There's a fairly wide variety of commercially made heated clothing available, and some of it is very high quality stuff. Unfortunately, it can also be very expensive. If you've got the money, and can find what you're looking for, go to it. If you're cheap, read more and you might want to follow what I have done.

DIY electric clothing does have some drawbacks. Until you get the bugs worked out of your designs, you WILL have reliability problems. The most common area for problems is in connecting the heating wire to the harness wire.

The simplest, cheapest way to warm up your clothing is with some very fine wire. There are a few gotcha's to watch out for, however. The wire has to be flexible enough to not break every time you move. The insulation has to be able to stand up to the temperatures. And, you have to be able to find the stuff.

My original information came from a site that I can't find anymore. So, kudo's to the unnamed person who started this off. What I've used is a wire that I get from Newark Electronics. It is 30AWG stranded, with a Teflon insulation. It comes in a 100' roll, which is enough to do 3 vests. The part number is 02F7447, and the last cost I had was $22.05.

There are other materials out there, including real heating element conductor and conductive fabric, but this is what I have experience with.

I used a large needle to stitch the wire into the inner layer of a couple of vests I already had. I kept most of the wire between the inner layer of fabric and the filling, only coming out often enough to hold it in place.

To connect to the bike's wiring, you need a heavier wire (or else you'll be breaking it off all the time, in addition to wasting heat). The connection between the thin wire and thick wire is a weak point. Here's what I've been happiest with so far: I use extra-flexible wire for the bike-side of the harness, and run the two wires together for about 4" to the connection (which is soldered). I then take some 3/16" adhesive-lined shrink tube to cover both wires. After the shrink tube hardens, I used some tie-wraps to strap the whole bundle to the inside of the vest.

There might well be better ways to do this; the big deal is to keep the stress of pulling on the wire harness from pulling on the thin heating wire and breaking it.

At the bike end of the harness, use some kind of plug-in connector that you're happy with. I've got some 2-pole trailer connectors from an auto-parts store ($1.50/pr) that are working well. Once again, keep any stress at the splicing point distributed so that you don't pull the splice apart. Here, I used a solder joint, covered with short piece of adhesive-lined shrink tube, with both wires bundled inside some braided sheathing.

Now that you've got warmth, you're going to want to be able to turn it down, or you'll get too hot. The simplest way is to unplug yourself, but that's hard to do while riding. The next step up in complexity is a switch, but you will soon get tired of turning it on and off. You might think that a potentiometer (rheostat) would do the trick, until you start getting prices for one capable of carrying the 4 amps that the vest will draw at full load. Enter the Electronic Heat Controller.

Electronic Heat Controllers are available commercially. However, they're just as pricey as heated clothing (well, they used to be). So, being a cheap person with not too much money, I started looking for a way to have that functionality for less money.

A newly available item may likely change the cost/benefit ratio for you. Hot Grips (a maker of heated grips) has developed a compact integrated version of this for a very reasonable price. See HotGrips for details.

Anyway, if you still want to try it yourself...

There's an electrical principle called Pulse Width Modulation. It was originally used as a precise method of controlling electric motors. The basic idea is to use electronics to turn the power on and off very quickly, and vary the motor's speed by varying the ratio of On time to Off time. This ratio is called Duty Cycle, and is expressed as a percentage. Ideally, you want to be able to control your heat output from 0% to 100%, and anywhere in between.

I found several control circuits designed for motor controls, but they were always more complex than I wanted, with adjustments designed for motor control that I just didn't need. Finally, I came across this: dimmer.jpg. I adapted this circuit to my needs by changing the capacitor from 10nF to 2.2uF. This brought the frequency down to around 300 hz. The potentiometer does not mount to the board, but rather to the inside of the case. The output from the comparator (LM393) goes to the gate of a remote MOSFET (think of it as an electronic relay).

All the commercial Heat Controllers I had seen were set up to mount to your clothing near your waist. I didn't like that, so I made mine mount to the bike. It fits on a bracket near the clutch lever, and has a status LED so I can see it's brightness vary as I adjust the heat.

I can use skinny wire going to the controller, and mount the MOSFET's remotely nearer the actual outlet for the clothing. The original drawing calls for an IRF540, which I used. I later found that you can get an IRF540FI, which is isolated so that you can fasten it to the frame and do away with the need for a heat sink.

Run the +12V supply to the heated clothing with heavy wire, directly from the battery (with a fuse, of course).

If you use a connector with an exposed pin, make sure the exposed pin is negative, or you will be blowing fuses as it flops about when not used.

The pot on this list is a miniature, weatherproof model with an integral knob (the knob is about 3/4"D x 3/8"H). The box is approximately 1" x 2" x 3". The prototyping board is ~4" x 6", which is much more than needed. The actual circuitry covers ~1" square, and the board is cut large so it doesn't rattle around too much in the box.

These are current prices when this was written. This is a large electronics supplier, and prices fluctuate throughout the year. At least you've got a ballpark.

The biggest disadvantage to this control circuit is that only the middle third of the potentiometers travel adjusts the heat. In other words, from zero - 1/3, it's all the way off; from 1/3 - 2/3, it adjusts; from 2/3 - full, it's all the way on. The drawback to this is that it's difficult to make small adjustments with heavy gloves.

A big advantage to doing it this way is being able to have the controller in front of you, where you can see it. Another advantage is the ease of adding additional outlets. All that is required is another MOSFET and some wire, controlled from the same pot.

Well, folks, there it is. If you like to roll your own, this should be all you need to try it. If you want reliability and someone to blame if it quits, go buy one.

I'm still waiting for the first person to tell me they quit using electric clothing :-)