Cell Phone controlled home appliances

Prototype of the cell phone controlled home 

appliances

Rectifier

A rectifier is an electrical device that converts alternating current (AC), which periodically reverses direction, to direct current (DC), which flows in only one direction. The process is known as rectification.









Half wave rectification

4000 Series IC

                       There are many ICs in the 4000 series and this page only covers a selection, concentrating on the most useful ICs. Most gates and a few counters are covered. For each IC there is a diagram showing the pin arrangement and brief notes explain the function of the pins where necessary.

555 Timer 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.
                                     
 

Clock Controller

                    The Clock Controller V1.1was designed to be an exemplary of using 'C' language to control timer0interrupt, 7-segment LED and keypad scanning. It provides 1-bit sink currentdriving output, for driving a relay, opto-triac, say. Many projects requiring7-segment display and keypad interfacing may get the idea from the Clockcircuit and software.
 

                       

                        Circuit diagram of the Clock Controller  P10-P1.7 drives 7-segment commonanode LED with sink current. P3.0-P3.3 also drives a base pin of 4-PNPtransistor, 2n2907 with sink current. As shown in the figure, the 2nd 2-digitLED that connected to P3.2 and P3.3 is rotated 180 degrees to the 1st 2-digitallowing the pt. segment to be used for 1 second blinking. P3.0-P3.3 alsoconnects four momentary switches while the other legs are tied to inputport P3.4. During display and key switch scanning, a logic '0' is shiftedfrom P3.0 to P3.3,  if there was a key pressed, P3.4 then became low.P3.7 is a 1-bit sink current driving, an example in the circuit uses a2n2907 to drive a small electromechanical relay 5V.

For more:.....................

Multiplexing

Multiplexing is a very efficient technique for controlling many components wired together in a matrix/array.  In this example, I'll be talking exclusively about multiplexing an array of LEDs, but the same basic principles apply to other multiplexed components (sensors, buttons, etc).

   
In a multiplexed array of LEDs, only one row of LEDs is on at any given time.  It seems like this would limit the types of shapes we can display on the LED matrix, but it actually doesn't.  This is because the arduino (or whatever is sending data to the array) is switching through each row so quickly (hundreds or thousands of times a second) that we do not perceive the flashing on and off of each consecutive row.  You can read more about this phenomenon, called persistence of vision, on wikipedia.            
                                  

So how do we send data to one row at a time?  If we connect five volts (red) to one row and connect ground (blue) to the other three rows and cycle through each row one by one, it will look something like figure 1.  Now image that while one of the rows is at +5, we connect one of the columns to ground.  As shown in figure 2, this will cause the LED at the junction of the +5 row and GND column to light up.  This way, we can address each of the 16 LEDs in the matrix individually using only eight leads (four to the rows and four to the columns).



Now look at the image below.  Imagine if we very quickly turn on the LED in the upper left corner (position 1,1), then the LED at (2,2), then (3,3) and (4,4), and we cycle between these four LEDs very quickly (hundreds of times a second).  It will appear that all four of these LEDs are on a the same time (as shown in right image in the image below).  Study the diagram below and convince yourself that this is true.
                    

Soldering Techniques

1.     Study the diagram and PCB layout.

2.     Check all the components and study their pins and orientation.

3.   Clean the leads of components if needed to remove rust or grease with a blade.

4.     Place resistors first then IC base, capacitors etc.

5.     Use little flux to the joints to increase the melting point of solder lead.