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Safety wiring 2x30a roboclaw

Posted: Sat Jun 01, 2019 9:02 am
by Jbot2019
Hello, first post and I'm pretty green when it comes to higher level electronics. I have decent levels of experience with automotive electronics and wiring.

My question is, I have my setup wired as the rc wiring diagram shows. I read further down the user manual and got to the safety wiring portion... I'm lost.

From what I understand, I need a diode across the safety switch to allow the regenerative current back to the battery in case the main switch is opened with the robot still in motion? This seems like a runaway scenario where the robot is moving without my input, the safety switch is opened to stop power to the motors, the voltage created by the inertia of the robot continuing to turn the motors will spike at the main board without a safe path back to ground (the battery), poof there goes another $120 up in smoke... and not the good kind.

If this is correct, is it too simple to just turn off the regenerative portion of the controller, if that is even possible? I have a very basic understanding of diodes, one way path for electricity. I've never wired one into a system and I dont know anything about the different types.

My original plan, I'll apologize in advance, is to use a 25amp circuit breaker as my safety/cutoff switch. I dont think this provides any protection for the leftover regenerative energy when the breaker is tripped. The ground will still be connected but I'm doubtful if this will provide a path for the extra energy to safely dissipate.

Hopefully this gives enough background of my ignorance, knowledge, and problem at hand. Of course I can provide any information that may be needed.

Thank you guys, and gals. I'm really looking forward to using my first creation! I've built rc cars in the past but this will be my first large scale project. Remote control zero turn lawnmower. 😁

Re: Safety wiring 2x30a roboclaw

Posted: Thu Jun 06, 2019 10:36 am
by Basicmicro Support
The first diagram shows the simplest wiring to run the motors. The second shows the recommended wiring with(power switch, fuse, diode).

Almost correct, the diode is used to bypass the power switch(and optionally the fuse) so if you flip the switch off while running the motors you still have a path for motor regeneration. Without that diode if you flip off the switch or back drive the motors(like pushing a rover around on the ground) you can produce enough motor regeneration to cause a high enough voltage to damage the controller.

The diode bridges the switch on the main battery + wire. Never put your switch on the ground wire. If you break the ground connection while under power the battery may just find a new path to ground instead(burning holes in things to do so).

Regeneration is NOT an optional part of running a motor. All motors regenerate at some point when slowing down or when being back driven(eg the motor is just a generator in reverse). You dont "turn it off" no matter how much we wish we could.

If you use a breaker make sure it is DC rated for the voltage and amps. Not all breakers are DC rated at all and most will be rated for lower voltage/amps when using DC instead of AC.

As you said, no the break doesnt offer any extra protection over a regular power switch/fuse combo. You still have to deal with motor regeneration. It does combine the fuse and switch into one which is nice but you need to make sure it will actually open under a reasonable load(eg if it wont open until it seas a current higher than your batteries can ever produce its kind of pointless) and you want it to break quickly. If it takes a minute to break under a short condition on your battery its also not much use. I recommend fuses open between .1 and 1 second at around 80% the batteries maximum current capability. The breaker should be rated about the same as a fuse would be.

Re: Safety wiring 2x30a roboclaw

Posted: Mon Jun 10, 2019 12:08 pm
by Basicmicro Tech
Please see the link below for a discussion about hardware safety precautions.

https://resources.basicmicro.com/motor- ... ecautions/