Many of you probably have technical interests besides electronics. In my case, I have been doing a significant amount of metal work lately, including producing castings from aluminum. To melt aluminum requires a melting furnace, and, as these are fairly expensive, I built my own. The basic furnace is uncontrolled other than watching the interior heat up, and trying to estimate the temperature by the color. When I built my furnace I was disappointed by the lack of a proper controller to carefully adjust the temperature. I checked into buying a controller but found the price prohibitive, so I decided to design and build one myself. For you that may also have an interest and knowledge of metal casting, or have some other reason to control significant AC power, I have posted the design on a web site so you too can build a controller.
Just out of curiosity, what made you decide to heat your furnace by electricity rather than with a burner? 7 Kw must set your electricity power meter disk spinning at a takeoff rate .
I built a propane burner ( also easy - there's plenty of info onthe web) and a furnace that can melt up to 10kg of aluminium. Have not had a chance yet to cast anything other than making ingots from scrap :wink:
Have fun,
Klaus
I used to do controls for furnaces and ovens, and I was told that people like electric furnaces when they want special atmospheres. Every now and again someone would put in an electric furnace because the Electric Utility would give them a kickback ("Incentive") but they were always disappointed by the performance, and they cost much, much, MUCH more to build and, I suspect, operate.
The reason that I built an electric furnace is that I planned to use it for more than just a metal melter. I actually built two of these and used one for burning out investment casting molds. I also used one of these as a furnace to test materials at specific temperatures where highly accurate temperature control and lack of contamination were of great importance. The furnaces each only hold a four pound crucible, so the total power consumed is rather small. I used maybe a dollar or two a day worth of power for my castings and tests.
It seems over-engineered, for its purpose. I'm sure we could come up with something much simpler, which would suit you. (though I can't do it right now, I'm about to go out..)
No criticism of what you have. Just a thought that next steps might be a microcontroller to allow implementation of other strategies such as PI, PID, etc. I have lots of experience with industrial controls - none of it with microcontrollers however I've surfed thru some sites and was left with the impression that others have written the code for these and other control strategies.