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I currently have a push solenoid connected to my standard Arduino board. The Arduino is powered via its USB cable, while the solenoid is powered using a 12V Huawei adapter (in conjunction with a MOSFET driver module).

How can I switch out the push solenoid for a servo motor? The operational voltage of the servo is 4.8 to 7.2V (with a stall torque of 13 kg-cm) to give you an idea of its size. I have been told to buy a DC-DC step-down module (to adjust the Huawei supply from 12V down to 5V) but I think it could be easier to power the servo using some sort of USB?

Or other suggestions are welcome. I want the easiest solution (since I am NOT tech savvy) and I can't buy parts until I am for certain the solution will work (that's research for you). Thanks!

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3 Answers 3

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You will have to check in the servos datasheet for the maximal current, that it draws (motors draw more current, when inhibited by mechanical force, so be sure to get the maximal current from the datasheet). From the data, that you gave us, I think it will draw rather much current. So you should not power it over the USB port of your PC (which gives 500mA at maximum). Also you should not use the 5V pin of your Arduino, or you may fry components like the diode, that lies in the current path from USB to 5V pin.

For your step down module, you will also have to check, if it can provide the current, that the servo needs, or you may kill it. If you want to use USB, you can use a standard USB charger or powerbank. Often these can provide more than 1A (depending on the actual product). Most USB wallwart chargers have a current specification on them. But (as said earlier) don't provide the power through the Arduino. Provide it directly from the source, so that the possibly high current for the servo does not have to pass trough the Arduino. You can also power the Arduino with the same source in parallel to the servo, so that you don't need two sources or a converter.

For more info, you will have to provide more information about the servo

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  • Hey thanks so much for your reply :). I am going to be using the TowerPro MG995 servo. According to their website: Current draw at idle 10MA No load operating current draw 170MA Stall current draw 1200MA So I could buy a standard usb charger plugpack to power the servo (eg. 5V, 2A)? Then my next issue would be cutting and soldering these parts together I assume...
    – Stacey1234
    Nov 3, 2018 at 4:27
  • Yes, that should be sufficient. You can either cut the USB cable (charge-only cables only contain 2 wires), or you can solder your own wires directly to an USB plug. The outer contacts are connected to power. Be sure to use the correction polarisation, so that the charger is not connected the other way round.
    – chrisl
    Nov 3, 2018 at 10:58
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I don't know if i understand your question properly, but if you want to connect the servo to the Arduino try connecting it to the 5v Output of your board.

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Getting a DC-DC step down converter would definitely work and would be a good way to do it. However,realistically you will be fine if you connect the servo to +5V from USB, since you said it only draws absolute max of 1.2A. Almost all USB ports can handle that.

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