The main topics presented
1. Electronic code (Code Lock)
The assembly shown is very special useful when limiting access to an area. It is only allowed on the basis of a four-digit code.
The electronic cipher (Code Lock) presented is made by Velleman, in the unassembled version, the construction allowing the mounting of the device directly in the wall.
Along with this kit, there is also a face mask that solves many of the design problems of the case, problems that electronics engineers encounter during installation. The selection of the access code is done hardware.
Description of the wiring diagram
Figure 1 shows the electrical diagram of the assembly, noting its simplicity. Its heart is the integrated circuit CD4066 - logic switch.
It contains in its capsule 4 switches, marked in the figure in the article with ES1… ES4. Their command is made with logic level "1" received from the keyboard (SW) buttons.
The four logic switches are cascaded, the output of one commanding the input of the other, so that the priority is the correct application, in order, of the logical level 1, in turn, from the input of ES1 to that of ES4.
The lines of code are numbered with CODE A… CODE D, they go to the control inputs of the switches ES1… ES4.
2. Switching power supplies (III)
In the previous articles, the basic structures of switching sources were presented, describing the physical principles of operation of the component blocks.
In this article several schemes are commented, which can be realized practically, with accessible components and a reasonable cost. The schemes are presented in ascending order of complexity, emphasizing the particularities in the functioning of each.
Electronic diagrams presented
- Switching stabilizer with LM317;
- Switching stabilizer for mobile phone;
- L4960 switching integrated stabilizer.
3. 13.8 / 1A linear source with battery for back-up
Medium current power supplies (1… 3A) with back-up battery are often used in the field of "security" to power more complex systems, whose power supplies in their central units can not supply currents greater than 500… .1000mA. Of course, this is not the only area of applicability.
The presented installation finds its applicability in various fields such as the uninterrupted supply of alarm systems, access control with electromagnetic yalla, in closed circuit video surveillance systems, emergency / safety lighting, etc.
The electrical diagram (figure 1 in the article) is built using the integrated circuit LM317T in TO220 capsule, which can withstand a current limit of 1.5A.
The circuit benefits from overload or short circuit protections common to all three-terminal linear regulators. The diagram is the classic application of the LM317T control circuit.
4. TDA1560Q (40W car radio high power amplifier)
TDA1 560Q is a monolithic integrated circuit audio power amplifier, which operates in class H with the load connected to the bridge, providing an impedance of 8 Ohm a power of 40W, with total harmonic distortion of 10%.
The integrated circuit is mainly intended for automotive applications. In figure 1 (from the article) is presented the block diagram, and in figure 2 and table 1 the configuration, respectively the meaning of the pins. The circuit is "offered" in the capsule DBS17P.
- very high output power;
- low power dissipation for music signals;
- automatic switching on a reduced delivered power when the semiconductor "chip" overheats;
- the typical application requires very few external components;
- fixed internal gain;
- reduced cross-over distortions;
- lack of start and / or stop noises;
- operating mode selection switch;
- low offset voltage at the output;
- short-circuit protected on output;
- protected from electrostatic discharge;
- thermally protected;
- diagnostic facilities;
- flexible terminals.
5. 40W RMS audio amplifier
As a concrete application of the TDA1560Q circuit, there is an audio amplifier intended for use in the automotive field, so with power supply from a low voltage source with high current capability.
The wiring diagram is a direct application of the TDA 1560Q circuit according to the catalog data and the typical application diagram.
The amplifier works both in class H and normally at low powers. The total harmonic distortions, at maximum power, have a value of THD = 10%. The voltage gain of the amplifier is fixed internally to the value of 30dB. The current consumed in standby does not exceed 50uA.
The presented assembly allows to exploit to the maximum the characteristics of TDA1560Q.
6. PC frequency meter
The presented application is a PC interface with which you can measure the frequency of a digital signal.
The interface is made with microcontroller AVR RISC, model AT90S2313. Basically, only three port lines are used, one for reading the digital signal and two for the data bus - Tx / Rx, for communication with the PC.
The microcontroller is piloted by a quarter on 4MHz. U2 type circuit MAX232 (or any equivalent produced by another company ICL232, ADM232) is the data interface, converter from digital signal to signal for RS232 standard and vice versa.
The measuring signal is applied to the Fin terminal. Switch S1 initializes the measurement operation, respectively the program. The measurement result is transmitted to the PC on the serial port.
7. TDA7293 - Applications
TDA7293 is a monolithic integrated circuit mono power audio amplifier, operating in AB class, made by SGS-THOMPSON in a Multiwatt 15 capsule and which is intended for Hi-Fi applications (stereo amplifiers, active speakers, high class TVs etc. .).
Due to the wide range of supply voltages and the high capacity of the output current, the circuit can provide high powers on both 4 and 8 Ohm loads.
The presence of the muting circuit eliminates noise at start or stop. It is possible to connect several integrated circuits in parallel with the help of pin 11 (buffer driver).
In this way, high powers can be obtained on low impedance loads, while optimizing heat dissipation.
8. Effective voltage converter - direct voltage
Measuring the effective component of a voltage with a certain waveform is difficult to achieve. Even for a sine waveform, the use of a classical peak detector consisting of one or more rectifier and capacitor diodes (configuration from which the effective value is easily extracted) introduces large errors due to diode voltage drops and nonlinearity. them.
The optimal solution seems to be the conversion of voltage based on the thermal effect, knowing that the effective value of a voltage applied to a load resistor, produces the same heating of the resistor as in the case of the application of a direct voltage of the same value.
The current value converter (RMS) - DC voltage presented in this article is made with the integrated circuit AD736 produced by Analog Devices. The extremely small number of external components, the lack of control elements and the outstanding performance of this circuit in terms of conversion errors, wide frequency range and response time make it possible to use it in a wide range of professional applications.
The internal electrical diagram of the AD736 circuit is presented in figure 1 (from the article).
9. FM mini-transmitter
This simple "FM mini transmitter" makes the connection between a home audio system and a portable radio.
Using this idea of electronic editing, music enthusiasts can remotely listen to music directly from their own audio system.
At the base of the wiring diagram is the integrated circuit IC1 (MAX 2606). This is a voltage controlled oscillator with integrated varicap diode.
The nominal oscillation frequency is given by the value of L1. Using a 390nH inductor, the base frequency is 100MHz. Potentiometer R1 allows you to scan the entire FM range between 88… 108MHz. The output power is around 21 dBm on a 50 Ohm load.
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