Motor wiring to prevent back feed Cytron

Is there any issues with my phidgets motor sending power back to my Cytron if I leave the motor against the steering wheel and it get spun from the steering wheel while it’s turned off? If this is a problem has there been an easy solution to prevent voltage going backwards? I am sure I have seen this before but was having trouble finding details.

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I am confused, is there a pin there to connect to ground all the time to disarm brake or just when the switch is off? I have never seen this before

Just when the switch is off.
This will completely disable cytron.

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I don’t have a cytron, but would it then be OK to just connect that “brake pin” to pwm2?

I just use a relay to break the circuit between the motor and cytron, triggered by pwm2. That way there is no braking and no voltage coming back to the cytron

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Sorry, I do not known how pwm2 used in code.
You could connect it to any pin on arduino or esp32, but it should controlled by code.
You can use this “brake pin” instead of relay directly without any optical isolation or level shifter, but you need to desolder this 2 components.

Without desoldering you MUST NOT output 5v or 3.3v to this “brake pin”, without desoldering it could work just like this, but tests needed:
-arduino/esp32 - pinMode(pin, OUTPUT); - md13s disabled
-arduino/esp32 - pinMode(pin, INPUT) - md13s enabled

With desoldering it can work like this:
pinMode(pin, OUTPUT);
-arduino/esp32 - digitalWrite(pin, LOW); - md13s disabled
-arduino/esp32 - digitalWrite(pin, HIGH); - md13s enabled

More details how it works:
Driver used in md13s is DRV8701.
It has nSLEEP pin - with voltage lower 1.5v it sleeps, with voltage 1.5v-5.75v it works.
On md13s board there are 10k resistor from power rail and 3v zener diode BZT52C3V0.
You can desolder them to use nSLEEP pin directly.
DRV8701 also has current output pin, but it does not used on board, can be soldered to chip, but it has very small pins.
If you need current output, you can use Pololu G2 High-Power Motor Driver 24v13, it has the same driver, but it costs 30$.



Do you use the relay to break both wires? Is there power on either wire depending on rotation?

My thought was a double pole double throw relay set to NO and then when I step on switch to engage autosteer it closes this relay. Totally separate from Pcb and Arduino setup, just an old fashioned light dimmer switch to open/close this relay. Will there be any harm to phidgets if there is no where for the power to go or how does that work if both wires are open?

I just cut one cable. Guess when the circuit is not closed, no current can flow, no matter which direction the motor turns

In current INO pwm2 is controlled just as required (when motor driver set as Cytron) , 5V when steering active, 0V when inactive.

So, it’s really a very simple setup, just carefully remove the two components and connect a wire from the nSLEEP pad to NC in connector. Easy to connect to pwm2 in pcb with the included grove cable, no extra components and wiring needed. Just tested and works like a charm.



Current ino ? V5 ino also ?

Oh, sorry. The latest beta. Looks like it is the same way in 4.3.10 but haven’t tested.

Thanks, I will try tomorrow if I’ve got time.

Which two components need to be removed just to be clear? So once this is done it will prevent the motor from sending power back to the Cytron? Or at least if motor sends power back nothing will be hurt?

The resistor and zener diode (?) marked with red cross in the pic I posted earlier. Can do with a soldering iron, just be careful not to rip off the pads from pcb.

The modification allows pwm2 to control nSLEEP pin on drv8701, basically disconnecting the motor outputs and allowing the motor rotate freely when autosteer is disabled. @d1ken can probably explain better, I was just following his instructions.



Generally motor will generate some energy when rotating by hand and push this energy to boost converter, but this is not a problem, since we can not generate so much voltage by hand to burn something.

Ok, thanks. That’s good to know

Hi, where find this in new v5 ino ?

Just posting to give this a bump.

Tried it and it works great no need to ever take the gears off the steering wheel. This modification should be included in the manual.