Will this wire burn me or melt my clothes ?

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Here's a 12 volt dimmer that is suspose to be rated at 7.5 amp.
Without the plate and a smaller knob, it might work for you.
http://www.dyersonline.com/Products/12-Volt-Light-Dimmer-Switch__18-0600.aspx"
 
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dlgoff said:
Here's a 12 volt dimmer that is suspose to be rated at 7.5 amp.
Without the plate and a smaller knob, it might work for you.
http://www.dyersonline.com/Products/12-Volt-Light-Dimmer-Switch__18-0600.aspx"

DC or AC?
 
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DrAlloway said:
Actually, when I first started designing this project, that was my daughter's first reaction:

"This sounds like a ball of fire roaring down the road."

I have now finished sewing all four loops of wire into my jacket.

I have a bunch of plugs to solder over the weekend - connecting 32 gauge Teflon insulated wire to plugs is not easy - if you pull on the plug to make a connection you can break the 32 gauge wire - and wearing gloves only makes it more likely.

?? still no suggestions on how to convert a 120vAC digital light dimmer to 12vDC ??

I can't help you with the 120VAC dimmer because I have no idea how it is designed.

This circuit looks good for your project though.

PWM_unit_for_interior_fan_regulation.jpg


The power rating is depends on the FET transistor so you can replace it with the one that suits your need.
 


How about this as a possibility: use an on/off control or thermostat of some sort. I've been trying to think of what could be used for cheap.

The best I can think of for on/off would be the safety cutoff bimetallic strip trip for a Hair Dryer. They are apparently designed to cut off power at around 60 degrees C, so as to not burn skin. You could insulate this directly around the heating wire, or wrap a few heat wire loops around the sensor deliver more heat to it, and leave it uninsulated to allow strip to cool after after acting. This also acts as a good safety feature incase you are in a situation where heat loss from the coat drops for a while (ie. in traffic) and the wire would start heating up beyond what it was while moving on the bike.

http://home.howstuffworks.com/hair-dryer4.htm

The other thing that may or may not work would be to grab a thermostat from a toaster oven, clothes dryer...


http://sunnergroup.manufacturer.glo...9/pdtl/Toaster-oven/1008140892/Thermostat.htm

http://sanchang.manufacturer.global...599/pdtl/Thermostat/1008870226/Thermostat.htm (has plus minus 2 degrees C control)

http://www.appliance411.com/parts/showcase.dryer-thermo.shtml

You could maybe sew one of these devices in close prox. to the heating wires, then set it and foget it.
 
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Redbelly98 said:
DC or AC?
Humm. I assumed it was DC since the site was advertising "RV Lighting Accessories" but they really don't say. Maybe it is AC in which case it wouldn't work. Here's their "Indoor Lighting" page.
http://www.dyersonline.com/Departments/RV-Lighting-Accessories/Indoor-Lighting.aspx"
 
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That RV Accessories dimmer looks good - it says 12vDC and that it saves energy (by which I deduce that it is some kind of PWM like the schematic provided above).

I did tease some info out of a commercial maker's tech support before they shut me down.

Guy said the frequency needed to be like 1 Hz, otherwise the simple regulators on motorcycles get confused. The frequency on light dimmers is typically above 60 Hz so the eye doesn't notice it is really being turned off and on, rather than dimmed. I have no idea if 60 Hz is OK or not - as the bait I threw at tech support mentioned thousands of times per second.

But keep thinking guys - the right answer IMHO - is CHEAP.
 


I'm looking to make my own battery-powered heated fingerless gloves for working outside in winter, and this thread has been helpful, as has the similar guide at instructables.com.

I'd like to recommend this inexpensive pulse width modulation dimmer (designed for LEDs), which may be the heat control you're looking for. The pwm will modulate the heat without lowering the voltage or output power. http://www.usledsupply.com/shop/led-controllers-dmx/controllers-dimmers/pwm-3a-uc-dimmer Or search for other pwm LED dimmers, which may fit your dash better. They all seem to work with 12V DC input.

The instructables article is here: http://www.instructables.com/id/DIY-heated-clothing/

Best of luck.

-Imp
 
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Wow - excellent find - I looked for a cheap PWM for 12vDC and couldn't find one. So I designed my electric motorcycle clothes with multiple circuits - each with a different wattage - so I just plug in whatever circuit is appropriate for that day's weather.

If I had this PWM when I started I would have designed it differently. They also have 8 amp models. The 3 amp would be perfect for gloves or socks. The 8 amp for jacket or pants.

Would make the whole project less complex and only add $20 for 3 amp and $25 for 8 amp.

Again, great find.
 


try a temperature controller also and integrate in the circuit. it will get rid of your heating problems.
 


I would have said that it is vital to avoid high temperatures (hot spots) in the jacket. This means a long length of relatively thick wire which will dissipate the power at a lower temperature because it has a larger surface area and is in contact with more of the fabric of the suit. You can choose many combinations for a given resistance / power output; the choice will probably be the wire that doesn't cost too much - which would be copper, rather than anything else - you are after just a couple of Ohms (see below), which corresponds to quite a few metres of 'thinnish' wire. Enamelled, rather than plastic covered might be better as its temperature will not be too high and it won't melt the insulation. You will need to zig zag it so that it can stretch and move with your body. Sandwiched between layers of a material that isn't too insulating - like cotton - and it won't overheat or melt.
You could look inside an old 'electric blanket' to get an idea of suitable cnstruction.

Of course you need plenty of insulation on the outside of the jacket but you don't need much more heat supplied than your metabolism produces. You will overheat very rapidly if you have too much heat supplied. My opinion is that you only need 'just enough' to keep you comfortable. The 72Watts seems reasonable. If you wanted a rapid warmup, you could always do the old 'series / parallel switching' trick that old electric cooking hobs used. Two resistors in parallel produce four times as much heat as they will in series.