DIY heated gear

Linkex

Linkex

Linkex

Associate
Joined
4 May 2011
Posts
1,065
With winter approaching, I've been reading up on diy heated gear. The process seems fairly simple, but there are a few things I’m not sure on. Firstly, most of the things I've read are based on voltage against length of wire to control the heat. While this looks like it works, it means that I’m stuck with 30 feet and will have no temperature control. If I want to do a pair of heated gloves for example, I can’t fit 30 feet of wire in there. So, I assume I need to fit something to lower the voltage if I want control, or shorter runs and this is where my electrical skills fall down – I don’t know what I need. A variable resistor? Some kind of transformer? – what thing do I buy that takes 12v in one end and lets me choose the volts out the other end?

Secondly, I’m concerned about power draw budget. I’m looking at around 50 watts per 30 feet. Assuming I did head to toe covering (I’m not going to, but this is worst case), I could be trying to draw 150 watts from the bike. I know bikes will all be different, but what sort of range should I expect? Is 150 watts reasonable from any bike, only big bikes, or that be too much for any bike? If it’s out of reach, what sort of spare wattage would a 600 generally have?
 
I foresee this happening....

Iebedc0.png


Good luck though, sounds an interesting project
 
I suspect 150 watts would be somewhat beyond the spare capacity of most sports bike generators, and certainly any small bikes. That's an extra 12.5 Amps @ 12v.

For example the total output of a CBR600 generator is around 340 watts @ 5000RPM. That would leave 190 watts to power everything else including fuel pump, ignition, injection and lighting. Bear in mind that main beam on the headlamps will be 2*55 = 110 watts.

The big touring bikes tend to be a bit better specified
 
Linkex said:
Following more research, this is the kind of thing I'm talking about, although obviously one designed to be integrated into the set up rather than plugged into a 12v connection. Anyone know what the internal part would be called from somewhere like RS components?

http://www.ebay.co.uk/itm/ALL-RIDE-...-VOLTAGE-/281113603086?_trksid=p2054897.l4275
Click to expand...

It's called a voltage regulator. That one is usless for your needs since it will only supply up to 1 Amp.

A linear voltage regulator is the simplest design, but the excess voltage which is drops is burnt off as heat so with a heavy load you will need some serious heatsinking.

Better suited to your needs are either a "switching" regulator or just a PWM controller, either of which is far more efficient than a linear regulator in most situations, but also a more complex. Something like this would do the job.
 
Thanks Dogbreath, that's exactly what I needed to know :)

Just to check my understanding - if I run 12v through 30 feet of RS Components Part Number 177-0621, it will generate around 50 watts of heat (According to the article I’m looking at). Does that mean that 6 volts through 15 feet of same will generate 50 watts of heat? And if that assumption is correct, is there any such thing as a non-variable switching or PMW voltage regulator? The reason I ask is I’m trying to figure out if I could run 30 ft in a jacket, 15 ft in my gloves, have 2 sets of wires coming off the variable controller, 1 to each, but with a static regulator between the controller and the gloves. The idea being that I then have a single controller for both jacket and gloves, without putting to much juice through the gloves circuit.

Or am in totally the wrong ball park?
 
what sort of mileage are we talking about?
jacket n trousers with a thermal lining, winter boots and a good pair of glove are all that really needed.
handle bar covers or heated grips an option also.
you don't want to be running the generator near capacity or it will get very hot and shorten it life also your mpg will be higher with all the extra drag
 
ShakenNstirred said:
what sort of mileage are we talking about?
jacket n trousers with a thermal lining, winter boots and a good pair of glove are all that really needed.
handle bar covers or heated grips an option also.
you don't want to be running the generator near capacity or it will get very hot and shorten it life also your mpg will be higher with all the extra drag
Click to expand...

Um, I don't think that's how motorcycle generators work...
 
Linkex said:
Um, I don't think that's how motorcycle generators work...
Click to expand...

the more power you draw the more drag on the rotor

As the generator turns it induces a voltage in stator windings (the coils around the rotor).

When this voltage is connected to a load a current starts to flow. This current then induces a magnetic field that opposes the rotor magnets (generators typically use electromagnets for their rotor magnets, not permanent ceramic magnets).

This opposing magnetic field creates a counter-torque(drag) on the rotor that is proportional to the current draw. This counter-torque, unless compensated for(more power), would slow the rotor. Slowing the rotor would lower the output voltage which would then lower the output current (V = IR, from Ohm's Law).

Lowering the output current lowers the amount of counter-torque, and the process continues until the rotor is stopped.
 
Last edited:
The drag caused by the drawn current would be absolutely insignificant and even if it weren't, the rectifier draws all the current whether it then passes it on or burns it as heat, so adding load on to the rectifier isn't going to change that anyway.

I appreciate your input, but commercial heated gear exists, so its clearly viable. If you have constructive criticism about the parts I want to use or my approach, I'm all ears, otherwise, I'd like to get back on topic please:

Linkex said:
Thanks Dogbreath, that's exactly what I needed to know :)

Just to check my understanding - if I run 12v through 30 feet of RS Components Part Number 177-0621, it will generate around 50 watts of heat (According to the article I’m looking at). Does that mean that 6 volts through 15 feet of same will generate 50 watts of heat? And if that assumption is correct, is there any such thing as a non-variable switching or PMW voltage regulator? The reason I ask is I’m trying to figure out if I could run 30 ft in a jacket, 15 ft in my gloves, have 2 sets of wires coming off the variable controller, 1 to each, but with a static regulator between the controller and the gloves. The idea being that I then have a single controller for both jacket and gloves, without putting to much juice through the gloves circuit.

Or am in totally the wrong ball park?
Click to expand...
 
no the rectifier does not always draw the absolute maximum power the alternator can produce, and the extra load will affect fuel consumption.

Do you really think the ****** little heat sink on your reg/rec burns off hundreds of watts of power!?

For someone who couldn't even figure out how to alter voltage a few posts ago you seem a little confident of the much more complex electrical systems...
 
Tefal said:
no the rectifier does not always draw the absolute maximum power the alternator can produce, and the extra load will affect fuel consumption.

Do you really think the ****** little heat sink on your reg/rec burns off hundreds of watts of power!?

For someone who couldn't even figure out how to alter voltage a few posts ago you seem a little confident of the much more complex electrical systems...
Click to expand...

I wouldn't sound quite so cocky, since Linkex is perfectly correct. The regulator on a motorcycle is a shunt regulator. It controls the alternator voltage output by effectively shorting it's output to ground when the voltage exceeds a preset threshold. The majority of the heat that results from this is dissipated in the (oil cooled) stator within the alternator itself, but since the switches (SCR's) within the regulator are not perfect they also dissipate some heat. The reason that modern MOSFET regulators run cooler is because they are better (lower resistance) switches so they drop less voltage, even though they are passing a similar current. This means the windings dissipate the extra heat when a MOSFET regulator is used.

All this means that the alternator is producing maximum output all the time, any spare output not used by the ancillaries is shunted to ground. It's a bit of a wasteful system to be honest, but it's very simple and perfectly suited to alternators that use permanent magnets. In a conventional car alternator, the rotor is an electromagnet, and the output is controlled by regulating the relatively small amount of current passing through the rotor winding.

Linkex said:
Thanks Dogbreath, that's exactly what I needed to know

Just to check my understanding - if I run 12v through 30 feet of RS Components Part Number 177-0621, it will generate around 50 watts of heat (According to the article I’m looking at). Does that mean that 6 volts through 15 feet of same will generate 50 watts of heat? And if that assumption is correct, is there any such thing as a non-variable switching or PMW voltage regulator? The reason I ask is I’m trying to figure out if I could run 30 ft in a jacket, 15 ft in my gloves, have 2 sets of wires coming off the variable controller, 1 to each, but with a static regulator between the controller and the gloves. The idea being that I then have a single controller for both jacket and gloves, without putting to much juice through the gloves circuit.
Click to expand...

You you certain that's the correct RS code? It is described as basic hookup wire, not resistance/heating wire which I was expecting.

Power = V^2/R

If you half the resistance (half the length of wire) and half the voltage, then you get 1/2 of the power. To get the same power from 1/2 the length of wire, the voltage needs to be reduced by a factor of 1/sqr(2)=0.707. 12*0.707 = 8.5 volts, as close as damn it.

You can certainly build a non-variable switching regulator, though for the currents you are looking at a ready built module might be expensive. You could simply use the variable speed motor controller and replace the potentiometer would a couple of fixed resistors, which would be a cheap and simple way of doing things.
 
Dogbreath said:
I suspect 150 watts would be somewhat beyond the spare capacity of most sports bike generators, and certainly any small bikes. That's an extra 12.5 Amps @ 12v.

For example the total output of a CBR600 generator is around 340 watts @ 5000RPM. That would leave 190 watts to power everything else including fuel pump, ignition, injection and lighting. Bear in mind that main beam on the headlamps will be 2*55 = 110 watts.

The big touring bikes tend to be a bit better specified
Click to expand...

but that's at 5000rpm at lower revs it kicks out lower watts
so riding around a about 2-3k will be a lot lower wattage
the slower its spins the lower the power output of the gen, that's one of the reason you have an alternator on a car not a generators anymore
 
Last edited:
Dogbreath said:
You you certain that's the correct RS code? It is described as basic hookup wire, not resistance/heating wire which I was expecting.

Power = V^2/R

If you half the resistance (half the length of wire) and half the voltage, then you get 1/2 of the power. To get the same power from 1/2 the length of wire, the voltage needs to be reduced by a factor of 1/sqr(2)=0.707. 12*0.707 = 8.5 volts, as close as damn it.

You can certainly build a non-variable switching regulator, though for the currents you are looking at a ready built module might be expensive. You could simply use the variable speed motor controller and replace the potentiometer would a couple of fixed resistors, which would be a cheap and simple way of doing things.
Click to expand...

Its the RS code that's mentioned in this article - http://www.hastie.org.uk/heatedjacket.html - chosen I think for its low cost. I wasn't aware that you could get wire specifically for this, will have a hunt around. If you have any specific recommendations, please let me know.

Took me a minute to get my head round that maths, but now I have, it’s actually a much simpler formula than I thought it would be to calculate the volts for different lengths of wire, thank you for that.

I’m now thinking that rather than trying to add multiple volt regulators in and running a master regulator, I will create a bike mounted project box, and add one PWM voltage regulator per body area (So, head, legs, helmet/gloves, feet) and a master on off switch. That way I can adjust specific body parts on the fly, rather than trying to pre-set relative temperatures. Plus, it should be a little simpler.

Now I just need to figure out what sort of connector to use and I can get started.
 
ShakenNstirred said:
but that's at 5000rpm at lower revs it kicks out lower watts
so riding around a about 2-3k will be a lot lower wattage
the slower its spins the lower the power output of the gen, that's one of the reason you have an alternator on a car not a generators anymore
Click to expand...

Unless you are trickling along in traffic a 600cc sports bike won't spend much time under 5000 RPM! The word "generator" can refer to any electricity generating device, so covers both alternators and dynamos (which is what old cars and bikes used to use).
 
Last edited:
Cheers. Have ordered the parts to get a prototype up and running, will prob create a new thread for it once I start building.
 
englishpremier said:
A variable resistor could be used to control temperature.
Click to expand...

Practically speaking, it would be a very poor choice. The power dissipation requirements would mean a rheostat would have to be very large and it would get very hot. Low loss electronic control (e.g. PWM) is always going to be a more practical solution in this case.
 
You must log in or register to reply here.
Back
Top Bottom