Let's Make Robots!

Build a 8A (4A per motor) dual motor driver for under $10

Drives 2 DC brushed motors. Holds 4A per motor.

Need a 8A  motor driver but don't have a lot of cash, look no further this article describes a simple and cheap solution.

This project uses just few electronic components, and can be build on a perforated board using hook-up wires.

Texas Instrument's SN754410  is know to be a half-bridge driver suitable for low power applications it's rated current is 1A per channel. Costing only $1.55 it's a great choice for small robots on a budget.

Now what do you do if you need more power ? Multipy!  Bruteforce ! Without much talk below is the schematic:

motor_driver_schematic.png

Sorry LMR scaled down the image, for higher resolution image see  http://starlino.com/motor_driver.html

This schematic is easier to explain in words , than to follow. First note that "DOUBLE" near SN754410, this means that each chip is doubled by soldering another chip on top of it, I also added a heatsink.

Each SN754410 chip has 4 input channels: 1A..4A  , and four corresponding output channels 1Y..4Y. We combine channels 1 & 2  and then 3 & 4. Thus each of our driver's input will use 4 channels (2 from each chip each capable of 1A).

As far as enable inputs we combine 12EN &  34EN for each chip. This is where we'll send our PWM signal.

If confused have a look at SN754410 Datasheet. I promise it's not that complicated ! According to page 2 of the datasheet SN754410 already has clamping diodes that should protect the chip from back EMF.

I built my driver on a peforated board using hook-up wires. With so many inputs and outputs it's easy to get confused so everything was labeled using my label maker. Have a look at the result:

IMG_1089.jpg

 

My tracked robot has 2 gearmotors with a stall current of about 3.7 amp. Octodriver handles up to 4A per motor. But I also used 2 resetable fuses with hold current of 2A , that would trip at 4A. Better safe than sorry :)

I'll try to keep you posted about the driver's performance with time. For more pics and updates check the main post of this project:  http://starlino.com/motor_driver.html

Hope this was helpful !

Cheers,

//starlino//

 

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It would probably work with 3 chips stacked , but look at the cost, instead of paying for 3 chips  you can pick up a

TLE 5205-2 that gives you up to 5A and it's about ~$6-7 each same as 3 x SN754410. 

 http://mouser.com/Search/Refine.aspx?Keyword=TLE+5205-2

http://www.infineon.com/dgdl/tle5205-2.pdf?folderId=db3a304412b407950112b4381da46a3c&fileId=db3a304412b407950112b4381e296a3d

sample product here:

https://sjvalley.com/shop/index.php?page=shop.product_details&flypage=flypage.tpl&product_id=13&category_id=2&option=com_virtuemart&Itemid=63&vmcchk=1&Itemid=63

 

Sweet!

Thanks for the info

Or for five bucks you could just pick up a relay which can deliver 20 amps and go berserk :)
Is this limited to 4 amps or can you stack 3 on top of eachother to get 6amps?

I use resettable fuses connected in series with each motor (see http://en.wikipedia.org/wiki/Resettable_fuse ).  A good guideline is your motor stall current, so if you're mottor stall current is 4A choose a fuse with trip current of 4A. The "hold" current is usually half , meaning your fuse will start increasing resistance as it goes from 2A  to 4A , and will trip at 4A. I find these types of fues a good protection against high currents, it protects my chips but also my motors (diodes will not protect your motors against stall situations).  As far as kickback diodes you should probably also use them if you want to be on the safest side.

 

cool, thanks for the info  ;)

good job! I always had curiosity to see this "hack" in action!!  are you sure that this IC has the EMF protection diodes? because this subject has been discussed a lot in this forum and I think the conclusion is that the diodes are for ESD protection only. You can see a better explanation here. I know that a lot of people has been using this IC with absolutely any problem regarding power being kickbacked.

I would apreciate a lot if could you tell us a bit more about the fuses.. what fuses are being used and how do you integrate them in your circuit?

Good job on your project

it's nice to know that people out there are actually trying to find a cheap solution 

to controll your motors.

 

I just had one quick question 

can you stack 3 to get 6 amps per motor?

I've have seen and built a design where I paired up outputs of a line driver to get more current, but stacking the whole chip and heat sinking it is really cool! I look forward to finding some big motors to test this with.

I'm using a driver similar to this setup on my balance bot. Quiet happy with it to be frankly.

Nice work demonstrating it. Will follow this subject :)