Let's Make Robots!

Help with Mr Basic

I have assembled Mr Basic with 4xAA bateries, and tried L293D and L298N but with no luck, seems that it needs more power.

I would love to have some help building an H-Bridge with some kind of transistors, I know a lot of websites with lots of schematics, but I don´t know what are the best transistors to use, any help would be appreciated  :-)

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Those driver chips will take volts some off, but not that much. Your circuit must be wrong. Did you take it one step at the time? I am also dabbling with L293D on a breadboard. The easiest setup is to use the chip as a simple amplifier first. Then later use it as an H-bridge.

Motor lead to ground, the other one to L293 output. Tie enable pin of L293 to V+ (pullup resistor?). Give the chip GND and V+. And make sure to give the chip a second V+ for the motor. Could be the same as the V+ for logic. Just for the experiment.

Now put a 10K pullup resistor on a test wire. put onse side the in logic V+ rail. Use the free end to touch the input on L293. This should make the motor turn. Maybe use your Voltmeter instead of a motor. Or both.

Definitly there is something wrong with my circuit.. must double check everything  ;)

I also have no luck with my Pololu Low Voltage Dual Serial Motor Controller. It can drive 5A for each motors, so there shoud be enough power. The motors just moves only a little bit, when I send a command. Maybe the initial current needs are to high, or my crude building is the problem. Tomorrow I will make some tests with smaller motors and resistors in the motor line.

 

I tested it out with my Qik 2s9v1 and it seems to be working.  The motors were moving at a pretty good clip.  I need to do some better wiring before it gets the real test.

http://www.pololu.com/catalog/product/1110

 From their site:

This small, inexpensive motor controller allows variable speed and direction control of two small, brushed DC motors using a simple serial interface, making it easy to add motors to your microcontroller- or computer-based project. The motor supply voltage range is 4.5 to 13.5 V; the continuous current per channel is up to 1 A (3 A peak). The logic supply can be as low as 2.7 V, allowing operation with modern microcontrollers running at 3.3 V.

 

For Arduino users I have a library out at:

http://code.google.com/p/qik2s9v1arduino/

I got my Pololu Low Power Motor Controller working. But I need an extra power supply for the controller electronic. These motors draws too much current when start running. It is also not recommended to start the motors form 0 to maximum speed in one step. That will cause a reset of the controller electronic. Maybe some big buffer capacitors may help. 

Interesting controller the Qik 2s9V1. Mine is a bit oversized for this task, but I didn't have another choice. 

Correction: I own a TB6612FNG Dual Motor Carrier board. It has the same motor controller 2x1A. I will give it a try.

OK, all I can say is give Mr Basic all the power you have :D 

I tried 7.2V battery pack + L298N and I almost couldn´t stop him       LOL