MCU resetting after short time

Other Hardware Motors, Mechanics, Power and CNC
1

Hi,

I'm making a small turn table out of leftover parts. I'm using an Arduino Pro Micro board together with 28byj-48 steppers with the ULN2003 boards (the smd version). However, my boards appears to be resetting after a few seconds.

I'm using 3 steppers. To keep them in sync and not use all my pins I soldered the same input pins of all 3 boards together. Power is connected to the raw pin of the arduino with power being supplied by USB.

The steppers turn for a few seconds and then the board resets. When that happens, the LEDs on the ULN boards seem to fade off over a second, as if supplied by a drained battery. It runs a little longer if I only use 2 steppers and does not reset if I only use one (by disconnecting the power pins).

This makes it seem like the steppers draw to much power. Google says that each stepper needs up to 250mA. If my PCs USB port happens to be only 500mA (I don't know its rating), then It would explain why there is not enough power. However, I also connected the board to a power bank which can supply several Ampere on the port, so the steppers should get enough power (since I use the raw pin).

That leaves the 4 control pins for the board. I'm wondering if they draw to much power from one set of pins for 3 (2) boards. However, I didn't find how much power the ULN board draws on those pins (although I would expect it to be very little)

Does anyone have any ideas?

2

How much current are the 3 steppers taking when they run ?

3

There is a 500mA resetable fuse on the pro micro. You are probably blowing it.
Every time it blows and resets, it's resistance increases a little.

4

Separate power for the steppers.

5

I was looking at the boards ratings but the ones I saw never listed the max current for the board (only for the pins, if any). I didn't know about the fuse and expected at least a little more than 500mA for the entire board (like 1A or 2A).

This makes it clear what is happening. Also, the resistance increasing after it blows also explains a few things.

I will have to update my circuit.

Thanks for the help

6

In general, you should not power any high current devices from the 5V pin especially if you are powering the board via the Vin pin. Most motors and solenoids should have a separate supply.

For the pro mini I would not source or sink any more than 15mA from any I/O pin.

FYI: The max current for the ULN2003A input pins can be as high as 1.35mA

7

This topic was automatically closed 180 days after the last reply. New replies are no longer allowed.