A4988 Stepper driver problems. Help needed!

I am trying for a week now to run a simple Stepper Motor with an A4988 and Arduino Uno and I am about to give up.

I am using the standard circuit as provided by Polulu and the example sketch that runs the motor left and right. From what I can tell, my circuit is exactly the same. I am gettint the power from a bench top power supply.

I measured the voltage on VDD and GND and this is only 3.6V. But when I measure the voltage at the Arduino when it is not connected it is 4.6V. The coils of the stepper get 0 volts. Could the chip be turned of? Even with sleep and reset jumped? The current draw from my power supply is 30ma consistently.

I tried different steppers, different drivers and even switched out the bredboards. I don´t know what I could do anymore. I also tried running the Arduino with a USB wall socket. At first I thought I did a mistake when soldering the A4988 headers on. Now I even tried a pre-assembled one with heat sink. But it would not work!

(The extra chip is there so you can read the labels underneath.)

Post a link to the datasheet for your stepper motor.

This Simple Stepper Program works for me with that Pololu wiring diagram. Just make sure the code and the physical connections match.

Photographs of the hardware are not a substitute for a photo of a pencil drawing of the connections.

I don't see the big 100µF capacitor in your photos.

I'm a bit of a luddite. If it was my project I would try powering it with an unregulated power supply or a 12v or 24v battery. However my motors work with power from a 20v laptop PSU.

...R

Check which power input you are using on the arduino. If you are using the power input which goes into the Uno's 5V regulator, then it needs to be 7 volts or higher.

Try actually connecting the Enable input to ground.

I'd review the device datasheet to determine what the sleep and reset inputs are. It doesn't seem very logical or obvious to me to connect two inputs together, the resulting voltage on those inputs may be indeterminate, unless this is a specific recommended connection.

I'd also connect a LED and resistor to the step signal, to make sure you are actually pulsing that input.

michinyon:
It doesn't seem very logical or obvious to me to connect two inputs together,

That is the correct thing to do - or at least my motors work with the Pololu wiring connections.

...R

It doesn't seem very logical or obvious to me to connect two inputs together, the resulting voltage on those inputs may be indeterminate, unless this is a specific recommended connection.

One of the inputs (/sleep) is pulled high by a resistor on the driver board, which explains why this is the "specific recommended connection".