# H-Bridge Severe Voltage Drop When Motor Connected

Hi guys, I am testing my Freetronics 2-Channel H-Bridge Shield with a simple example code on my Uno clone. I have tried powering the set up with both 8v and 11v power supplies and both show the same results. When under no load, the output channel measures the full 8v or 11v, but as soon as my 8v motor is connected, the voltage drops to 0.1-0.3v. Any guidance on this is highly appreciated.

Are you sure the motor's ok?- I wonder if it's not faulty and presenting a dead short. Or if not, perhaps it's in any case of too high a current rating for that driver?

Measure the resistance across the motors' power input, then get the stall (ie, start up) current from I=V/R.

goodSamaritan:
Are you sure the motor's ok?- I wonder if it's not faulty and presenting a dead short. Or if not, perhaps it's in any case of too high a current rating for that driver?

Measure the resistance across the motors' power input, then get the stall (ie, start up) current from I=V/R.

Thankyou for the reply. I should have mentioned that when connected directly to the 8v battery, the motor works well and worked well when it was being used as a normal RC car.
When measured with a multimeter between the positive and negative motor connections, the resistance reads 1 ohm more than just touching the two multimeter probes together. Therefore, using that method, I get 8/1. However, I ran this motor using breadboard jumper wires, so I wouldn't think it'd need more than 1 amp. Am I calculating this wrong?
The shield looks like it can supply max 40v and 2A

The page for the motor driver shield is below:

If the motor winding is 1 ohm, then yes the startup current is 8A, and a 2A controller would not cope (unless somewhere in the docs it says the controller has a higher limit for short spikes like at startup.)

If you give the motor a spin by hand, does it start?

goodSamaritan:
If the motor winding is 1 ohm, then yes the startup current is 8A, and a 2A controller would not cope (unless somewhere in the docs it says the controller has a higher limit for short spikes like at startup.)

If you give the motor a spin by hand, does it start?

It sounds like that's the case then. Spinning the motor by hand doesn't start it

Maybe I should just buy a properly rated ESC haha