l293 motor driver

[Trumpkin]

I should be able to use this diagram for controlling motors with the $50 robot, and other microcontrollers, right?

[Admin]

So you decided to ditch the servos, eh?

Yeap, that diagram will work.

[Webbot]

You need to add 4 diodes as well to prevent the motor frying the chip!! If your current requirements are low (say 500mA) then use the L293D instead - this has got the diodes built in.  Check the datasheets and you will see the L293 can provide higher current but you will need to add the diodes yourself - in which case look at the L293D datasheet to see how the diodes are connected.

[Trumpkin]

Okay! thanks 

So you decided to ditch the servos, eh?

No, I haven't, it just seems like I always have dc motors laying around that I would like to use. Here is a new schematic I found http://www.freewebs.com/isuru-c/motor_driver.htm but I'm not sure what pins go to the microcontroller.

[Trumpkin]

It seems like there should be 3 pins per motor that go to the microcontroller but I only see 2 pins per motor.

[Webbot]

Not quite sure what you mean. The circuit diagram you attached showed 2 connections per motor - where does the '3 connections' come from?

[izua]

there are three pins on input, each pair of push-pull drivers has an enable (pwm) signal

[Trumpkin]

Not quite sure what you mean. The circuit diagram you attached showed 2 connections per motor - where does the '3 connections' come from?

It seems like there should be negative, positive, and signal wires that go to the microcontroller for each motor, like a servo, but I only see 2.

[Webbot]

Here is a new schematic I found http://www.freewebs.com/isuru-c/motor_driver.htm but I'm not sure what pins go to the microcontroller.

The diagram should show that pins 1 and 9 are input 'enable' pins. These give you the third input from your microcontroller and can be pulsed (PWM) to change the speed

[ixarka]

Here is a new schematic I found http://www.freewebs.com/isuru-c/motor_driver.htm but I'm not sure what pins go to the microcontroller.

The diagram should show that pins 1 and 9 are input 'enable' pins. These give you the third input from your microcontroller and can be pulsed (PWM) to change the speed

Alternatively, if you want to save an output pin from your microcontroller, you can wire the enable to +5V and use PWM on either of the other two pins to control speed. To turn the motor off, set both pins either high or low.

[izua]

enable = pwm