Let's Make Robots!

Motor Controllers For BIG Motors...

Hey all,

I'm working on building an electric bike... well, doing the research for it anyway.

Right now I'm thinking about motor controllers - which are pretty expensive to buy already built.

My thought is that I could just build my own. I'm just not sure if I could use the same schematics for an h-bridge, but just upgrade the components to ones rated for higher voltages.

I'll be working in the 24V to 36V range if that helps at all.

In my head there's no problem with it... but then again I'm still pretty new to the electronics bit. 

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Ha... Good question. No it doesn't. I can't believe I didn't even consider that. When I hear motor controller my brain automatically thinks "H-Bridge!".

I want a pretty high level of control with speed. I'll be using a throttle to control speed (basically a 10k pot) 

Get a nice, hefty IGBT (Insulated Gate Bipolar Transistor) to drive your motor. They can take large voltages and amperages, and are very tolerant of high frequency PWM. I presume you're going to use a microcontroller to interface the pot/etc with the motor drive?

Ideally I'll be building my own, so yeah.

I'm not sure if this makes sense... but I'll try to be clear.

What would be nice is to have a transistor that allows high voltages, like you said, but the base would take a low voltage, such as turning one of my Arduino pins HIGH.

I could then use a piece of equipment that I already have and know how to use... I just don't know anything about the IGBT's yet, so I'll have to do some searching. 

Here's one I've used before: 16A, 600V, only requires 3-6V to turn on =)
If you need more current, but the transistors you're looking at are starting to become expensive, you can always use a few cheaper ones in parallel and share the load.

Am I reading that right? This can handle up to 600 volts? I'd friggin' kill myself with that much voltage! :)

I assume that using 24V on this would be fine then... 

Yep, 600V blocking capability, even I haven't been able to kill one of these yet =D

Although 600V is total overkill, you will want a solid overhead relative to your 24V supply. As you may already know, stopping or rapidly decelerating a DC motor will cause it to dump the magnetic field energy back into your circuit, which is seen as a large voltage spike aimed directly at your motor driver in most cases. Will the ability to take 600V you have little to worry about.

Also these guys only cost ~US$2.50, so it's not like that high voltage ability is costing you anything extra.

The voltage spike can be virtually eliminated with a reverse-voltage diode and an over-voltage zener arrangement.

From what I read, they generally have quite a bit of pull, but I don't know specifics yet because I don't know what motors I'll be getting.

Do the motors suck?

 

In amperes?