low temp heating element

If you don't need precise closed loop control then a hot water heater or electric range heater element connected to a variac might be sufficient. These elements are normally 220V and running them from a 110V variac might be sufficient depending on what you are doing with them.

Also check out:

They have inexpensive kiln heaters and controllers.

It's going to depend a lot on what you're tyring to heat (liquid, solid, air), the size of the object, heat losses, etc. Any specifics?

you have two basic methods:

1. - open loop method - use a heading element, and adjust the power to it with a lamp dimmer, monitor temp with a thermometer and you ASSUME that heat losss will be pretty constant, so once you get it set, you leave it alone.

1. closed loop method - use same heading element as above, but add a temp controller that measures the temp and adjusts the power to the heater either proportionally or by cycling it on/off. You can also use a PTC thermistor for the heating element. You don't offer any idea of the power you need, if it's a few watts, PTC thermistor is a good choice, if it's hundreds or thousands of watts, then you want a heating element and a suitable controller.

You need to decide if you really need a temperature controller or not. How accurately do you need to maintain the chosen temperature?

A simple heater would a series of incandescent lamps under the item to be heated, run off a dimmer. That would provide open loop control only, of course.

Jim

I would mount several high-wattage resistors (the type with a heatsink) on one side of a piece of Al of the required size, and pass a high current through them. A suitable sensor could be used to measure the temperature and control the power delivery to stabilise it at the desired value, using a microcontroller and PWM. It'll be quite expensive unless you can design and build it yourself.

Leon

If this is a serious application, the easiest, fastest, best way is to buy a mica strip heater of the appropriate dimensions and use a thermocouple embedded in a flat plate with a commercial temperature controller.

Best regards, Spehro Pefhany

If you can use mold heaters, Ive got several 55 gallon drums full of brand new ones, from .250x1" long to .75x24" long.

Nearly all are round rods, with armored cables coming out of them in various lengths. Brands include Big Chief, Calrod and so forth.

They will look like these

I also have a dozen or two brand new temperature controllers (new old stock with analog dials) along with quite a number of Type K termocouples of all different types and styles. The temp controllers IRRC run on 220 volt, but are easily stepped up or down by a transformer.

Chuckle..if you can make it to Central California, Id let you browse though the heaps of such and simply let you haul off what you needed.

Gunner

"As physicists now know, there is some nonzero probability that any object will, through quantum effects, tunnel from the workbench in your shop to Floyds Knobs, Indiana (unless your shop is already in Indiana, in which case the object will tunnel to Trotters, North Dakota). The smaller mass of the object, the higher the probability. Therefore, disassembled parts, particularly small ones, of machines disappear much faster than assembled machines." Greg Dermer: rec.crafts.metalworking

Tear an old electric oven apart All the components are in there.

Specify heat, not temperature. Otherwise we have no idea what you have in mind.

On 31 Oct 2004 08:16:27 -0800, snipped-for-privacy@beaconts.com (Rich) calmly ranted:

A friend of mine makes bird incubators and found some heaters and controllers at the Westpack expo we attended a few (gosh, 6 now!) years back.

might get you in touch with some of the thermoformer vendors who use elements of that nature.

Another good source (without temp control) is old coffeemakers. I found a 30-cup percolator for $5 at Goodwill, with an 800-watt encapsulated element in it. I made a "digital flatiron" using that, some 1/2" al jigplate, a thermocouple and a little surplus Omega controller. It controls to within 1 degree from ambient up to about

450. I wanted precise temp control for laminating.

Gunner's heat cartridges and c>As usual Don, a great idea.

Guess I need to provide a little more info. As for power, I definitely don't need anything in the "thousands of watts" range. What I want to do is melt hot melt glue along a length of about 12 inches. So we're talking about something in the range of a home appliance, like maybe a hairdryer (what's that, about 1200 W?). The temp I want to maintain (about 300 deg F) should melt the glue quickly and uniformly. I'm pretty handy electrically (I rewired two homes) but I don't know what to call the things I need. Hope that helps

sobo

By "open loop" I assume you mean something where the power cycles on and off in response to the temp. That would be fine. I actually want to do this as cheaply as possible. My only requirement is that the cycling is automated. I can accept a wide temp range too--probably as much as 10 degrees on either side would be ok. I don't think the light bulbs will work though. I want the heat concentrated on a metal strip about 12 inches long, by about 1/2 to 1 inch wide. This heating strip should melt a bead of hot melt glue. Nothing fancy. Thansk

Now we're getting somewhere. Don, I think you've got me on the right track. A flat iron was actually the first thing I thought of, but I wasn't sure about the actual heating strip--I assumed the entire "sole" of the appliance was the heating element. Actually, what I'm trying to construct is probably very close to your laminator.

I want to build a book binder that uses thermal binding tape. I think this is basically a strip of ribbon w/ hot melt glue applied to it. Heat the strip, stick in a stack of paper, and fold the edges of the tape around the spine of the document to the front and back cover. The tape actually becomes the spine of your book. I'm not worried about the mechanical parts (for folding the tape), but the heating parts are not something w/ which I'm really familiar.

Can you tell me a little more about controlling the temp? That Omega controller thing sounds interesting. Commercial binding machines that do this cost in the thousands. That seems a bit much for what is essentially a desktop hot glue gun with an integrated clamper. But I'm sure you know that w/ your experience with your laminator. Any pics on that? Thanks.

Rich

Yes, that helps. Do a Google search on "strip heater". Lots of hits.

My crude heatsink program sez a 2 x 2 square running 25 watts will run at about 300F, so I'd guess 2 x 12 might take about 150 watts. If you have a control you might want 300 watts and let the controller cycle it. You could probably nick a termperature controller out of an old iron, but a thermcouple controller would be considerably better.

You might even try a big solder>Guess I need to provide a little more info. As for power, I definitely

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Nope -- that is a form of closed loop. The sensor which turns it on and off closes the loop.

Open loop means just feed it a known power, and expect losses to keep the temperature close enough. Like a fire in a fireplace -- you pile on the wood, and hope that it produces the right amount of heat. If somone keeps opening the door or doing other such things, you really need closed loop to keep the temperature close to what you want.

It sounds as though you do need some form of closed loop controller.

Good Luck, DoN.

On 5 Nov 2004 13:02:30 -0800, snipped-for-privacy@beaconts.com (Rich) calmly ranted:

get you started, but see below first.

Is hot-melt glue a Librarian Approved material, sir?

Purty pictures from a GlobalSpec search:

Heaters and controllers:

-- Sex is Evil, Evil is Sin, Sin is Forgiven. Gee, ain't religion GREAT?

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Sin-free Website Design

Not sure about "librarian approved". I'm not looking to produce heirloom books, just quickie commercial booklets for office use and such w/o resorting to 3-ring binders or combs or crappy clamps. Here's a link to a commercial product:

I'll buy the commercial binding tape that a machine like this uses

Thanks for the links.

Rich