How to avoid DC gear motor damage if you can't avoid stalls

I've got some small DC gear motors running at 5 volts, but sometimes they end up stalling if the loads they are trying to move get beyond their maximum torque. These are fairly high gear ratio motors to give slow high torque motions, such as a 298 to 1 gearing. On occasions when they have been doing things like running the wheels on a robot which has crashed into a wall, or turning a moving part of a 3d printed system which can sometimes jam, they have not only staleld but anaged to strip out parts of their fine metal gearing. Are there any tips for how to avoid such gear stripping damage when stalls can't always be avoided? My electronic systems around them don't have any practical places in which an encoder could be added, no spare GPIOs to monitor it with, nor any easy way to add current monitoring to the input of the H bridge driver. What else could I try to ensure that a stall doesn't do lasting damage?
Thanks

Infraviolet:
My electronic systems around them don't have any practical places in which an encoder could be added, no spare GPIOs to monitor it with, nor any easy way to add current monitoring to the input of the H bridge driver. What else could I try to ensure that a stall doesn't do lasting damage?

Maybe you could put something in the drive-train downstream of the gearbox which would fail at a torque that is below the point at which gearbox damage occurs. There is a technical name for that sort of thing but right now I can't remember it.

If that is not an option and as you seem to have ruled out all possible preventive measurements the only other thing I can think of is using a more robust motor and gearbox.

...R

lasting damage?

If your moter is not selfhealing, any damage is lasting :slight_smile:
Just ensure that the curent dies not exeed the maximum allowed current. This also means that you need a datasheet of your motor and actually read it.

zwieblum:
If your moter is not selfhealing, any damage is lasting :slight_smile:

It's not the motor that is failing, its the gearbox.

...R

Infraviolet:
I've got some small DC gear motors running at 5 volts, but sometimes they end up stalling if the loads they are trying to move get beyond their maximum torque. These are fairly high gear ratio motors to give slow high torque motions, such as a 298 to 1 gearing. On occasions when they have been doing things like running the wheels on a robot which has crashed into a wall, or turning a moving part of a 3d printed system which can sometimes jam, they have not only staleld but anaged to strip out parts of their fine metal gearing. Are there any tips for how to avoid such gear stripping damage when stalls can't always be avoided? My electronic systems around them don't have any practical places in which an encoder could be added, no spare GPIOs to monitor it with, nor any easy way to add current monitoring to the input of the H bridge driver. What else could I try to ensure that a stall doesn't do lasting damage?
Thanks

Sense the motor current to detect a stall and cut the drive, or add current limiting to the motor driver so it can't output too much torque. If you can't do that the only recourse is a slipping clutch.

The underlying issue is that the motor is mismatched to the gearing. With modular stacked planetary gear systems its commonly the case that the multistage reduction setups are capable of overloading the last gear stage. A proper gear train gets beefier down the stack, but that's not very modular as you can't reuse a 1000rpm 10nNm divide-by-6 gearsection for 10rpm 1Nm stage, so all the sections would need to be rated for very high torques, dwarfing the motor in size and weight.

Its probably best to design using gear motors of modest reduction, and add a beefier final reduction step that can handle the torque. Or to use a bigger motor (oversized) that comes with more solid gearing, then limit the current.