DC motors running slow: How to use a multimeter to test the circuit?

Other Hardware Motors, Mechanics, Power and CNC
1

Hi there!

I´ve followed all steps (http://www.instructables.com/id/Control-your-motors-with-L293D-and-Arduino/?ALLSTEPS) in creating my first robot, but my DC motors aren´t reveiving much energy, because they are excessively low.

I´ve asked about this before, and all responses lead me to the one and only conclusion: I needed to get a voltimeter in oprder to check the current voltage.

Now I´ve got one, but how may I test how much current the motors are receiving? I haven´t found a video or instructable to get a dc motor checkout.
Should I turn on the arduino and while the motors are running (very slowly) should I touch each motor cable with the two cables that come with the voltimeter?
Both cables that came from the DC motors are not positive nor negative ones... how may I choose in which order to test it?

The Vin pin is attached to three AA batteries that came with the robot, maybe those are the problem? (I´ve grab one of those and tested it and it says 1.4 -I´ve set the voltimeter to the "200" in its left side-).

Sorry for my lousy english... and my very, very basic question!
Thanks for your help!
Rosamunda

2

That type of h-bridge can cause a 1-2v loss on the supply voltage. You may need to add another battery or two.

3

Thanks for your reply.
I´ve added 7 AA batteries and it won´t work...