The Goldilocks Zone
2. Too High, Too Low, or Just Right?
Okay, so what's the magic number? Unfortunately, there isn't a single "best" PWM frequency for every DC motor. It depends on a few factors, including the motor's characteristics, the load it's driving, and the application itself. However, there are some general guidelines.
If you go too low, say below 100 Hz, you might start hearing a distinct buzzing or whining sound coming from the motor. This is because the motor's windings are physically vibrating at the PWM frequency. It's annoying, and it can also cause premature wear and tear on the motor. Imagine listening to nails on a chalkboard all day — your motor feels the same way!
On the flip side, if you crank the frequency up too high, say above 20 kHz, you can run into other problems. At higher frequencies, the switching transistors in your PWM controller might not be able to switch on and off fast enough, leading to increased power loss and heat generation. Also, some motors can experience increased electromagnetic interference (EMI) at higher frequencies, which can wreak havoc on nearby electronics. Nobody wants their robot's brain to fry because of a noisy motor!
Generally, a good starting point is somewhere in the range of 1 kHz to 20 kHz. Many applications work well with frequencies between 5 kHz and 10 kHz. Experimentation is key! Start with a frequency in this range and then listen to your motor. If it's buzzing, increase the frequency. If your controller is getting unusually hot, decrease the frequency. You'll find the sweet spot eventually.
