Powering stacked motor shields with one power supply

[mnbram]

I'm about to purchase an Arduino Uno R3 and two Motor Shield V2 kits in order to power three 5V small reduction stepper motors (https://www.adafruit.com/products/858) -- the product page doesn't say anything about current draw, but I believe I read somewhere on these forums that it isn't terribly high. I'm a little unsure from the information available, however, of the best way to power them. Ideally, I would like to minimize the number of power supplies and the number of cords that need to be plugged into an outlet. If I buy a 5V 4A regulated power supply (https://www.adafruit.com/products/1466), can I power the Arduino and both shields with that one supply plugged into the terminal blocks of one of the shields? And what would I have to do to connect the power to the other shield? The only other components plugged into the Arduino will be an RTC module and three Hall effect sensors.

[adafruit_support_bill]

A 4A supply should be plenty to power all that. The motors themselves are only a few hundred mA each.

You can run power to the terminal block on one shield and jumpers to the terminal block on the other shield. However, you must remove theVIN jumpers from both, since the minimum VIN voltage for an Arduino is 7v.

You could power the Arduino from that supply as well - bypassing the Arduino's on-board regulator. To do that, you would need to run another jumper from the positive side of the external power terminal to the +5v pin. Please note that there is no reverse voltage protection when powering it this way, so double check all your connections before applying power. Also note that this bypasses the automatic power select circuitry of the Arduino, so you should not power it this why while it is connected via USB.

[mnbram]

Upon doing some further reading, some folks suggest that rather than plugging straight into the 5V pin, one could cut up a USB cable and connect to the power and ground wires, ignoring the data wires. The advantages to this approach are that it prevents accidentally sending power via USB and the 5V pin at the same time, and it takes advantage of the Arduino's in-built 500 mA thermofuse. As an added convenience, it would leave open the original 5V pin for power out. Do you see any problem with this plan?

As a minor point, splitting the power from the external DC supply using something like this: https://www.adafruit.com/products/874 and running the wires separately to the terminal blocks on the motor shields is the same as wiring directly to one terminal block and running jumpers to the other, correct?

Also, is 22 AWG solid core wire sufficient for the power lines? I have found a lot of conflicting information, but I don't know much about voltage drop, etc. and I'm trying to be conservative about what "a few mA each" means for these motors. As an aside, I really wish Adafruit provided more detailed information about a lot of their products, such as the conductor and insulation materials for the hook-up wire and the actual current rating of the small reduction motors. Makes me want to buy those components elsewhere.

[adafruit_support_bill]

The USB cable is a good solution for 5v power to the Arduino.

Those block connectors should work fine for power distribution as well.

22 AWG is OK for those small motors. Although I would recommend using stranded wire if they will be subject to much movement. Solid core wire tends to harden and break near attachment points when subjected to repeated flexing or strong vibrations.

As for detailed product information, we do publish what the manufacturer provides - and we investigate and correct that if necessary

These motors are commodity items. There are many manufacturers producing similar motors with the same part number. Not all are identical. They vary in gearing, coil resistance and wire color coding. If you search on the part number, you will find conflicting specifications from various sites.

Samples I have tested vary considerably, but all pull < 200mA/Phase for the 5v versions and proportionally less for the 12v.

[mnbram]

Thanks, you have been extremely helpful!