PTC Fuse tripping prevention

Hi, we have built a dr4b with a 1:7 gear ratio, that uses two motors, and a power expander. Sometimes, our lift seems to stop, most likely due to it tripping the circuit breaker or doing something to the PTC fuse. Is there any way we can prevent it from breaking the circuit without adding any extra motors, or doing anything to the gear ratio? (i.e. slowing the lift down or something) Thanks

Have you got elastic bands on your lift to help counter the force of gravity? This will reduce the current needed by the motors to lift the lift and reduce the chance of the PTCs tripping.


Yeah I don’t have that problem. Make sure to do a triangular design.

We do have rubberbands that are arranged in a triangular form, yet the problem persists. Any ideas?

I can only think that your motors may be bad. Is your lift made of steel or aluminum? How many motors on your Power Expander? Any friction on your motors on the lift? 2 motor 1:7 should not burn out.

or friction on the axles with spacers

A picture or a weight measurement of the arm would help. 2 motors at 7:1 has two motors at 49 inch pounds so just under 100 inch pounds of force max output before things get nasty in the PTC department.

Rubber bands help tremendously as they add force to help you. Weight, arm length, and friction are the areas taking away from what you want.

We’ve replaced our motors a couple of times, lift is made of aluminum, and there are only the two lift motors on our power expander. However, we don’t have any PID control on our lift. Are PID loops and efficiency of lift motors related somehow? Thanks.

Not really, PID loops just make it more efficient but the motor itself should be good. I think it might one of your extension wires or motor controllers. Check if there are any loose wire connection from the actual motor.

@Tegicupala One issue I have seen fairly often is the PTCs tripping due to subtle mechanical issues with the lift. A quick test for this could be pulling the axles out of the motors and trying to move the lift by hand—you should be able to do so without much resistance aside from gravity. The problem could be something as simple as extra friction from an over-tightened hinge or missing spacers.