I have connected the VNH2SP30 to +5v vin and have connected both A inputs to +5v and both B inputs to GND. I have also connected both PWM inputs to +5v (the +5v is the output from an Arduino board). On the other side of the board I have +6v coming from 4xAA battery. If I connect one of the motors to either side of the board it works just fine. If I connect both motors at the same time then I hear a high pitched whine and there is no motor movement. Also, both the green and orange LEDs light up on both sides of the VNH2SP30.
I am assuming that the issue is somehow related to the voltage or current supplying the motors but I couldn’t find the information on the web site. Any help would be much appreciated!
One other piece of information that may be useful … if I connect both motors directly to the power source and bypass the motor driver entirely then both motors run fine.
When you say you connnected “VNH2SP30 to +5v vin” Do you mean you connected +5V to the pin labeled VIN ,or did you connect it to the pin labeled “+5V (IN)”? Connecting 5V to the pin labeled VIN would short it to your motor supply voltage.
Since your system work with either motor, but not with both, I suspect you have a power problem. Can you measure the voltage of VIN when you hear the high-pitched whine? Can you try using a higher-power supply? If that does not help, can you post a picture of your setup and your connections? It might help us notice something.
Are you using four alkaline AA cells? Since the nominal voltage of those batteries is 6 V and the undervoltage shutdown on the VNH2 can trigger at up to 5.5 V, I suspect what might be happening is that the combined current draw of both motors starting is causing the battery voltage to dip below the undervoltage threshold and triggering a shutdown. If you do determine this to be the problem, a more appropriate battery to use might be 5 or 6 NiMH cells, such as the kind often used in RC cars.
Thanks for the responses. They make a lot of sense. The motors are intended for use at 6V although the description says it should be safe to operate them at 9V but it may shorten the motor’s life.
I went to my local Radio Shack to get some rechargeable NiMH AA batteries but they were $16 each so I passed on that. Would it be safe to try 6 Alkaline AA batteries? Sorry to ask such simple questions but I am new to all of this … are NiMH better because they have a higher current or do they just last longer?
I went ahead and tested this with 6 x Alkaline AA batteries instead of 4 and now both motors are spinning. Yay!
Thanks again for the help. I have been struggling with this for a while and can now finally complete my first robot. I will do some research on NiMH batteries.
$16 is a lot for a single battery! (That’s in USD, right? Are you sure that wasn’t for a pack of 4?) You can probably find a better price by shopping around, but we also do sell some NiMH batteries and battery packs.
NiMH batteries are better than alkalines at supplying high currents because they have lower internal resistances. Being able to recharge them is a benefit as well; depending on how much you run your motors, you could easily use up lots of alkaline batteries quickly.
