4 ms·

Assuming modern microwaves have a microchip on which computation can be done, and an electric motor of controllable speed, couldn't the microwave calculate the

by SeoxyS 14y ago

Assuming modern microwaves have a microchip on which computation can be done, and an electric motor of controllable speed, couldn't the microwave calculate the speed required for the specified time to end at the right angle, with no delay?

ebiester 14y ago
Too many people (like me) take things out of the microwave a second or two early as to avoid the obnoxious beep. :)
joezydeco 14y ago
You're assuming too much. Appliance manufacturers go for the cheapest parts possible that still perform reliably under the warranty period. The motor driving that turntable is not a precision stepper or brushless motor with variable microprocessor speed control. It's a cheap A/C motor (perhaps with a drive belt for torque) that's switched to line current by a 30-cent mechanical relay. You can tell it's A/C when the turntable starts in a random direction each time it's energized.
- planetguy 14y ago
  Interesting observation on the random direction, I'd always wondered why that was. The other thing to remember is that in the 1990s a microwave oven cost several hundred dollars at least. Now you can pick one up for fifty bucks, possibly forty. Losing extraneous features like "boomerang turntable" is presumably part of how the manufacturers managed to respond to the downwards price pressure.
- raldi 14y ago
  Most microwaves I've seen just alternate between directions. It's not random.
  - joezydeco 14y ago
    It is random. You need a larger sample size. There is no need to put an expensive polarity-reversal circuit (with mechanical or electronic memory) in the assembly just to alternate the turntable direction. The cooking effect is the same.
    - femto 14y ago
      Based on my observations, I'd say it actually does alternate. My theory is that the motor speed is slow enough and consistent enough, as is the friction, that the motor consistently overshoots by half a pole when it stops. Thus, it moves in the opposite direction when turned back on. If it was moving faster, it might well be random. What's the chances of it displaying bifurcation then chaos? :-) Given that the period of my oven is bang on 12 seconds, averaged over many revolutions, I think it's probably a synchronous motor.
deleted 14y ago
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by SeoxyS 14y ago

ebiester 14y ago

Too many people (like me) take things out of the microwave a second or two early as to avoid the obnoxious beep. :)

joezydeco 14y ago

You're assuming too much. Appliance manufacturers go for the cheapest parts possible that still perform reliably under the warranty period. The motor driving that turntable is not a precision stepper or brushless motor with variable microprocessor speed control. It's a cheap A/C motor (perhaps with a drive belt for torque) that's switched to line current by a 30-cent mechanical relay. You can tell it's A/C when the turntable starts in a random direction each time it's energized.

planetguy 14y ago
Interesting observation on the random direction, I'd always wondered why that was. The other thing to remember is that in the 1990s a microwave oven cost several hundred dollars at least. Now you can pick one up for fifty bucks, possibly forty. Losing extraneous features like "boomerang turntable" is presumably part of how the manufacturers managed to respond to the downwards price pressure.
raldi 14y ago
Most microwaves I've seen just alternate between directions. It's not random.
- joezydeco 14y ago
  It is random. You need a larger sample size. There is no need to put an expensive polarity-reversal circuit (with mechanical or electronic memory) in the assembly just to alternate the turntable direction. The cooking effect is the same.
  - femto 14y ago
    Based on my observations, I'd say it actually does alternate. My theory is that the motor speed is slow enough and consistent enough, as is the friction, that the motor consistently overshoots by half a pole when it stops. Thus, it moves in the opposite direction when turned back on. If it was moving faster, it might well be random. What's the chances of it displaying bifurcation then chaos? :-) Given that the period of my oven is bang on 12 seconds, averaged over many revolutions, I think it's probably a synchronous motor.

deleted 14y ago

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