General > General Technical Chat
Microwave oven PWM frequency
tooki:
--- Quote from: Halcyon on February 13, 2018, 02:26:34 am ---They just vary the duty cycle (or in the case of inverter models, the output power) of the oven throughout various stages of cooking based on a program. Some programs might start off slow then ramp up towards the end of cooking, some might stop part way through and prompt you to stir/turn whatever you're cooking. It's really nothing fancy or complicated, they are just based off tried and tested recipes by the manufacturer. The microwave doesn't "know" when the food is actually done, it just bases it off pre-programmed weights, cooking sequences and power levels.
--- End quote ---
That's not necessarily true. Various microwave oven models over the years have used various sensors to actually try and gauge the cooking progress. For example, a different variant of my Panasonic microwave/convection oven/quartz grill/steamer uses infrared sensors for automated defrosting. And I know there have been microwaves with microphones in them to literally listen to the popping frequency of popcorn to cook it automatically. (Since the way to know it's done is when popping slows to about 2-second intervals.) And of course some models have thermometer probes.
Halcyon:
--- Quote from: tooki on February 13, 2018, 02:39:17 am ---
--- Quote from: Halcyon on February 13, 2018, 02:26:34 am ---They just vary the duty cycle (or in the case of inverter models, the output power) of the oven throughout various stages of cooking based on a program. Some programs might start off slow then ramp up towards the end of cooking, some might stop part way through and prompt you to stir/turn whatever you're cooking. It's really nothing fancy or complicated, they are just based off tried and tested recipes by the manufacturer. The microwave doesn't "know" when the food is actually done, it just bases it off pre-programmed weights, cooking sequences and power levels.
--- End quote ---
That's not necessarily true. Various microwave oven models over the years have used various sensors to actually try and gauge the cooking progress. For example, a different variant of my Panasonic microwave/convection oven/quartz grill/steamer uses infrared sensors for automated defrosting. And I know there have been microwaves with microphones in them to literally listen to the popping frequency of popcorn to cook it automatically. (Since the way to know it's done is when popping slows to about 2-second intervals.) And of course some models have thermometer probes.
--- End quote ---
Indeed, I was simplifying it. Mine has "sensor" printed on the front (what the sensor is exactly, I don't know, temperature, humidity? It's not obvious by looking inside the cavity). But despite those sensors, it's largely based on pre-programmed recipes and some fuzzy logic. The oven doesn't truly know when food is cooked or not, it just guesses. I find the auto-defrost function on mine actually a bit too much, it tends to start cooking parts of the chicken as opposed to just defrosting it and the pizzas come out ridiculously hot and over-done.
Having said all that, I suspect they err on the side of "over-cooked" as opposed to "not cooked enough" to meet certain food safety guidelines.
NiHaoMike:
If regular microwave ovens are "off" a bit more than half the time it's running, why hasn't Wifi in 2.4GHz detect for that and try to put packets in those times? Or does the IEEE expect that most microwave ovens will go inverter and thus make such a mechanism less useful?
Halcyon:
--- Quote from: NiHaoMike on February 13, 2018, 02:46:51 am ---If regular microwave ovens are "off" a bit more than half the time it's running, why hasn't Wifi in 2.4GHz detect for that and try to put packets in those times? Or does the IEEE expect that most microwave ovens will go inverter and thus make such a mechanism less useful?
--- End quote ---
They do, in a sense. Wi-Fi won't broadcast if it detects that the channel is "busy". This is why if you have many radios nearby on the same channel, your performance sucks, because it essentially waits for a break in transmission to avoid collisions with other Wi-Fi devices.
Why don't they don't do this with other sources of interference? Probably because it's a little pointless. In the case of microwave ovens, they SHOULDN'T leak enough to cause significant problems with Wi-Fi (see my comments above).
The way TCP/IP is designed, if the client doesn't receive the expected response within a certain time, it just times out, disconnects the session etc... Same for your Wi-Fi access point, it won't just buffer every single TCP/IP packet that comes its way, if it can't deliver it within a timely manner, it won't deliver it at all. If your Wi-Fi router or access point had to wait for all sources of interference to cease in built-up areas, no one would be transmitting anything. Wi-Fi is a half-duplex system, while a radio is listening (or receiving data) it's not transmitting.
Which brings me to another point that I feel I should mention. Most consumer-grade Wi-Fi routers will have an "auto" channel function. Usually, this only operates at the time the router boots to listen for the best free channel. It does not continually monitor the spectrum and channel hop. For it to do this, it would need a dedicated radio that does the monitoring or disconnect all clients from the network, monitor the spectrum, then allow all clients to re-connect (the latter is obviously not ideal).
Most enterprise grade wireless gear will either have dedicated access points connected to the controller through various parts of a building/campus which act as "monitors", that's their full-time job, to provide the controller feedback on channel interference and other radios in that area so it can change the channel on nearby access points. Alternatively some dual-channel access points will have a third and sometimes fourth built-in radio to do this, like the Ubiquiti UAP-AC-SHD.
The auto channel feature on consumer gear is next to useless (like MAC address "security"). Let's just say you had a local power failure and all your neighbours lost power too. Assume your router is the first to boot up and decides that Channel 11 (on 2.4GHz) is the most "clear" so it picks that and starts accepting clients to connect. Then all of your neighbours' routers boot up, some have auto channel (which would at this point avoid Channel 11) but some are configured to only use Channel 11 (which is very common). All of a sudden your "clearest" channel is congested and performs like crap. Your router won't detect this and change channels, it will just continue doing its best in an RF-noisy environment.
Red Squirrel:
Technically your wifi should not be affected by the microwave. I don't know how good of a test this is but I did a ping -f to my phone's IP and microwaved a glass of water on high with phone sitting next to the microwave and I had no packet loss.
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