# Building electric clothing

Discussion in 'Equipment' started by HellSickle, Jan 8, 2006.

1. ### NesbocajEarth, we're #1

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Hmmm, at 3.4 ohms that means your jacket is putting out 54 watts.
So a Gerbings jacket has about 77 watts of power. Your wire is about 0.1ohm per ft, so you need about 57' of wire, no?
More wire, more resistance, more heat. Unless I have this backwards??

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Actually, I think you do have it backwards. Heat energy in Joules is current squared times resistance times time. So current has a much bigger effect on heat than resistance. Less wire equals less resistance, which equals more current, which equals more heat. Kind of counter intuitive.

Here's two examples assuming 12 volts for ease of computation:

30 feet of wire

3 ohms
4 amps
(4^2)*(3) = 48 Joules per second

40 feet of wire

4 ohms
3 amps
(3^2)*(4) = 36 Joules per second

All of that said, I'm a little embarassed to say that I checked my wiring with my multimeter when I got home tonight, and found that the jacket is producing infinite resistance. Hmmmmmm. Testing the various components revealed that there was no current getting through the switch I used. Making a straight connection without the switch seems to have restored the jacket to about 3.5 ohms. I went and plugged it into the bike and it definitely was producing more heat. We'll see how warm it keeps me tomorrow.
3. ### harderkevSlab Sucks!

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So less wire will get hotter but pull less wattage and cover a smaller area. More wire (same guage) will draw more wattage and cover a larger area but produce less heat?

Kev.

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Not quite; you're right about the area covered and heat produced, but not about the wattage. Less wire will get hotter and pull more wattage but cover a smaller area. More wire will draw less wattage and cover a larger area but produce less heat.

Watts = volts x amps, so less wire will pull more wattage (less resistance means more current (amps), and voltage stays the same). Actually, now that I've puzzled it out on paper, heat energy in Joules per second is the same as watts. Heaven knows how much mental energy I've unnecessarily expended computing Joules when I could have just figured watts.
5. ### zeroBeen here awhile

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Just got myself some 0.1mm nichrome wire (best i could get tbh) unfortunately its unsealed, but am thinking of useing some heat shrink sleeveing (since it shoudl be able to cope with 200odd degrees)

The other thing i'm thinking, because it can be usefull to use less wire, PWM units.. these work by switching on and off rapidly.. from 10% up to 90% on a simple type, now suposedly altering two of the resistors will alter the minimum and maximum "duty cycle" so if one was replaced you could go from 90% max to 40% max, this way greatly reduceing the ammount of wire needed and doign it safely..

does this make sense?

(another cx rider, and i lurve it!)
6. ### harderkevSlab Sucks!

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So we can caluculate using Ohm's Law that a Gerbing jacket liner (6.4 amp draw at 12 volts) has a resistance of 1.875 ohms?

I = V/R or V/I = R therefore 12/6.4 = 1.875 ohms.

Maybe I should have bought the 26ga wire at .041 ohms/ft. instead of the 30ga at .1 ohms/ft. to get more even heating and cover a larger area?

Kev.

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I think that's right. 30 feet of the 26 ga wire would give you 1.23 ohms of resistance, drawing 9.75+ amps, and 117+ watts, which would probably be too hot. To get the same wattage as the Gerbing (6.4 x 12 or about 77 watts), you'd need about 45 feet of the 26 ga wilre.

Looking at that though, it doesn't seem to make sense. If I've computed it correctly, the heat goes up as the diameter of the wire increases and resistance goes down. But that would mean your battery cable should get practically molten, which it doesn't.

What gives?

By the way, I tried the electric jacket this morning with the straight hook up (no switch). It wasn't real cold, about 55 degrees, but with just a cotton work shirt, the jacket and my Road Crafter 2-piece I was fine. Apparently, electrically heated clothing works much better when there's electricity actually flowing through the wires.

Anyway, I don't think you have to get too hung up about even coverage. I'm 6'4", so I have a pretty long torso and long arms. 35 feet of wire was enough to put 6 strands of wire each in the front and back of the jacket, and 4 strands down the full length of each arm. The heat felt pretty evenly distributed to me this morning.
8. ### zeroBeen here awhile

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You battery cable isn't high resistance wire

Still scrambleing for parts for the pwm module, only plsaes that do them you need a trade account for, not paying £10 (\$20?) for an 80p part :/
9. ### harderkevSlab Sucks!

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I bought my complete PWM here:
http://www.aseanexport.com/Division/TechnologyKit/MX.php
I had to buy two, so I may have one available once I decide I don't want a second controller. Scroll down to the MX033.

Another place you can buy them individually, but they were backordered, is here:
http://store.qkits.com/moreinfo.cfm/MX033

I also bought more 30ga teflon wire than I think I'll need, so I may be able to offer a kit including the wire and PWM for anyone who might be interested.

Kev.
10. ### ArbyNavBoxer Fan

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Why doesn't the battery cable melt?
This is a quick list of what's happening in the electrics:
Your voltage regulator is going to do it's best to keep the voltage across the battery (or wherever else you start your electrical system) constant - about 12 Volts (V)
Power, measured in watts, at the work load (motor, light bulb, resistance wire) is Watts (W) = Volts (V) x Amps (I)
If the volts are constant, thanks to the voltage regulator, the only way to increase or reduce power (which is equal to heat in your wires) is by changing current (I).
Current is dependent on voltage and resistance (I = V/R). Since voltage is constant, the only thing you can change is resistance. Lowering resistance will increase the current. You can lower resistance by using less wire, or a thicker wire. Think of it as a pipe, with resistance as friction. The less pipe a liquid has to travel through, the less the walls of pipe interfere. Likewise, a bigger pipe restricts flow less. So if you shorten the wires, more heat.

So why doesn't the battery cable heat up? The power in your system is put out in a serial fashion in the line. If you have a light hooked up, it glows brightly, but the more lights you hook up (in series), each glows dimmer. If you have different watt bulbs, each takes a different load. Now the final part - the voltage dropped in total along the line (series) equals the sum of the individual parts. It'd take a lot longer to explain, but basically your battery cable is accounting for almost no voltage drop, while the high resistance wire is dropping almost all the load. If you used a low resistance wire for the heater element, it'd be a whole different story - you'd be blistered and the battery cable would be heating (and your voltage regulator/generator would be toast if you didn't use a fuse) Thats also why a long run or small gauge of power cord to a high power motor may cause the motor to lug, as the voltage drop on the supply line becomes very significant (length of wire drives up it's resistance - same as using a higher resistance wire). If your battery cable had more resistance, it'd drop more voltage, and then it would begin dissipating power (heating up). If you feel such a supply cord trying to handle the load, you'll find it very warm or hot.
If the battery cable was the only thing on the circuit, then it'd have to dissipate all the power - if the cable has almost zero resistance then the watts would be something like Power (watts) = 12 / 0, which is almost unlimited and a very bad thing for your generator to try (user hint, it will try but will never make it - the power generated will roughly correlate to the dollar cost of fixing the damage)
ArbyNav
11. ### RSLLong timer

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Regarding the suitable type, gauge, and brand of wire to use for electric heated clothing, consider the following:

1. Gerbings and Warm-n-Safe have long since figured this out, so use their products as benchmarks.

2. Google for "electric heated jacket" or similar key words, and you'll find plenty.

3. IBMWR website has archives about how to make electrically heated clothing, with guidelines on design, materials, sources, prices, layout, etc..

4. The US Army Air Corps and others were using electrically heated high altitude flight suits in WWII, so there is nothing new in this idea. These suits frequently appear on eBay, so you could ask the seller about the wiring.

5. I have Gerbings' jacket liner, pants liner, and glove liners, along with one HeatTroller unit. The HeatTroller works well with just the jacket, but adding gloves and (especially) pants liner, and it's not so hot, except around the waist, where it's too hot. There are some areas that are not hot enough, so this tells me my Gerbings could use a tune-up.

6. It would work better to have several different HeatTrollers or other suitable pulse width modulators, to control different areas with different heat settings. The multiple HeatTroller does this and has a warranty, but a PWM from an electronics supply house would be cheaper if you don't need a warranty and your time fiddling & tweaking has no monetary value.

7. A good second-hand Gerbings or Warm-n-Safe set will probably be cost-competitive with whatever you can make yourself, without the hassle.

8. Fuggetabout using a vest (without sleeves or in some cases a collar) if you live in a four-season climate or plan long rides. The 'warm body core keeps hands and arms warm' theory is inoperative for more than short rides in cold weather.

9. Somebody posted that they bought a down jacket liner (with sleeves) at Target for ~\$40, and that it packs pretty tightly. TELL ME WHICH TARGET STORE!!! This would make a nice addition to my Gerbings set and works off the bike, too. Great idea.

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Thanks for the laugh and the explanation. Sometimes I wish I paid more attention in Physics class.
13. ### falcnSquidless Soul

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If'n you don't look in the right places you will end up wasting that much money....

I found www.cruzanengineering.com and had Chrissy do my wife's jacket liner. Nothing but props for her company!
14. ### KL5ABugs are the new black

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Some folks have built their electric stuff and found that it maybe wasn't quite warm enough, myself included, I modified mine just a bit (shortened the wire) but if you go too far that direction you start to scrifice coverage. So how does a guy increase the power without taking out so much wire that the coverage goes away?
Why not build a garment with a couple of circuits in parallel and switch them on and off as needed?
I've been thinking about doing this-running 2 or 3 circuits. Lots of wiring involved but wire is cheap, I think I paid \$9 (with my ham radio discount) for a 100' spool of 30g teflon coated stranded wire and switches are chump change at rat shack.

I built one of ZZR Ron's controllers, works fine, the hardest part was finding that pot for the control. I came very close to building a resistor network and just switching from like low/medium/high, but a trip to Fry's while I was on a trip to Kali yielded the right part.

If nothing else, it's fun to play with and you can make it work just the way you want.
15. ### Night_WolfLong timer

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Can I have first dibs on the setup if you do sell the extra's

16. ### lowflyerDoubleplusgood

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I considered making my own, but decided it easier to buy a Warm-n-Safe liner and Heat-Troller. I am very happy with it. The quality is first-rate and the thing works extremely well.

Now that I have one that I know works, I plan to tinker with making my own. I usually wear the FieldSheer Highlander suit (Roadcrafter knock-off) for winter commuting. I think I might wire up the liner in it using some of the techniques I have read about here.

17. ### harderkevSlab Sucks!

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Consider yourself first in line.

Kev.
18. ### harderkevSlab Sucks!

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I'm getting ready to start threading my pants and jacket and I've been giving a lot of thought to what others have said about making sure the wire is close to your body. The jacket and pants I'm using are a Starter Drystar windproof, breathable 100% polyester exercise suit I bought at Wally World. It has the mesh liner and is just as effective as my Motoport AirTex liner at keeping wind off me while riding. It also doesn't look so hideous that I would actually wear it to walk around in once I'm off the bike, and the smooth shell slides very nicely under my Motoport Air Mesh gear when dressing or undressing.

I bought the smallest size suit I could comfortably wear but it is still a little loose in several places, more than I would like. I turned the jacket inside out last night and started collecting the sleeve along the seam to approximate how much I might take it in. I then noticed the liner is only attached to the shell at the cuffs, waist and collar. I collected up just the liner and realized its mesh construction allows it to stretch! Viola! I don't have to take in both the inner and outer layers of the suit to get a snug fit!

Kev.

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That is me ... it is a regular down jacket that i bought 1 size too small, so it fits under my leather jacket.

The down jackets are famous for compressing better than anything else, and providing the best heat-bulk-weight ratio of them all.

The store i bought it from is in Exton, PA

http://www.target.com/gp/detail.html/sr=1-11/qid=1163434554/ref=sr_1_11/601-4819310-6746541?ie=UTF8&asin=B000GUNAZ6

I am 6f 2 in tall .. long torso and arms ... 44 inch chest ... 32 inch waist size MEDIUM for fit as a liner.

I am wearing it right now ... cozy and warm!!