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Registered Member #96
Joined: Thu Feb 09 2006, 05:37PM
Location: CI, Earth
Posts: 4061
Hi all.
I am looking into modifying a domestic or industrial (higher power = useful) microwave so that it can be used as a poor man's kiln when the inside surface is replaced with a multilayer insulator such as fire cement.
A useful addition would be to remove the useless rotation motor and put the K type thermocouple through the resulting hole in the base plate with some sort of RF feedthrough so microwaves can't leak out.
Yes I have a leakage tester
A while back one of my experiments used a microwave with a B/W video camera placed over an existing hole in the top casing, so that it could be used to see inside the cavity during operation without the door getting in the way.
Has anyone done anything like this?
Note, using an inverter would make things a lot simpler, as these can be precisely controlled and power feedback is a lot easier when digital signals are used rather than old fashioned relays.
See And Also Also relevant as I have one of these inverters,
Registered Member #2099
Joined: Wed Apr 29 2009, 12:22AM
Location: Los Altos, California
Posts: 1716
Please let us know how it goes.
I think it'll work best if you keep the heated volume much smaller than the cooker box. Perhaps cut a cavity in a block of low density firebrick. What refractory material will you use to absorb the microwave energy?
I have to fault the Hackaday page for saying "smelting metal" when they really mean melting metal.
Registered Member #230
Joined: Tue Feb 21 2006, 08:01PM
Location: Gracefield lower Hutt
Posts: 284
Conumdrum I have hacked several inverter uWaves for high temp chemical reaction chambers @ work. The opto isolators one each direction are for control. For the in direction to the power module. this runs at around 200 hz with the mark space ratio being directly related to power output. You cannot go below 30% power as there is not enough heat in the filament below this for reliable operation. For powers lower than 30% the control pcb starts turning the oven on and off just like convenional ovens. The other opto changes state when the inverter output is true. I used a small micro PWM output pin to control the power pcb
A good crucible would be silicon carbide or tungsten carbide both soak up uwaves very well
Registered Member #3414
Joined: Sun Nov 14 2010, 05:05PM
Location: UK
Posts: 4245
Hacking microwave oven inverters isn't easy. I looked into it a while back. There is an old thread here somewhere. You need some form of protection to prevent transients in the mains from causing voltage peaks that destroy the IGBT. There are other issues as well, I'll see if I can find a l;ink later.
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Microwave hacking
