Author Topic: ~3V motor controller?  (Read 5669 times)

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Offline emmannuelTopic starter

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~3V motor controller?
« on: July 27, 2008, 09:12:56 PM »
I've been using the TI SN754410 as my dual motor controller but I'm interested in on my next project using a circuit I'd like to keep at just 3.3V.  The SN75441 sadly is for 5V I know I can use stepup voltage regulator but I was wondering if anyone knows a simple part I could use that is similar to the SN754410 cause I had no luck.

Offline Admin

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Re: ~3V motor controller?
« Reply #1 on: July 30, 2008, 09:45:56 PM »
Just to clarify . . .

You want your microcontroller at 3.3V? Why are you running the microcontroller at 3.3V?

And your battery is 4.8V or 3.6V?

And you want a motordriver that operates with these two requirements?

If you are using 3.3V just to save power, its not really worth it when you have motors draining 99% of the power . . . And motors don't work well under low voltages.

Offline emmannuelTopic starter

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Re: ~3V motor controller?
« Reply #2 on: July 31, 2008, 12:33:15 PM »
Well I haven't decided on the batteries yet but I decided the motor I am going to use is this worm gear motor http://www.pololu.com/catalog/product/73

In its datasheet http://www.pololu.com/file/download/re_260ra.pdf?file_id=0J17 it mentioned nominal voltage range of 3V.

So I was thinking of making the controlling circuit in the 3.3V range since there seem to be quite a few devices that support it.

Closest thing to what I wanted so far seems http://www.rohm.com/products/databook/general/pdf/bd6211f-e.pdf not sure how hard a SOP pavkage is to solder :P

Right now though I'm probably just going to go with a 5V circuit.  Giving the motor controller a lower duty cycle to control the motor at to keep it around around 3V for the motor.  This way I have most of the pieces already.

The goal is to make an efficient system that would only turn on the motor for a few seconds every hour.

Offline izua

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Re: ~3V motor controller?
« Reply #3 on: July 31, 2008, 02:04:28 PM »
You do know that you can control the motor at 5V in pwm, and get a lower voltage at a high efficiency, right?
Check out my homepage for in depth tutorials on microcontrollers and electronics.

Offline bens

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Re: ~3V motor controller?
« Reply #4 on: July 31, 2008, 06:15:24 PM »
The Tamiya motors are intended for 3 V operation, but they definitely work at higher voltages.  The only down side is that using a higher voltage shortens their usable lifetime.  One customer of ours did a fairly detailed study to see how voltage affected the lifetime of the motor used in the Tamiya gearboxes.  You can find his results here:

http://www.pololu.com/docs/0J11/all

Another thing worth noting is that many popular, inexpensive H-bridge ICs (e.g. the L298N) have voltage drops between the input voltage and the output voltage, and the drops can be as large as 3 V at 1 A.  What this means is that if you use a 6 V power supply with something like the L298N motor driver, you would only have around 3 - 4 V on your motors.  Your best best might be to use something like four NiMH batteries as your power supply, which would give you a voltage of around 5.5 - 4.5 V as they go from fully charged to depleted.

Lastly, the Tamiya motors are very noisy (electrically), so make sure you solder caps across the motor terminals.

- Ben

Offline Spoil9

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Re: ~3V motor controller?
« Reply #5 on: August 01, 2008, 02:09:02 PM »
I am using Tamiya's motor gear box for a project as well. I've been told though that even though it's only 3v, they like to draw a lot of current, so I was recommended to buy this motor controller:
http://www.pololu.com/catalog/product/120
It works up to 7v, and can handle up to 5A per motor (2x motors) or up to 10A if set up for only one motor.
Although I have not been able to use it yet cause I'm still working on the programing, I do believe it will be worth the investment.
Hope this helps.
- Bill
Knowledge is Power. Power Corrupts. Study Hard. Be Evil.

Offline bens

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Re: ~3V motor controller?
« Reply #6 on: August 01, 2008, 02:18:29 PM »
The LVDSMC (low voltage dual serial motor controller) is specifically designed for low-voltage toy motors such as those in the Tamiya gearboxes, so hopefully you will find it to be a good investment.  It's worth noting that another option when using the Tamiya gearboxes is to replace the motors with Solarbotics RM3 replacement motors.  These are higher voltage, lower current motors (800 mA stall at 6 V instead of around 4 A stall at 6 V for Tamiya's Mabuchi FA-130 motors) that generate less electrical noise than the Tamiya motors, and they have the same form factor, allowing them to be used as direct replacements for FA-130s.

- Ben

 


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