this post was submitted on 15 Aug 2024
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DC motor speed control (lemmy.ca)
submitted 4 weeks ago by m0darn@lemmy.ca to c/askelectronics@discuss.tchncs.de
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I'm trying to achieve variable speed control on two brushed DC motors powered by a 3s or 4s LiPo battery (~12V or 15V). This is for a nerf blaster I'm modifying, which is why I'm not using a pre-made speed control ie I want control over the shape/layout. I'd like to vary projectile speed with a thumb knob.

I just finished watching ElectricMonkeyBrain's YouTube video on the TL494 PWM chip.

I was initially planning to vary the duty cycle with a potentiometer on the chip's control pin, to get a PWM signal and feed that into a MOSFET. But in the video he mentions that the chip has an integrated over current protection function. Ie the chip will

monitor the voltage across a sense resistor in series with the load

and will

kill the output if the sensed voltage/current goes above a reference voltage

It occured to me that I could actually adjust the reference voltage as a way to control the motor speed.

Would this be a better way to achieve speed control and protect my motors/battery? Or is it a terrible idea altogether.

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[–] m0darn@lemmy.ca 1 points 4 weeks ago

Thanks. Yeah you're recommending what I was initially thinking.

You should probably use a simulation tool to check the circuit before you start destroying chips.

Fair!