Microwave Croaked

On Wed, 27 Dec 2006 17:20:51 -0800, "Joel Kolstad" Gave us:

ALL microwaves have a stirrer. It cannot be that efficient, however, or we would have no need for turntables.

Watts are Watts. I use 15W instead of 60W for the same task that as a child in the sixties, I was unable to do. Conservation has its place, and steering the energy beam makes way more sense to me than steering the target mass.

You're nuts. An old synchronous clock motor runs the beam stirrer, and a dedicated geared set-up runs the platter. One is in the to of the chassis, and the other is in the base.

I hope you weren't envisioning the overhead fan set-ups like in the saloons of the forties, with a leather band pulling on all the pulleys with a single motor. :-]

Between power variance, and or duty cycle, with good beam diffusion in the cavity, we could see microwaves that actually do a good job and save even more energy doing it. Not just the platter motor savings, but duty cycle programs allow the heat to soak in better. Takes a bit longer, but actually costs less.

I find that hard to believe, but I admit to not being an expert on microwave ovens. I've never even completely disassembled one.

Yeah, but some watts aren't worth going after. :-)

From a purist point of view I agree, but from a pragmatic point of view it really only makes sense if you can figure out a way to do it inexpensively. I certainly encourage you to research it...

I was under the impression that -- for the sake of cost reduction (even when not on sale a new cheap microwave is, what?, $39?) -- there was only one motor in a typical (cheap) microwave, that ran all the fans, stirrers, and the platter.

Not quite that bad. I *know* there's a belt going between the turntable and the "guts" of the microwave oven on an old Sharp I have -- that I've seen with my own eyes. And I also know that there's a fan inside that blows out plenty of air through vents in the back...

Newer Panasonic microwaves claim that their "inverter technology" actually changes the power output of the microwave continuously rather than just changing the duty cycle of an on-off microwave source; I thought that was a nice little advancement.

Here's a diassembly of a microwave:

---Joel

Saw the ear off the cup. :-)

Ed

I doubt that - rotational speeds of these items are at least 2 orders of magnitudes apart, so I suspect more economical is 2 motors - a fan motor and a separate gearhead motor with low output shaft RPM to turn the turntable. I suspect both of these would consume roughly 5-10 watts each...

- Don Klipstein ( snipped-for-privacy@misty.com)

Never seen one without it except perhaps the First Amana RadarRange.

snip

but have a look at

martin

On a sunny day (Wed, 27 Dec 2006 17:20:51 -0800) it happened "Joel Kolstad" wrote in :

Not in the ones I have taken apart, Sharp and Daewoo? have a very small motor unit with internal gear for the turntable, located under the turntable, and a huge one for the fan, located next to the magnetron (blowing against it).

I think to make the turntable always stop at the same point a simple sensor and electronics would suffice, but have never seen it anywhere.

On a sunny day (Wed, 27 Dec 2006 18:19:15 -0800) it happened "Joel Kolstad" wrote in :

The problem with controling a magnetron is that it is only stable on frequency from a specific applied power or volatge level. Some amateur radio experimententer tried phaselocking the magnetron output to some reference by vaying the DC, I have seen the graphs, it did nolock very well..... I have heard of the Panasonic design, there is a cost issue, and a reliability issue. Normal big transformer and capacitor + diode is _very_ reliable. I have repaired many switchmodes for TVs......

Only advantage would be weight, nice for in an airplane.

On a sunny day (Thu, 28 Dec 2006 09:43:18 +0100) it happened martin griffith wrote in :

Nice :-)

I've seen them where part of the cooling air is diverted into the chamber, and the air flow turns a vaguely propellor-shaped beam stirrer.

Cheers! Rich

AIEEEEE!!! IT'S ALIVE!!!!! =:-O

;-) Rich

But...but...but...it then will not be able to *hear* !

On Thu, 28 Dec 2006 09:43:18 +0100, martin griffith Gave us:

Cool!

We live in the atmosphere filled annular space between the earth and outer space. :-]

I guess that means that earth is a big solidified alka seltzer bubble.

There is (or was) a model that does that. I remeber seeing the adverts on TV (hmm, many years since I saw a microwave advertised on TV). My mewmory says Panasonic (so it was probably Toshiba)

They mostly use synchronoius motors, so they rotate at an exact speed. time it to do 10 rotations.

Bye. Jasen

My old microwave used vanes pushed by yhr cooling fan to redirect the beam.

last one I looked into the stirrer was powered by the draft from the fan (which flowed over the the magnetron and and up the waveguide to get there.)

Bye. Jasen

If you know the gear ratio of the motor a simple cycle counter (or timer) would do it.... this could be done in software.

Bye. Jasen

On a sunny day (29 Dec 2006 12:43:45 GMT) it happened jasen wrote in :

and

do

Look close, there is a glas splatform on rollers. There may be quite a bi tof 'slip'.

One mechnical solution would be to make a (glass) platform like this, with a dent in it on the outside at one place, and a micro switch falling in the dent at the back of the oven:

back microswitch _________________________________________ 120V ^------------ | . | . | | . \\/ . | / . . | / door switch . glass . | | . platform . --- motor | . . | under platform | . . | | . . |__________________________|_ 0v

front

When the door opens, the platter will keep rotating until the microswitch fall is in the dent. This way the platter always ends up in teh same position, and can be easily taken out.

An alternative would be a reflective or dark strip and a photocell with LED, possible when it is a more expensive magnetron with a microprocessor.

Correction:

This is better, does not short mains so much, sorry.