monitoring the current sensor output)? Also, what kind of power source are you using for your motor power?

Brandon