I'm making a circuit that I used for a previous project on a bread board to power two electromagnets. I'm using the same wiring and parts as the first time. It's a simple circuit using an Arduino to control a motor bridge.
Here's the problem: when I try to operate it from the arduino, nothing happens. When I run the logic pin (and Vref, etc) through the 12v power supply I would use for the electromagnets (instead of the arduino), everything works fine.
Using an voltmeter, the arduino looks fine with volts going up to (and a little over) 5v. The motor bridge is 4.5~20v. Instead of a magnet, I'm just using a voltmeter for testing. The ground is run through the power supply, not the Arduino
Here's the circuit: circuit http://www.e-alexander.net/slippers_img/circuit1.gif and the schematics for the ta7291P http://www.electronicaestudio.com/docs/1437_2_4025.pdf
I have multiple ta7291P motor bridges and all have the same problem: all worked fine last year when I did the project, but now none of the work from the arduino, none of them work from a 5v constant current used instead of the arduino (second input pin is grounded in that case), all of them work with 12v used to power everything.
Are my chips just aged/abused or am I missing something?
Thanks in advance!