Hi i’m a EE college student in senior design. We are having to construct a robotic car and I am in charge of the drive motors. However, I am not sure how the motor controllers work. The following is one I have been looking at:
Adafruit Motor/Stepper/Servo Shield for Arduino v2 Kit - v2.3
We will be using 4 12Vdc drive motors with encoders. Can i use this controller with motors w/encoders? Also how will they connect to the controller? Thank You!!
Hi,
Do you mean the RB-Ada-94?
If so, one of the the most important questions is does it meet the voltage and current requirements of your motors?
The datasheet for this motor controller specifies this:
This means your 12 V DC motors will be fine voltage wise. What is the continuous current (with load)? What about the stall current? Of course, the lower the continuous current compared to the maximum of the motor controller (1.2 A), the less it will heat-up (and risk shutting down after prolonged use).
The shield itself uses the I2C interface for communication by a serial protocol, so all the other digital pins are available to read your motor encoders with.
If this shield can provide anough current for your motors then you should have no issue using it with your motors and withe encoders. If you are using quadrature encoders (likely as they are the most common), we recommend that check out this detailed article on the Arduino website. It offers a rather complete explanation of how to read the inputs of encoders and how to use them using various methods (various polling and interrupt driven methods).
Sincerely,
Yes thats what I meant, sorry. Ok so from the motor spec sheet the Max No-Load Current is 0.20A and the Max Stall Current 4.9A @ 12VDC, not sure about the current with load…However, we do plan on running the motors with a voltage less than 12 Vdc.
Hi,
If you run the motors at a lower voltage for the same load, the current requirement tends to go up (they are both related).
Also, a good rule of thumb is to assume continuous current under load should be roughly around 25-35% of the stall current (where the motor may overheat / get damaged / etc.).
25% of 4.9 A is roughly 1.225 A, so you may be at the limit with this motor controller. If you load is very light (possible since you will have 4 motors), you may be ok. We recommend that you run some tests using a multimeter in series to measure the current used by your motors while directly connected to a power supply (not a motor controller). You can vary the load / simulate one by adding resistance to the shaft.
Sincerely,
Ok i understand. The max load we will be carrying might be roughly 25 lbs. So an alternative motor I have has a Free-run Current @ 12VDC of 300mA so that would be 0.075 at 25%? Is that correct? So another controller that you carry is the Arduino Motor Shield V3. This has a 2A per channel so that should be fine for both motor choices. How many motors can be connected to the V3? Thanks
Hi,
The free-run current means “no load”, where the shaft of the motor is not connected to anything. The 25-35% approximation for the continuous current (with load) is based on the stall current, not the free-fun current.
The RB-Ard-35 has 2 motor channels capable of 2 A maximum each. Please note that an secondary external power source is required to power the motors (the Arduino-compatible board the shield is placed on will not be able to provide the required power or voltage).
Since you wish to control 4 motors, we recommend that you look at motor controllers that are not in shield form factor. They are just as easy to use and will provide you with many more options (probably less expensive / more powerful ones, too).
You can browse our motor controllers (< 10 A) here.
Sincerely,
Yes we plan on supplying the motors with a separate voltage supply than what will be supplying the to board. So after looking over the page I saw this controller: RB-Dag-55. I don’t see specified what the max current per channel is. Is it 2A? Will this work with Arduino or raspberry pi?
Hi,
This motor driver does seem to imply 2 A per channel, but the manufacturer is rather vague about it. You can contact them directly to obtain more information here: [email protected]
Sincerely,
Hi,
I have another question and just to say I didn’t make a mistake on motor calculations but have corrected it. I wanted to get your opinion on two motor controllers you sale. Product Code: RB-Dag-55 & Product Code: RB-Dag-105…I plan on using mecanum wheels 4 drive motors from Pololu: RB-Pol-125
Before I make the purchase I just want to make sure they will handle the motors and just to say I do not plan on running the motors at a full 12Vdc. I believe closer too between 7V-9V is what I will run them at so that stall current wont be 5A like the specs say.
I like the ComMotion Board just because it can mount on top of the arduino that we will be using and the other Dagu(RB-Dag-55) will not. However, I cannot find much information on the ComMotion Board.
Thank you
Hi,
Unfortunately, all the information we have available concerning the RB-Dag-105 is on its product page and datasheet.
Also, please take note of this information mentioned previously:
If the load is the same (and therefore the power required, in W), the power input will not changed. With a lower voltage, the amount of current required will go up for the same amount of power.
Since both motor controller boards you mention have peak currents of 4 A maximum, we recommend running your motors at around 6 V DC. According to the specs for the RB-Pol-125, this should make the motors manageable by the motor controllers. The manufacturer does not provide any data for running the motors at 7-9 V DC, but it may be fine too. We recommend that you test is first with one motor (from no load) and slowly add load/resistance to the shaft and see how the current consumption is (using a multimeter).
If you need more detailed information on either of those motor controllers, we recommend that you contact the manufacturer directly.
Sincerely,
