Home/Lab made heating element?

I am trying to construct a heating element, preferably out of nichrome, for heating a small box (24 * 40 * 13 cc). The box is covered on all sides, so the heat dissipation from the box will be very low, as per estimate. I think a 12V supply would suffice for the nichrome wire. The only thing is, I need to maintain the box at an ambient temperature of about 38 degrees. Any thoughts on how I could go about constructing the heating element?

sort by: active | newest | oldest
Psyclops (author) 6 years ago
Well, I did end up ordering a heating foil for the same purpose. My prof was not willing to let me handle nichrome wire all on my own. Could not use a light bulb as the inside of the box has to be EMR free. The next thing now on the agenda is to get the fan incorporated into the box, because as Sean rightly pointed out, circulation is very important to keep the ambient temperature stable. Just to ask, at what speed did you operate the fan for the box you mentioned Sean?
kelseymh6 years ago
Sean and Rick both have good ideas. If you're going to buy parts anyway, you might as well buy the right parts for the job. Google "heating tape" and you'll find good inexpensive resources. Incandescent bulbs, with a thermostat-controlled dimmer, work great for this job (I my lab, we used three 100W bulbs in a cubic meter box and got it up to 50C), and are cheap.
As a nod, one need only remember the Easybake oven. One 75W lightbulb as I recall. (sister had one but I liked the cake!)
rickharris6 years ago
I agree by the time you have insulated the nichrome wire etc you may as well just use an standard incandescent ligt bulb. You can easily make a dimmer to control the temp and no need for anything other than bulb and bulb holder.
I like that idea. Simple, economical, and creative. However, I do believe that a fan is important. In our industrial app we found that circulation was critical for ensuring that the temperature was uniform within our enclosure.
seandogue6 years ago
I'd recommend looking at kapton heaters.

an example mfg is

These gizmos can often be found at discounters and ebay for less than the retail price.

We used a small (1.5" square) heating tape for a similar ( same?) purpose in a sensor box to elevate it beyond ambient in order to reduce thermal fluctuation related noise (basically to reduce changes in gain due to temperature), in order to improve our functional resolution for a set of pressure sensors. The enclosure was, as I recall, ~12"x 9" x 4". A small fan was also used internally to the box to circulate air so that hot pockets didn't form, and a semiconductor thermostat (Dallas semiconductor...now Texas Instruments? Maxim?) was used to control the heater element.

Doing so with nichrome raw? idk. Sounds sketchy, since the nichrome can sag and so short circuit.
jtobako6 years ago
Incandescent light bulb?

Depends on if you can get enough current for the thickness of the nichrome wire you have available. What are you using as a controller?