Author Topic: Mosfets and H-bridge help  (Read 1637 times)

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Offline Its_FridayTopic starter

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Mosfets and H-bridge help
« on: March 07, 2009, 01:09:03 PM »
I need an H-Bridge for my robot but i've never built one. Putting it together shouldn't be a problem, but choosing the right MOSFETs is proving to be difficult.

The motors are hooked up to a 12V battery.  I know i need 2 PNP, and 4 NPN MOSFETS.

I'm trying to buy the MOSFETs off of Newark but i don't know what the specifications for the MOSFETs should be.

Offline Trumpkin

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Re: Mosfets and H-bridge help
« Reply #1 on: March 07, 2009, 05:39:42 PM »
How much current do your motors draw? You actually only need 2 PNP and 2 NPN.
« Last Edit: March 07, 2009, 05:40:40 PM by Trumpkin »
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Offline Its_FridayTopic starter

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Re: Mosfets and H-bridge help
« Reply #2 on: March 07, 2009, 06:41:15 PM »
My mistake about 4 NPN, i must have been looking at the wrong diagram^^'    The motors draw 111 mA at no load. Not sure about at full load. Maximum torque is 3.59 Kg/cm. 

Offline Trumpkin

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Re: Mosfets and H-bridge help
« Reply #3 on: March 07, 2009, 08:48:08 PM »
You could just use an SN754410 http://www.sparkfun.com/commerce/product_info.php?products_id=315 and save yourself the work of building an H-Bridge.
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Offline want2learn

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Re: Mosfets and H-bridge help
« Reply #4 on: March 08, 2009, 03:39:02 AM »
You actually only need 2 PNP and 2 NPN.

True, but you do get 6 transistor H-bridge variants.

The motors draw 111 mA at no load. 

I've used small signal transistors @12V/200mA in 6 transistor H-bridges with no apparent problems thus far.

You could just use an SN754410 and save yourself the work of building an H-Bridge.

This would be the simplest solution
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Am I, or the others crazy?

Offline Its_FridayTopic starter

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Re: Mosfets and H-bridge help
« Reply #5 on: March 08, 2009, 09:42:43 AM »
Thank you for your help guys. To keep things simple, i'm getting the ICs.^^

Offline Its_FridayTopic starter

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Re: Mosfets and H-bridge help
« Reply #6 on: March 15, 2009, 11:56:51 AM »
To control the speed of the motors via PWM using the axon, do i hook up the Digital I/O pins to the IC pins: 2,7,10,15?

Offline Admin

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Re: Mosfets and H-bridge help
« Reply #7 on: March 15, 2009, 09:10:58 PM »
If you really want to simplify things just buy a full motor driver. Such as at http://www.dimensionengineering.com.

 


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