# Can I use stall detection as my only obstacle detection or will that damage the DC motors over time?

I plan to build a robot that is likely to bump into a lot of things quite often. I know I can detect if a motor has stalled by measuring the amps it is pulling and would like to use that as a simple way to detect any collisions, but I'm worried that this might damage the motors if used a lot. Can this be applied safely without harming the motors over time?

• I doubt that would work because bumping into things typically does not stall the tires. – Janka Mar 12 '17 at 19:07
• braking current may be comparable to collision current so it depends on Vinput as well. – Tony Stewart Sunnyskyguy EE75 Mar 12 '17 at 19:14
• is this a hobby or for an actual product? I ask because there is an annoying number of "stall detection" patents out there for what is essentially an obvious thing to do – JonRB Mar 12 '17 at 19:18
• Speaking of patents, there is a very nice stall detection patent (expired) at google.com/patents/US5367236 . Have at it! – Tom Anderson Mar 12 '17 at 23:16

Seriously, if you do not allow the overcurrent to heat up the motors, they will be fine. $I^2 t$ is what kills most things. Do not exceed that as specified by the datasheet.
For a small motor the thermal constant might be say 10 minutes or 600 s. Derate the full load to 99 % and assume the bump current is 500 %. This means that you have $${600 - 99\% \cdot 600\over 25} = 240~ms.$$