# A 'space heater'

#### GreenAce92

Jul 8, 2011
16
I'm trying to build basically a space heater if you will, heat is generated through heating coils of wire like Ni chrome or a better material.

I have a wall adapter which puts out 12.6V at 6Amps

I'm wondering if this enough to generate between 350-400 degrees Fahrenheit

If I heat a coil of wire say 6in long, I don't know the exact math for the resistance but my heater is going to be an indirect method of conducting the heat to air.

So I'm trying to heat a small volume of air up to 400 degrees F.

I am looking at it like this:

Adapter > dial/regulator (temp control) > coil of wire

However I don't know if this is enough power to generate this much heat

Also could you guys be specific on materials? Gauge and length etc...

I appreciate the help

If this is not enough power how could I develop the power source or at least what is a readily available part(s) that are relatively inexpensive?

And lastly how do you regulate the voltage? I imagine it's just a simple dial that I would splice between the adapter and the actual coils.

#### duke37

Jan 9, 2011
5,364
What is wrong with Nichrome that you need something better? You can search for details of Nichrome, Kanthal and Constantan on the web.
You will need about 2.5 ohm of wire so choose a diameter and length to suit.
Nichrome can easily go up to 1000C so 400F would be a doddle. The temperature obtained will depend on the power input and the heat loss, you may need to make a little oven insulated with glass fibre (in US, fiber).
Control could be achieved by using a plug-in lamp dimmer and plugging the adapter into that. If your adapter has a stabilised output, then this will not work, a simple transformer is what is needed or an external resistance which will get hot.

#### GreenAce92

Jul 8, 2011
16
Wow thank you...

So do I need to know like the volume of the area which I am trying to heat?

I am using a stable 12.5V 6A output... rectified and all so I could not do as you said

What 'size' of a transformer am I looking at?

What is a wall rated at? 110V 250A?

Also does having alternating current vs. direct affect the fact that I am trying to in essence short circuit or transfer the energy to the surrounding air?

#### TBennettcc

Dec 4, 2010
292
Depends on where you're at in the world.

In the U.S., the typical wall outlet (circuit) is rated for no more than 20 amps at 120 volts. That means that every appliance on that circuit combined cannot exceed 20 amps. Some are rated for 15 amps. You'll have to look in your circuit breaker panel to see what the circuit you want to connect to is rated for.

Is there a specific reason you're using the 12V 6A adapter? You'd probably be better off hooking directly to 120V. (With the necessary fuse / circuit breaker / 1:1 isolation transformer, of course, for safety).

Is there a reason you're not just going out to purchase a space heater? Consumer appliances like space heaters are tested and backed by safety commissions. If something were to happen, something you built yourself will not be covered by insurance.

#### duke37

Jan 9, 2011
5,364
It would help if you could say just what you are tying to do. Your power supply will provide about the same amount of heat as a light bulb so will have little effect in a room.
AC and DC current has the same effect in a resistor, the AC measurement is chosen to be the same as the DC even though the AC voltage goes up and down and even reverses.
You should not be shorting anything, a short is a zero resistance (or nearly) and you should be connecting a specified resistance suitable for the job.
The volume of the air does not matter, what does matter is the rate of heat loss. To heat a small volume of air to a high temperature with little power, you will need to reduce convection currents and provide thermal insulation around the area.
The term 'space heater' is usually used to describe a room heater, is this what you are trying to make?
My advice would be to keep away from high voltages until you are sure you know what you are doing.

#### GreenAce92

Jul 8, 2011
16
All valid points gentlemen...

Indeed I don't really know what I am doing... but I would like to learn!

The reason I was using this 'fixed' power source was because it was something that I had, from my planes when I used to cut cores for flat land thermal gliders and slope planes.

Well... I am not really trying to do this project anymore however we are still on the right track

I am a model aircraft fanatic and I do deal with electronics sometimes...

One thing I have always wanted to make was a power supply with a voltage regulator for cutting airfoil 'cores' out of foam with a hot wire.

Also this same power source can charge my lithium polymer batteries

Some are rated pretty high on power, therefore the power source needs to be variable, lipo batteries are special, I've got a charger for any cell count / size but my power supply limits me...

I guess the old saying or coining of something bigger goes towards the smaller well as far as power goes anyways... charging batteries I'm speaking of.

--| |--

I got along fine using a meter of wire and my 12.5V 6A adapter however the temperature was fixed... therefore I had to cut the foam at a specific speed

Often it wasn't nearly hot enough.

Perhaps I'll read this book my CAD teacher gave me back in High School called : ENERGY: Electricity/Electronics by Miller Cullpepper

2400 watts eh? That's pretty damn good

I'm in New York by the way

But I appreciate the help fellas.

So back to the 'project' now I'll re-title this soon once everybody catches up or at least sees the change in path.

Objective: Develop a variable DC power source ranging from 12 - 18 V (not sure on amperage)

Something like Wall plug > transformer > bridge rectifier > light dimmer > end cables (attach to alligator clips on charger)

Is a car battery a DC? Well hell yes it is I would imagine

But that is one common power source used by these chargers...

Some of these lipo batteries are pretty hefty

And my current power supply is incapable of supplying power

Granted I only have small batters with 45A max burst

But when I actually get to the big leagues where they use 6-7 Cells with 30C
I mean each cell is 3.7 volts that's already over 20 volts

This is where the bigger power supply comes in.

I feel like I'm going in circles, I apologize for this but I regardless I appreciate the time you guys put in.

At least you guys know these simple questions

I asked around yesterday at home depot and an actual electric store as well as radio shack about whether or not I was capable of using my current power supply and generate 355-400 degrees of temperature...

I guess it is too small of an application but they had no clue... I mean granted it's a vague question...

#### GreenAce92

Jul 8, 2011
16
Just a side note, could you theoretically take a super conductor, get it to be struck by lightning and then it would be 'charged' with immense power? Which could then be used to say charge my cell phone for a hundred years?

I was just wondering if there is such a thing as 'flash-power' where lightning is so instantaneous and so powerful but can that energy be captured and slowly sipped away like gas in a car (not true these days) ?

#### TBennettcc

Dec 4, 2010
292
So, are you wanting to design a space heater, or a foam cutter?

#### GreenAce92

Jul 8, 2011
16
A power supply to satisfy either needs.

My primary focus is, a stable power supply with safety features, say I just took the two output wires and touched them together, the system would have a failsafe and either a) divert the energy elsewhere or b) shut off

#### TBennettcc

Dec 4, 2010
292
Safety features = a ground fault circuit interrupter (plug your device into one of these, usually installed in the wall as a replacement for a standard electrical outlet in the US) AND a fuse in your power supply design. Depending on what you're looking at for a current rating for your power supply, install a fuse just above your rating. Say you want a 4-amp power supply. Install a 6-amp fast-blow fuse. Between that and the GFCI, you should be set for safety.

And remember, all the safety devices in the world are no match for a clear head thinking rationally and carefully.

Replies
8
Views
930
Replies
3
Views
2K
Replies
3
Views
618
Replies
3
Views
1K
Replies
5
Views
1K