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Powering EasyDriver and Netduino

Started by Andre Trollip, Aug 26 2014 12:24 PM

stepper motor

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2 replies to this topic

#1 Andre Trollip

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68 posts

LocationGauteng, South Africa

Posted 26 August 2014 - 12:24 PM

Hi Guys,

I would like to power my Netduino and Stepper motor (via EasyDriver) from the same 12V power source. How can I protect my Netduino from the current "backdraft" as the motor starts and stops? Or is it not quite that simple?

I remember having to do that for a normal DC motor on a different project a while back.

Thanks in advance.

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#2 Paul Newton

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LocationBerkshire, UK

Posted 28 August 2014 - 06:16 PM

Hi Andre,

If the EasyDriver you are referring to is the SparkFun EasyDriver, then the A3967 IC on the board has built in protection diodes so that its internal transistors are not damaged by back emf.

You are right to worry about the motors affecting the Netduino. I was using a similar circuit with a 9V battery supply (6 x AA 1.5V) for my buggy and had to give up powering both from the same supply because the Netduino kept re-booting when the motors turned.

I was never aware of any damage to the Netduino - I think it was just brown outs, or maybe noise that was enough to trigger a reset..

If you are worried that the driver board will feed current back to the 12V supply, then add a rectifier diode in the positive line between the battery and the driver so it can only take current - that should protect the Netduino from high voltages.

(Note that the EasyDriver circuit does not have any protection for its own logic supply, so I don't think they are expecting any problems like this. However they do have a 30V tolerant input.)

You might also add a similar diode to the Netduino supply input and add a big capacitor after the diode so that short brown outs are less likely to reset the Netduino.

Let us know how you get on.

Have Fun - Paul

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#3 Andre Trollip

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68 posts

LocationGauteng, South Africa

Posted 29 August 2014 - 11:54 AM

If you are worried that the driver board will feed current back to the 12V supply, then add a rectifier diode in the positive line between the battery and the driver so it can only take current - that should protect the Netduino from high voltages.

(Note that the EasyDriver circuit does not have any protection for its own logic supply, so I don't think they are expecting any problems like this. However they do have a 30V tolerant input.)

You might also add a similar diode to the Netduino supply input and add a big capacitor after the diode so that short brown outs are less likely to reset the Netduino.

Thanks a lot Paul. The feedback is exactly what I was worried about. I had the first diode in place and the cap as you recommend, but not the second one.

I will let you know how it turns out. I think I damaged the driver somehow because it stopped working at some point while I was fiddling. Waiting for a couple of new ones I ordered. At the same time I ordered some Polulu ones (Allegro�s A4988). I'd like to compare the two.

Thanks for your help.

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