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Topic: Powering 1/2hp dc motor (Read 994 times) previous topic - next topic

uler3161

I have a 1/2 hp 12vdc motor on a piece of equipment. I don't have the motor specs in front of me, but a web search suggests it is a 1700 rpm motor that uses between 10 and 60 amps.

Currently it has speed control in one direction, but a set speed in the other. I want to be able to replicate this ability and power the direction and speed from my Arduino if possible. I might even want to control speed in both directions. I may also look into updating to a 3/4hp motor at some point (10 to 75A), so I'd like to get a controller I could still use with that.

I'm pretty new to electronics, but I'm guessing I need some kind of H-bridge for this? All the ones I find seem to be for smaller motors. Is there something out there that someone can point me to? I'd be willing to build an H-bridge if I can get a good grasp on what components I need. Thanks.


Erdin

You need a full H-bridge.
You could build a H-bridge with power mosfets.
But also a number of mosfet H-bridge modules can handle that current.
You might have to figure out yourself how to connect them.

This one is too expensive, http://www.robotpower.com/products/osmc_info.html
And I can't find others right now.

AWOL

Quote
10 and 60 amps.

60 amps at 12V is more like 1hp. (1hp = 740W)
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uler3161


Quote
10 and 60 amps.

60 amps at 12V is more like 1hp. (1hp = 740W)


Thanks. The amperage values were what someone posted on a forum somewhere. 60A would be equivalent of running a 1/2hp on 6V wouldn't it? I know the existing motor controller has a 12V input, but maybe it's actually only allowing up to 6V to the motor.

afremont

My guess is the 60A is the locked rotor current + inrush current.
Experience, it's what you get when you were expecting something else.

uler3161

I found http://hades.mech.northwestern.edu/index.php/Driving_a_high_current_DC_Motor_using_an_H-bridge. Since my input is 12V, could I simply lose the dc-dc converter and be ok?

Assuming this circuit would be ok, how would I be controlling it on a arduino? It sounds like to be stationary, I need to write a value of 127 to it? Closer I get to 255 would mean faster in one direction, while closer to 0 would mean faster in the other direction?

Chagrin

Wouldn't it be a lot simpler just to throw in a DPDT switch so you can reverse the leads on the motor?

wizdum


Wouldn't it be a lot simpler just to throw in a DPDT switch so you can reverse the leads on the motor?


Or even something like this with DPDT relays:
http://www.homebuiltrovs.com/howtorelays.html

Thats a lot of current, I doubt there is a cheap solution using MOSFET H-Bridges.

EDIT: Scratch that, didn't notice the speed control requirement.
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uler3161


Wouldn't it be a lot simpler just to throw in a DPDT switch so you can reverse the leads on the motor?


I do think it should be simpler to reverse the leads like that. I'm guessing the schematic I posted is done that way so that only one wire is used to control both direction and speed? Or am I just reading it wrong?

Chagrin

My point was that you already have variable speed in one direction. If you use a DPDT switch on the motor leads to reverse them then you can use the same variable speed to go in the other direction.

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