I'm doing a floor cleaning robot project. I'm using a L293D shield and 3 motors 12V, whith a power source of 9V. The motors work normally, put when i put in the floor, they don't spin and don't move the robot. What could be the problem?
You need to tell us the specifications in a lot more detail.
What are the motors? What is their voltage and current rating?
What is your power source? What are its ratings?
A L293 Shield seems very inadequate for the power you are talking about...
12 V motor, 9 V source, a voltage dropping ineffective L293.You can't but fail. Measure the voltage at the motor when you expect it to run. How far is it from 12 V?
Welcome to the forum.
Please read the first post in any forum entitled how to use this forum.
http://forum.arduino.cc/index.php/topic,148850.0.html then look down to item #7 about how to post your code.
It will be formatted in a scrolling window that makes it easier to read.
Can you please post a copy of your circuit, in CAD or a picture of a hand drawn circuit in jpg, png?
Your 9V supply, is it one of these?