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28

Commercial line out specification is to be able to drive 1 milliwatt to a 600 ohm load. For a sine wave, this means a voltage of 0.77 volts RMS (2.2 volts peak-to-peak) and a current of 1.3 milliamperes RMS (3.6 milliamperes peak-to-peak).


26

Simply because having more bands not only requires a very versatile chipset, but also extensive antenna design! To explain: It's impossible to make the perfect antenna for all frequencies, but you can make "compromise" broadband antennas. You can do that in a lot of ways, but in the end, you need to integrate those into a mobile device. And that's where it ...


16

This is the data I can share with you after having run my own set of experiments and having search (extensively) through the Web for other people's real hands-on tests. I have discarded / omitted the data which I have been unable to reproduce: The impedance of the standard Apple miniature hands-free microphone, the one integrated with the headphones they ...


14

Unfortunately there is a lot of "audiophile" nonsense around headphone amplifiers and headphone impedance. Probably the top 5 results for "headphone impedance" on Google are just wrong. This site contains some useful information (though a lot of it is wrong too). But anyway if you look at the graphs which I assume are correct, you can see that in the audio ...


11

None of the smartphones today have dedicated GPS chips in them, they only have a GPS capability that stems from byproduct features of the modem chips. That's not true. GPS functionality in phones is done either with a dedicated chip, or with a dedicated GPS receiver within a System-On-Chip (which is effectively the same as having a dedicated chip). ...


9

This is in addition to PkP's answer. While "line level" audio is typically 1 mW into 600 Ω, and this comes out to 1.1 V p for a sine, audio is far from a sine. Even if the spec is adhered to and you only get 775 mV RMS on average, the peaks can be considerably higher than 1.1 V. It is generally good to accept and handle without distortion peaks up ...


8

There is no hard-and-fast rule for headphone jacks; be it a laptop, MP3 player or a regular stereo system. I would say that a typical headphone output adheres to Line Level specifications, although for headphones they become more of a guideline than a stringent set of figures. As you have already discovered, different devices have different output levels. ...


7

You want a compass. Like the normal analog ones, it senses the orientation of the earth's magnetic field.


5

Generic: Connect each button between one of the stereo output channels and the microphone input, along with some resistors for attenuation and possibly a capacitor for DC blocking (suitable audio input circuits have been published, you can search for them as readily as I can). Have your app output an audio tone of different frequency on each of the left ...


5

Not having used said app I believe it is a master of assumptions and averages. The far field of a transmission line with two opposite current conductors is essentially zero. However the near field on anything other than a solid screen co-ax will always have a unbalanced component around it. The maximum unbalance will be when the two current conductors are ...


5

The D+ and D- (I think you made a typo in your question) lines must be held to 2.7 V to support 12 W charging. Unfortunately I don't have access to the Apple MFi Specification (which would be the best source), but this forum entry and subsequent answers by TI employees indicate that 2.7 V is the correct value. Furthermore, this schematic below uses a ...


4

The arduino would need a higher voltage. Use an non inverting OP amp on the line which should bring the voltage to about 2ish Volts, something which is better for the arduino. :) http://www.instructables.com/id/Arduino-Audio-Input/step3/Non-Inverting-Amplifier/


4

Very small scale, undocumented parts. You'd need smd desoldering tools, and then spend days on trying to figure out how it maybe works. Not worth it.


4

Taking the Android specifications, you need 2.2Volts in series with a 2.2K resistor. Like this example from the Android specs: You can probably use 3V (2 AA Cells of 1.5V each.) 5Volts through that 2.2K probably won't hurt anything either. Example for using Scope: simulate this circuit – Schematic created using CircuitLab


4

How a device interacts (if at all) depends on the device (for example: a phone) and the charger. Problem is that there is no universally applied standard for USB charging so many manufacturers "do their own thing". I found here an application note by Maxim. From this the following picture confirms that chargers can be different in how they treat the D+ and ...


4

That's not going to work. An iPhone needs a minimum of 5V / 500 mA to charge. This comes out to 2.5W, which is five times higher than the output of your TEG.


4

You might think that your phone is directly charged from the powerbank/charger, well it is not. The powerbank or charger only have the job to provide 5 V up to the current stated on the device. So 5 V, 1A means a load (like a phone that's charging) can draw up to 1 A. The voltage is and must be 5 V. The phone determines how much current it chooses to draw....


4

Define "heavily damaged". If the screen is crushed just replace it with a new screen and digitizer, swap out the battery, and it may well power up perfectly fine, you can enter in the pass code and go from there. Any cell phone repair shop can do that for less than $100 in a few hours. You don't need the charging circuit, the microphone, the camera or even ...


3

Have a look at this project. From what I gather, its an open source project and has some documentation on it (I didn't actually read it) Android Oscilloscope They used the microphone input (similiar to what you are doing) and then displaying it through an app (also open source). If you go over their stuff, you should be able to figure out, how they are ...


3

The reason the stylus worked even through layers of wool is related to the very nature of capacitance: It is not about conduction (except at the electrodes themselves), it is about the insulation between the plates: Wool is about as good a dielectric as dry air, if it is not woven with some metallic fiber. The way capacitive touch screens typically work is ...


3

I can tell you data transmission through sound is possible, although it is very hard to achieve higher bitrates or long distances due to echo, multipath and attenuations. I've created a transmission protocol in order to transmit information bits between a PC speaker and a smartphone, or between 2 smartphones. I've implemented a QFSK and 8fsk non-coherent ...


3

Based on your question, it sounds like this is what you are trying to do: There are so many different aspects to this project, you cannot just post such an open ended question like this and expect anyone to help you! Do you know anything about RF signals? About microcontroller hardware and software? Do you know how to control an AC device from a small ...


3

You indicated Bluetooth doesn't satisfy your requirements, and I agree. But that's classic Bluetooth. Are you familiar with BLE (Bluetooth Low Energy, part of the Bluetooth 4.0 spec)? The maximum range is anywhere from 50m to 450m, depending on the module used. (That last figure is not a typo, here is the BLE121LR -- LR for long-range. And it still runs ...


3

That depends on what you mean by interfere. If you mean as if there were nothing there but air, then no. But if you mean the cell phone still works, then yes. By putting metal near the phone, this metal will intercept some of the electrical field emitted by the antenna. Consequently, there will be some RF currents in the metal. These currents will circulate ...


3

First of all, as Ignacio Vazquez-Abrams commented, not all water is the same. At the extreme ends, salt water is 100,000 times more conductive than distilled water (so don't drop your iPhone in the ocean!). Tap water is in-between at 1000 to 10,000 times more conductive than distilled, depending on the amount of total dissolved solids (TDS). But I assume ...


3

This will do absolutely nothing. What you could consider doing is picking up a pair of antennas and a length of coax cable for the correct cell band. I think that would be around 800 MHz. It should be possible to get a couple of cheap 800 MHz antennas and maybe 20 feet of coax with the proper connectors for around $20 or $30. If you know where the local ...


3

A battery in an iPhone is a Li-Ion battery, to fully charge it needs to be at around 4.2 V, there's a charge control chip between the USB input and the battery. Let's be optimistic and assume this chip drops 100 mV or more. So for 4.2 V we would need 4.3 V at the USB input. Lets also assume that the charging current is 0.5 A Let's discharge the capacitor ...


3

Could someone help me understanding the markings of this schematic? What the little numbers I circled in red and yellow are The numbers you have circled in yellow, are the BGA ball numbers on that IC (cut off on the right side of the schematic photo you included). The numbers you have circled in red, are the page numbers in this schematic diagram where that ...


3

When looking at an iPhone logic board, it is clear that it is designed to withstand a lot of abuse. The critical and usually larger IC's, such as the SoC, PMIC, NAND are usually encased in a strong underfill while some of the passives, especially those near FPC connectors, are also covered in a softer epoxy. The vast majority of the passive devices are 0201 ...


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