Hi Jehiel - I really don't have enough information on your hookup but many times when something works with one load and fails when a second load is added it is because of an inadequate power supply. Check to see what happens to your voltage level with one and then two motors. Are your logic circuits tied to the same power supply? This can be an additional problem as voltage spikes from the motors need to filtered out.

John

John is right on the money with this one

Very DeJaVu as we answered a similar question just a few weeks ago

1. Are you powering the motors from the controller, if you are, dont, unless it is a real small motor it will cause problems, especially with two.

2. As John already said, Is your PSU up to the job and is it coupled to the motors correctly, you need only have a common ground between the motor controller and the micro-controller board

3. Draw us a picture and post it showing your connections and components (Even a cell phone picture will do, make sure it is well lit and shows all the parts

4. Attach or post you code in this thread for us to review for you

5.  wait for us to review it all and get back to you, (That's is usually the quick bit)

6. apply changes recommended and if it is still not working go to 3 and repeat

7. If all is working well, post your results (Other can benefit from your experience and you get points for it) and pat yourself on the back for a job well done

Thank you for your reply.

Here's the problem more detalied. Sorry for the crappy solder job. I was soldering and desoldering things trying to fix it

WHEN I CONNECT  THE MOTOR DRIVER VCC TO THE POSITIVE JOINT ON THE BATTERY PACK WITH A ALLIGATOR CLIP. IT WORKS!!

THEN I CONNECT THE DRIVER VCC TO POSITIVE 5V ON THE OUTPUT OF THE L7805 WITH AN ALLIGATOR CLIP. IT WORKS!!

OK! I WILL SOLDER THE DRIVER VCC TO THE OUTPUT OF THE L7805. IT DOESN'T WORK!!

there is no simple reason the lsat two should not behave the same way

there is an observation on the routing of your wire though

in the working version where you connect to the output of the 5V reg will clip, the wires are away from the cpu pins

in the soldered version your running the power to the driver right over the XTAL pins, dont so that, route the power to the motor away from the CPU pins, especially the oscillator. This may fix your issue , th theory being the noise from the motor is affecting the CPU oscillator

also add a small value decoupling capacitor at the motor connector end of your pcb maybe 100nF ish, this will help to eliminate the noise feeding back from the motor control

Worth a shot and fits your symptoms

let me know what your results are

told you it would be quick

I also just realized you seem to be using NMIH Rechargeable batteries, or a version of Rechargeable battery

These are only 1.2V each and you appear to have only 4 in your holder, this adds up to 4.8V before the regulator, the reg also requires 2V more on the input to get the designated output (5V in this case). This would require nearer 7V from the batteries

If you can simply try replacing the rechargeable with a fresh set of Alkaline to see if that is all it needs to make things work, re-routing the wire is also still a wise thing to do

Do you have a meter to validate the voltage coming out of the regulator without the motor running and then with both motors on ?, if so what are the readings

Regards

peter

I had something similiar happen to me on a circuit a while back. As it turned out my load had a capacitor that was pulling my Vcc low and resetting my arduino. When I used the jumper wires it worked ok. The jumper wires have a measureable resistance compared to the direct wiring and this acted like a buffer that prevented the microprocessor from resetting. Try putting a low value resistor in place of the direct wire if you want to test this possibility.

John

I put a 100nF capacitor between the VCC an ground of the motor driver.

Re-route the conector avoiding pass it through the processor.

Power it up with a Bench Power Supply ay 9 volts.

Still not working.

Thank you. I will try it.

It works!!

Thanks for all your help! Now its working fine.

Here's how I fix it:

1. Filtering Noise with a 100pF capacitor

2. Moving vcc source away from the microcontroller.

3. Four 10 ohms resistors between the Motor Driver vcc and the battery power source.

4. Replace batteries with 4 AA Alkaline.

It works perfect. There's just one problem the resistor ladder it's getting very hot. I have to replace them with Mora capable resistor.

Thank you all for your help.