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Newbie question simple motor setup

Hello, I’m 100% a newbie so this is going to sound like a stupid question. All I’m wanting to do is use two small motors (probably two 380:1 Micro Metal Gearmotor HPCB 12V) to spin at a constant speed (say, 80 RPM) but in opposite directions (one clockwise, one counterclockwise). No speed adjustment needed. So, as a total newbie, I gather that I need two motor drivers (a dual one won’t work because the two motors will be physically separated in such a way that I can’t wire from one driver to two motors. The site suggests this driver for the motors I’m looking at: MAX14870 Single Brushed DC Motor Driver Carrier. Do I also need a micro controller? Please pardon my ignorance.

Hello.

I responded to your email, but I missed that you also posted this same question here on the forum. In the future, please let us know if you contact us in multiple ways. Also, in cases like this where people contact us in multiple ways, we generally prefer to continue the discussion on the forum so the content can also serve as a resource for others. Accordingly, I am copying my reply below. Please continue the discussion here on the forum.

In general, these kinds of motors have speeds that can vary by as much as +/-10%. If that level of variance is okay for your application, then you probably do not even need a motor driver if you just plan to directly connect the motors to your battery through a switch. Note that as your battery drains and its voltage drops, the speed of the motors will also drop. To prevent that drop in speed, you could do something like add this voltage regulator in between the battery and each motor.

If you want to achieve a speed other than what the motor would produce with your battery and your load, you would need to use a motor driver like the MAX14870 you mentioned (which would be a suitable driver for that motor). Note that this generally requires you to use a microcontroller to send control signals to the motor driver. With an open-loop system like this, you could control the speed of your motors, but not super accurately since the actual speed will still vary based on your load and external forces.

If you determine that you need to accurately maintain a specific speed, then you would need a more complex closed-loop system, which would work with something like tachometer feedback. To do that, you would need to get the dual-shaft version of that gearmotor and solder an encoder disk to the back of the motor.

If you let me know what kind of performance you need from those motors, I can point out some appropriate hardware.

Hi Jonathan,

Thanks for your swift response!

The motors won’t be powered by a battery but by a 12V AC-DC adapter, so there shouldn’t be a significant variance in the voltage supplied.

I don’t need to maintain a specific speed, but having both run at about the same speed (close enough that it wouldn’t be visibly obvious if they’re quite the same), but I’d prefer the speed stay fairly constant - probably around 80 RPM or so. I do need them rotating in opposite directions.

It sounds like if you were to get two particularly well-matched motors, you might be able to achieve acceptable results with just a switch and your power adapter. It should also be straightforward to test this out once you have the motors. In case you were not already aware: to get the motors to rotate in a different direction, you just reverse the polarity of the connections to the motor leads (i.e. instead of + and - going to left and right motor terminals, respectively, connect the + and - right and left terminals, respectively). Also, if your 12V power adapter terminates in a 5.5mm barrel jack like many do, you might find this particular terminal block adapter useful.

Great! I was initially hoping I could maybe do it with just the motors. I’ll put in an order for two and test it out. Thanks so much!

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