Project Blog

A few years ago I made a BBQ smoke generator. I was fairly happy with the design, but felt that for the “next time” I would make a few changes.

One of my main issues was the size. I really wanted to make it smaller, but I didn’t want to pay for a small cartridge heater.

It occurred to me a couple of days ago that I might be able to modify a stock toaster-oven heating element to make a smaller heater. If I cut out a small section and drove it at a proportionally smaller voltage, I wondered, could I get a small heater with the same temperature as the big boy? It turns out that the answer is yes.

I went through a few fits and starts getting this thing to work. My main issue is that I’m still learning to weld, and welding wire requires a lot of finesse. I’m not going to bother with the trials and tribulations though. Here’s how I made a custom heating element:

Cut to Length

A heating element is a nichrome coil embedded in a steel tube using ceramic. In a toaster-oven they wire 2 in series, so each element is designed to see 60V. I had a 12V power supply, so I wanted to use 1/5 of the total element length. A pipe cutter made quick work of the cuts.

Ream

I needed to attach metal contacts to the wire. To give myself enough wire for a bond, and to have room to support the contact, some free space would be required. A metal file and some elbow grease left me with a 1/4″ cavity at each end of my cut section.

Weld

Attaching things to nichrome is a tricky proposition. Because it gets so hot you can’t use solder, and mechanical connections are unreliable. I decided TIG welding was the way to go.

Easy in theory, blindingly difficult (for me) in practice. In the end though, welding for 250mS at the lowest setting created a permanent bond bond between contact and wire.

Insulate

To keep this welded bond electrically isolated, and to give the contact some rigidity, I filled the previously-created cavity with furnace cement.

Next time around I might do this in several small additions rather than all at once. I think that would give me a more solid fill.

Burn Baby Burn

It actually works! I applied 12V to the element and was easily able to make some wood smoke. It didn’t get red-hot, but I suspect this is because my cut section was a bit long. At any rate, I’m really excited at the prospect of making inexpensive small heaters for use in my projects. I should probably get some more welding practice first though.

This entry was posted on Wednesday, April 4th, 2012 at 7:38 am and is filed under Mechanical. You can follow any responses to this entry through the RSS 2.0 feed. You can leave a response, or trackback from your own site.