HOW LCD DISPLAY WORKS?

How LCD Display Interface Circuit works?
An LCD -liquid crystal display is an electronically-modulated optical device made up of any number of pixels filled with liquid crystals and arrayed in front of a light source (backlight) or reflector to produce images in color or monochrome.
They can be optimized for static text, detailed still images, or dynamic, fast-changing, video content.
Old type of LCD are monochrome types which only display one certain color while the modern types are colored ones that can display rich text and images.
LCD's resolution of display depends on the amount of pixels into it, the highest amount designed looks and displays best.

Now, LCd wont work without a light source and a reflector to drive it pixels to form an image information.
This typical block diagram below will help us a brief explanation oh how the LCD can produce an text and images on mobile phones handsets. 
The block diagram shows the LCD gets a data source from the application processor, so therefore LCD is being controlled by the application processor to produce a detail images,
LED is a light emitting diode that can produce light, this light source of an LED is the one that reflect at the back of an LCD, without this LED light reflection on the back of an LCD  it will result a black or dark screen displays.
LCD also needs a power supply voltage to activate its liquid crystal arrays inside of it, so that is why a voltage supply is also very important for that matter.

 An LCD Display Circuit Schematic diagram of a mobile phones below interprets how the whole circuitry of an LCD being connected and designed. A circuit start from an application processor that controls and sends data to LCD connector which where the LCD is being connected. Before the data reach to the LCd connector it is being filtered for Electromagnet Interference protection. The LED light circuit and a power supply voltage is also provided for it is also work an important part on LCD circuit.

The picture below interprets the schematic diagram above on how  each components layout are being mounted on a particular mobile phones printed circuit board.

Always keep in mind that LCD needs the following sources to make it work completely,
1. Data control signal from the application processor
2. LED light that reflects on it back so that display will reveal completely.
3. A power supply voltage to turn the LCD activated.

 A failure of these three sources will result on display problem issues.

UNDERSTANDING MOUTHPIECE OR MICROPHONE, EARPIECE AND IHF OR BUZZER SPEAKERS CIRCUIT ON MOBILE PHONES

A mobile phones microphone or mouthpiece is a component used to convert sound signal into an electrical signal. The earpiece speaker is the one that converts electrical signal into a sound signal, likewise also the IHF , buzzer or ringer speaker do.
These certain parts works as a user interfaces components on a mobile phone.
And controlled by an Audio Codec Circuit which is the part that relatively controls and converts all audio frequency signal.see picture below

A picture below is an schematic diagram microphone or mouthpiece circuit,
A typical and modern designed  of mouthpiece circuit is being protected by anEMI- Filter to prevent sound interruption, before it then feeds the audio signal to the audio codec circuit. Some microphone circuit other mobile phones have no EMI Filter like the one showed below. The microphone line signal is being presented into positive and negative polarity, and those two polarity lines is being filtered again by two capacitor after being pass by from an EMI-Filter, in order to remove the DC (direct current) coming from the EMI-filter.

The earpiece circuit is also filtered by inductor coil to reduce sound saturation cause by any radio frequency interruption.

 And same also in an IHF speaker circuit. The IHF speaker also have two lines which is positive and negative line.

A vibrator motor although this is not a sound converting device but it generates a vibration which generates sounds, this one is also included in audio circuitry.

Here's an example mapping layout of a Microphone, Earpiece, IHF speakers and Vibrator  motor connections on a mobile phones printed circuit board. Each connection were both separated and apart from each other but all  of each line is being pointed towards in audio codec circuit.

The above picture is only an interpretation of how audio circuit is being connected or mounted in a mobile phones printed circuit board.

UNDERSTANDING MOUTHPIECE OR MICROPHONE, EARPIECE AND IHF OR BUZZER SPEAKERS CIRCUIT ON MOBILE PHONES

A mobile phones microphone or mouthpiece is a component used to convert sound signal into an electrical signal. The earpiece speaker is the one that converts electrical signal into a sound signal, likewise also the IHF , buzzer or ringer speaker do.
These certain parts works as a user interfaces components on a mobile phone.
And controlled by an Audio Codec Circuit which is the part that relatively controls and converts all audio frequency signal.see picture below

A picture below is an schematic diagram microphone or mouthpiece circuit,
A typical and modern designed  of mouthpiece circuit is being protected by anEMI- Filter to prevent sound interruption, before it then feeds the audio signal to the audio codec circuit. Some microphone circuit other mobile phones have no EMI Filter like the one showed below. The microphone line signal is being presented into positive and negative polarity, and those two polarity lines is being filtered again by two capacitor after being pass by from an EMI-Filter, in order to remove the DC (direct current) coming from the EMI-filter.

The earpiece circuit is also filtered by inductor coil to reduce sound saturation cause by any radio frequency interruption.

 And same also in an IHF speaker circuit. The IHF speaker also have two lines which is positive and negative line.

A vibrator motor although this is not a sound converting device but it generates a vibration which generates sounds, this one is also included in audio circuitry.

Here's an example mapping layout of a Microphone, Earpiece, IHF speakers and Vibrator  motor connections on a mobile phones printed circuit board. Each connection were both separated and apart from each other but all  of each line is being pointed towards in audio codec circuit.

The above picture is only an interpretation of how audio circuit is being connected or mounted in a mobile phones printed circuit board.

HOW AUDIO CODEC DO ON MOUTHPIECE, EARPIECE, IHF SPEAKER OR BUZZER AND VIBRATOR ON MOBILE PHONE CIRCUITS

The Audio Codec is a circuit that controls sound signals in a cellphone circuits. It acts like an audio amplifier or an audio mixer or a sound booster.
Audio codec is the main area in a mobile phone where all audio properties is being process, during transmission and receiption. It converts the sound signal into radio frequency signal, and also converts radio frequency signal into a sound signals.
Like for example a microphone's sound signal is being amplified then converts and feeds to radio frequency before it send to the network airwaves. Opposite to that process is the conversion of radio frequency into an audible or understandable sound, and that sound is that what we hear on the earpiece speaker.
A typical block diagram below show  how audio interfaces being connected to anaudio codec circuit.

The Audio codec is the main part which control all audio properties from all audio interfaces like the microphone, earpiece, IHF (integrated hands free) speaker or a buzzer, ringer, head set and vibrator motor. A typical audio circuit is being filtered from any sound interference signal to avoid sound interruptions.

HOW DO LED LIGHT BULBS WORKS ON MOBILE PHONE CIRCUIT

An LED - light emitting diode is used to illuminate keypads keys and LCD screen displays on all mobile phones handsets. It is being controlled by a voltage or current draws on its terminal leds.
a picture below is an Schematic Diagram that tells us how does the LED circuit works on cellular phone whole circuitry.

On schematic diagram  we notice that the LEDs is driven by an LED driver chip's, and an Switching Control circuit that also being packed in a chip. The LED driver is being used to stabilized the voltage and current and do take control on engaging ON and OFF status of an LEDs to light up or not.
It also drives  the amount  of  brightness or dimming status of the LEDs by applying Pulse Width Modulation signal from the Switching control circuit.

The block diagram below interpreted a component and section or parts of  an LED circuit to work during application process.
The Switching control circuit feeds and release a Pulse Width Modulation Signal (PWM) to switch and light up the LEDs light bulbs. A pulse width modulation signal is a type of digital frequency signal range up to 1khz to enable and implement to take control of  LED brightness.
Once that certain signal is being received by the LED driver, the LED driver now will engage and release the voltage or current that being feeds up from the mobile phones battery supply voltage;
The output voltage release by the LED driver is the one that draws the LED light bulbs to light up. 

LED drivers is a high frequency, synchronous boost converter with constant current output to drive up to 5 white LEDs. This device circuit is designed  for maximum safety,  it integrates overvoltage  and short circuit protection when the output is being shorted to the ground. Meaning this chips circuitry will not easily  breakdown for it is designed to protect when short circuit happens.
like for example, the two LED light bulbs commits short circuit to its terminal 
In mobile phones application methods; the switching control circuit that release pulse switching signal is also being synchronized programmed by the the application processor (CPU) to engaged a full control on how and which proper situation that the LED will be switch to light up or not. 
like for example the LED will only switch and light up, if the handset is being in used and remain off if the handset is not in used. 

The above image is an example of the LED circuit, how those particular stages and components being mounted on a phones circuits. Note that the LED driver and switching control circuits is being packed into an Integrated Circuit or ICs. 


To all beginners: A bunch of simplified STEP By STEP Procedures On Troubleshooting LED Problem issues on various mobile phones  product will be Posted Here Later.. Just keep on visiting this blog more often.

KEYPAD PROBLEM

Understanding the Keypad circuit may help and boost your knowledge on fixing keypad problem issues on mobile phones. Keypads is a part of user interface being used to navigate or enter numbers, letters and characters, browse application, sends information and etc.

An schematic diagram  below will help us understand how keypad circuits works and which components or parts did this circuit is being connected.
In this diagram the each and every key switching pads is being divided and grouped into rows and columns. Each rows and columns were group into 2 -5 keypads switch. This rows and columns have each corresponding lines according to each and every group of switching pads.

This lines of rows and columns is being filtered for EMI and ESD protection the EMI filter is made of tiny chip that used to protect such EMI and ESD interference.

This rows and columns lines are digital switching signals generated by the application processor to trigger or activate every corresponding digital datas that is being stored and programmed within the mobile phone system memory. This diagram below is an Application Processor that generates and feeds then receives digital data switching signals.

This digital data frequency signals corresponds and interpreted to each key characters that are marked on each keypads. Like for example a combination of row 2 and column 3 will triggered the number 3 when hitting on it. 
 this block diagram below shows how the switching signal is being triggered to process a command data.

Various mobile phones have different keypads layouts and specification. A joystick and a volume switch is also parts of keypads switching circuits. Some keypads module designs are made into a flexible wire like those Slide Type package of mobile phones. Some flexible wires are very vulnerable  and common cause of keypad malfunction. There are few methods in tracing and mapping the keypad layout on a mobile phones keypads on printed circuit board. One of this quick and very easy method is by using an schematic diagram, if that certain mobile phones have available unto it. Schematic diagram is very useful guide in every aspects of hardware troubleshooting.

Now assuming that you already have knowledge how to use and read it, follow this simple steps below.
 Browse to bottom of the pages where yo can locate and find like the picture below., it is the keypad  circuit section. In that schematic layout you will notice that each corresponding key characters is being group into lines. This group of keypad switch lines  is being marked with rows and columns.

  trace each and every lines where those keypads switch symbols is being connected, once you been manage to trace it. configure and trace it on the printed circuit board by using an analog or digital multimeter, just set it the resistance value X1 and attach both probes to corresponding keypads groups in  every rows and column

Practice this kind of method with an aide of schematic diagram, in this way if you're skills grows further, you can then trace any other mobile phones without any schematic diagram available at first hand.

INSERT SIMCARD

A SIM Card also known as Subscriber Identity Module, A SIM is a Smart Cardthat can store data from a cellular phone. Those data like identity, location and phone number, network authorization data, personal security keys, contact lists and stored text messages. Security features include authentication and encryption to protect data and prevent eavesdropping.

But how does this SIM card works within the mobile phones circuit? How does mobile phones reads and write data unto it?
In those particular questions above, If we learn answers unto it, we can solve problem issues regarding SIM related problems, like Insert Sim Card and etc.

Now here's a brief explanation on how does SIM Circuit Works on a mobile phones circuit.

A Sim Card have six pads that also corresponds to the six SIM connectors pins, but only five has totally have connection on the entire layout.
SIM DATA - this is a digital data that being stored on a SIM memory
SIM Clock - this is a clock frequency signal that being synchronize to the digital data to create data signal in order transfer or sends and receive data information.
SIM Reset - this is also a frequency signal that triggers or reset all synchronization process.
VSIM B+ Supply Voltage- This a power supply voltage used to activated the SIM circuit.
SIM Ground - a ground line voltage
The other one is not connected

A Typical block Diagram above shows on how SIM Circuit Works on a Cellular phones circuits.
In the layout the Sim Interface Connector connected directly to SIM Control Circuit. The SIM Control Circuit is the one the generates Clock frequency that triggers the SIM data storage, once the SIM is now being  triggered, it is then now sends data information to the application processor to  begin the process with. The application processor is the one that gathered  all data information from the SIM memory, initiate and activate it, if all information is in desired status.
Those three particular lines of signal flows associated in the circuit shows how the synchronization is being applied. If one of those lines being cut off the sending and receiving process will breakdown, and  will result to SIM problem issues. The Power Supply Voltage through the SIM is also remain stable otherwise a lack of voltage will not activate the SIM to work.

In a picture below an EMI-ESD Filter has been added to protect  the circuit to an Electro-static Discharge and Electro-magnetic Interference disorders. This type of SIM connection circuit is an advantage to mobile phone technician for troubleshooting SIM related problem issues. Thus, type of particular EMI filter is very vulnerable  and mostly create breakdown to the entire SIM connection.

The picture below is an equivalent layout of  an EMI filter and its internal circuitry,
only both frequency and data lines is being filtered.

The EMI Filter is a tiny chips designed to protect  SIM DATA, SIM Clock and SIM Reset data  signals that flow across trough the SIM connector.

 The EMI-ESD Filter is a highly integrated device designed to suppress EMI(Electromagnetic Interference) and RFI(Radio frequency Interference in a circuit. This filter includes ESD protection circuitry which prevents damaging the mobile phone application when subject to ESD ( ElectroStatic Discharge) surges up to 15 kV.

Here's an example of how the the SIM data signal  flow across the printed circuit board.
Note: this is only shows where the signal flows from component to componentconnections.

 

 A picture above is an alternative way by many mobile phone technician dealing with SIM problem issues on most Nokia Mobile Phones.