Heated Insoles

Heated clothing extends the motorcycle riding season significantly.

I have a pretty complete Gerbing's outfit that includes a heated jacket liner, heated pants, and heated gloves.

Because the collar of the jacket liner is heated and extends up into my helmet, my head stays nice and warm.

So the only area that can get pretty cold when the temperature drops are my feet. This page details how I came about to make my own heated insoles. Click on the small photos for larger images.

Gerbing's makes heated socks, but they don't work well for me for two reasons:

My boots (Sidi Champions) are pretty snug and the thick socks are too tight a fit.
Although wired socks are very warm, the wires are very uncomfortable to walk on.

So I set out looking for alternatives.

I found an interesting product called Hotronics footwarmers that use a thin metal disk in an insole that supplies heat from batteries that attach to ski boots. They have an interesting treatise on why feet feel cold, and what to do about it here.

I liked the idea, but really wanted to draw power from my motorcycle (although there is an appeal to being able to keep your feet warm when walking away from a bike, because although the rest of my gear is very insulated, the soles of my boots are not).

The Hotronics are also a bit pricy, about $170 per pair (with two batteries), and I wasn't convinced that they'd be as comfortable as I'd like (they're usually used in ski boots with thick socks).

So, I thought there might be another approach, one that uses an interesting material called Gorix. This is an unusual fabric, produced in England that actually gets warm when current is applied to it.

The fabric is thin, about the same thickness as shirt fabric, so I knew it would be unobtrusive. I got some 3" x 3" samples of the material that came complete with soft braided wire leads attached to the fabric.

I also got some Cambrelle insole liners (paper thin and self adhesive) so I could sandwich the Gorix patch between the liner and the insole of my boot. The photos above show the Cambrelle and Gorix, and how the patch is placed on the Cambrelle and then inverted onto the insole (so the wires are on the underside when assembled. I reinforced the edges with some thin strips of black gaffers tape and used solder and shrink tubing to fit Gerbing's style connectors to the ends of the wires.

When I attached the insoles to a 12 volt power supply, as I expected, the patches got way too warm (about 135 degrees Fahrenheit, or more).

So I had to figure a way to reduce the voltage. I looked at a few alternatives (resistors, rheostats, etc) but I really wanted something more sophisticated. The answer came from Radio Shack. They make a device that plugs into a cigarette lighter, and provides output voltages selectable from 3 to 12 volts in 1.5 volt increments. It also uses an internal resettable circuit breaker for added protection. Extra treats include a power and overload lights, and regulated power for anything under 12 volts output.

So, disassembled the unit, stripped out the electronics and coerced it into a small electronic box. I added a toggle switch at the top as an extra cutoff.

I used some Dual-Lock connectors (sort of an interlocking Velcro-like fastener) to attach the new box to my existing Heat-Troller power supply, and I clip them both to my jacket belt using clips designed for cell phones.

I use one channel of the Heat-Troller to power my Gerbing's gear, and the other channel as a simple switch to supply power to the new insole box.

An interesting note is that the Heat-Troller is a pulse modulated power supply... essentially pulsing short bursts of 12 volts as output. However because the Radio Shack device is regulated under 12 volts, and I've found that 3 volts or 4.5 volts is the most comfortable, the device maintains power (probably using a capacitor) instead of pulsing with the Heat-Troller. So anything over about 50% setting on the Heat-Troller is enough to power the insoles full time (anything below 50% doesn't activate the insole power supply at all). So the Heat-Troller is effectively just acting as an on-off switch providing 12 volts to the insole controller.

So how does it work? Great!!!

When I walk, I can't feel the patches or wires at all. When connected, the Gorix patches take the chill off nicely. As mentioned, when using 3 or 4.5 volts, I don't feel that my feet are warm (even when 25 or 30 degrees outside), they're just not cold (which is exactly what I want). However, it's nice to have the option to switch the voltage up a couple of points if the temperatures drop significantly.

All in all, an interesting little fabrication project.

If you have comments, please visit the Guestbook.