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I am trying to make a robot and I have some problems with the L298N motor driver. I supplied it with 9 V and used its 5 V output to one of the pins. I put two motors at both motor outputs and the motors don't move or move erratically.

I measured the voltage across several points:

  • I tried measuring the voltage across the two input terminals and it was 5.1 V.
  • When I took out the motors and measured the voltage between the output two output terminals for one of the motors it was 5 V.
  • When I put back the motors and measured the same terminals again it was 0.2 V.
  • When I replaced the motors with LEDs, the LEDs lit and the voltage between the terminals was 3.6 V.

My question is: why is the voltage across the output terminals so low when I connect the motor?

This is the circuit

ocrdu
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Joshua
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1 Answers1

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The PP3 9 V batteries you use are only suitable for loads that pull very small currents; they are nowhere near powerful enough to supply your motors (unless your motors are really tiny and pull currents in the low mA range).

When connected, the 9V battery's voltage will drop immediately, and it will last only a very short time.

This is made even worse by the use of an L298N motor driver: these are very inefficient and will drop the voltage across the motors by about 1.4 to 1.8 V.

You need a proper power supply that can supply the current the motors need. If you need 9 V for the motors, even 6 1.5 V AAs in series would be better than using a puny 9 V battery.

A more modern and efficient motor driver would be nice also, but won't solve this problem as it is caused mainly by the battery choice.

ocrdu
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  • Alternatives to the L298N motor driver ? – ManuelJE Jan 04 '21 at 14:07
  • Maybe [this](https://electronics.stackexchange.com/questions/108686/l293-l298-and-sn754410-h-bridge-drivers-on-low-voltage-power-supply) older questions is helpful, there are a few alternatives in the answers – Michael Brown Jan 04 '21 at 15:58
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    Thanks for the advice. I changed it out for a 4.8v but much higher amps battery and it works well. – Joshua Jan 09 '21 at 14:34