[Mark Rehorst] The $ 200 worth of motorized driving hardware informs us of a tragic event involving premature death and shares a common circuit so that we can prevent such tragedies in the future. His Arakis sand table project involves several motors, and by forgetting to add limits to the software, he hits a motor-driven mechanism on a specific part of the table. The EMF on the back of the motor generates an energy explosion, expelling the motor driver, controller board and power supply.
As soon as the postmortem was completed, he had to prevent it from happening again – especially on the hardware. Based on a small apnot of Gecko Drive, he designed a simple PCB that shuts off the motor with the help of a high-power resistor, as soon as current flows in a direction where it is not supposed to flow. He goes deeper into the way the circuit works and the reasoning behind the part selection, as well as showing an LTSpice simulation and sharing PCB files. KiCad had his first PCB design, and we believe he did a great job! This worklog is a must read if you want to know how such circuits work and what it takes to create one.
He describes it as a “bank account security” circuit and we can be absolutely related. It’s not just CNC tables that require this kind of protection – we’ve seen, for example, a solution for small Hacky temporary electric vehicles. The generative properties of a motor are not always a problem, however – here is just one example a hacker tries to make good use of them.
We thank you [P-Storm] To share with us!