IR Project - Viewsonic Monitor drives IR module nuts

[dxpwny]

I've worked with IR projects for years. My last one, about 8 years ago, used an Atmel AT89S8252. I just started another one - using a Dallas 89C450.

Anyways, my troubles now are not micro-controller related - but IR related. I just wired up my project and the IR output of my IR module, a Sharp GP1U52x, is quite noisy. I tried a few modules, all are very noisy.

Smelling a rat ... I started to turn off lights. Thought maybe it was my compact flouresants. No ... it was my 28 inch Viewsonic monitor. With it off, everything is well, and my IR module is quite .. only responds to IR from my remotes.

With the monitor ON ... and the light from the monitor visible by the module, its very noisy on the output. I put some papers in between the two and it quiets down.

I use red plastic ... the type of plastic you might see covering the LED display of a digital clock, to cover the IR modules - I had thought they provided some simple light filtering.

I've tried all sort of caps on the IR module power input ... nothing seems to quite it down.

Anyone have suggestions on how I can work on my IR project - and still use my 28 inch monitor to develop the code ?

 

[Fish4Fun]

Hrmmm, form your description it would seem that the "noise" is coming from the monitor's light output and NOT more traditional EMI....This would suggest one of two things: 1) The monitor is putting out light in the IR range, 2) The Monitor is putting out pulses of light near the carrier frequency of your module. In either case the simplest answer is to shield the IR module from "line-of-sight" of the monitor. You might consider a small, temporary "tube" attached to the IR detector as a "quick and easy solution". Noise rejection is a common problem with IR, handling noise rejection gets more complicated as you try to maximize effective range//sensitivity...If the only trouble you are having with the monitor/receiver module is involved in the debugging phase, then simply shield the module from the offending source ;-)

Fish

 

[Arouse1973]

Have you tried increasing or decreasing the refresh rate of the monitor. To verify if it's the screen and not EMI what about turning the brightness down and see if that makes it better.
Adam