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Emergency Stop SSR - Blowing up Microcontroller

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J_W97
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Emergency Stop SSR - Blowing up Microcontroller

Good afternoon all,

I've a VESC 6 Mk5 that I am using in conjunction with a Teensy 4.1 in an escooter application.

To provide a robust and reliable emergency stop, I have a big ol' red e-stop button hooked up between the VESC and Battery via a solid state relay.

 

When testing this system whilst riding the scooter, it appears that disconnecting the +ve battery connection has caused some form of voltage spike that has fried the Teensy (connected to the +5v & GND pins of the VESC). No components appear to be visibly damaged on the Teensy, but it does not power up and I'm not reading any voltage on it's 3.3V pin.

Does anyone know why this is? I was under the impression that when killing power to the VESC the motor would just freewheel/not cause a voltage spike.

To resolve this failure in future, would a suitable solutuioin be placing a diode inline with feed to the Teensy?

J_W97
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I realise I accidentally posted this twice. If an admin stumbles across, feel free to delete the duplicate post.

frank
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You should never disconnect the battery from the VESC. The emergency stop is wired into either ADC1, ADC2 or PPM.

Settings can be made in :

App Setting >> General >> Kill Switch Mode

If you cut off the battery under load ( while driving the motor ) you can easily blow the VESC up.

 

J_W97
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Interesting.

It sounds like that given that this estop method is the preference, there is no way to have an emergency stop that isolates the battery?

Is this correct?

J_W97
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Also, is there a recommended wiring setup for this kill switch?
E.g. if I feed it into ADC2 with 5V going through the e-stop as the 'running' condition, do I then need a pull down resistor to ground to prevent this ADC signal from floating when the switch is disconnected?

frank
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ADC should only see 3.3V max. You can decide to drive ADC high and the switch pulls it to GND or vice versa. A 10K pulldown resistor should do the trick.

PPM can use 5V.

You can still use the ultimate battery cutoff emergency, but that might kill the VESC, create shorts on the Mosfets etc. Especially when braking (recuperation) you should never detach the battery.