driving 2 12v 2A DC motors with Mega

Hey everyone, I am building a controller that needs to drive two 12V dc motors (2A) independently of each other. I am looking for the best Shield/drivers to do this. Are there any suggestions? I am new to this and could really use the help.

Is 2A the "running" current or the stall current? The rated voltage and stall current are specifications that are important when choosing a drivers.

Some Pololu motor drivers.

Ok so the two different motors I am attempting to run are linked below. I am new to this and don't know exactly how to tell. I assume it is the running Amps though.

https://www.amazon.com/gp/product/B0791YL351/ref=oh_aui_detailpage_o09_s00?ie=UTF8&psc=1

https://www.ebay.com/itm/Dual-Head-BPT-Tube-Lab-Dosing-Micro-Self-priming-Peristaltic-Liquid-Pump/362164888278?ssPageName=STRK%3AMEBIDX%3AIT&var=631375460094&_trksid=p2057872.m2749.l2649

If you could help me I would really appreciate it.

Someone on another forum reccommended this type of driver

https://www.amazon.com/gp/product/B01M29YK5U/ref=oh_aui_detailpage_o00_s00?ie=UTF8&psc=1

The L298 motor driver is ancient and inefficient technology. They drop 2 to 4 volts and dissipate the power as heat. If your motor supply is 12V, the best that the motor will see is 10V, probably less. Modern motor drivers use MODFETs on the output and drop very little voltage and therefore waste much less power.

Do the pump motors need to run in reverse or only in one direction? If they run in one direction the driver is much simpler. A logic level MOSFET rated for the stall current is a simple driver. The flyback diode is necessary to protect the MOSFET from high voltage when the motor shuts off.

dc motor driver.jpg

They only need to run one way.

I was working on inserting the driver schematic when you replied. I asked the seller for the stall current. Hopefully he knows. If not, we can estimate the stall (starting) current by measuring the winding resistance. Do you have the motors? Do you have a multimeter to measure Ohms?

I have a generic voltmeter I could use. And thank you so much for helping! This is looking promising.

Measure the resistance between the positive lead and the negative lead of the motor power. The stall (starting) current is the rated voltage (12V) divided by the measured resistance. For instance, if the resistance is 2 Ohms: 12V / 2 Ohms would be 6 Amps. When measuring low resistance, short the test leads together and measure the test lead resistance. Then measure the winding resistance and subtract the measured test lead resistance to get a true(er) winding resistance measurement.

Ok I will measure it now. I will need to find the meter so I may not reply today.

Here is what it says I’m not sure if I did it right though.

Put the meter on the X10 scale, and make sure that the meter is properly zeroed (connect the multimeter leads together).

Ohms are read right to left off the green scale.

This is what I got after touching leads and having it on X10

This takes me back, I haven't used an analog meter for, well, a while.

This is what I got after touching leads

To zero the meter you hold the leads together and physically adjust the meter to read 0 Ohms. Carefully adjust the screw in the yellow box till the needle lines up with 0 Ohms. Then, please post a new reading.

meter.jpg

meter.jpg

The zero adjust screw on the front, at the base of the pointer is for zero Volts, not Ohms!

Most meters of that type also have a zero adjust thumb wheel for Ohms, as zero is the other end of the scale. You have to adjust both.

Instructions on meter reading.

Sorry, like I said it has been a (long) while since I used an analog meter and I do now remember the Ohms adjust.

meter knob.jpg

Ok so I put it on X10 and adjusted the meter. and this is the reading that I got.

Did you follow the instructions to zero both ends of the scale first?

What is your interpretation of the indicated value?

yes I zeroed in both ends of the scale. it seems like it is 1.8 ohms.

1.8 Ohms sounds reasonable, in which case the start/stall current, operating from a 12V supply, would be around 6.7 Amps. A 10 Amp motor driver should work.

Or, follow this tutorial for a MOSFET driver bildr High-Power Control: Arduino + N-Channel MOSFET - bildr

Contrary to the advice given in that tutorial, you should use a logic level MOSFET, like the one recommended.

jremington: 1.8 Ohms sounds reasonable, in which case the start/stall current, operating from a 12V supply, would be around 6.7 Amps. A 10 Amp motor driver should work.

Or, follow this tutorial for a MOSFET driver http://bildr.org/2012/03/rfp30n06le-arduino/

Contrary to the advice given in that tutorial, you should use a logic level MOSFET, like the one recommended.

Ok so the tutorial makes good sense and all. Now On one of the motors I need to be able to connect the Optical sensor to the Single-head pump. This is what will controll on/off. So I would need to run the sensor in-line with the mosfet between the gate and the arduino?