1. Not finding help here? Sign up for a free 30min tutor trial with Chegg Tutors
    Dismiss Notice
Dismiss Notice
Join Physics Forums Today!
The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

Play with a handyboard from MIT?

  1. Nov 10, 2008 #1
    Anyone ever play with a handyboard from MIT? From what I gather, you can't use a high current motor with the stock handyboard unless you want to fry board, as it will only handle up to~600mA or so. How could one use a handyboard to control a high current, high speed ducted fan motor.

    Many thanks
     
  2. jcsd
  3. Nov 10, 2008 #2

    Danger

    User Avatar
    Gold Member

    Re: Handyboard?

    I'm not familiar with the product, but can't you just use it to drive a power amp or relay?
     
  4. Nov 10, 2008 #3
    Re: Handyboard?

    The handyboard uses pulse-width modulation for speed control of the motors, I was wondering if a relay is fast enough to handle it. I guess a solid state relay might be the better option here? What about a ULN2004A High Voltage / High Current Darlington Arrays, how much current can they handle?
     
  5. Nov 10, 2008 #4

    mgb_phys

    User Avatar
    Science Advisor
    Homework Helper

    Re: Handyboard?

    You don't drive a motor directly from the PWM signal - you use it with a comparator to turn on a power transistor.
    Somethign like this http://www.solorb.com/elect/pwm/pwm1/
     
  6. Nov 10, 2008 #5
    Re: Handyboard?

    Just use a mosfet. Im assuming the fan you are driving is for a model aircraft? Try to find a mosfet rated around 50V and 20 amps or more. also, if your pwm driver doesn't have both current source and sink, you need to build a driver for it since mosfets are controlled with capacitance. This can be done easily with a pnp and npn transistor. If you need more current you can run multiple mosfets in parallel.
     
  7. Nov 10, 2008 #6
    Re: Handyboard?

    The microcontroller on the handyboard pwm signal goes to a TI L293D motor controller h-bridge, which is essentially the same thing as in the link posted previously as I gather. The problem is that this chip can only handle 600mA. There is a similar chip that can handle up to 1.2A, but that isn't enough either. I guess I could hijack the output signal from the mc to go to a solid state relay to switch on the motor which is separately powered. Solid state relays can be switched directly from the mc, without the need of a transisor correct?
     
  8. Nov 10, 2008 #7
    Re: Handyboard?

    No, that isn't a good idea. Solid state relays were not made to switch that quickly, some even have internal delays that wait a few seconds to turn on or off a load. Best bet is to use mosfets, almost all commercial and hobby speed controls use them. You can drive the mosfet(s) off of the H-Bridge if you want, just be sure to place a resister ~20 ohm, between it and the gate of the mosfet.
     
  9. Nov 10, 2008 #8
    Re: Handyboard?

    Great, thanks!
     
Know someone interested in this topic? Share this thread via Reddit, Google+, Twitter, or Facebook

Have something to add?



Similar Discussions: Play with a handyboard from MIT?
  1. Playing with transistors (Replies: 20)

Loading...