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12v motor help
Moderators: adafruit_support_bill, adafruit

Please be positive and constructive with your questions and comments.

12v motor help

by Pchung on Wed Apr 20, 2016 2:56 am

Hello Adafruit,

I am creating a science project and I want to power a 12v DC motor at 20 rpm and be able to charge the batteries connected to it. I want to be able to just plug a usb into it and have it automatically charge without swapping the batteries out. I will also need to control the speed of the motor and do not know which variable controller to purchase (do I need a variable controller?) the motor will already be 20rpm, I'd like to control the speed of the motor. I attached a link as a reference to what motor I have.

I am confused and do not know what to purchase from your website. Any help will be great!


http://www.amazon.com/Nextrox-Mini-Torq ... m+dc+motor

Pchung
 
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Re: 12v motor help

by adafruit_support_bill on Wed Apr 20, 2016 6:39 am

How precisely do you need to control the speed? The motor in your link will run at approximately 20 RPM at 6v with no load.

If you need exact speed and/or constant speed under load, you will need some type of feedback in addition to a motor driver.

Also, do you need to control the direction too, or just the speed?

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Re: 12v motor help

by Pchung on Wed Apr 20, 2016 1:26 pm

I do want to control the exact speed when it is under load.

Having go into different direction would be a plus.

Pchung
 
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Re: 12v motor help

by adafruit_support_bill on Wed Apr 20, 2016 1:42 pm

To control the exact speed, you will need an encoder on the output shaft. http://www.robotshop.com/en/encoder-disks.html
Direction control requires a controller with an H-bridge. There are many to choose from. But first you need to know the current requirements of the motor. I do not see any current requirements listed in the link you posted.

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Re: 12v motor help

by Pchung on Wed Apr 20, 2016 2:05 pm

Great! I will see if I could figure that out.

Whats the best thing to use to charge the batteries. I want to be able to just plug a usb into it and have it automatically charge without swapping the batteries out and run the motor

Pchung
 
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Re: 12v motor help

by adafruit_support_bill on Wed Apr 20, 2016 2:40 pm

You will want to choose a battery pack with the same, or slightly higher voltage than your motor rating.

There are plenty of 6v and 7.2v NiMH rechargeable packs. If you check with the major battery vendors, you should be able to find a suitable charger for it too.

LiPo packs and chargers are also available in 7.4v.

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Re: 12v motor help

by Pchung on Wed Apr 20, 2016 2:50 pm

Will this work? or does Adafruit create one that can do 6v and powe the motor?


https://www.adafruit.com/products/1944

Pchung
 
Posts: 6
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Re: 12v motor help

by adafruit_support_bill on Wed Apr 20, 2016 3:07 pm

It might work. But first you need to understand the current requirements of your motor.

In general, it is better to choose your primary battery voltage to match your largest load (i.e. the motor). Using a boost circuit such as the PowerBoost is not the most efficient solution. Your LiPo cell will need to be capable of supplying about 150% of the motor current due to the proportional current loss from voltage boost, plus another 10% or so because the boost conversion is not 100% efficient.

If you need exact control of the motor speed under load you need to select a motor and power supply that are capable of running faster than that with no load. A 6v motor that runs at 20 RPM with no load will run slower at 5v, and even slower at 5v under load.

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Re: 12v motor help

by Pchung on Wed Apr 20, 2016 7:31 pm

Their is no information regarding my current requirments for the motor I am using, so I guess my next solution is to find a different type of motor that would be 5v? in order for me to use the rechargable 5v (link). I thought using a DC motor at 20rpm from Amazon would do, but I guess their was a lot more to it.

https://www.adafruit.com/products/1944


I'm learning a lot more about my science project then I am at school..

Pchung
 
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Re: 12v motor help

by adafruit_support_bill on Wed Apr 20, 2016 7:52 pm

Another good source for gear motors is www.pololu.com. They have a wide range of motors and publish detailed specifications for them.

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Re: 12v motor help

by Pchung on Wed Apr 20, 2016 10:01 pm

Thank you Adafruit_support_bill!!!

Pchung
 
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Joined: Wed Apr 20, 2016 2:42 am

Please be positive and constructive with your questions and comments.