UPDATE 05/25/2010 - A mailing list for the discussion of induction heating and heaters has been established. You may subscribe by clicking here.03/22/2010 Update - Our commercial web site, http://www.fluxeon.com is now up and running. Still in a preliminary stage so don't be too hard on us. That is the place to go to buy kits and complete induction heaters.09/16/09 Update - Please read this page for a basic description of the heater and then go here for a very significant upgrade.10/19/09 Update - Increase the power output of this heater to >1500 watts for less money than a rectified mains power supply using a Power Factor Correction (PFC) Board12/17/09 Update - The commercial auto-tune, auto-power-control version of this heater is almost ready for market. A new company has been formed, Fluxeon. Keep an eye on www.fluxeon.net for developments. Note: Please email Garett for any business-related inquiries. Only email me with technical questions, as I am not involved in the business.01/02/10 Update - My friend Jonathan has just put up a website here that documents his 2kW PLL self-tuning heater. I worked with him quite closely on this project. An excellent design.02/18/10 Update - See my new open source heater, the Royer architecture. Even better than this one.Presented here is an approximately 500 watt induction heater that you can build at home from commonly available parts. It is easy to build and easy to use and is capable of many metal heating applications. The particular heater shown here was designed for heating "getters" and electrodes in gas discharge lamp assemblies. The result is that the work coil is attached to the electronics box. It could easily be located in a "wand" at the end of a cable.I'm going to assume that you've read Richie's page that covers the theory of induction heating and specifically the parallel resonant architecture that I chose for this heater. The heater consists of three basic parts * An oscillator * A power amplifier * A resonant tank circuitPlus, of course, the power supplies and ancillary hardware. This is known as a manual tune unit. That is, the frequency of the oscillator must be manually adjusted to the resonant frequency with the work piece inside the work coil. This is made easy by virtue of the tuning meter. The frequency is simply adjusted until the meter peaks, that is, displays the highest reading. | | | Here is a photo of the finished unit. The peaking meter is on the left. The large black knob controls a variac that sets the power output. The 10 turn pot underneath the Variac is the tuning control that sets the operating frequency. On the lower right side of the box is the work coil. When in operation, this coil has several hundred amps of RF current flowing in it.| | Several views of the inside of the box. Important note: The heat sinks shown in the photo are NOT large enough for continuous use. With fan cooling they're good for about a minute. That's more than enough for processing getters and lamp electrodes. If you plan on using this heater for longer durations, you MUST fit larger heat sinks. | |
| Two views of the tank circuit. Because several hundred amps flows in the tank, the conductors must be heavy. The current must be spread across many capacitors. The capacitors are polypropylene "Orange Drop" caps. There are 24 0.022uF, 400 volt caps and 2 0.1uF 400 volt caps for a total capacity of 0.7305uF. This resonates with the 5 turn coil at about 300khz.| |
| These photos show some details of the enclosure. While you probably won't use the same enclosure that we did, the photos illustrate some important features.The first point is that the box and everything surrounding the tank is non-metallic. We would not want to be heating the enclosure! The pink electrical fiberglass...