Emergency stop button

Hardware Other Hardware
1

Dear Ardupilot community,
I’m currently developing my own system (it’s an ArduRover, to be specific) and I want to include an emergency stop button in my project. I’d like one of those big red mushroom-like buttons, such as the one in the figure:

My Pixhawk 2.1 came with a safety switch (http://ardupilot.org/rover/docs/common-safety-switch-pixhawk.html) but it’s not an ideal solution. In fact, each time you press the switch you either enable or disable the outputs to motors. In an emergency situation, you don’t want the output being restored by accidentally pressing the button again. In fact, typical emergency stops can be pressed only once, then you have to release the button, usually twisting it in the specified direction (clockwise for the button in the figure). So I don’t think connecting the emergency stop button to the safety switch port of the Pixhawk would work.
Another option is probably to cut the PWM signal from the Pixhawk into the ESC. In such a way the vehicle certainly stops but I’m concerned that the ESC could be damaged by some back EMF if the circuit is suddenly opened. My question is: are you aware of any sturdy emergency button implementation for Ardupilot driven vehicles? Thanks for your priceless help!

2

Have you considered having the e-stop completely cut power to your entire vehicle? So put it immediately in-line with your power source (battery).

Another option: You are probably providing input power to your servo-rail at some point. Put the e-stop to cut off this power, thus electrically disabling the motors, while not cutting power to the PixHawk computation itself.

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3

Thanks @hunt0r for your help! Actually I power the motors and the Pixhawk with different battery sets, so I can cut power to the motors without affecting the Pixhawk. So I’m not concerned about damaging the Pixhawk but rather the ESC. The two options you suggested seem good ideas to me, but I honestly can’t say if I can possibly damage the ESC doing so, because I’m not an expert in electric stuff. I know that the ESC on my rover costs ~200$ so I want to be careful with that :smiley:

4

I don’t know what might damage an ESC, so maybe someone else can help?

5

You might check the systems used to satisfy the results of the Medical
Express Outback Challenge.

Generally you want to consider why you’re putting the button-to-press in
the middle of the whirling-blades of death.

Consider instead the model used by the farmer using ArduPilot for his
grain hauling - multiple remote disable switches.

Yours,

1 Like
6

Thanks for your suggestions, @peterbarker. Since I’m developing a rover, there aren’t really blades to be worried about. I’ll consider the approaches you recommended.