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34 votes
Accepted

Why can I see remote control radiation on my phone but not with my eyes?

Building on the good answer by nanofarad, "But why white?" is a good follow up. We don't know what the precise sensor in your phone is, or how good the IR filter in front of the lens is, but ...
P2000's user avatar
  • 3,177
21 votes

Why can I see remote control radiation on my phone but not with my eyes?

The remote control emits infrared light, typically around 940 nm, while the human eye is receptive to ~400-700 nm. However, the CMOS optical elements in a phone camera have a response up to 1000 nm (...
nanofarad's user avatar
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13 votes

How does a mobile phone send signals?

There is no "power issue." In the simplest case, base station (in the cell tower) transmits to your phone with about the same power level that your phone transmits. The base station also transmits ...
JRE's user avatar
  • 72k
7 votes
Accepted

How does a mobile phone send signals?

Radio is a lot more effective than people think. Radio telescopes can listen to distant galaxies. Shortwave propagates around the world; amateurs with medium-sized sets compete to find the furthest ...
pjc50's user avatar
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5 votes

How does a mobile phone send signals?

some numbers here The noise floor for electronics is (we'll use logs here) -174 dBm/rootHertz at room temperature. [In non-log non-dBm, we multiply Boltzmann Constant by the Kelvin Temperature; for ...
analogsystemsrf's user avatar
5 votes

How does a mobile phone send signals?

In a ideal condition (say free space) the energy (RF power) needed in one way = the power needed in the other way around, it's pure physics :) But this assumption is wrong in practice, because even ...
yo3hcv's user avatar
  • 573
5 votes
Accepted

Is it possible to transfer provider from one SIM card to another?

If that "another" SIM card is not a blank one then most likely no, you can't. Even if you can, the new SIM will likely fail on network authentication due to the unknown or mismatched ...
Rohat Kılıç's user avatar
4 votes

ESP-WROOM-32 resets when I load a page from my cellphone's Chrome app but not when I load the web app from Chrome on my PC

I encountered a similar problem on ESP32. One nice aspect of Arduino environment is lots of libraries that do what you need. However, these libraries are contributions from many different people, and ...
bobflux's user avatar
  • 79.1k
4 votes

How can a mobile phone being charged kill by electrocution?

Yes, a shady charger with inadequate isolation (creepage) or possibly even conductive debris inside (see both). Possibly transformers made badly (eg. with magnet wire rather than triple-insulated wire)...
Spehro Pefhany's user avatar
4 votes

Why do we need AC to charge our mobile phones?

The phones use DC to charge. Your phone charger converts the AC mains to a suitable DC voltage to charge your phone i.e. typically 5V. The main reason why phone chargers work on AC input is because it ...
PCBCrew Engineer's user avatar
4 votes

What type of embedded sytem is used in a mobile phone(cell phone)?

The usual terminology is "SoC" for "system-on-a-chip". This includes a CPU and a whole bunch of other stuff. Qualcomm seem to like calling theirs a "platform", but that's ...
pjc50's user avatar
  • 46.9k
3 votes

Replace phone battery with power supply circuit BL-T5

The TH pin is most likely for a thermistor (temperature sensor) built in to the battery. Very common on lithium batteries like this, also common in power tools etc. Most commonly as far as I know, the ...
Klas-Kenny's user avatar
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3 votes

How can a mobile phone being charged kill by electrocution?

The problem is with cheap chargers that are not isolated. One or the other pole of the charger has a straight through connection to the wires in the outlet. That is to say, one of the wires on the ...
JRE's user avatar
  • 72k
3 votes

How Mobile Phone Call Works

TL;DR Almost every phone today is digital for all (Mobile, VOIP) or most of the call path. We think of phone calls as analog because they were for the first 100 years or so and because the human voice ...
manassehkatz-Moving 2 Codidact's user avatar
2 votes

How to add 0.2V per Ampère that device draws? (Voltage drop compensation)

Here is an example solution. Schematic is from link: If you want your power supply to compensate for cable voltage drop without sensing the actual voltage at the load, then your power supply needs an ...
bobflux's user avatar
  • 79.1k
2 votes

Using a "Normal" powerbank for a "Super Fast Charging" phone, are there any potential damages?

Surely the phone tries to negotiate what kind of power supply there is, and then it will draw only standard amount of current if there is no fancy high current charger present.
Justme's user avatar
  • 155k
2 votes

How does a mobile phone send signals?

There is, both at the base station and at the cell phone, a transmitter and a receiver working off a common antenna. They utilise a full-duplex communication system in which simultaneous two-way ...
vu2nan's user avatar
  • 18.7k
2 votes

Batteries have a constant charging speed from 0%→70% instead of being any faster at 0%?

Constant charging speed from "conditional 0" to 60% is a simple matter of basic standard Li-Ion charging method - the charger is in CC - constant current mode. See more details here.
Ale..chenski's user avatar
2 votes

Batteries have a constant charging speed from 0%→70% instead of being any faster at 0%?

Maintaining the exact same charging speed from 0% to 60% batterlevel is in my opinion a bad design choice. Yes it charges your battery faster but it also puts more stress on it. At least these phone ...
Bimpelrekkie's user avatar
2 votes

Is it possible to transfer provider from one SIM card to another?

The subscriber identity module includes secrets known only to the provider, the only way is to get a replacement SIM from the cellular service provider and then have them change the account to use the ...
Jasen  Слава Україні's user avatar
2 votes

Would a program for circuit diagnostics with image recognition be useful?

As others have said, it'd be really difficult (or impossible) to create a circuit diagram from an arbitrary PCB, however if you impose some constraints, the project becomes more plausible - but still ...
jayben's user avatar
  • 1,445
2 votes

Replace phone battery with power supply circuit BL-T5

TH pin is a connection to a thermal sensor inside the battery pack - either a resistor (e.g. NTC) or a fancy 1-wire thing. The phone's internal circuitry uses it to measure the battery temperature for ...
Rohat Kılıç's user avatar
2 votes

Phone handpiece teardown - what could this chip be?

Any idea what that chip is? Apple stuff has a little chip for modulating the microphone input with short changes in impedance and ultrasonic frequencies when you press any other buttons besides play/...
jms's user avatar
  • 8,661
2 votes

Why do we need AC to charge our mobile phones?

We actually use DC to charge our phones but, if we want to do this wirelessly, DC won't work so, we use AC for the wireless link and then convert to DC for charging. Also true for transformers; there ...
Andy aka's user avatar
  • 462k
1 vote
Accepted

ESP-WROOM-32 resets when I load a page from my cellphone's Chrome app but not when I load the web app from Chrome on my PC

There are three possible solutions to this problem as I could find (found on github), more details on the last update of the original post, the possible solutions and are as follows: One solution is ...
vram's user avatar
  • 158
1 vote

How does a mobile phone send signals?

Base stations do NOT use the same antenna for transmitting and receiving. Usually there are 2 receive antennas and 1 transmit antenna. This means the receiving end at the base station is more ...
Keith's user avatar
  • 11
1 vote
Accepted

Telephone Call and Electromagnetic Waves

You are correct, a cell phone antenna is bombarded constantly with radio waves from other phones, broadcast radio and TV stations, satellites, wifi routers ... it is a very long list. Several systems ...
AnalogKid's user avatar
  • 20.9k
1 vote
Accepted

How to cut a nano SIM out of a 8-pin SIM?

Yes, those are the right pads to cut off. Though, I have to warn you, it is possible to cut that card so that it gets stuck to the phone. Nano-SIM is also thinner than Mini-SIM so you have to slice ...
TemeV's user avatar
  • 1,431
1 vote
Accepted

If I need to send GPRS commands is it better to use a "proper" modem, arduino or a mobile?

If you want (or need) reliability, then you should stick with a commercial modem. If you use an Arduino with a modem module, then you will end up writing software for the Arduino and for your ...
JRE's user avatar
  • 72k

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