I need a good IR absorbing surface

Black electrical tape works very well at blocking all the light from (Si) photodiodes. I don't know how much is absorbed vs reflected. But it's easy to try.

George H.

Even though the thing says it is motion activated I think it just detects its own reflected light because when the garbage can is slid under the counter the lid opens and stays open. No motion required. So I think it does not have a PIR detector but instead sends out pulsed IR and when it is reflected back the lid opens. Just holding my hand over it will cause the lid to open and stay open. Eric

That's what I'm thinking. Black felt opr black construction paper. My camera should be able to tell me how reflective something is. Eric

Thanks for that Joe. I am going to need some flat black paint to paint the inside of some optics assemblies in the not too distant future. Eric

Drink Black Velvet? There are plenty of recipes for Black Velvet Cake.

Eric,

It has been a few years since I dealt with IR, and that was near IR (e.g. your typical remote control):

I was attempting to make a small robot's IR reflectance sensors work so it would follow a black line, but a number of visible-light "black" substances did not have any effect (the sensor couldn't distinguish them from plain white):

- InkJet black ink (water-based) - Permanent markers (those tested) - Black acrylic paint - At least one marker claiming to be "pigmented"

These _were_ noticed:

- Laser printer "black" (fused plastic toner) - Black tempera paint - Strips of black supermarket-chicken containers (both the foamy kind and the flat plastic kind)

I was _told_ that most "pigmented" paints, markers would absorb IR (at least near IR), but my own results were mixed -- possibly a tribute to American Marketing's triumph over providing clear information. ( Sigh. )

Just for grins, if you have access to a laser printer, try printing a solid black square of "sufficient size" and hold/tape it in place to see if it helps.

Good luck...

Frank McKenney

Not likely any good.

You want flat black, not shiny.

And start out with some thing like a sheet of black velvet which should be a pretty good absorber.

Good Luck, DoN.