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Author Topic: Wheelchair Motor Driver Schematic?  (Read 11612 times)

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Offline MaltiKTopic starter

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Wheelchair Motor Driver Schematic?
« on: January 17, 2009, 07:12:46 PM »
I looked into Airman's guide using relays, but I want speed control, errr pwm. I ordered two 24v Wheelchair motors (I don't know the amp, I didn't receive it yet), does anyone have a good schematic for 24v motors that is easy to interface with sayy an avr chip? (atmega8 :))
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Offline Webbot

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Re: Wheelchair Motor Driver Schematic?
« Reply #1 on: January 17, 2009, 08:19:07 PM »
Without knowing the maximum current your motors will need then its impossible to say. Lots of H-Bridhe chips can do 60v. So Voltage ain't the problem - its all about current.
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Offline airman00

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Re: Wheelchair Motor Driver Schematic?
« Reply #2 on: January 17, 2009, 08:31:09 PM »
I'd estimate that you probably have around 35 amps peak current drawn from each motor ( 35 being on the safe side)
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Offline MaltiKTopic starter

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Re: Wheelchair Motor Driver Schematic?
« Reply #3 on: January 18, 2009, 06:12:44 AM »
Without knowing the maximum current your motors will need then its impossible to say. Lots of H-Bridhe chips can do 60v. So Voltage ain't the problem - its all about current.
Ok, say it was around 35amp max, what would be the ideal circuit that is compatible with an atmega8 (code wise)
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Offline Admin

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Re: Wheelchair Motor Driver Schematic?
« Reply #4 on: January 21, 2009, 08:59:52 AM »
You don't want to make your own motor driver, just trust me. Especially not one for 35A . . .

You want to buy battle-bot grade motor drivers. It's pricey, but thats the cost of making a large robot.

you can buy some from here:
http://www.robotmarketplace.com/store.html

And other places if you search around . . .

Offline TrickyNekro

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Re: Wheelchair Motor Driver Schematic?
« Reply #5 on: January 21, 2009, 10:42:09 AM »
You don't want to make your own motor driver, just trust me. Especially not one for 35A . . .


Why don't??? Apart from having parallel MOSFETs and a driving circuit.... (Probably an Op - amp) What's so... difficult....
Well.... With PWM an op-amp is needed cause harmonics can be created and MOSFETs never work....
But apart from that... I don't think it's so difficult.... :-\
For whom the interrupts toll...


P.S. I've been inactive for almost a year... Don't give promises but I'll try to complete my tutorials. I'll let you know when..

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Offline MaltiKTopic starter

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Re: Wheelchair Motor Driver Schematic?
« Reply #6 on: January 21, 2009, 02:15:50 PM »
You don't want to make your own motor driver, just trust me. Especially not one for 35A . . .

You want to buy battle-bot grade motor drivers. It's pricey, but thats the cost of making a large robot.

you can buy some from here:
http://www.robotmarketplace.com/store.html

And other places if you search around . . .


Alright, what is one you would recommend/well documented?
Oh, and do I want to base the motor/speed controller's specs based off the motor's AMps, or the Battery's Ah? I am about to purchase two 12V 18AH sealed lead acid batteries for two 24v Wheelchair motors, is this good? And should I search for a 40A motor driver?

And if I were to base the motor driver specs off of the motors, would I take each individual motor's amp and add them or keep them for the driver. For example, I have two 24v motors /w 10A, do I want a 10A motor driver, or a 20A motor driver.
Would a better bet just getting 8 20A relays?
« Last Edit: January 21, 2009, 02:21:21 PM by MaltiK »
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Offline Webbot

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Re: Wheelchair Motor Driver Schematic?
« Reply #7 on: January 21, 2009, 02:38:45 PM »
Quote
Oh, and do I want to base the motor/speed controller's specs based off the motor's AMps, or the Battery's Ah?
You need to measure the motors stall current, make sure the motor controller can supply it, and then buy batteries that can supply a peak of the stall current but will also last for a 'reasonable' time when just supplying the 'average' current'

Quote
I am about to purchase two 12V 18AH sealed lead acid batteries for two 24v Wheelchair motors,
12V batteries for 24v motors. So the motors will run with less torque. Which may be ok - depends on your motors and what you want. If you believe that your average current is 10Amps then they will last for 18/10 hours (ie 1.8 hours).
 
Quote
And if I were to base the motor driver specs off of the motors, would I take each individual motor's amp and add them or keep them for the driver. For example, I have two 24v motors /w 10A, do I want a 10A motor driver, or a 20A motor driver.
You need to check the controller datasheets. Look for one that provides 10A per channel.

Quote
Would a better bet just getting 8 20A relays?
But then you would have no speed control. Just fwd, backwards, stop.
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Offline ArcMan

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Re: Wheelchair Motor Driver Schematic?
« Reply #8 on: January 21, 2009, 04:27:15 PM »
I think he intends to connect the two 12V batteries in series to produce 24VDC.  That's what I did for my yard robot.  I used 33 AH SLA batteries.

 


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