NEMA 17 200 step/rev 12V motors in circuit with Arduino MEGA shorting

We stacked two Adafruit Motor Shields V2 for Arduiono Mega to run 3 1.8-stepper motors (12 V) and controlled movement with buttons. We are directly powering one shield with a power supply of 12 V and over 1.2 A of current. The motor connected to the shield that is directly supplied with 12 V (bottom shield) tends to stall and move with more difficulty than the motors connected to the shield not connected to power supply (top shield). Each button controls one direction of movement for each motor (total of 6 buttons).

However, we kept running into the trouble with the circuit and it kept shutting off. The circuit runs for a while and then shorts and stops working. The power light on the shield shuts off even when the Arduino board remains powered and we have to turn the power supply on and off again to get the motors working again. We think it is due to overheating but we don’t know the exact cause and how to resolve this problem. We added heat sinks on the drivers to help with the overheating, but we still are having problems. Our end goal is to be able to move the three motors for separately and in different directions for a significant amount of time.

Any help or thoughts would be appreciated!

Those motor shields are a very poor choice for driving a stepper motor. They are meant for controlling DC Motors.

Have a look at Stepper Motor Basics

You need to post a link to the datasheet for your stepper motors. Nema 17 only defines the width of the front face (1.7 inches)

...R

We stopped using the shields and built the circuit with A4988 driver with a 1.2A 12V NEMA 17 stepper motor.

We built the circuit based on the following instructions:

We are powering the motors with a DC power supply set to 12 V. However, when we turn on the power supply and if the motor is connected the power jumps to current limiting mode drawing only 0.6 Amps at 6 V. We can't figure out why the stepper motor is drawing so much current when the power supply should be able to supply up to 30 A.

We checked to make sure the A4988 wasn't fried by measuring voltage without the motor connected (checked voltage at the 1A, 1B, 2A, 2B) and we made sure the Arduino is working as well.

The data sheet for the motor:
http://www.pbclinear.com/Download/DataSheet/Stepper-Motor-Support-Document.pdf.

Information about A4988:
http://documentation.echopen.org/CAT-daughter_board/DB-motor_control_v3/doc/pololu_a4988.pdf

Data sheet for power supply:
https://cdn.testequity.com/documents/pdf/bk/1762_datasheet.pdf

Does anyone have any ideas why motors are drawing so much current from the power supply or any idea what could be happening?
Any help would be appreciated!

shg55:
We stopped using the shields and built the circuit with A4988 driver with a 1.2A 12V NEMA 17 stepper motor.

That is NOT what the datasheet says. The datasheet says the motor current is 2 amps and the coil resistance is 1.04 ohms. Ohm's law will tell you that 2 amps and 1.04 ohms gives 2.08v. If you connect 12v directly to that motor it will try to draw 11.5 amps and the smoke will probably escape.

A A4988 will struggle to supply 2 amps even with a large heat sink and a cooling fan. Either run the motor well below its rated current (i.e. at 1.4 amps instead of 2 amps) by suitably adjusting the current limit on the A4988 or else get a more powerful driver -- perhaps one with a TB6560 chip

We checked to make sure the A4988 wasn't fried by measuring voltage without the motor connected (checked voltage at the 1A, 1B, 2A, 2B) and we made sure the Arduino is working as well.

That does not work and doing that may have fried the driver. The voltage at the motor pins is irrelevant and in any case would only make sense if it was connected to the motor, And then you would need to use an oscilloscope to get sensible data.

...R

Maybe the following information is helpful for your project and tells you exactly how to set up the current limit:
Current adjustment for A4988 / DRV8825

BTW: a DRV8825 would imho better fulfill your requirements as it is more powerful than the A4988 and is (almost) pin compatible with an A4988.