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Motor controllers...

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By Anonymous
2008-06-11 12:49

I've been going through the picaxe 28 manuals and the part about motor controllers is a little confusing.

When is it appropriate to use the Lxxx motor driver chip and when should one use the darlington chip?

My understanding is pwm technique is when we have neither of the above chips?

 

I'm using the Tamiya twin motor http://www.pololu.com/catalog/product/61 some of you have used.  For this motor, do I need one power source or two? And darlington or will Lxxx motor driver suffice?

 

Thanks a bunch for your inputs!

‹ I am new to Robot. Compatiblity Question??? Nothing's happening... ›
By fritsl @ Wed, 2008-06-11 14:12
fritsl's picture

You should only use the

You should only use the motor-driver for the motors - no darlington.

It is optional weather you want to use one or two power-sources, the "Lxxx" can do both.

It is my personal experience that it can be hard to draw enough power out of the Tamiya twin motor - so I'd use only 2 cells for the logic, and 4 for the motors.

Things will make sence after a while :) Perhaps this will be good help. 

By zack (not verified) @ Wed, 2008-06-11 14:32

Thanks Fritz! That clears

Thanks Fritz! That clears things up a bit. Will follow your suggestions and see how it goes.  Here's what I'm planning to do. Remove the darlington chip, insert the Lxxxx chip, put in that 330 R (from your first tutorial) into the darlington socket, connect the motors to the A/B points in the picaxe 28 board, change the jumpers to take two power supplies, hook it up. Either I hear the whirrr of the motors or see the magic smoke! Either way, a good learning experience! :)
By jgillick @ Thu, 2008-06-12 00:41
jgillick's picture

Is the Lxxxx chip pin

Is the Lxxxx chip pin compatible with how the darlington chip is setup with the Picaxe?  I think the 28 board has a dedicated DIP socket for the motor driver chip.
By zack (not verified) @ Thu, 2008-06-12 01:07

It is L293D ... didn'thave

It is L293D ... didn'thave the number at the top of my head, so wrote it as LXXX! :)
By fritsl @ Thu, 2008-06-12 07:01
fritsl's picture

2 different chips, 2

2 different chips, 2 different sockets and pre-routing on the 28 standard board.
By zack (not verified) @ Thu, 2008-06-12 10:29

I misread your question. 

I misread your question.  If my understanding is right, the darlington chip in the 28x board, is connected to the output pins. The output from the Lxxxx goes to the 4 points marked A and B.
By jgillick @ Thu, 2008-06-12 17:31
jgillick's picture

This is correct, but the

This is correct, but the L293D has power, ground and output on both sides of the chip too.  The socket for the darlington chip probably doesn't match the same power/ground pins as the motor driver.

I'm pretty sure the 28x board has 3 DIP sockets: 1 for the Picaxe, 1 for the darlington and 1 for the motor driver.

Is this what your board looks like: http://letsmakerobots.com/node/75

In Frits's "First Robot" tutorial, you'll notice that he uses the bottom socket (depending on which side of the board you thing is top) for the motor driver: http://letsmakerobots.com/node/17

The cool thing about this dedicated socket is that it's pre-wired for the  L293D chip to the 4 - 7 output pins and the board has an "A" and "B" area where you can solder your motor leads to.

To be honest, I haven't played with the 28x board yet, so this is all from what little I know about it. :)  I've been working with the 18x board, and had to make a custom pin harness to adapt the L293D chip to the darlington sockets, since that board doesn't have a motor driver socket.

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