Play with a handyboard from MIT?

[AstroRoyale]

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

 

[Danger]

I'm not familiar with the product, but can't you just use it to drive a power amp or relay?

 

[AstroRoyale]

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?

 

[mgb_phys]

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/

 

[famousken]

Just use a mosfet. I am 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.

 

[AstroRoyale]

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?

 

[famousken]

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?

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.

 

[AstroRoyale]

Great, thanks!