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Old 7th July 2015, 18:48   #5311
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Default Re: The Home Appliance thread

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Originally Posted by mvadg View Post
From what I'm guessing, it is scanning all the channels and is simply stating what the WiFi chip on the phone is reporting. Don't know if it the chip is looking at all the frequencies (in an analog sort of way).
It does look at all frequencies in 2.4 / 5 GHz band and reports on quality of signals. If an analog device like microwave is emitting in 2.4 GHz band, it will cause frame drops that should be detected by Chip and reported by WiFi Analyzer.

I'll try and see:

1. If a phone is placed inside microwave, does shielding degrade WiFi signal ?
2. If phone is close to microwave that is turned on, does that degrade signal ?

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Originally Posted by DerAlte View Post
Both the ovens I have are 900MHz (yes, I am an old man). I haven't detected interference with wifi when the microwave was working and I was sitting near it.
Makes sense, 900 MHz would not interfere with 2.4 GHz WiFi. But all microwaves that operate in 2.4 GHz should.

Here is a video that shows microwave interference on 2.4 GHz WiFi observed with an spectrum analyzer.

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Old 8th July 2015, 09:58   #5312
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Default Re: The Home Appliance thread

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Originally Posted by NetfreakBombay View Post
It does look at all frequencies in 2.4 / 5 GHz band and reports on quality of signals. If an analog device like microwave is emitting in 2.4 GHz band, it will cause frame drops that should be detected by Chip and reported by WiFi Analyzer.

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Thanks for the inputs NetfreakBombay, DerAlte

My other question then would be: Does the WiFi chip scan every frequency in the range? Because the each channel is distinct with a fixed frequency (+/- some spread on either side I guess). Also the graphic shown by the WiFi Analyzer app, is it accurate? I am guessing again, that it is a prettified representation of the strength of the signal reported by the chip, i.e. the chip reports a value x and the app simply draws a parabola around it. It could just as well have been a bar graph. Would it be possible to create a spectrum analyzer (like the one in the video) using the hardware on the phone (restricted to the 2.4 Ghz spectrum) or maybe around the other radio frequencies the phone uses (bluetooth, 2G, 3G...)? Just curious.

Also, (I haven't tried this) how would you place the phone in the oven to test? I was guessing the antenna would be parallel to the magnetron output face (so parallel to the right side of the microwave oven, where the oven's magnetron is?) so as to take the same path back to as close to the source of the microwaves. As DerAlte stated, depends on the leakage paths.
Very informative video, by the way. Thanks.

Finally, if the phone is able to receive the WiFi signal inside the oven, does this mean there is a serious leak? Because a very weak signal is able to pass through and reach the phone, so the oven is what, approx 1 KW power and the WiFi router is maybe 1 Watt? (Don't know if the phone/router is automatically boosting the signal)

Last edited by mvadg : 8th July 2015 at 10:05. Reason: Quoting a video or a long post hampers readability for our mobile users.
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Old 8th July 2015, 13:19   #5313
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Default Re: The Home Appliance thread

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Originally Posted by mvadg View Post
... Does the WiFi chip scan every frequency in the range? Because the each channel is distinct with a fixed frequency (+/- some spread on either side I guess). ...
No, it would be a waste of time for the WiFi chip to scan every frequency. By definition (ref to IEEE 802.11 B/G/N), there are 11 (14 actually, but 12-14 is / was used only in Japan) fixed center frequencies over which the transmitter can transmit. The center frequencies are spaced 5MHz apart, starting from 2412MHz (2.412GHz).

The spread of frequencies for modulation around each center frequency (channel width) is 22MHz for 802.11B, 20MHz for G/N, and 40MHz for N.
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Old 8th July 2015, 13:47   #5314
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Default Re: The Home Appliance thread

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Originally Posted by mvadg View Post
Also the graphic shown by the WiFi Analyzer app, is it accurate?.....Would it be possible to create a spectrum analyzer (like the one in the video)
WiFi Chip does not work like spectrum analyzer. It only reports RSSI (in dBM) for each MHz in 2.4 GHz band.

RSSI is "arbitrary" measure of "signal quality". More details : https://supportforums.cisco.com/docu...to_Noise_Ratio

There are WiFi chips (specially in Android dev boards) that can act as spectrum analyzer, but those are usually not present in consumer phones.

Quote:
Originally Posted by mvadg View Post
Finally, if the phone is able to receive the WiFi signal inside the oven, does this mean there is a serious leak? Because a very weak signal is able to pass through and reach the phone, so the oven is what, approx 1 KW power and the WiFi router is maybe 1 Watt? (Don't know if the phone/router is automatically boosting the signal)
I think :

1. Phone WILL receive WiFi signal inside Microwave (though signal will be degraded).
2. Microwave does leak RF as measured in video above.

I doubt this leakage would be enough to cause a concern.

Maybe, a good way is to test the microwave in a way it was discovered (Engineer noticed that radar was melting chocolate in his pocket). Keep a chocolate bar next to microwave and see if it melts when microwave is on.
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Old 8th July 2015, 13:56   #5315
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Default Re: The Home Appliance thread

Folks

Need some information.

Have any one used water softeners in apartments (BLR)? If yes what types and brands are recommended. Need for my apartment which uses bore well water. Appreciate your reply.

Regards
Sandy
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Old 8th July 2015, 14:59   #5316
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Default Re: The Home Appliance thread

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Have any one used water softeners in apartments (BLR)? If yes what types and brands are recommended.
I am using one for my washing machine. It was bought from the technician who came for installation. I have to check the brand name. I am not even sure of the effectiveness.
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Old 8th July 2015, 18:01   #5317
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Question Re: Rakshak Gas Guard?

Has anyone been using this gas saving and safety device? They say it saves around 25% of gas and also acts as a safety device. It would be installed between the regulator and the cylinder.

http://rakshakgasguard.com/

Please advice.
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Old 9th July 2015, 11:13   #5318
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Default Re: The Home Appliance thread

Anyone using something like this to ensure the gas is not left switched on by mistake?
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Old 10th July 2015, 16:06   #5319
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Default Re: The Home Appliance thread

Issue with my Godrej 2 door Refrigerator

Last month, my fridge was not cooling at all. The freezer had lesser cooling also. Since it was a very busy week, we were delaying the call to get it serviced and managed in the meantime by putting essentials in the freezer. Finally on a Saturday night, I rummaged through my papers to find the manual and tried to follow the trouble shooting guidelines. It ended up asking me to call service. I checked the helpline number and thought, lets see if this call goes through. I was not expecting anyone to pick up because I have had an experience with the Bosch washing machine helpline, who have better working hours that most of us salaried people. But to my surprise at 10:30 pm,on a Saturday, a helpline person picked the phone on the 2nd ring! They had all my details from the caller id itself. I explained the problem. He assured that a person would come on the next working day and fix the issue. He even informed the service charges (375/-).

On Sunday I got a call from the service centre at Bangalore (Mariya refrigeration for Jayanagar area), saying that a person would come on Monday. SMSes from Godrej were coming which confirmed my complaint booking number and the mechanics name etc. Till now I was on cloud nine, feeling proud of having bought an Indian brand and still getting excellent service.

Service visit 1 : I was at work when the first visit happened. The service guy fiddled with the fridge for 5 minutes and then the cooling started. He said it was an issue with the fan getting stuck and that for now it is solved. If it happens again, it will need changing, he said. Wifey paid him 400 and he was gone. He called me and asked me to take AMC for ~3000/year. I said I would think about it. A day later the cooling came down again. I called in to the helpline who reopened the complaint and said some one would be sent to take care it. They also specified that I wouldn't have to pay service charges since the same complaint has been recorded within a month of first servicing

Service visit 2 : This was a more knowledgable guy and I was home due to some reason. He changed the 'fan motor' and its 'relay' (EOP?) and demonstrated the cooling and all. I was happy with it. He started charging me including the service charge. I informed him that I had the servicing done only a few days back, on which he substracted the service amount from the total bill. I noticed that the fridge was continously running, without the usual stoppage Two days later, there was a lot of water condensation in the fridge. Also eggs which we had kept in there, had cracked. I did not call the helpline and called this service person itself. He said he couldn't understand what I was saying and I was told to call the helpline again. Again the same assurance and reopening of the complaint. To his credit, the service person dropped in on a sunday,on his own will, to check the fridge. He also saw the condensation. When I told him that the fridge was not stopping, he said maybe there is a problem with the Bi metal switch. Since he didn't have any spares with him he left.

Service visit 3 : Not a visit actually, this was a call. The guy sounded like a real estate goon trying to be polite. He said that this could be due to some drainage block and told me to leave the fridge switched off for 24hrs and to check for water in the tray below ("What Tray?? This is a frost free refrigerator!" running in my mind) and kept the phone. I got a message from Godrej ,saying that the complaint has been closed. I waited for a day, switched on the fridge and then a day later, the cooling again came down. Frustrated I did the helpline call again, with the usual reopening of complaint.

Service visit 4 & 5 : Different service guy, who seemed not as experienced as the one before. He opened the freezer compartment to see a thick block of ice covering the 'Heating Coil'. He said that we will have to switch off the fridge and wait for the ice to melt to rectify the issue. He said he would be back the next day and asked us to keep clothes on the floor around the fridge to soak up the melted water.
Next day, we saw that the clothes were all dry and he opened the freezer compartment to see no ice also. I still have no clue where all that water went! He was saying the heating coil must have vaporised the ice. I was pretty wild after having raised the same complaint again and again, that I argued a little harshly that the fridge was not powered on for the heating coil to do its job. whatever. In the end he replaced the bimetal on my insistence and the 'defrost timer'. I did not pay him a service charge and paid only for the parts, to which he had no issue.

Now it seems to be running on higher cooling than usual, because even though I have kept it on the lowest cooling setting, some nights the milk in the fridge reaches the semi ice state. I'm so sensitised to the issue, that whenever I cross the fridge, my ears are open to the sound of the compressor running. I am relieved when the fridge cuts off in between. Will have to see the dent on my future electricity bills to see if the new defrost timer is making the fridge compressor work overtime.

From this experience, I have learned how a fridge maintains the frost free function. Feel free to correct me.

At first the compressor runs to cool the fridge. A fan runs to circulate the cooled air from the freezer down to the fridge compartments. There will be a accumalation of ice on the different parts of the fridge. The time the compressor+fan runs is controlled by a defrost timer. It has a cut off relay in it which cuts off the compressor and activates the heating coil routed through a bimetal thermo-switch. This heating coil is used to melt the accumulated frost if any. The bimetal thermo switch mounted near the heating coil senses the higher temperature after the heating coil has done its work and cuts off the heating coil. In the meantime the defrost timer will have counted down the interval and restarts the compressor + fan which starts the cooling again.

What I don't understand is, how does one control the temperature in the fridge? As I see it, the compressor is controlled by a defrost timer. Is there any influence of the thermostat on the defrost timer? Is there a sensor that senses temperature and decides that compressor has cooled enough?

Last edited by nijelj : 10th July 2015 at 16:21. Reason: Grammar, Spelling mistakes
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Old 10th July 2015, 22:22   #5320
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Default Re: The Home Appliance thread

That sensor is exactly what the thermostat is!

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Originally Posted by nijelj View Post
What I don't understand is, how does one control the temperature in the fridge? As I see it, the compressor is controlled by a defrost timer. Is there any influence of the thermostat on the defrost timer? Is there a sensor that senses temperature and decides that compressor has cooled enough?
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Old 11th July 2015, 18:28   #5321
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Originally Posted by khoj View Post
That sensor is exactly what the thermostat is!
You are right about the cycle, and the Bimetal remains submerged in water. This 'Bimetal' replacement is a big scam in BPL, and I suspect with Godrej and other assembled brands too. The bane of frost free fridges, simply because of the quality of the replacement (sourced from a local Bangalore vendor). Our 400L BPL has worked flawlessly for the last 12 years, except for this frosting over every couple of years. We've changed the defrost timer needlessly once and the Bimetal @375 atleast 5 times. The service guys are frank in saying they get paid for the part and service call, so they are not complaining.

I've learnt to just switch off the fridge over the weekend, or 48 hours, report and wait for the service guy. It's a 5 min procedure, but the freezer has to be frost free to reach the Bimetal. There is really nothing wrong with the fridge, just this locally sourced component. Hope this helps.
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Old 13th July 2015, 12:29   #5322
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Default Re: The Home Appliance thread

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Originally Posted by NetfreakBombay View Post



I think :

1. Phone WILL receive WiFi signal inside Microwave (though signal will be degraded).
2. Microwave does leak RF as measured in video above.

I doubt this leakage would be enough to cause a concern.
Happy to report that I placed my phone parallel to the edge with the magnetron, and upon closing the door of the oven, channels 9 through 11 just disappeared on the WiFi Analyzer App. [I took a video with my SJ4000, but unfortunately it did not record as it was in 'car mode' and expected power from a charger] - I am safe.(I guess)
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Old 17th July 2015, 14:55   #5323
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Unhappy Re: The Home Appliance thread

Electrolux Microwave - it finally gave up!


It worked for a few days after I fixed the fuse, but apparently the High Voltage transformer was on its way out. This time it made it clear - smoke signals.

Oh well, I learnt quite a bit in the meantime about microwave ovens and microwaves. I'll remove the HV Capacitor and the magnets. Hey, the control panel should be good for some timer project! The capacitor will augment the mosquito killer cap on the bat - should put out some good sparks!
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Old 17th July 2015, 21:56   #5324
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Default Re: The Home Appliance thread

Looking at the discussions on this thread I see two things catching my fancy:

Microwave response of mobiles will also depend on whether they are in the 800 (CDMA) or 900MHz band or the 1,800 MHz band.

Inverter refrigerators do not have on-off switches. They rely on varying the speed on the compressor. This may be using a variable frequency AC drive or lately (I hear) BLDC (brushless DC) motors.
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Old 18th July 2015, 14:00   #5325
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Default Re: The Home Appliance thread

I have a problem with my refrigerator power supply. If there is a powercut and the power returns the switch for thw fridge in the main board in the house trips.
It's a 5 amp power supply. The refrigerator works perfectly well. This happens 25% of the time.
Will connecting a stabilizer help. I may not be able to change the circuit breaker.
I have used the refrigerator on two houses and the same happens.

Last edited by BenjiRoss : 18th July 2015 at 14:03.
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