is there a best place to drill into a microwave oven?
is there a best place to drill into a microwave oven?
(OP)
I wish to insert ~1/2 inch OD glass and/or plastic tubing through a commercial microwave oven cabinet wall. The question is, might there be a particulaly safe location to do drill? I refer possibly to the corners of the cavity, a mathematically calculated position like 1/2 wavelength in from an edge, or in the direct center of a wall. I know the loading can shift the hot nodes but they might not ever form in certain locations; and that would be the best point for drilling. The microwave of choice is fed from the side and not the top, if that makes a difference.





RE: is there a best place to drill into a microwave oven?
RE: is there a best place to drill into a microwave oven?
It sounds like you want to heat liquid via the tube. If this liquid is water, then the 0.5 inch hole will allow RF to propagate out the hole when the water flows and you may create a problem.
Waveguide cutoff is 0.5 * 11. 803/ 2.45 Ghz = 2.41 inches, but with water dielectric = 81 flowing thru, the cutoff dimension becomes 2.41/sqrt (81)= 0.27 inches.
Hence, it may be necessary to use smaller below cutoff holes and combine them (if the dielectric of your liquid flowing thru the tube is high like water).
If you have some 2.45 Ghz phones available to detect the leakage, it may give you a hint of just how bad the leakage is. With a potential leakage problem, having the hole nearer the corner of the oven may be best. i.e. the corner furthest away from the power source feed.
So how large is the heating need, slight or max?
kch
RE: is there a best place to drill into a microwave oven?
The waveguide aperature is long way horizontal and is below the midpoint of the short end wall; so your suggestion is to drill into the corner where the opposing wall and top wall of the cavity meet and to do so midway between the corners?
Furthermore, just to spice things up even more, the starting temperature will be -100 C and I am trying to see how well I can couple to the rock and the moisture within it.
RE: is there a best place to drill into a microwave oven?
"suggestion is to drill into the corner where the opposing wall and top wall of the cavity meet " Yes, go as far away from the waveguide aperture as possible, I think the top far corner is probably the coolest field location to make your entry hole.
I once used marshmallows to find the hottest spot in an oven, arraying marshmallows on the bottom of the oven and whichever one blows up the tallest shows the hottest spot. Don't fill the entire bottom, maybe 50% or less. It gives a hint of the power levels anyhow, not a perfect situation, but is interesting.
If you need to limit the power to your unit, place a water filled tupperware inside the microwave to absorb the power. Cold water might be best, since it'll take longer to boil.
You will still have leakage out the hole you cut. You may want to get some threaded pipe (2-6 inches long)and cut the hole the same size and thread a tiny bit of the pipe into your hole (0.1, 0.2 inches). If only a little pipe comes inside the oven up in the corner, you won't get arcing. That'll reduce the leakage out the hole due to cutoff waveguide losses and will also help support the plastic pipe and stop it from being cut by the sharp edged hole you make in the oven wall.
I'm curious what you're finding in this experiment? What gas is contained in a volcano?
kch
RE: is there a best place to drill into a microwave oven?
Purpose is to use uwaves to extract water from soil on an unspecified unearthly body. Need vacuum and cryogenic temperatures to approximate the environment.
BTW, how might one employ a cell phone to find leaks? All I found was a claim that if one was put inside a closed uwave oven, it could still receive a call and ring.
RE: is there a best place to drill into a microwave oven?
And cheap too...
RE: is there a best place to drill into a microwave oven?
This 2.45 Ghz phone isn't a cell phone I noted, but a home cordless phone. Home phones come in different frequencies, but the 2.45 Ghz ones seem to be the most popular.
The phones hear the interference from the microwave oven and it sounds like static noise in the phone earpiece.
You could tell if the oven leakage jumps alot by how far away you have to be when the phone picks up static.
kch
RE: is there a best place to drill into a microwave oven?
RE: is there a best place to drill into a microwave oven?
Calibrated devices cost several hundred dollars.
RE: is there a best place to drill into a microwave oven?
My home microwave 12 yrs old suddenly developed a hotspot at the front center bottom. After running the unit for 3 minutes, the plastic lip seal had melted and scorched. I found that the "stirrer" in the top was not turning and concluded that the belt was broken, so replaced it, and then patched the damaged front seal with similar plastic molded with a hot air gun.
Now it still gets hot after 3 minutes.
Is there a problem causing this local heating, or is there a requirement for the repaired seal to be "tighter to the front door?
The unit is not replaceable since none of the appliance companies make a combination range/microwave any more.
I'd very much like to rescue the unit since it works fine.
RE: is there a best place to drill into a microwave oven?
My home microwave 12 yrs old suddenly developed a hotspot at the front center bottom. After running the unit for 3 minutes, the plastic lip seal had melted and scorched. I found that the "stirrer" in the top was not turning and concluded that the belt was broken, so replaced it, and then patched the damaged front seal with similar plastic molded with a hot air gun.
Now it still gets hot after 3 minutes.
Is there a problem causing this local heating, or is there a requirement for the repaired seal to be "tighter to the front door?
The unit is not replaceable since none of the appliance companies make a combination range/microwave any more.
I'd very much like to rescue the unit since it works fine.
RE: is there a best place to drill into a microwave oven?
RE: is there a best place to drill into a microwave oven?
The Rf sealing function on a microwave oven is not from the plastic seals. The sealing of RF inside the oven is from the overlap in the door to the housing being set to 1/4 wavelength (electrical length) at 2.45 Ghz to make a quarter wave open = a short circuit. That's 1/4 wave electrically, which includes the dielectric constant of the plastic on the door edge. Adding goop to replace the original seal needs to be the same dielectric constant as the original seal, or the 1/4 wave length changes and the seal becomes poor.
I'd bet you are leaking alot of RF outside your oven, I'd suggest throwing the unit away, or find another one and replace the door. Get a leak detector to check it.
kch