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I have assembled the motor driver circuit using L298N seen below, hoping that it would work without any problem. For some reason that I do not understand, the output power is constant. I say constant because;

  1. When nothing is connected to output, I measure 21V (such a drop is expected).
  2. When a 1k resistor is connected, I measure 0.394V.
  3. When a 10k resistor is connected, I measure 3.914V.
  4. When 1M resistor is connected (basically open circuit), I measure a value close to 21V.

I don't even know what may be wrong about the circuit, tried many things but no luck. I am hoping you guys can help. Even if you can give me a tiny tip, it would be very helpful because I can dig out the rest.

Additional Info:

  • Vcc: 24V (Supplied from an industrial power supply with enough power output capability, so I am sure there is nothing wrong with the power supply)
  • L298N: I plan to replace this IC with a more modern one, but I have to use this right now.
  • Arduino: is powered by USB port of my laptop.
  • Circuit: I have triple checked the connections and cables.
  • Also: There are four 1N4004 diodes connected to OUT1 and OUT2, moreover four more diodes connected to OUT3 and OUT4 (in order to prevent back emf.)

enter image description here

JRE
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Ekrem Kılıç
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1 Answers1

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You can't leave CS pins open, nephew.

enter image description here

As you can see from the block diagram above, the emitters of the bridge transistors go to the CS pins. So, connect these pins to GND directly, or through a low resistance if you are planning to measure the load current.

Rohat Kılıç
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    I had looked through the datasheet but thought that it was optional to use that pin for current sensing. That's why I left it open, yet you were right, it worked. Many thanks for the help! – Ekrem Kılıç Nov 10 '21 at 08:54
  • The CS (current sense) pin is the ground to the motor driver. You put a (very small) resistor there, and internally to the driver, an analog converter reads the (very small) voltage on that pin. The datasheet will give you info on how to calculate the size of this resistor, but effectively if the voltage on the CS pin exceeds a certain level, it will use this to go into "overcurrent protection" – Brydon Gibson Nov 10 '21 at 19:50
  • nephew?! same last name... lol – user253751 Nov 10 '21 at 21:12
  • @user253751 yeah, he's my nephew - son of one of my uncles :) Haven't seen him for so long, though. – Rohat Kılıç Nov 10 '21 at 21:34