Open source motor controller

Discussion in 'The Projects Forum' started by hspalm, Oct 23, 2010.

  1. hspalm

    Thread Starter Active Member

    Feb 17, 2010
    Hello everyone!
    I have been looking for a high power motor controller to use in my projects. It's not the actual cost of a complete controller that gave me the idea of making my own. All tough the complete controllers don't cost much money, I think many of them are a bit overpriced, and I love the idea of a schematic, PCB layout and the overall design of a circuit being open source. When finished, this project will be available to others as a kit, a design (free, of course), just the PCB or (maybe) pre-assembled.

    I hope you will help me on this one. As the parts that may be sold will probably not even be sold be my, I hope no-one thinks I am using you to earn a profit on this!

    Explaining what I want:
    (Generic) A versatile high power DC motor controller. Power to be controlled by potmeter mounted on either PCB or maybe handlebars of a kick-scooter or similar, connected by wires.
    (Detail) Analog voltage from pot is converted by a uC ADC to a 0-100% PWM which is amplified by mosfets through an h-bridge controller.

    Hopefully I can ask both generic and detailed questions, and anyone is of course welcome to suggest anything for this circuit, even though it may involve a drastic change to the design. Hopefully we will soon be on the track of a very specific design that just needs improvements. The goal is to design an easy-to-understand and as-cheap-as-possible design.

    I have made a sketch that will make the fundamentals of my idea. And here goes my first questions!
    - What could a ~maximum achievable power rating of a product like this be?
    - Is it preferable to use another set of five transistors to fully switch on the h-bridge fets, so I don't have to be limited to the logic level fets?

    I am aware that designs like this is widely available all over the internet, but I also want this to be a sort of learning project for my self!

    Thank you so much, and please comment on anything you want. Both to my intentions of this project, and the design it self.

    A link to the schematic picture, which will soon be scaled down to fit the forum:
  2. SgtWookie


    Jul 17, 2007
    First off, you need at least a high-side driver for the upper MOSFETs. Otherwise, they will get fried in a twinkling. You'd need to be able to raise the gate to 12v+5v, and there is no way the uC will do that by itself.
  3. bertus


    Apr 5, 2008
  4. hspalm

    Thread Starter Active Member

    Feb 17, 2010
    Is there no logic level transistors to use with high enough specs? A high-side driver, that is another transistor to pull the gate voltage higher?

    You really got me thinking here. But I have decided to keep on doing this thing, so I will learn. But thank you for the link!