Can a microwave oven have its output imited?
mm
like adjusting the AGC on a TV? Or on combo devices, radio,
cassette, CD, tv, there is usually a pot on each of those, adjusted so
the volume stays the same when one changes functions.
I didn't like my old small microwave oven because it was so small, and
I also had to cook longer than instructions said, because it was low
power. (So I was in the habit of mulitplying the time given by 1.1 or
1.3, but I was hoping not to have to do that anymore.)
Now I have a new, one-year old, full-size Sharp microwave -- I can
provide the model number if it matters -- and it is too powerful.
Things cooked in their packages according to instructions have their
water boiling over and taking some of the food with it, and I presume
other food is being cooked more than instructions or recipes call for.
It has a power control that will lower the power by 10% for every push
of the button, but I would have to use that button every time.
Is there any chance I can turn the full power down by 10%, for every
use?
(As an aside, it's interesting that on 90% power, for example, I can
tell when the microwave part is functioning because it makes more
noise during the 90% than the 10% of the time. The old no-name-brand
only had one other power level, Defrost, but it made the same noise
all the time, and to see how much of the time it was making heat, I
had to turn on a nearby AM radio and tune to a weak or no station, and
listen to the radiation from the microwave.)
ne...@jecarter.us
wrote:
The "power control" is a "per cent on" control. 90% for one minute
means the unit runs at full power for .9 * 60 seconds or 54 seconds,
usually in semi-equal segments such as on 18 seconds, off 2 seconds or
on 9 seconds, off 1 second.
John
Michael A. Terrell
mm wrote:
>
> Can a microwave oven have its output controlled, limited, by something
> like adjusting the AGC on a TV? Or on combo devices, radio,
> cassette, CD, tv, there is usually a pot on each of those, adjusted so
> the volume stays the same when one changes functions.
>
> I didn't like my old small microwave oven because it was so small, and
> I also had to cook longer than instructions said, because it was low
> power. (So I was in the habit of mulitplying the time given by 1.1 or
> 1.3, but I was hoping not to have to do that anymore.)
>
> Now I have a new, one-year old, full-size Sharp microwave -- I can
> provide the model number if it matters -- and it is too powerful.
> Things cooked in their packages according to instructions have their
> water boiling over and taking some of the food with it, and I presume
> other food is being cooked more than instructions or recipes call for.
>
> It has a power control that will lower the power by 10% for every push
> of the button, but I would have to use that button every time.
>
> Is there any chance I can turn the full power down by 10%, for every
> use?
Can you write code for the microprocessor in the control panel? The
power function is hard coded into the controller.
> (As an aside, it's interesting that on 90% power, for example, I can
> tell when the microwave part is functioning because it makes more
> noise during the 90% than the 10% of the time.
That is a form of 'Pulse Width Modulation'.
--
You can't fix stupid. You can't even put a Band-Aid™ on it, because it's
Teflon coated.
mm
<mike.t...@earthlink.net> wrote:
>
>mm wrote:
>>
>> Can a microwave oven have its output controlled, limited, by something
>> like adjusting the AGC on a TV? Or on combo devices, radio,
>> cassette, CD, tv, there is usually a pot on each of those, adjusted so
>> the volume stays the same when one changes functions.
>>
>> I didn't like my old small microwave oven because it was so small, and
>> I also had to cook longer than instructions said, because it was low
>> power. (So I was in the habit of mulitplying the time given by 1.1 or
>> 1.3, but I was hoping not to have to do that anymore.)
>>
>> Now I have a new, one-year old, full-size Sharp microwave -- I can
>> provide the model number if it matters -- and it is too powerful.
>> Things cooked in their packages according to instructions have their
>> water boiling over and taking some of the food with it, and I presume
>> other food is being cooked more than instructions or recipes call for.
>>
>> It has a power control that will lower the power by 10% for every push
>> of the button, but I would have to use that button every time.
I can see how this is ambiguous.
>>
>> Is there any chance I can turn the full power down by 10%, for every
>> use?
>
>
> Can you write code for the microprocessor in the control panel? The
No. :(
>power function is hard coded into the controller.
I didn't have in mind changing the power function, but changing the
circuit that makes the microwaves. Maybe at the stage at or just
before the microwave tube. So they would be weaker. By changing
the bias on the output transistor, or something like that. I was
hoping there might be a pot there already.
The power function would still work, turning the radiation on X% of
the time and off 100-X% of the time.
>
>> (As an aside, it's interesting that on 90% power, for example, I can
>> tell when the microwave part is functioning because it makes more
>> noise during the 90% than the 10% of the time.
>
>
> That is a form of 'Pulse Width Modulation'.
Good to know.
Thanks.
Michael A. Terrell
Magnetrons don't work that way. They run at full power over their
useful life. That's why they have to use PWM to control the average
power level.
> The power function would still work, turning the radiation on X% of
> the time and off 100-X% of the time.
>
> >
> >> (As an aside, it's interesting that on 90% power, for example, I can
> >> tell when the microwave part is functioning because it makes more
> >> noise during the 90% than the 10% of the time.
> >
> >
> > That is a form of 'Pulse Width Modulation'.
>
> Good to know.
>
> Thanks.
mm
<mike.t...@earthlink.net> wrote:
Makes sense. Okay. I'll give up the plan. That's one more thiing I
don't have to do.
Thanks again.
Jim Yanik
UNLESS you buy an inverter oven,that can actually regulate the power
delivered to the magnetron.(and thus it's output power)
but you still have to program that each time you use the oven.
--
Jim Yanik
jyanik
at
localnet
dot com
Michael A. Terrell
mm wrote:
>
> On Sat, 14 May 2011 19:19:28 -0400, "Michael A. Terrell"
> <mike.t...@earthlink.net> wrote:
> >
> > Magnetrons don't work that way. They run at full power over their
> >useful life. That's why they have to use PWM to control the average
> >power level.
>
> Makes sense. Okay. I'll give up the plan. That's one more thiing I
> don't have to do.
>
> Thanks again.
You're welcome. That's why I have two microwave ovens. :)
GS
wrote:
I use two. A big sears 800 watts, and little Panasonic inverter 1200
watts. Weird but true. Always use the inverter for frozen dinners.
I think you have to wide pulse the magnetron, like many seconds.
A little weird, the inverter takes about 3 seconds to fire up after
pushing start.
Greg
mike
I'd considered adding another cap at half the value.
Not sure how to to the HV switching safely with affordable
components.
Michael A. Terrell
The Magnatron filament is turned on and off to pulse the output. It
takes a fraction of a second to warm up.
Michael A. Terrell
Just program the cook power, or get a smaller oven. The power supply
in a microwave can kill you in a heartbeat.
klem kedidelhopper
wrote:
> mike wrote:
>
> > n...@jecarter.us wrote:
> > > On Sat, 14 May 2011 14:35:51 -0400, mm <NOPSAMmm2...@bigfoot.com>
I was just reading this thread and it brought a question to mind. What
if theoretically speaking you dropped the line voltage to the HV
circuit but not the control section? This would reduce both the
filament voltage as well as the HV secondary voltage on the
transformer. The result I would think would be a reduction in output
power, wouldn't it? Lenny
spamtrap1888
> Can a microwave oven have its output controlled, limited, by something
> like adjusting the AGC on a TV? Or on combo devices, radio,
> cassette, CD, tv, there is usually a pot on each of those, adjusted so
> the volume stays the same when one changes functions.
>
> I didn't like my old small microwave oven because it was so small, and
> I also had to cook longer than instructions said, because it was low
> power. (So I was in the habit of mulitplying the time given by 1.1 or
> 1.3, but I was hoping not to have to do that anymore.)
>
> Now I have a new, one-year old, full-size Sharp microwave -- I can
> provide the model number if it matters -- and it is too powerful.
> Things cooked in their packages according to instructions have their
> water boiling over and taking some of the food with it, and I presume
> other food is being cooked more than instructions or recipes call for.
Take it back and buy one that puts out the power level your recipes
call for.
But beware: we have an 800 watt oven that used to be compatible with
recipes, but now all the recipes are for 1100 watts.
Michael A. Terrell
It will stop oscillating, if you reduce them very much.
mike
at most settings. You can easily ruin stuff by overcooking it 15
seconds at a time.
or get a smaller oven.
I shoulda bought an inverter, but the cost was prohibitive.
The power supply
> in a microwave can kill you in a heartbeat.
Yep, that's why I used the word "safely".
>
>
Cydrome Leader
>>
>> On May 14, 8:49 pm, "Michael A. Terrell" <mike.terr...@earthlink.net>
>> wrote:
>> > mm wrote:
>> >
>> > > On Sat, 14 May 2011 19:19:28 -0400, "Michael A. Terrell"
>> > > <mike.terr...@earthlink.net> wrote:
>> >
>> > > > Magnetrons don't work that way. They run at full power over their
>> > > >useful life. That's why they have to use PWM to control the average
>> > > >power level.
>> >
>> > > Makes sense. Okay. I'll give up the plan. That's one more thiing I
>> > > don't have to do.
>> >
>> > > Thanks again.
>> >
>> > You're welcome. That's why I have two microwave ovens. :)
>> >
>> > --
>> > Teflon coated.
>>
>> I use two. A big sears 800 watts, and little Panasonic inverter 1200
>> watts. Weird but true. Always use the inverter for frozen dinners.
>>
>> I think you have to wide pulse the magnetron, like many seconds.
>> A little weird, the inverter takes about 3 seconds to fire up after
>> pushing start.
>
>
> The Magnatron filament is turned on and off to pulse the output. It
> takes a fraction of a second to warm up.
Some of the older US made units from Litton or Tappan had a giant reed
relay, and the HV was actually switched on and off for the defrost mode.
They made a nice sound switching on and off.
Jim Yanik
news:iqrnjj$7ss$1...@reader1.panix.com:
> Michael A. Terrell <mike.t...@earthlink.net> wrote:
>>
>> GS wrote:
>>>
>>> On May 14, 8:49 pm, "Michael A. Terrell"
>>> <mike.terr...@earthlink.net> wrote:
>>> > mm wrote:
>>> >
>>> > > On Sat, 14 May 2011 19:19:28 -0400, "Michael A. Terrell"
>>> > > <mike.terr...@earthlink.net> wrote:
>>> >
>>> > > > Magnetrons don't work that way. They run at full power over
>>> > > > their
>>> > > >useful life. That's why they have to use PWM to control the
>>> > > >average power level.
actually,like any other vacuum tube,power output depends on plate voltage
and current. If you lower the plate voltage,the magnetron WILL produce less
power. that's how the inverter ovens work.
But originally,it was too expensive to control plate voltage,so the
manufacturers went for duty cycle operation instead.("pulsed")
You can do that with a cheap relay and timer circuit.
Now,it's cheaper to use an inverter because the heavy iron transformer
costs so much more than a smaller HF switcher transformer,and a switcher
can control it's output voltage.
>>> >
>>> > > Makes sense. Okay. I'll give up the plan. That's one more
>>> > > thiing I don't have to do.
>>> >
>>> > > Thanks again.
>>> >
>>> > You're welcome. That's why I have two microwave ovens. :)
>>> >
>>> > --
>>> > You can't fix stupid. You can't even put a Band-Aid? on it,
>>> > because it's Teflon coated.
>>>
>>> I use two. A big sears 800 watts, and little Panasonic inverter 1200
>>> watts. Weird but true. Always use the inverter for frozen dinners.
>>>
>>> I think you have to wide pulse the magnetron, like many seconds.
>>> A little weird, the inverter takes about 3 seconds to fire up after
>>> pushing start.
>>
>>
>> The Magnatron filament is turned on and off to pulse the output.
>> It
>> takes a fraction of a second to warm up.
>
> Some of the older US made units from Litton or Tappan had a giant reed
> relay, and the HV was actually switched on and off for the defrost
> mode. They made a nice sound switching on and off.
>
it's cheaper to switch the transformer side instead of the HV side,and the
HV switching probably wears out quicker.
William Sommerwerck
> a giant reed relay, and the HV was actually switched on and
> off for the defrost mode. They made a nice sound switching
> on and off.
I'm curious as to how my GE works.
If, at 50% (say) you were full "on" for one minute, then off for one minute,
you'd be running in that first minute at a power level that would cause
localized boiling. (This is a problem with soups and oatmeal.)
I do not see that. Therefore, I have (???) to assume that PWM with a cycle
of less than one second is used.
Cydrome Leader
1 second seems pretty excessive. I don't recall what the timing cycle on
the Tappan ones were, but it was less than a minute for sure, but not
every few seconds.
I really liked those older machines. They were easy to use. I still don't
get why a microwave oven needs multiple buttons pressed to heat food. It
used to just be, turn the timing knob and press start. That's it.
William Sommerwerck
news:iqs93v$lv7$1...@reader1.panix.com...
> William Sommerwerck <grizzle...@comcast.net> wrote:
>> I'm curious as to how my GE works.
>> If, at 50% (say) you were full "on" for one minute, then off for one
minute,
>> you'd be running in that first minute at a power level that would cause
>> localized boiling. (This is a problem with soups and oatmeal.)
>> I do not see that. Therefore, I have (???) to assume that PWM with a
cycle
>> of less than one second is used.
> 1 second seems pretty excessive. I don't recall what the timing cycle on
> the Tappan ones were, but it was less than a minute for sure, but not
> every few seconds.
What do you mean by excessive? If a magnetron can be modulated by varying
its B+, why shouldn't each PWM cycle be just one or two seconds long? You DO
NOT want the magnetron running at full power for "long" periods, followed by
even longer periods off (eg, one minute, four minutes off, for 20%).
> I really liked those older machines. They were easy to use. I still don't
> get why a microwave oven needs multiple buttons pressed to heat food.
> It used to just be, turn the timing knob and press start. That's it.
My GE has six instant-start buttons, for one through six minutes.
Michael A. Terrell
Mine cycles over 10 seconds.
--
You can't fix stupid. You can't even put a Band-Aid™ on it, because it's
Teflon coated.
Cydrome Leader
> "Cydrome Leader" <pres...@MUNGEpanix.com> wrote in message
> news:iqs93v$lv7$1...@reader1.panix.com...
>> William Sommerwerck <grizzle...@comcast.net> wrote:
>
>>> I'm curious as to how my GE works.
>
>>> If, at 50% (say) you were full "on" for one minute, then off for one
> minute,
>>> you'd be running in that first minute at a power level that would cause
>>> localized boiling. (This is a problem with soups and oatmeal.)
>
>>> I do not see that. Therefore, I have (???) to assume that PWM with a
> cycle
>>> of less than one second is used.
>
>> 1 second seems pretty excessive. I don't recall what the timing cycle on
>> the Tappan ones were, but it was less than a minute for sure, but not
>> every few seconds.
>
> What do you mean by excessive? If a magnetron can be modulated by varying
> its B+, why shouldn't each PWM cycle be just one or two seconds long? You DO
> NOT want the magnetron running at full power for "long" periods, followed by
> even longer periods off (eg, one minute, four minutes off, for 20%).
If you like switching a kilowatt sized transformer on and off every
second, power to you. Same for a reed relay rated at kV at hundreds of mA.
It would obviously be easier with one of those switching power supply
microwaves, but that's not how the old microwaves worked.
William Sommerwerck
> William Sommerwerck <grizzle...@comcast.net> wrote:
>> What do you mean by excessive? If a magnetron can be modulated
>> by varying its B+, why shouldn't each PWM cycle be just one or two
>> seconds long? You DO NOT want the magnetron running at full power
>> for "long" periods, followed by even longer periods off (eg, one minute,
>> four minutes off, for 20%).
> If you like switching a kilowatt sized transformer on and off every
> second, power to you. Same for a reed relay rated at kV at hundreds
> of mA.
> It would obviously be easier with one of those switching power supply
> microwaves, but that's not how the old microwaves worked.
As far as I know, my 10-year-old GE is a "newer" model.
This has become one of those "inquiring minds want to know" questions. There
are leakage meters, which would show changes in level. Does anyone make a
power meter you can place in the cavity?
Cydrome Leader
You might get by with a cup of water and a light bulb. Neon lights with
the leads twisted together was the standard "indicator" for microwaves
when I last touched these things. You really want the cup of water as a
dummy load when putting weird stuff in a microwave.
I just ran at test like that on my made in 1981 samsung microwave. It
surprisingly has a digital clock and numeric keypad- space age stuff for
the time. This thing was clearly made when they were terrified of
microwave leaks. There are a whopping 20 torx screws alone holding the
glass in the front door, plus more holding the door together.
Anyways, in defrost mode, the magnetron is clearly cycled on and off in 15
second intervals. I could tell when it was on from when the small
lightbulb lit up.
Michael A. Terrell
Connect a voltmeter across the power line. You will see the voltage
change as the oven switched between a couple Watts to 700-1100 Watts. I
can hear a change in the hum from the HV transformer on my oven.
--
You can't fix stupid. You can't even put a Band-Aid™ on it, because it's
Teflon coated.
Jim Yanik
> William Sommerwerck <grizzle...@comcast.net> wrote:
>>> Some of the older US made units from Litton or Tappan had
>>> a giant reed relay, and the HV was actually switched on and
>>> off for the defrost mode. They made a nice sound switching
>>> on and off.
>>
>> I'm curious as to how my GE works.
>>
>> If, at 50% (say) you were full "on" for one minute, then off for one
>> minute, you'd be running in that first minute at a power level that
>> would cause localized boiling. (This is a problem with soups and
>> oatmeal.)
>>
>> I do not see that. Therefore, I have (???) to assume that PWM with a
>> cycle of less than one second is used.
No,it's longer than that. probably a minimum of ~10 seconds.
you can tell by the change in sound of the oven,the magnetron loads more
when it's cooking.
>
> 1 second seems pretty excessive. I don't recall what the timing cycle
> on the Tappan ones were, but it was less than a minute for sure, but
> not every few seconds.
>
> I really liked those older machines. They were easy to use. I still
> don't get why a microwave oven needs multiple buttons pressed to heat
> food. It used to just be, turn the timing knob and press start. That's
> it.
Maybe it's cheaper to use a digital timer than a mechanical timer.
Although ISTR seeing some low-end MW ovens that still had the mech.timer.
But people want the flexibility of using their MW for more than simple
reheating/cooking tasks. My GE has all sorts of functions I never
use,mostly sensor cooking.
William Sommerwerck
news:Xns9EE874DE4C417...@216.168.3.44...
>> 1 second seems pretty excessive. I don't recall what the timing
>> cycle on the Tappan ones were, but it was less than a minute
>> for sure, but not every few seconds.
The problem -- as I've repeatedly stated -- is that if the "on" part of the
variable-power cycle is more than a few seconds -- possibly as short as 5
seconds, and /definitely/ 10 -- you're going to have localized boiling.
I occasionally see the oven's lights changing brightness, and hearing
various "cycling" noises. I'm going to have to check into this...
GS
> Cydrome Leader <prese...@MUNGEpanix.com> wrote innews:iqs93v$lv7$1...@reader1.panix.com:
I started using my combo oven turbo/microwave and I was disappointed
it only had 15 second increments. Later I found out Turing the dial
while it's cookin, you can reset the time in fin increments which is
really neat, without having to stop and start.
In one case I replaced a digital timer with a mechanical timer, which
both me and dad really liked. It was just like the old heath kit oven.
Greg
hrho...@att.net
Our Panasonic cycles in the 5 - 15 second range.
mike
Use containers with straight vertical sides. The thinnest part of the
material
boils first in a typical bowl. I've been acquiring HUGE ceramic coffee
mugs to cook soup.
The other thing you can do is siphon off the energy with a cup of water.
Varying the amount of water and the power cycling can accommodate most
needs.
In some cases, a microwave browning dish can average the long-duration
PWM of the oven.
I've done some experiments with a dish that looks like a lemon juicer.
The donut shape of the liquid gets energy from all sides and can help
moderate the edge boiling. You'd really not want any thickness of the
subject material to be any thicker than the microwaves can penetrate.
William Sommerwerck
news:iqvrjt$tt1$1...@dont-email.me...
> There are a few things you can do.
> Use containers with straight vertical sides. The thinnest part
> of the material boils [???] first in a typical bowl. I've been acquiring
> HUGE ceramic coffee mugs to cook soup.
I use huge ceramic cereal bowls. Heating soup or oatmeal at full power still
causes localized boiling.
> The other thing you can do is siphon off the energy with a cup of water.
> Varying the amount of water and the power cycling can accommodate
> most needs.
With my oven, simply lowering the power does the trick. A big bowl of
oatmeal cooks in 6 minutes at 50% power, with no boilover.
> I've done some experiments with a dish that looks like a lemon juicer.
> The donut shape of the liquid gets energy from all sides and can help
> moderate the edge boiling. You'd really not want any thickness of the
> subject material to be any thicker than the microwaves can penetrate.
It seems to me that's exactly what you want.
Ron D.
on and 50% off. The ON time may be longer based on service info for a
Sharp Microwave, It takes time for the filament to warm up and there
may be reduced or no output. This is taken into account.
Michael A. Terrell
Which still results in a 50% on to off output from the Magnetron.
Just how long do you think it takes for the filament to reach full
operating temperature? We aren't talking about 12 volt tubes with 150
mA filaments that take ten seconds to warm up.
--
It's easy to think outside the box, when you have a cutting torch.