Can a microwave oven have its output imited?

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

Can you write code for the microprocessor in the control panel? The power function is hard coded into the controller.

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.

I can see how this is ambiguous.

No. :(

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.

Good to know.

Thanks.

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.

--
You can't fix stupid. You can't even put a Band-Aid? on it, because it's
Teflon coated.

Makes sense. Okay. I'll give up the plan. That's one more thiing I don't have to do.

Thanks again.

snipped-for-privacy@jecarter.us wrote in news: snipped-for-privacy@4ax.com:

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

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.

eir

ng I

s

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

I've got the same problem, but need more like 50%. I'd considered adding another cap at half the value. Not sure how to to the HV switching safely with affordable components.

The Magnatron filament is turned on and off to pulse the output. It takes a fraction of a second to warm up.

--
You can't fix stupid. You can't even put a Band-Aid? on it, because it's
Teflon coated.

Just program the cook power, or get a smaller oven. The power supply in a microwave can kill you in a heartbeat.

--
You can't fix stupid. You can't even put a Band-Aid? on it, because it's
Teflon coated.

ng

so

nd

1 or e

r.

sh

and

nd

r

upply

s

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

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.

It will stop oscillating, if you reduce them very much.

--
You can't fix stupid. You can't even put a Band-Aid? on it, because it's
Teflon coated.

Cook power doesn't help 'cause it stays on for 15 seconds at a time at most settings. You can easily ruin stuff by overcooking it 15 seconds at a time. or get a smaller oven. If I'd wanted a smaller oven, I'd have bought a smaller oven. I shoulda bought an inverter, but the cost was prohibitive.

The power supply

Yep, that's why I used the word "safely".

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.

Cydrome Leader wrote in news:iqrnjj$7ss$ snipped-for-privacy@reader1.panix.com:

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.

it's cheaper to switch the transformer side instead of the HV side,and the HV switching probably wears out quicker.

--
Jim Yanik
jyanik
at
localnet
dot com

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.

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.