Author Topic: Augmented Microcontroller with breadboard  (Read 2835 times)

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Offline CentaurTopic starter

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Augmented Microcontroller with breadboard
« on: March 18, 2008, 11:48:42 PM »
So I've been looking into all the parts I will need to get into robot building and I had some questions. 

In the motor tutorial it is recommended that capacitors are placed across the motor leads to extend motor life.  I also have looked at a schematic for power regulation, and the battery monitoring circuit.

I was thinking of purchasing the L298 kit http://www.robotshop.ca/PDF/kit-motor-controller-l298-solarbotics.pdf, which only has a 5V drop out regulator (the Axon, which I plan to purchase, will require at least 5.4V, recommended 6V).  Additionally, the kit has a capacitor but I'm pretty sure it's for the actual L298 chip, and not the motors. 

To make the modifications of I was thinking of purchasing a breadboard for the capacitors, switching BEC, voltage regulator, battery monitoring circuit, and a fuse.

Questions
1.  If I purchased the L298 kit, I would put the capacitors after the motor outputs, just prior to the motor input leads, and this would give the desired result of extending motor life correct?  (and regeneration from rapid reversals?!?)
2.  Is there a way to raise the peak current of the L298 (heat sinks maybe?)  It's rated for 3A per channel, and the motors I'm thinking of purchasing max at ~4.5A.  I want to do rapid reversals so I'll probably stall frequently.  What part of the motor driver would I actually heat sink?  The L298 chip itself?
3.  This means that my robot will have an augmented microcontroller and an additional breadboard for supporting circuitry.  Is this normal?  I was looking at many of the tutorials and I didn't notice robots with both an augmented microcontroller and another breadboard.
4.  Is there an easier way to accomplish what I am trying to do that I'm completely missing because I'm a noob? - for example, with all the modifications I'm going to do would it be better to just make a complete H-bridge on my own without buying the kit?

Note:  Right now I plan to use a 12V battery pack, since the motors I plan to use are rated for 12V.

I'm a mechanical engineer so this electronics stuff is mostly new to me (besides physics and a basic EE course tailored to mechanical engineers.)  I'm also very tired right now so I apologize if this is a confusing post.

Any intelligent fool can make things bigger, more complex, and more violent.  It takes a touch of genius - and a lot of courage - to move in the opposite direction.  ~E.F. Schumacker

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Re: Augmented Microcontroller with breadboard
« Reply #1 on: March 30, 2008, 01:36:50 PM »
There are actually three types of capacitors you need, in terms of how you use them.

First, you solder small value caps to the leads of the motor itself to extend motor life.

Next, you put medium size and small size caps around your voltage regulator to remove electrical noise from your control circuits (microcontroller, sensors, etc).

Lastly, for batteries that don't have very high output currents, you'd want a large capacitor right after the battery. My Axon can handle like ~40 something servos, so if the user turned on all of them at the same time, the sudden surge power draw would be greater than what the battery could handle - hence a large cap would be needed.

Quote
Is there a way to raise the peak current of the L298 (heat sinks maybe?)  It's rated for 3A per channel, and the motors I'm thinking of purchasing max at ~4.5A.  I want to do rapid reversals so I'll probably stall frequently.  What part of the motor driver would I actually heat sink?  The L298 chip itself?

Heat sinks will help. You can also put two L298's in parallel for double the current.

Quote
This means that my robot will have an augmented microcontroller and an additional breadboard for supporting circuitry.  Is this normal?

Yeap!

Quote
Is there an easier way to accomplish what I am trying to do that I'm completely missing because I'm a noob? - for example, with all the modifications I'm going to do would it be better to just make a complete H-bridge on my own without buying the kit?

Well, the easiest way would be to spend lots of money :P
However, if your goal is to learn how the circuits work, better to make it then to buy it . . .

Quote
the motors I'm thinking of purchasing max at ~4.5A

If I were to do this - given that I already know how it works and have money to spend - I'd buy this, or something like it:
http://www.dimensionengineering.com/Sabertooth2X5RC.htm

And it has all the caps you need in it already. ;D

 


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