0
\$\begingroup\$

I'm new to this platform and knows very little about electronics. Please forgive if any of this is dumb.

I wish to create an inrush current protection for my L298N Motor Driver, which drives a 7.5V DC motor.
The Motor draws nearly 2.5A (Please see waveform) during start which according to L298N Datasheet is above maximum.

Waveform under no load waveform under no load

Loaded waveform when loaded

To prevent inrush, I came up with a circuit as given below. The capacitor would be charged at all times and the IRF740 MOSFET is set to turn on when the motor starts. The capacitor would discharge through the mosfet to provide the initial current requirement. Diodes prevent reverse current.

enter image description here I don't know if this would work or if this has any problems. Please tell me whether this circuit would work. If it has any problem, suggest a good method to prevent this inrush.

\$\endgroup\$
4
  • \$\begingroup\$ #Rishab Navaneet, Welcome & nice to meet you. I have been playing with L298N for the last couple of years, and I think L298N is the best for newbies to learn basic electronics etc. Recently I switched to BTN7971B so perhaps I can answer your general question on BTN797B or more details you might like to read my answer to the follow Q&A: Protecting circuit from piezoelectric disc voltage spike: electronics.stackexchange.com/questions/528419/…. Have a great project. Cheers. \$\endgroup\$
    – tlfong01
    Commented Apr 16, 2021 at 1:56
  • \$\begingroup\$ Thanks a lot for the suggestion. But I also needed to know whether this circuit would work \$\endgroup\$
    – Rishab Navaneet
    Commented Apr 16, 2021 at 2:57
  • \$\begingroup\$ Ah, I found your circuit a bit confusing, and a bit problematic, even it works intermittently. Questions: (1) You seem to use a charged cap to drive the motor. How can you be sure the charge is enough to drive the motor? (2) You stared with L298N with 4 NPN BJTs and built in flybacks. But your question uses only one power MOSFET and the flyback does not seem to include the back EMF current path stuff. Perhaps you can show how you modify the L298N (or a part of it) and let us see the big picture. \$\endgroup\$
    – tlfong01
    Commented Apr 16, 2021 at 3:12
  • \$\begingroup\$ Your circuit cannot generate the correct Vgs values for that PMOS FET for one thing. \$\endgroup\$
    – user16324
    Commented Apr 16, 2021 at 10:56

1 Answer 1

Reset to default
5
\$\begingroup\$

Use pwm from the Arduino to ramp up the power to the motor. No need for extra circuitry.

\$\endgroup\$
2
  • 1
    \$\begingroup\$ Generally known as softstart. \$\endgroup\$
    – jusaca
    Commented Apr 16, 2021 at 7:05
  • \$\begingroup\$ Thanks a lot for the suggestion... it was very simple... But since the spike happens in every sudden turn on, I'm confused... Let me confirm if it works... \$\endgroup\$
    – Rishab Navaneet
    Commented Apr 16, 2021 at 12:10

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service and acknowledge you have read our privacy policy.

Not the answer you're looking for? Browse other questions tagged or ask your own question.