The main topics presented
1. PC - Parallel port
The parallel port of the PC is interesting due to its simpler programming compared to the serial port which requires a very precise transmission protocol.
Originally reserved for the connection between the printer and the computer, the parallel port is often used today in other applications due to its high speed of transmitting digital information.
It can be connected to this port, either the scanner or a reader for high capacity discs, as well as various measuring instruments or various electronic cards.
Without claiming to fully address the particular aspects of this interface, some important and useful information is presented to amateur builders.
The parallel port has the following lines:
- 8 data lines;
- 4 control lines,
- 5 status lines (to check the status of the printer);
- several table lines.
2. 80W amplifier
The article presents an audio amplifier that allows obtaining a musical power of 80W on a 4-8 Ohm load.
Using a specialized integrated circuit - TDA7295 - allows much reduction of passive external components, mounted on the wiring, resulting in a device of reasonable size.
The amplifier can be used to equip Hi-Fi audio-video equipment, to create active acoustic enclosures or to configure stereo power amplifiers.
3. 4-channel remote control station
The appearance on the market of the set of miniature transmission / reception modules - in SMD technology - manufactured by VELLEMAN under the name Tx433or rxxnumx made possible the realization of a small remote control station - the transmitter is an easy-to-wear keychain in a key connection - and of negligible own consumption, in the conditions of average performances.
The system presented in the article ensures radio connection at a distance of approx. 200m (in radio-released areas), enough to be able to visually follow the remote control model.
- Transmission frequency: 433 MHz;
- RF power: 8 mW;
- Channel: 4 independent, digitally encoded;
- Power supply: 12V (battery A23, G23, V23, etc.).
4. Multifunctional stable / monostable
The tilting circuit shown can be used as a pulse former for various electronic counters or as a broad spectrum pulse generator.
The described assembly ensures a special flexibility, being recommended for fast configurations of stable or monostable tilting circuit.
The topological modification of the scheme is done quickly, by executing a few straps with fluoride on the wiring.
On the same wiring, of reduced dimensions (39 x 32mm), seven operating modes can be configured, three in stable mode and four in monostable mode.
At the base of the assembly is the integrated circuit CD4047, made in CMOS technology whose supply voltage is in the range 3-18V.
Jongland with the values of the external components, respectively R6 and / or C1, timing times between 1ms and 60s are obtained.
5. Dynamic lights software
Numerous dynamic lighting schemes can be found in electronics magazines for amateur manufacturers, which are very popular, especially by young people.
The assembly shown it is controlled via the parallel port usually used to connect the printer.
It is a solution in which the most important share has the software section. Reduced to the simplest expression, the hardware part includes only the light sources that are controlled directly through the data outputs D0… D7.
6. 5V / 3A stabilized source
In specialized magazines and books are proposed various electronic assemblies that are powered by low voltage, 4.5 - 6V for which we must have such a source.
Powering modules with TTL logic circuits requires a stabilized 5V voltage.
In order to meet the working conditions in the laboratory, it is proposed to make the presented assembly that offers a stabilized 5V output for a maximum current consumption in load of 3A and with the possibility of adjusting the voltage by +/- 30% around 5V.
The wiring diagram in principle has the "skeleton" on the integrated voltage regulator LM317, well known to readers because it is in a multitude of power supply applications.
It is somewhat similar in typology to the scheme of the stabilized voltage source (12V / 5A) presented in issue 4/2000 of the magazine.
Note also the presence of strap 1-2; if the alternating voltage at the input comes from a transformer with a medium socket, it is not mounted using a transformer with a single secondary winding, it is necessary to mount this strap.
The increase of the available power at the output is made with the power transistor Q1, type BD912, in capsule type T0220.
7. Portable calibrator for unified signal
In many applications, unified current signal is used to transmit analog information.
For the quick verification of the equipment or devices that work with unified current signal, the device presented in the article can be used.
Scheduling has the advantage of low voltage operation, has good accuracy and does not use many components.