In the CD4094 data are synchronized on the rising edge and the LCD display will take on the falling edge shows us that this signal can be shared.

Well, then at the rising edge CD4094 transfers the data of the new byte out and fall on the side of the LCD display reads. Keep in mind that this method can not read LCD information display.

Now comes the hard part: How to separate text commands. LCD has a pin for this: RS pin. When this command for 0 accepted, as accepted in a text (ASCII characters). How do you solve this?

Before sending a character to initialize a timer on CD4094 500uSec. The resistor R1 will load capacitor C5. Then send the character to the CD4094 as quickly as possible. Thus, the capacitor simply does not have enough time to discharge. The LCD display will accept it as text. In order to command is the same, only in reverse. The capacitor has to be discharge.

Emitter follower T1 formed to protect the network R / C. The reason for this is that the LCD RS input is a TTL input signal and we put it to work quite well.

Program C Language

#include <hidef.h>
#include "derivative.h"

#define LINE1    0x80
#define LINE2    0xC0

#define DTASHT   0x01     // PTA0
#define CLKSHT   0x02     // PTA1
#define STBSHT   0x04     // PTA2

#define CTRL     1
#define DATA     0

void Shift(char, char);
void Delay(int);
void Write(char, char*);
void Init_Dsp(void);

void main(void) {

CONFIG1 = 0x01;
CONFIG2 = 0x00;

DDRA    = 0x07;
PTA     = 0x00;

Init_Dsp();

for(;;) {
Init_Dsp();
Write(LINE1,"  Hola Mundo    ");
}
}

//=====================================

void Init_Dsp(void) {
PTA |= CLKSHT;
Shift(CTRL,0x06);
Shift(CTRL,0x0E);
Shift(CTRL,0x38);
Shift(CTRL,0x80);
Shift(CTRL,0x0C);     // Cursor off
Shift(CTRL,0x01);     // Clear Display
}

void Write(char pos, char *text) {
Shift(CTRL,pos);
while(*text) Shift(DATA,*text++);
}

void Shift(char donde, char dato) {
int i;

for(i=0; i<8; i++){
if(dato & 0x80) PTA |=  DTASHT;
else            PTA &= ~DTASHT;

if(donde) {
PTA &= ~CLKSHT;
Delay(200);
PTA |=  CLKSHT;
}
else {
PTA &= ~CLKSHT;
PTA |=  CLKSHT;
}
dato <<= 1;
}
PTA |=  STBSHT;
PTA &= ~STBSHT;
if(donde) Delay(2000);
}

void Delay(int time) {
for(; time>0; time--);
}

As seen in the IR Wireless Headphone schematic, transmitter circuit is very simple here. The transformer assembled as a matching impedance, and low impedance windings are connected in parallel with the TV or radio speaker. IR diodes are commonly used. 10 ohm resistor that limits the current through the IR diode should be 1 mg. This 9Vdc powered transmitter that can be provided either by regular batteries or AC / DC adapter.

As the receiver is concerned, the same infrared light captured by the phototransistor, it is pre-amplified and amplified by transistors BC549C and then gives enough power to move the speaker of headset through the output transistor.

This receiver, like the transmitter is also powered from 9Vdc, but in this case must inevitably be provided by the battery, because with AC / DC adapter all this will be useless. Would look funny, right? When we use a wireless Headphone. But still use power supply with cable.

Remember that the audio is transmitted must have line of sight between the transmitter and receiver.

You can extend the range of the transmitter by placing more transistors BD140 with more IR LEDs.

The unit of density in the International System of Units is tesla.

Is given by:

where B is the magnetic flux density generated by a load moving with velocity v at a distance r from the load, and ur is the unit vector connecting the load to the point where B is measured (point g).

or :

where B is the magnetic flux density generated by a conductor through which flows a current I, at a distance r.

The formula of this definition is called the Biot-Savart, and magnetism is equivalent to Coulomb’s law of electrostatics, as used to calculate the forces acting on moving charges.

The field induction, B, or magnetic flux density (the three names are equivalent) is essential in the field H electromagnetism, since it is responsible for the forces on the moving charges and is, therefore, the physical equivalent to E.

The analog to digital conversion is based on theoretical sampling theorem and the concepts of quantization and coding.

A first classification of the A / D, is the following :

• Conversion direct transformation.
• Converters with conversion (D / A) intermediate auxiliary.

Capture and holding circuits (S / H: Sample and Hold).

The Capture and holding circuits are used for sampling the analog signal (during a time interval) and then holding this value, usually in a capacitor during the duration of the conversion A / D itself.

The basic layout of a  Sample and hold circuit, and its simplified representation, is given in the figure above

The operation of the circuit of the figure is as follows: The A / D converter sends a pulse width tw by line C / M, which activates the electronic switch, charging the capacitor C, during the time tw. In the ideal case, the capacitor voltage follows the input voltage. Then the capacitor keeps the voltage acquired when the switch opens.

Response of a sampling and hold circuit

The graph has an ideal character, since both the charging and discharging of the capacitor are closely related to its value and that of the resistances and parasitic capacitances associated with the circuit.

Emphasizes the fact that the control signal C / M is from the A / D converter, which is the only one to know the time that the conversion is complete signal.

A / D converter with comparator

It is the only case in which the processes of quantization and coding are clearly separated. The first step is performed by comparators that discriminate between a finite number of voltage levels. These comparators receive at its inputs the analog input signal with a reference voltage, different for each. Being staggered reference voltages, it is possible to know whether the input signal is above or below each of them, which allow to know the state that corresponds as a result of quantification. Then will need an encoder that give us the output.

Basic diagram of a converter with comparators.

This converter is a high speed, since the direct conversion process is rather than sequentially, thereby reducing the time necessary conversion to the sum of the propagation times in the comparator and the encoder. However, its usefulness is limited in cases of low resolution, since for an N-bit output are necessary 2N-1 comparators, which leads to excessive complexity and higher cost is desired as a high resolution.

Using the simple circuit of A / D and basically consists of the elements shown in the following figure :

Basic diagram of a converter with counters

A comparator, clock, circuit capture and holding (S & H) counter D / A converter and output buffers.

Once the trapping and holding circuit (S / H) is sampled analog signal, the counter starts running counting the pulses from the clock. The result of this count is converted into an analog signal by a D / A converter, proportional to the number of clock pulses received up to that moment.

The analogue signal obtained is introduced to the comparator in which a comparison is made between the input signal and the digital signal converted to analog. At the moment when the latter reaches the same value (actually slightly larger) than the input signal, the comparator output toggles its stoppage occurs and the counter.

The counter value becomes the buffers and becomes the digital output corresponding to the input signal.

This converter has two drawbacks:

• Low speed.
• Conversion time variable.

The second drawback can be easily understood with the help of the following figure, which shows that the number of clock pulses (time), needed to achieve the value Vien the D / A converter depends on the value of Vi.

Said conversion period is given by the expression :

Each time you press the doorbell generator creates a Ding-Dong weak audio signal with the sound of bells. The signal is high in volume by the amplifier and is reproduced by the speaker. The power supply circuit provides the voltage necessary to operate. The interface circuit to connect the rings fed centrally as buildings or intercom.

The circuit is powered through the point marked V + and ground. The heart of it is the integrated HT2811, developed by the firm koreana Holtek. For the pin 1 enters the trigger pulse, telling the chip to produce the sound “Ding-Dong”. Pins 2 and 3 are connected to sets RC establishing each of the sounds (2 = “Ding” / 3 = “Dong”). Altering these components is achieved by varying the sound of bells. Pin 4 is the mass. By the pin 5 leaves the audio signal which is amplified by a pair of transistors used in darlington configuration. The terminals 6 and 7 are connected to a 680K resistor which adjusts the gain of the internal preamplifier chip. Finally the terminal 8 enters the feed to the chip which is current limited by the resistance of 100 ohms and 3.3v stabilized by means of zener diode. The 100μF capacitor filters the possible ripple left in the power line.

In case of using this bell at departments or locations where you can not modify the wiring in the bell push is necessary to use this interface. It receives at its input an AC or DC voltage and rectifies through PR the bridge rectifier whose output is filtered by continuous capacitor 470μF and subsequently attacks the small coil of a reed relay. The key to this relay trips the main circuit as would a conventional switch. The rectifier bridge (PR) can be either formed by diodes 1A 250V or more. While the voltage of the relay coil must be the same as the voltage of the previous original buzzer ring (usually 12V). While the relay can be operated without rectifying the line or filter is not suitable because the alternating current would act to relay as a buzzer, opening and closing your key 50 times per second and this can cause some damage in the mechanism after a time.

This section of the circuit adapts the voltage from the power supply required by the household the equipment. It also enables battery power for all occasions when the power fails. The transformer reduces the voltage AC 4.5v. The bridge rectifier (PR) converts AC power continuously, which is filtered by the capacitor of 2200μF. The 1N4007 diodes act as source selector system by operating the mains or batteries as needed. The fuse protects the transformer section 220v. The bridge rectifier (PR) can be any voltage which is greater than 250V and whose current is not lower than 1A. Point + V represents the output of the source, while the batteries (4 in series) input by the points + Bat and-Bat.

This metal detector electronics circuit also detects metal objects and magnets. When the magnet is near the 10 mH coil, a metal detector project can be supported by a power supply that can provide a DC output voltage of 6 volts to 12 V. If the metal is closer to the coil L1, it will produce a change in the oscillation frequency of the output, which will produce sound at 8 ohm speaker.

Parts list :
R : 47K
C : 2.2uF (2) 10uF
L : 10uH
IC : 555
Speaker 8 ohm
Supply voltage 6-12V

This Simple FM circuit does not have a section that determines the frequency. In the following circuit and all that follows, which determines the frequency of operation is called a resonant circuit or tuned circuit and consists of a coil and capacitor.

This Simple Mikro FM 90Mhz circuit does not include this feature.
The transistor turns on via the 47k and it puts a pulse through the 15 turn winding. The magnetic flux from the winding passes through the coil 6 and in turn the transistor base via the 22n capacitor. This pulse is amplified by the transistor and the circuit is kept active.
The frequency is determined by the 6 turn coil. By moving the whole turns, the frequency decreases. The circuit transmits at 90MHz. It has a very poor and consumes 16mA. The coil is wound on a 3 mm drill and uses son of 0.5 mm.

In the example given in Figure 3, A2 anode is alternately positive and negative, while the trigger is negative (pulling power) when the transistor is conducting.
By observing the table, we say that the triac operates in quadrants 2 and 3. Different combinations can be obtained. It should just point out that Mode 4 should be avoided, due to excessive consumption in the range above 100 mA against only 50 mAin modes 1, 2 and 3 for a triac type ’standard’.
Indeed there is a model called ”sensitive”, which require low gate currents of 5 to 10 mA. This is important because the intensity of the load must be greater from the intensity of the trigger, and that is why dimmer on Trade found, in addition to the indication of the maximum load, minimum load indication, if not triac does not work anymore.
The principle is that the triac is initiated after a control pulse to the next zero crossing of the wave field. The command can be impulsive and Figure 4 provides such a circuit, which is much less demanding than the continuous control of Figure 3.

This type of circuit can then be powered by an RC network from transformer if the control circuit does not consume too much. A level 0 on input C blocks the triac.
The power output is maximum in this case since the triac is initiated immediately afterthe zero crossing of the AC voltage, but we can intervene in different ways for each control pulse delay in order to vary the intensity applied to the load.

A simple way to achieve this is an RC network like Figure 5. The offset depends on the values ​​of these two components R and may vary. The diac trigger placed on the phase shift results in a more importantly, it does lead that when the voltage reaches 30V.

There are, however, other more sophisticated ways to obtain complete phase shifts (180°) and automatic systems for modulating the intensity according to various phenomenasuch as light or temperature.

Figure 6a and 6b show the power applied to the function of the load in the delay from the relative control pulse to zero.

The main drawback of this type of setting is easily lead noise and especially on the receptor MW / LW.

These can be partly eliminated by the addition of a LC circuit comprising a network asthat of FIG 7, wherein the two capacitors (optional) are provided for alternatingnecessarily class (X2) and to self calibrated depending on the intensity required.

This assembly is suitable for circuit ”dimmer”, but if you want to just use a triac switch is better to use a special circuit in the control of the zero wave sector.
These include for example an opto-triac OMC 3041 with ”zero crossing” is planned forthis application and the pinout is shown in Figure 8.
Moreover, the isolation of a optotriac, some 7,500 V, and the control current of ten milliamperes give safety and ease of use highly significant for switching loads of several amperes at a voltage of 230 V or more.
Don’t forget that mounting a TRIAC, with or without a power transformer, if they are not equipped with optotriacs or similar devices are connected directly to the mains and which should be very cautious with this kind of circuit.
Figure 9 shows a universal interface for controlling various devices connected to the mains using, for example, a computer.

The control is effected by applying a positive level of the LED, the opto-triac in turn controls a triac that there will be chosen according to the respective load. We can equipthe suppression of this interface in Figure 7.In some cases, particularly if the load is highly inductive, it may be necessary to add a protection circuit. Figure 10 shows an effective way to protect the triac.

Finally, we must not forget to equip each of its triac sink if the power involved requires it,usually you start to place a radiator from a 100 W power for conventional models 6/8 A.Be aware that there are triacs provided for a current of 40A.
To end this article, Figure 11 shows you a very simple TRIAC scheme is however sufficient, allowing you to remove the doubt about how each of your triacs.

By adjusting the potentiometer P2 to a high pitch, can enter the circuit into oscillation by emitting a continuous whistle.In this case, we must reduce degradation of sound with the potentiometer P1. For installation components, follow closely the diagram layout.

Bell Electronic Parts list :

All resistors are 1/4 watt unless otherwise stated.
R = 68 ohms
R2 = 1 kohm
R3 = 10 Kohm
R4 = 470 ohms
R5 = 82 Kohm
R6 = 22 Kohm
R7 = 270 ohms
R8 = 10 Kohm
R9 = 47 ohms
Pl = 4.7 MohmsA.
P2 = 220 Kohm A.
Cl = 22uF16V elec.
C2 = 1uF16V elec.
C3 = 0.1 uF 100 Vpol.
C4 = 0.047 uF 100 Vpol.
C5 = 0.047 uF 100 Vpol.
C6 = .47 uF 100 Vpol.
IC1,IC2,IC3 = 741
P = Push.
3 IC Supports 8-pin

These integrated circuits operating at 5 V and 9 V battery 6F22 certainly convenient, voltage is reduced and stabilized by a 78L05 regulator. By rotating the trimmer R2 from one end to another, will change the flashing between 0.5to 3 flashes per second.

This electronic flasher circuit can be placed in bags or placed in a belt to put on waist (when cycling,walking, etc..). You will see this safety circuit is highly efficient flashing in the darkness. Moreover, nothing prevents to build a (relatively inexpensive) and set them on someplaces (legs, back, bike, scooter …) to improve visibility.

List of electronic components Led electronic flasher:
R1 …………… 2.2 kOhms
R2 …………… 10 k trimmer
R3 …………… 220 Ω
R4 …………… 220 Ω
C1 …………… 47 uF electrolytic
C2 …………… 47 uF electrolytic
C3 …………… 47 uF electrolytic
DL1 …………. LED
DL2 …………. LED
IC1 ………….. integrated SN74HC132
IC2 ………….. integrated MC78L05
S1 …………… switch
(Unless otherwise noted, all resistors are 1/4 W 5%