298:1 Micro Metal Gearmotor HPCB 6V stalling with .1 A

For my project, I previously had HP motor, but replaced it with HPCB. The problem I experienced with the motors were that my robot wasn’t grabbing an object tight. I thought I needed stronger motors so I bought 298:1 Micro Metal Gearmotor HPCB 6V. However, this replacement didn’t fix the problem.

I’m using DRV8833 with it, and checked if the current I’m supplying was enough. So, what I read from DRV8833 datasheet is that each channel can supply up to 1.5 A which is enough for 298:1 Micro Metal Gearmotor HPCB 6V. However, I normally see .1 A. When it stalls, maybe .2 A. I checked with previous motors, and it goes up about .3 A.

I also used oscilloscope to check PWM and when it’s running, it WPM signals also look pretty smooth and all good, but when it stalls it shows filled yellow bar (multiple up and downs created this yellow mass).

I don’t want it to stall and drop the current. I want it to have high stall current while it squeeze the object. Does anyone have idea what’s going wrong here?

Thank you.

As we say on the product page, while the DRV8833 datasheet lists a maximum continuous current of 1.5 A per motor channel, the chip by itself will overheat at lower currents without sufficient additional cooling, so your problem could be related to this. Does the robot’s grip start tight and then weaken, or is it always weak? What are you using to power the motor driver, and what is your duty cycle when the motor is stalled? How are you measuring the current draw? Can you post some pictures of your system?

By the way, please note that in general, stalls can result in rapid (potentially on the order of seconds) thermal damage to the motor windings and brushes, especially for the versions that use high-power (HP and HPCB) motors, and they can also destroy the gearbox for versions with a high gear ratio (like the 298:1). However, if you are careful to limit the current by using a low supply voltage or PWM duty cycle, it might be possible to stall the motor safely.