Infra red wrist strap

Before spending a lot of $$, it’s worth checking out the optical properties of the plastic that the tube is made of (unless you’re thinking of drilling holes for the LED’s). My investigations didn’t look that promising when trying to ascertain that the plastic was transparent to IR wavelengths. When I use a thermotex around a tube, most of the heat I can feel is from contact with the tube (which absorbs the heat) rather than radiant heat.

If you buy a couple of those wrist bands and take them to pieces, there’s a good chance that you could create something that will fit inside the tube, but it would be a bit Heath Robinson.

Shiver,

Did you just invent a pump cylinder for holes for holding IR LEDs? PM me and let’s talk.

PE’rs,

Most plastic products (including acrylics) as I recall are opague to electromagnetic waves starting at 1 micron wavelength (near IR) and on out. I could be wrong, but most of the optical transmission spectragraphs I remember from my days in working with plastics and plastic-forming processes suggest plastics are very efficient in absorbing IR at most wavelengths and converting that energy into heat energy that is either very slowly conducted (due to low thermal conductivity) and/or re-radiated at wavelengths unique to the atomic structure of the plastic itself. Plastics tend to be good insulators (both electric and thermally, too) and poor conductors. Many plastic extrusion and sheet formation processes use IR heaters to heat the extrudate because plastic absorbs IR.

Shiver’s suggestion at drilling holes in the tube to accept IR-emitting diodes for heating purposes is correct in my opinion so as to get around the poor transmissability of plastic to IR.

All the Best,

MrTiPS

This chart shows that acrylic may be ok for near infrared. Far infrared is a different story.

The interesting thing is that my infrared wand has a plastic cover over the leds. I wonder if it is a special plastic.

Drilling the tube and inserting the leds would bring the leds in contact with the skin. Is that a good thing?

Assuming you could maintain the seal, the issue becomes heat. First, there’s the contact temperature of the LED. Most LEDs run very cool, but IR LEDS may be different if their plastic cases absorb the rays. I think we need a protototype.

Another graph showing IR transmission through acrylic. Look at the bottom of page 5.

http://www.desi gninfo.com/goto … moforming%2Epdf

With the exception of a few wavelengths, acrylic looks fairly transparent to IR. IR LEDs probably radiate at a well defined wavelength. As long as that wavelength avoids the troughs in the transmission spectrum, you should be good to go.

I guess the thing to do is set up an experiment. Maybe I can stick a temperature probe through a polska kielbasa, insert it in in a tube and see it it heats up. :)

This site says LEDs can’t output Far IR, what we perceive as heat.

Notes on LEDs

However, this site says that normal diodes (non-light-emitting) do produce FIR radiation:

LED | encyclopedia article by TheFreeDictionary

Normal diodes are even cheaper than LEDs.

Here’s a page that describes various sources used to generate IR heat. Notice that diodes and LEDs aren’t included. I suspect their power output is too low for most applications (although possibly not for ours).

Well, something is up with these infrared wands that have leds and certainly certainly produce heat. It looks as if I’m going to have to open mine up and see what’s inside.

I see that fiber optics cables transfer IR. I have no idea as to how to attach them to a tube.

What’s an infrared “wand?”

One of these thingies:

I couldn’t find anything about LEDs in the product description. But it did mention “bulbs,” which could only be replaced by a certified technician. I suspect the “bulbs” are old fashioned incandescent rather than solid state devices.

I’m going to open it up and see what’s in it. If it is bulbs, wonder how it can be an IR device?