LCD Display

                             

LCD display consists of an array

 

of tiny segments known as pixels that can be manipulated to present information. As a result of this technology, many types of this displays are used in applications like calculator, watch, messaging boards, clock, equipment, machines and a host of other devices that one can think of.

Most of the Display types are reflective, meaning that they use only ambient light to illuminate the display. Even displays that do require an external light source consume much less power than CRT devices.

An LCD basically consists of two glass plates with some liquid crystal material between them. The small size compared to CRT makes it practical for applications where size, current consumption and weight are the main consideration in electronics design.

A liquid crystal display is a thin, lightweight display device with no moving parts. It consists of an electrically controlled light polarizing liquid trapped in cells between two transparent polarizing sheets.

The polarizing axes of the two sheets are aligned perpendicular to each other. Each cell is supplied with electrical contacts that allow an electric field to be applied to the liquid inside. Figure below shows the typical LCD modules which will be able to display graphics or characters when interface with a microcontroller or microprocessor. 

Light is polarized by one sheet, rotated through the smooth twisting of the crystal molecules, then passes through the second sheet. The whole assembly looks nearly transparent. A slight darkening will be evident because of light losses in the original polarizing sheet.

When an electric field is applied, the molecules in the liquid align themselves with the field, inhibiting rotation of the polarized light. As the light hits the polarizing sheet perpendicular to the direction of polarization, all the light is absorbed and the cell appears dark.

Transmissive and reflective LCD display

LCDs can be used in transmissive or reflective modes. A transmissive LCD is illuminated from one side and viewed from the opposite side. Activated cells therefore appear dark while inactive cells appear bright. The lamp used to illuminate the LCD in such a product usually consumes more power than consumed by the LCD itself.

A reflective LCD, as used in pocket calculators and digital watches, is viewed by ambient light reflected in a mirror behind the display. This type has lower contrast than the transmissive type, because the ambient light passes twice through the display before reaching the viewer. The advantage of this type is that there is no lamp to consume power, so the battery life is long.

Customized or standard LCD design

Figure below shows an example of a LCD display which has segments that can be controlled to show +/- signs, readings from the 7 segment. It is interfaced to the PCB by using a rubber connector with carbon that connects the segments and COMs of the LCD to the ports of a microcontroller.

Most manufacturers have some standard design of LCD to choose from but if a customized design is needed, one have to engage the LCD maker to make a customized tooling for the LCD. In this case, the design will be unique and will only be sold to the dedicated designer.

In the application of the LCD, one needs to know the viewing angle of the users. The design have to be specified upfront whether the viewing angle is 6 o'clock, 9 o'clock, 12 o'clock or 3 o'clock as this will affect the viewing angle of the product that has been designed.

If cost is a major constraint in the electronics project that uses LCD display, it is normally advisable for the designer to choose from the standard catalogue of the manufacturer and purchase it.

Thanks & Regarded

  Nipul Prajapati

Constructional Timer Projects

                                        

Timer circuit has been used in many projects and there are basically 2 types that are used these days. One of them is the use of analog RC circuit where charging of the capacitor circuit determined the T of the circuitry. This type of circuitry has larger tolerance and is used in applications where the T is not so critical as the T is affected by the tolerance of the RC components used.

The other is the use of crystal or ceramic resonators together with microprocessor, microcontroller or application specific integrated circuit that need higher precision T in the tolerance of up to 5 ppm (parts per million).

555 IC

One commonly used circuit is the 555 IC which is a highly stable controller capable of producing timing pulses. With a monostable operation, the T(time) delay is controlled by one external resistor and one capacitor. With an astable operation, the frequency and duty cycle are accurately controlled by two external resistors and one capacitor.The application of this integrated circuit is in the areas of PRECISION TIMING, PULSE GENERATION, TIMING DELAY GENERATION and SEQUENTIAL TIMING.

A typical 555 IC block diagram is as shown below.

Monostable Operation

Figure below shows the monostable operation of a 555 IC.

In this mode, the device generates a fixed pulse whenever the trigger voltage falls below Vcc/3. When the trigger pulse voltage applied to pin 2 falls below Vcc/3 while the its output is low, its internal flip-flop turns the discharging transistor Tr off and causes the output to become high by charging the external capacitor C1 and setting the flip-flop output at the same instant. The voltage across the external capacitor C1, VC1 increases exponentially with the T constant T=R_A*C1 and reaches 2Vcc/3 at td=1.1R_A*C1. Hence, capacitor C1 is charged through resistor R_A. The greater the time constant R_A*C1, the longer it takes for the VC1 to reach 2Vcc/3. In other words, the time constant R_A*C1 controls the output pulse width. When the applied voltage to the capacitor C1 reaches 2Vcc/3, the comparator on the trigger terminal resets the flip-flop, turning the discharging transistor Tr on. At this time, C1 begins to discharge and its output goes to low.

Astable Operation 

An astable operation is achieved by configuring the circuit as shown above. In the astable operation, the trigger terminal and the threshold terminal are connected so that a self-trigger is formed, operating as a multivibrator. When its output is high, its internal discharging transistor Tr turns off and the VC1 increases by exponential function with the time constant (R_A+R_B)*C. When the VC1, or the threshold voltage, reaches 2Vcc/3, the comparator output on the trigger terminal becomes high, resetting the F/F and causing its output to become low. This in turn turns on the discharging transistor Tr and the C1 discharges through the discharging channel formed by RB and the discharging transistor Tr. When the VC1 falls below Vcc/3, the comparator output on the trigger terminal becomes high and the tmr. output becomes high again. The discharging transistor Tr turns off and the VC1 rises again. The frequency of oscillation is given as below. 

Frequency, f = 1/T = 1.44/[(R_A + 2R_B)C1]

Thanks & Regarded

  Nipul Prajapati

Types of Memory Devices used in Electronic Projects

Types of Memory Devices used in Electronic Projects

                                        

Introduction to Memory Devices

                             

                

Computers and many electronic gadgets usually rely on stored information which is mainly data which can be used to direct circuit afctions. The digital information is stored in memory devices. Memories can be divided into 2 categories based on what memory cells can be accessed at a given instant.

SAM (Sequentially Access Memory) is accessed by stepping through each memory location until the desired location is reached. Magnetic tape is an example of SAM.

The second category of memory devies is called RAM (Random Access Memory) where the memory can be randomly accessed at any instant, without having to step through each memory location. It is generally faster to access a RAM compared to SAM. Mostof the electronics gadgets memory are of RAM type.

Random Access Memory (RAM) Memory Device

RAM memory is "volatile" which means that the information stored in the RAm will be lost once the power to it is removed. Two common types of RAM are DRAM (Dynamic RAM) and SRAM (Static RAM). DRAM storeds a bit as the presence or absence of charge on MOSFET gate substrate capacitance.

As the capacitance has leakage, it must be refreshed every few miliseconds. SRAM is an array of flip flops of which the bit stored in the flip flop will remain until power is removed or another bit replaces it. SRAM does not need to be refreshed. DRAM is usually 1.5 to 4 times as dense as SRAM and hence cheaper. However, SRAM has faster access times than DRAM.

Read Only Memory (ROM) Memory Device

ROM is non volatile in that its contents are not lost when power to it is removed. All ROMs can be programmed at least once. Mask ROMs are programmed by having "1"s and "0"s etched into their semiconductors at the time of manufacturing.

Programmable ROM (PROM) can be written after manufacturing by electrically burning specific transistors or diodes in the memory array. EPROM can be erased and reprogrammed by using ultraviolet light.

EEPROM (electronically eraseable PROM) data can be erased electronically but it takes longer time compared to RAM. Read and write time for RAM is almost the same but PROM has slower write times. PROM must be erased before they can be reprogrammed and it often needs a higher programming voltage than its operating voltage.

ROM is usually used to store data or programs that do not change frequently and must still be there when power supply cuts off.

Non Volatile RAM (NVRAM) Memory Device

A NVRAM chip consists of both RAM and ROM. During power on reset, the contents of the ROM are copied to RAM. Before the power turns off, the system will copy the entire contents of the RAM into ROM for non volatile storage. The RAM in an NVRAM is called shadow RAM. NVRAM fills the gap between easily written memory and non volatile memory.

Thanks & Regarded

    Nipul Prajapati

                

CE Mark

What is CE Mark? 
                      

Products that are exported to the EC and that are placed on the market for the final end user have to carry this mark. The manufacturer or his representative is required to issue a declaration of conformity which must be kept available to the enforcement authority for 10 years following the placing of the products in the market. He is required also to affixed the mark on the products, or its packaging, instructions or guarantee certificate.

The CE mark is as shown below and must be at least 5mm in height.

What it means to have CE Mark?

When the CE Mark is affixed, it means that the products conform to EMC(Electromagnetic Compatibility) Directive and other relevant Directives that are relevant to the products. Many electrical appliances also have to conform to Low Voltage Directive. Electrical toys will have to conform to Toy Safety Directive.

The EC declaration of conformity must include components like :

a) Description of the products.

b) A reference to the specifications under which conformity is declared. The reference to the specifications does not necessarily mean that you have to test these specifications. Three scenarios are apparent.

i) The product intrinsically meets the requirements of the Directive and does not need testing. Most electronic products are not able to follow this option.

ii) Declaration is make on existing test results. If the products already conform to existing standards such as FCC for emissions and IEC 801 for immunity, then you may be confident that the product will meet the appropriate harmonized standards without further testing.

iii) Test fully to the harmonized standards or choose the technical file route. For complex and new products, this will be costly but is essential.

c) Signatory to bind the manufacturer or his representative.

d) where necessary, reference to the EC type examination certificate for radio transmitters.

Compliance with the CE Mark Directive

There are 2 routes for manufacturer to comply to the CE Mark Directive.

a) Self Certification

Most manufacturer will follow this route which is self certification to harmonized standards. Harmonized standards are those CENELEC or ETSI standards which are announced in the Official Journal of the European Communities (OJEC).

The advantage of certifying against standards is that there is no mandatory requirement for testing by an independent test house. The only requirement is that the manufacturer makes a declaration of conformity as mentioned above which references the standards against which compliance is claimed.

The manufacturer have to make sure that he tests the product to assure himself that it does meet the requirements of the standards and this can be done in-house. In the long run, it is cheaper to have its own basic in-house equipments to test the product instead of sending it to an independent test house which is costly most of the time.

By having these facilities, it will enable the manufacturer to design in the product to conform to the standards as most of the time, a lot of modification to the product needs to be done in order to conform to the standards.

b) The Technical Construction File

The second route is to generate a TCF(Technical Construction File) which will be held by the relevant authorites as soon as the product is placed on the market and for 10 years after the last item has been supplied.

TCF should describe the apparatus, the procedures used to ensure conformity and a technical report from a competent body. It may or may not contain test data. The difference between this route and the first route is that the technical report or certificate is issued by a competent body.

This route is normally taken when existing standards cannot be applied or when testing is not practical because of the size of the product.

This route is also taken when manufacturer decides to apply the harmonized standards in part only, or when the product has been tested to standards that are believed to have met the essential requirements.

       

   Thank & Regarded

       Nipul Prajapati

                 

Constructing your own Wireless Projects

      

Are you fascinated by the world of wireless and wondered how they worked? In the days before the advent of smart phones where WIFI and 3G/4G technology have become commonly available, simple infra-red and frequency modulation projects were the interesting projects for electronics enthusiasts.

Constructing these projects help to provide a good understanding and concept on the world of remote controls. The projects suggested will enable you to learn in greater details the concept of infrared, RFID and the principles of operation.

RFID Application and Design 
This project provides the basic of RFID and the application in the frequency range of 13.56MHz.

A typical RFID system consists of a transponder where a microchip with an antenna is embedded in an item. A reader with antenna is used to read data or write data to the transponder wirelessly. The data read is then passed to a computer where it is used for business transactions.

A study by IDTechEx shows that the market for RFID application in the year 2011 was USD6.51 billion and expected to hit USD7.67 billion in 2012. In the past, the cost of RFID tags was an obstacle to its use in mass quantity. However, as the wireless technology becomes more readily available and cheaper due to its demand in the global market, its use is expected to rise at a rate not imagined before.

There are basically 2 types of RFID in use today. They are passive and active types with frequency ranging from 125kHz to2.45GHz.

Passive Type

The passive tags do not have any transmitter and obtained its power supply from the electromagnetic waves emitted by the reader. This type of tags are cheaper and could range from 15 cents to 50 cents and require minimal maintenance. They have operational range of a few inches to 30 feet. The frequency used can range from 125kHz to 2.45GHz depending on the applications but usually lower frequencies components are cheaper. Passive tags are used in retail business and manufacturing processes.

Active Type

The active tags have transmitter and its own power source. The power source can be solar energy, batteries or from other sources. The transponder is able to communicate with the reader without getting the power supply from the reader. The range of communication is from 60 feet to 300 feet with higher frequencies used. Frequencies used are 455MHz to 5.8GHz.

The application of active type is in large inventory assets control and containers where they need to be tracked over a larger area or distance. Another application is in electronic toll collection system where the transponder will be active when it received a signal from the reader. It then communicates with the reader and do the necessary transactions after which it will go back to sleep or idle mode. In this way, the lifetime of the batteries used in the transponder is extended.

IR Remote Control Transmitter
This project is based on integrated circuit from Holtek Semiconductor HT6221/HT6222. These ICs are commonly used in television and VCR infra red remote controls, garage door controllers, car door controllers, security systems and other remote control applications.


Infrared Remote Control Decoding Project
This project based on Microchip 16C57 microcontroller decodes infrared remote control signals from television, VCR, air conditioner or other home appliances handset that uses NEC 6121 infrared format

Thanks & regarded

    Nipul Prajapati

 

Electronics Project and Design Blog

Welcome to our blog on electronics project and design. It will give you the latest updates on electronics projects, latest update on electronics components and also inform you of any new pages added into this website. 

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Battery Tester Project

Build your own dry cell and rechargable battery tester electronic project.

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EMC (Electromagnetic Compatibility)

EMC (Electromagnetic Compatibility) and its relevant standards

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Temperature Humidity Chambers for reliability testing Of Electronics Products

Using Temperature Humidity chambers to test the Reliability Of Electronic Products

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Test and Measurement equipments for electronics project design

Using Test and Measurement equipments in electronics project design

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25W Audio Power Amplifier

Construct your own 25W Audio Power Amplifier using National Semiconductor LM1875 amplifier module.

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Electronics Design Contest

Join electronics design contest and win prizes. Test your hardware and software skills against the best designers from the rest of the world.

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EMC Testing and Standards in Transient Immunity Testing, RF Immunity

EMC Testing and Standards in Transient Immunity Testing, RF Immunity

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RF Emission testing - Standard and Methodology

RF Emission testing, effect and Standard in accordance to EMC Directive

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Download your own free electronics design software

Free electronics design software - PCB layout, circuit analysis and simulation and other softwares.

Continue reading "Download your own free electronics design software"

Thanks & Regarded

 Nipul Prajapati

Simplify Your Printed Circuit Board Making

                

There are many different types of Printed Circuit Board materials in the market these days. The common ones are FR-1, FR-2, CEM-1, CEM-3 and FR-4 . The thickness of the PCB can be 1.0mm, 1.2mm or 1.6mm. They can be single sided or double sided with cooper clad of 1 oz or 2 oz.

These are the common low cost PCB that electronics hobbyist or students can use for their projects. Of course there are more complicated multilayer PCB that are used in the industry for various applications.

If you are an electronics hobbyist or students who are tight on the budget of making Printed Circuit Board, how do you make your own printed circuit board? If you were like me, I used to go through the many processes in making the PCB a few years ago.

I used to make the PCB layout, print the layout on a suitable transparency (one that can withstand the temperature of the laser printer and photocopy machines), use of photo-resist chemical (require a dark room to do this) on the PCB to ensure that the PCB pattern can be transferred to the PCB, transfer the layout from the transparency to the PCB by the use of ultra violet light, use of developer to develop the pattern on the PCB, etched the developed pattern on the PCB, washed the PCB, drilled the required holes, mount the components and solder the components.

Over the years, I have found out that with the advancement of technology, there are better ways to do the Printed Circuit Board processes. It helps to eliminate the use of darkrooms, photo-resist chemical, developer chemical, negatives/transparency, ultra violet lights and long waiting time to cure the photo-resist.

In simplifying the making of PCB, the direct benefit of this is it reduces the cost needed to set up the PCB making facilities.

The items below are the simplified steps of making simple single sided or double sided PCB for electronics hobbyists, students, or even electronics designer.


                       

PCB Layouts 

You will start by making a layout of the PCB by using a CAD software such as Eagle, Protel, Orcad and other suitable software. Of course there are lots of PCB layout of various projects that you can get from electronics magazines or CAD software. However, I find it more rewarding and one learns more by putting your hands on the available CAD software.

To do the layout yourselves, you need to draw the schematics and after that the PCB layout. Eagle, Altium and Autocratic EDA are some of the software that you can use to do the layout.

Printed Circuit Board Design Rule 

There are a few things to look out for when one does the PCB layouts. It is important to take note that the layout must take into consideration the cost factor as well as the practicality of making the PCB in-house. Listed below are some of the design rule that one should try to adhere while doing the PCB layouts. The detailed EMC(Electromagnetic compatibility) aspects will not be covered here.

PCB Electrical Clearance, Track Width Rules

In the PCB design of electronics circuit, it is important that one plan and has a checklist of the do's and don'ts before proceeding to do the printed circuit board layout. The understanding of the circuit is critical to the design, for example one needs to understand the maximum current and voltage that are carried by each conductor in order to determine the track width of the conductor and the type of PCB that will be used. Some examples of the IPC standard are provided here.

PCB Prototypes 

Once the PCB layout has been completed, one can start thinking of transferring the layout from the CAD software or even the layout from electronics magazines. The author would like to suggest that one jump over the steps of using transparency, photo-resist chemical, developer chemical and the use of Ultra Violet light. The use of Printed Circuit Board Transfer Film will eliminates the steps mentioned.

If your layout is in the CAD software, just print the layout onto this transfer file using a laser printer. If your layout is in the form of hard copy like magazines or artwork, all you need to do is to photocopy the layout into the PCB transfer Film. 

Thanks & Regarded

 Nipul Prajapati