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I am building a motorized, speed controlled turntable using an Arduino Nano and a 6V DC motor. I have read that the motor and the micro-controller should have separate power supplies because noise from the motor can damage the micro-controller. I was wondering, would it be possible to eliminate the need for a separate power supply by inlining a diode at the power input to the Arduino? I am guessing that this might be possible because the diode would eliminate damaging fly-back voltage from the motor coil.

My question is, would this work? I don't really want to try it without advice first because I don't want to damage my Arduino nano board.

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  • \$\begingroup\$ Not realistically, no. The issue is not what you are thinking, but rather that 6 volts is an insufficient input for the nano's regulator. You could re-work and re-clock it to work with a 3v3 regulator however... \$\endgroup\$ – Chris Stratton Oct 4 '20 at 2:50
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Of course it will work. Many things work on the bench, when you make one, but show problems over time.

There are ways that "work" but that hide unreliability and will leave you unsure when intermittent or unexpected operation occurs.

The problem here to consider will be interference between the motor and the Arduino, which is best handled with filtering.

What will you be powering it with? What will you use to switch power to the motor? Some of the available motor drivers will already have reverse EMF pulse suppression and some filtering.

  • How much current will the motor draw?
  • How are the Arduino controls getting to the motor driver?

This matters because the ground reference for the signaling matters, and the ground currents from the motor driver will introduce noise in the ground reference. If strong enough, it will interfere with the control signals from the Arduino, perhaps yielding sporadic operation, oscillation, and excess heat disipation.

Although in software we often say "there is only one way to be right", in hardware, there are many ways to appear right, but be unreliable, break down too soon or not work over temperature, supply voltage, or component variation. In the art, this is called "PVT", process (or component), voltage, and temperature variation. Making sure that the design works over the required PVT range is critical for building something you can depend on.

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  • \$\begingroup\$ I'm curious what part of this is unhelpful. In all probability, it will work, or seem to work. Even the earlier comment on the question about 6v being insufficient to power the regulator on the nano, while true, is incomplete. If one powers a nano from 6V, the nano works. Or, most nanos will work because most electronics operates with sufficient margins. You would be using some of that margin, but any specific device with a specific microcontroller and a specific regulator, would probably work. \$\endgroup\$ – cmm Oct 7 '20 at 0:20

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