This is my first contribution to the site, hope you like it!!
It's a work in progress, so I'll use this Intro page to share some stuff with you and ask some questions/suggestions (as I'm a begginer with electronics).The concept:
A shield for Arduino, with 2 full drive circuits, allowing you to drive:
- 4 continuous rotation motors OR;
- 2 continuous rotation motors and 1 stepper (bi/unipolar) OR;
- 2 steppers (bi/unipolar).
All using 4 pins on Arduino for control (2 pins per circuit).
NOTE: diferent codes are needed to drive each kind of motor, I'l include some references later...
The drives are based on the design from Arduino.cc:http://www.arduino.cc/en/Reference/StepperBipolarCircuit
I've opted for the L293 B instead of D (40%+ current output), so external rectifiers were needed, besides that the circuits are identical.
The L293B (datasheet
) is a four channel push-pull driver capable of handling 1A per channel (with non repetitive peaks of 2A), with the logic supply voltage between 4.5V - 36V.
Piggybacking may be used mostly to avoid overheating on the final shield, since I'm SURE I'll not need more than 1A per drive!! My intention is to use it with small, low-power motors, for learning purposes...
So far I only ran tests on my breadboard, with a much smaller motor, so I don't know if it will be necessary.
The L293B can be directly replaced by a SN754410 (datasheet
), not sure if there are any advantages (remember I'm a begginer), at least here in Brazil the SN754410 is more expensive and difficult o find!
...maybe it's more efficient?!? I don't know...
If someone could clarify the diferences between them, would be great!!The implementation:
Each drive circuit takes 10x15 holes on a standard .1" spaced perfboard, so you can put 2 of them on one single proto-shield.
If you intend to build your own shield (as I do), you'll have some more room to work with...
... my idea is to include the 12V power regulating circuit and some more logic, to be able to work with the drives in 2 diferent modes:
- 2 independent drives (normal mode);
- the second L293B paralleled with the first, for more current output (let's call this one "switched piggyback mode"... :)).
The functions should be acessed through jumpers or a dip-switch.
And that's where I stuck, the drive circuit is finished but I don't have much of a clue on how to implement that 2 modes idea.
Maybe I'm asking too much, as a begginer... hehehe!!! Am I?!?
I'll do some more research before soldering the second drive and wiring the whole shield (to do, as you can see on the pictures), for design flexibility sake.
The components layout is pretty much final, if you check the schematics you'll see that the wiring should be really easy (I hope!!!)!
Next steps will be much better documented (promise)...
All comments and suggestions will be most welcome!
You can check the link below for some more pictures and better resolution:http://s1124.photobucket.com/albums/l578/Rodrigo_Fonyat/Schematics/
--- EDITED ---
To be posted soon:
- Perfboard layout of the drive (10x15 holes);
- Schematics and perfboard layout of the 12V power regulator (3x4 holes).