Motor control circuit advice with L298N

Discussion in 'The Projects Forum' started by nezumij, Apr 7, 2012.

  1. nezumij

    Thread Starter New Member

    Apr 7, 2012
    1
    0
    Hi all,

    I'm looking at controlling 2 x DC Motors (FA-130's) using the L298N and an Ardunio Uno, and after reading numerous forum posts and data sheets I've concluded my understanding with the following schematic (see attached).

    I would like some clarification as to whether my understanding/circuit diagram is correct, and I also have a few questions around the circuit.

    Here are some additional details:
    - The motors are the small hobby DC type, operating Voltage is 1.5 - 3V (1.5V nominal) with a stall current of 2.2A. They are being used to drive a small Tamiya tank kit.
    - I have 2 power sources, 4.8V(Vs) to drive the motors (4xAA's - 1.2V NiMH) and 5V(Vss) regulated from the Arduino, I'm powering the Arduino itself with a 9V battery (PP3).
    - I've opted not to buy a motor shield for the Arduino as I would like to understand more of the electronics involved.

    And here are my questions:

    1) For R1 and R2 in the diagram, I'm not sure what resistance these should be. I'm simply taking the 0.5ohm rating from the L298N DataSheet, I understand that the rating here will depend on the draw from the circuit, but I have no idea what I'm using to calculate this.

    2) I haven't bothered putting in a voltage regulator on the 4.8V supply, my understanding is that the batteries could peak briefly to 6V, and the L298N will cause a 2.5V drop when the supply finally reaches the motors, so I figured I didn't really need one?

    3) Do I need to separate the 2 power supply grounds, and ground everything to the 'correct' supply or can I use a single ground rail and hook everything up to that?

    4) For the pull-down resistors on Ardunio it's seems common to use 1Kohm - 10Kohm, but I'm not sure of the exact science here, if I'm simply pulling logic to 0V could I not use something a lot smaller?

    Thanks in advance for any help!
    Joel.
     
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