Adding a blower fan to a stepper motor circuit makes my Arduino fail

Other Hardware Motors, Mechanics, Power and CNC
1

I'm building a pick and place machine. I've attached a very bad schematic drawing, but basically:

  • An Arduino Nano powered by host USB controls 3 Pololu A4988 stepper driver boards
  • The chips of the Pololus are powered by the Arduino via host USB; the motors are powered by a 28V 8A power supply
  • I've got a .1uf decoupling capacitor on each board and !SLP is tied to RST per Pololu's recommendation.
  • There's small heat sinks on the A4988 chips.
  • The steppers are rated for 1.7A each and I have the control pots of the Pololu boards dialed to 1/4 of capacity (2A rating)

Everything works for about 10 minutes, then the driver chips start overheating and resetting. Today I added a blower fan, powered by the 28V motor power supply, for more ventilation on the heat sinks.

But as soon as I plug it in the Arduino board resets, Windows plays the "USB device unplugged" sound, then I get a popup that the USB device is unrecognized. I can disconnect the fan and everything returns to normal, but I can never get the fan and the Arduino to run together.

Is this because the fan adds an inductive load so I need a diode? If so I have some 1N5817 1A diodes, will one of these work (or if not, what should I get) ? If this isn't the cause, can you tell me what else to look for or do?

Thanks as always.

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2

Itis because something is drawing too much current from the USB. They can only supply half an amp.

3

Well this was an interesting problem...it turns out it was a loose USB connector. The minor flex of plugging the fan into the breadboard is enough to momentarily break the link....

Maybe all those people going on and on about how much better micro USB connectors are than mini USB ones are right? Weird.

Anyway, thanks for your help grumpy_mike.

4

Maybe all those people going on and on about how much better micro USB connectors are than mini USB ones are right?

No I don't think so. Micro ones do drop a lot more voltage across them. Mind you the problem might be cheap USP connectors not conforming to the mechanical spec.

Glad you got it working.