Ti Lunchpad max current


I am part of a team building a planarized monopod using the actuator module for Sim2Real. Our robot is very close to done except we are noticing weird behaviour with max current. Currently we limit the max current to 5A which is around 1Nm based on the 0.025 motor constant and 9 gear ratio.

However, when we send a command with this max current the motor drivers start whining and half shut down into what feels like a safe mode. Based on the specs I expected the motor drivers to handle 15A each but we are well below this threshold.

If we have a max limit set to 0.5A the issue does not happen.

Any Idea what this issue could be? Maybe the power supply is not stable enough? I will be scoping the power lines in the next few days to see if that is the issue.


My first guess would be a power supply issue.
To do experiment with high currents we have used lead acid battery in the past, they allow having high current both positive (motor mode) or negative (regeneration phases).

Also, be aware that we can not run those motors at high current fore more than a few seconds, indeed they are designed for quadcopter where the propeller air flow, contribute to the motor cooling

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@thomas.flayols Thank you for the helpful reply. A new power supply fixed our issues. the voltage on the old power supply tanked on startup of the motors causing the TI to enter low voltage safemode. What is considered a reasonable continuous current the leg?

It seems i met the same problem you met.
Does the light of 8305 turn red when this behaviour occur?

You are right, most of the digital current sources cannot provide the instantaneous current required by the solo robot, which will cause a transient voltage change. You can observe this phenomenon through the oscilloscope. Once the voltage is reduced, the μdrive board will enter the protection state, you will see two red signal lights turn on and the motor buzzes. The solution is also very simple: use high current lithium battery, such as the lithium battery commonly used in the aircraft model.

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What type of power supply are you using?