Can someone help me understand amps?

Other Hardware General Electronics
1

Hi,

I currently have a bunch of parts on order for a big Arduino project I'm making. The two main devices I am using are DC motors/pumps and control boards to turn them on/off. I have been trying to understand if I am at risk of burning any components because I am afraid that kicking on like 6 motors at once will send too many amps to the control boards. I plan to wire up the control boards and motors to all share the same external 12V power supply in parallel. Here is a wire diagram:

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I have been watching a bunch of electronic basics videos on Youtube and I learned that (I think) amps are added up when you run devices in parallel. Each motor needs 400mA according to the datasheet I linked above. 400mA * 6 = 2.4A. So the total amps used by my circuit could be 2.4A but does that mean when all 6 motors are on 2.4A is going through each control board? because that will almost surely burn them up! Or does each board only experiance 800mA since there are only 2 motors per board?

Thanks in advance, im sure this is a stupid simple concept but I don't know anyone who can check my work irl

2

2.4A would flow from the power supply and divide among the motor drivers as required. Circuits draw current.

Don't forget to take into account the start/stall current of the motors, which is typically 5-10 times higher than the running current. So if the running current is 400 mA, the start current could be as high as 4 Amperes for each motor.

Your motor drivers must be able to handle the start/stall current, and motor power supply must be able to handle the total for as many motors as will be moving at once.

3

You need to add a GND connection from your Arduino to the motor driver power supply.

4

The connections between motor drivers and the Arduino are signals, very little current.

Those signals control the power circuit which is where the heavy currents are.

5

As long as your motor controller boards can support your motors and your power source can support your total loads you will be fine. At start up or stall your motors can draw currents well in excess of their normal run currents. Start currents are normal and figured into things. Stall or locked rotor currents can be a problem so placing an inline fuse on each motor won't hurt.

Ron

6

like @larryd mentioned, I should connect the - terminal of my power supply to my Arduino as well. Would it be safe to use the 12V power supply on the VIN pin to power the Arduino as well? I heard on the mega the VIN pin can handle a 9v-12v input.

Could it really be as simple as this?

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7

If all you are connected to is what is in the schematic, you will be okay.

7-9v on Vin is a better choice if you are powering any more I/O from the Arduino.