I need help choosing the right motor shield

Hi

I have been having some trouble choosing the correct motor shield for a project i have been given. In my project i am using two 12V DC planetary gear motors and one 12V DC pull action linear solenoid actuator which will be controlled by an Arduino. The links are bellow.

12V DC Planetary Gear Motor:https://www.servocity.com/html/313_rpm_hd_planetary_gear_moto.html#.Vn7X9ZN95E5

12V DC pull action linear solenoid:http://uk.rs-online.com/web/p/dc-d-frame-solenoid/0349709/?origin=null|fp&cm_sp=featureproducts-_-FeaturedProductsContent-_-0349709

I have been recommended a Pololu Dual VNH5019 Motor Driver Shield for Arduino (https://www.pololu.com/product/2507) to control both my DC motors, but now that i have added in the Solenoid Actuator i don't know if i have to add an other motor shield or buy a motor shield which can connect three motors?

I would greatly appreciate any help or advice that can be given

It looks like the solenoid just needs an on/off switch and it draws just under 1 amp at 12v. You should be able to switch the power with a transistor controlled from an Arduino I/O pin.

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The solenoid will also need a freewheel diode, note.

The motor has a stall current of 20A so you need a motor driver capable of that current level unless under-powering the motor (which means you would need a supply that doesn't cut-out when over-loaded, but current-limits instead).

That Polulo motor driver I've actually used myself with a similarly sized motor (but limited to 5A by the power supply) and it works fine, not even warm at that current level. It should be fine with that motor - getting the right power supply is important.

Thank you very much for the help! I appreciate it greatly :)

Since my university has given me a budget on what i can spend i need to make sure i choose the absolute correct equipment :P For the power supply i understand i am gonna have to use a 12 V power supply. However I am not 100% sure on which one will do the best job. Is there a good 12V power supply that you have previously worked with? What power supply did you use when you worked with the Pololu motor shield and similar sized motor ?

The motor will briefly draw the stall current every time it starts up, and the behavior of the power supply during startup is very important. If the power supply cannot supply the full stall current, it will either limit the current to a safe value (in which case the motor will still work) or it will shut down.

Unfortunately, manufacturers rarely specify that behavior, so you will probably have to experiment with several 12V power supplies. The more current the better.

I've had good luck with 12V power bricks from discarded LCD monitors. Some are capable of 7 amperes or more.