problem with inputs on driver shield

Drive a 4-wire bipolar stepper motor or a pair of DC motors from your Arduino. [Product page]
Post Reply
mmmmbeeeeer
Posts: 2
Joined: Wed Dec 30, 2015 8:16 am

problem with inputs on driver shield

Post by mmmmbeeeeer » Wed Dec 30, 2015 8:24 am

Hi ,

I'm trying to connect m Raspberry Pi to the H-Bridge driver shield. Assuming I can set the IOREF voltage to 3.3 volts from the RPI, I've connected the inputs directly from the configured GPIO outputs fro the RPI.

Everything is going great until I connect the inputs to the shield. Before connecting the inputs, they are at the expected voltages (low is around 20mV and high is around 3.2V), but once I connect them, the low voltage gets pulled up to around 1.9V. As far as I can see, it's only going into the input of an AND gate, so I don't see why this is being pulled up...?

Could it be that I've fried the 74HC08 when I was messing around getting the voltages right? At one point, I connected 8V to IOREF which I think exceeds the max for the CMOS chip??

Any thoughts?

thanks,

Pete

mmmmbeeeeer
Posts: 2
Joined: Wed Dec 30, 2015 8:16 am

Re: problem with inputs on driver shield

Post by mmmmbeeeeer » Wed Dec 30, 2015 11:22 pm

ok, so it turns out that I have a version 1.1 board which doesn't connect up IOREF - instead it powers the HC08 from the 5V line.

So by just powering up the 5V pin and testing the gate in isolation, it's definitely not working properly - 5V on both inputs to a gate gives about 2V output on the gate.

Seems like I got a dud and since IOREF isn't connected, I haven't overpowered the chip.

Any other suggestion before I take it back to Jaycar?

andrew
Freetronics Staff
Freetronics Staff
Posts: 978
Joined: Sun Jul 14, 2013 7:06 am
Location: Melbourne, Australia
Contact:

Re: problem with inputs on driver shield

Post by andrew » Sat Jan 02, 2016 8:17 am

Sorry to hear your board isn't behaving.
We'd recommend you exchange it at Jaycar.

Post Reply