Arduino Forum

Using Arduino => Sensors => Topic started by: brother6 on Mar 10, 2015, 05:57 pm

Title: Isolating 0-5VDC voltage reading
Post by: brother6 on Mar 10, 2015, 05:57 pm
Hey guys, thought I'd post here to get some help...
Here's my situation:

I want to isolate a sensor reading (basically, 0-5VDC reading) with the HCPL-7520, and I will be reading the value with my microcontroller (in this case, using the arduino board, but could be any other).

Now, here's the application circuit for the HCPL-7520:
(http://i.imgur.com/9iUIMeD.png)
And here's the link to the datasheet: http://www.farnell.com/datasheets/1266244.pdf

Here's the circuit, which I modified for my application:
(http://i.imgur.com/jZDNQCb.png)

I tried it about 10 minutes ago, and I wasn't getting anything on the output of the circuit.
Did I do something wrong?

Need your help!
Thanks :D

Edit: Accidentally connected Vref to ground instead of Vcc on my breadboard... rookie mistake ^^
I fixed that, but, after reading through the datasheet, turns out it's best for the input to be between the -200mV and +200mV range (for best linearity on output). So I added a voltage divider to bring my 0-5V input to 0-185mV. It is working now, only problem is that my output now varies between 2.48V and 4.32V, instead of 0-5V.

Note that the gain = Vref/0.512