Conex Club Magazine - no.11-12 - 2001

Conex Club Magazine - nr.11-12 - 2001 - TMP01 (Low Power Programmable Temperature Controller)

Reading time: 4 minute

The main topics presented

1. AD 820 (Single-Supply, Rail-to-Rail, Low Power, FET Input Op Amp)

This circuit, designed by Analog Devices, is an amplifier for dynamic or piezoelectric microphones. Optimally, this circuit works powered by 5V, when it has minimal noise.

The gain is between 20 and 40dB if the microphone has an impedance greater than 600 Ohm. The bandwidth is 20kHz, the distortions being 0.05%.

2. TPA 731 (700-mW, mono, analog input Class-AB audio amplifier with differential inputs)

The TPA 731 circuit is a low power mono audio amplifier with differential input and high immunity to radio frequency disturbances.

It is designed to work on a load with an impedance between 8 Ohms and 32 Ohms, when it has the optimal energy efficiency.

The maximum power consumption is 700 mW but at a voltage of 3.3V this circuit charges on the load only a power of 250 mW. It is powered by a voltage between 3.3V and 5V.

3. TMP 01 (Low Power Programmable Temperature Controller)

A type of monolithic temperature sensor that also includes a voltage reference and two comparators.

With or5mV / K solution, TMP01 works in the temperature range from -55C to + 150C. An application of this circuit is in the field of ventilation, the scheme recommended even by the manufacturer.

4. 1000MHz frequency meter

This frequency meter has two areas of measurement: the first for frequencies up to 60MHz and the second for high frequencies up to 1000MHz.

The device is equipped with an eight-digit display, which provides a convenient and accurate reading of the signal frequency applied to the input.

It is provided with two inputs, both with 50 Ohm impedance; one for frequency range up to 60MHz and another for very high frequencies up to 1000MHz.

In the first frequency range (60MHz) the measurement can be performed with a resolution of 1Hz and with a reading time of 1s or with a resolution of 10Hz, but with a faster reading period of 0.1s.

In the field of ultra high frequencies the frequency reading time is 0.64s, the measurement accuracy being 100Hz.

The frequency meter is equipped with integrated circuits (ICs) made in LS technology, with the exception of the first divider (U14) which is of the HC type to allow the measurement of frequencies up to 60MHz. Because of this fact electricity consumption is relatively low, this being mainly determined by the LED display.

5. TV service - The control block for TV receivers made with microprocessor type PCA84C841P

Microprocessor type PCA84C841P is made by Philips and is part of the microprocessor family PCA84 CX4X.

The family also includes other microprocessors used in TV receivers, among which we mention: PCA84C441, PCA84C444, PCA84C641, PCA84C644, PCA84C844.

The differences between the variants consist in the offered facilities (by microprocessor programming) and in the included software that allow the TV receivers that use them to ensure different functional options.

The article will analyze the variant PCA84C841P - FR17THV111, characterized especially by the fact that its software can ensure the digital control of a channel selector, via the I2C bus.

6. Fast charger for Ni-Cd, Ni-MH batteries

MAX713 and MAX712 are two specialized integrated circuits for fast battery charging.

Because the charging characteristics for Ni-Cd and Ni-MH differ, one of the circuits (MAX712) is specialized for Ni-MH batteries and the other (MAX 713) can charge both Ni-Cd and Ni-MH batteries.

7. Programs for calculating the impedances of the interconnection routes

In order to optimize the PCB design activity and reduce the time to choose the correct configurations in case of high speed digital signals, high frequency analog or microwave, some electronics software development companies have focused on creating specialized programs in determining the characteristic impedances. of the different configurations existing in practice, programs that have acquired the banal name of "impedance computers".

This article presents two such software specific to standard and microwave interconnect structures, CIT25 and TXLINE.

8. Signaler

Many times we encounter situations in which we want to read a CD, the operation is delayed and we do not know what is happening. If the unit used has a very low noise, all we have to do is wait for the computer message.

A good solution would be to install an electronic device that signals that the unit is at least powered and rotating.

9. Voltmeter 4 1/2 Digits

This digital voltmeter, made with integrated circuit ICL7135 is a precision A / D converter with multiplexed outputs in BCD format that ensures a guaranteed accuracy of +/- 1 of 20.000 counts for the scale head.

In addition to the ICL7135 integrated circuit, there are several external stages: the binary-decimal decoder, the thermostatic voltage reference (ICL8069), clock circuit, negative voltage circuit of -5V (ICL7660).

10. TDA1072A (AM receiver circuit)

This circuit, produced by PHILIPS, is a AM receiver recommended for household appliances and equipment mounted on cars. The internal electrical diagram highlights independent functional floors.

Note the possibility of use in exceptional conditions for CB communications when quartz crystals are mounted on the oscillator or for SSB emissions when FI signal is input at input (pin 14), the local oscillator becomes BFO, and AF signal is obtained at the output of the first mixer.

Circuit TDA1072A it also has an output for the intensity indicator of the received field.

11. ETCAI - Software for learning the basics of electronics (I)

Good news for novice amateur electronics enthusiasts but also for advanced hobbyists eager to test their basic knowledge of electronics "ETCAI Products", the company specialized in the development of educational programs in the field of electronics, has launched a new, improved version of a special package for pupils, students and enthusiasts of practical electronics.

"ETCAI - Electricity & Electronics" program is a software made in the Windows environment that contains six independent blocks designed to learn the primary elements of electricity and electronics.

The program is a real gem in the field of interactive education because, in addition to being friendly and does not require advanced computer skills, it is fully oriented to the practical aspects through the figures and animations presented.

12. Electronic cipher

The presented installation can be mounted as an interface for activating / deactivating the alarm for the apartment, electromagnetic actuation or for controlling the operation of some household appliances for children (TV, PC, etc.) having as output a 5A relay.

13. 50MHz / 28MHz transceiver

Having already the SSB signal formed in a transceiver 28MHz, with the help of the transceiver whose scheme is presented in the article, connections can be obtained in the 6m band, respectively on the frequency range 50-52MHz. This transceiver was published by DK7ZB in Funck Amateur since 1995.

14. Capacitance meter - adapter for frequency meter

This simple adapter allows the measurement of small capacities, of up to 1mF. The measurement is made by inserting the measuring capacitor in an RC oscillator.



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