PWM

[Kiwi Bruv]

I am building an electric bike.

I am going to build a PWM circuit using a 555 chip to generate the PWM signal and and MOSFET to switch the motor power supply.

I will drive it using a variable resistor initially and later a Picaxe microcontroller so I can do some fancy stuff.

My motor is 300W 24V.

What is the best frequency to drive the motor at and why?
How do I size the flywheel diode?
How do I decide the size of cap to put across the motor terminals?

 

[audioguru2]

Hi Kiwi,
Here is a link to the technical description of motor speed controls for wheel chairs and golf carts, many running on 24V. The 555 PWM speed control and its limitations are discussed and better circuits. Nearly everything is covered including coasting down a steep hill which generates a current in reverse through the speed control circuit.
http://www.4qdtec.com/pwm-01.html

 

[Alun]

Kev Bruv,
Just for future referance you could try searching the forum (there's a search button at the top of the page just next to where it says Electronics Lab Community) before asking a question because someone has already asked this question before:

http://www.electronics-lab.com/forum/index.php?topic=2988.0
http://www.electronics-lab.com/forum/index.php?topic=2373.14

 

[Kiwi Bruv]

OK, thankyou