The main topics presented
1. Lead-free electronics
The article presents the result of research conducted for the optimal implementation of RoHS Directive (2002/95 / EC) and its regulations in the Romanian electronics industry.
As a result, manufacturers are required to ensure that their products comply with the requirements of the RoHS Directive in order to be placed on the market, and designers and engineers involved in the design and development of electronic products are forced to change their strategy to meet the requirements of the process. lead-free soldering.
To find the optimal solutions experiments of SMT processes were performed (Surface Mount Technology) without the use of lead-based materials (Pb-free, lead free, LF).
An important requirement in SMT technology is selecting the soldering paste and defining a thermal profile of the soldering furnaces of SMD electronic components.
Due to the economic aspects, conditions for the reuse of some essential accessories will be established, such as pasta storage sieves.
In addition, the authors will present the influence of nitrogen in the lead-free soldering process. Finally, scientific and practical conclusions will shape the path of optimal transfer from classical lead to lead-free technologies.
2. Proximity sensor (proximity)
With the diagram in the article you can make a (pre) warning device for the situation in which a person approaches the door of the apartment.
The circuit is very sensitive if the negative pole of the power supply is connected to Earth. The proximity of a hand can be detected from more than 20 cm from the sensor.
It can be made of a metal plate, a thin metal foil or it can even be the seals on the door lock at the entrance. If the negative pole of the source does not connect to Earth, the sensitivity decreases a lot.
A piezoelectric buzzer will signal an alarm. The power supply of the assembly is made from the battery (accumulator) of 9V (12V). R14 and R17 must be multiturn potentiometers. When making the wiring, the input area comprising R16 will be shielded.
3. TC9153 (AP) - Digital volume controller, up-down
The TC9153 (AP) integrated circuit, produced by Toshiba, made in C2MOS technology, is intended for professional audio equipment for volume control.
Its main technical characteristics are:
- the attenuation can be controlled in the range 0dB….-66dB, with a step of 2dB;
- two channels, stereo, separate;
- possibility to be supplied from double or single voltage source;
- the circuit is piloted by an internal oscillator with external RC elements, an oscillator that controls the speed with which the attenuation is achieved by pressing the up (up, increment) or down (down, decrement) buttons;
- the realization in C2MOS technology allows a wide range of supply voltages, respectively VDD = 6… 12Vdc.
The maximum supply voltage is 13Vdc, and the input signal must not exceed in amplitude more than 0.3V of the supply voltage. The current consumed is 1… 3mA. The maximum dissipated power is 150mW per capsule.
4. Press'n'Pell Foil (PnP) - Practical Tips
Press'n'Pell foil (PnP) is a modern process for making prototype or small series printed circuits.
The quality of the resulting printed circuit, however, depends on several factors, which intervene from the moment when the decision was made to purchase a certain type of foil. (Blue or White commercial versions, or Wet version) until the moment of final processing (drilling, removing toner from uncorroded circuits, etc.).
There are two types of PnP foils on the market: Blue and White.
Folia Press'n'Pell White
White leaf (white) it is thicker, and printing (whether done with a laser printer or a copier is done on the glossy side of it. desirable.
There may be areas where there is no deposit and these are corrected with a permanent marker. Also in this process, there is a tendency to overheat the foil either by excessive temperature or by increasing the ironing time, and the result is a "stretching" of the toner, the wiring being deformed.
Technologically, White foil allows the realization of printed circuits with heights of widths up to 0.7mm guaranteed (the conclusion is the result of experiments).
The author obtained results that sometimes reached, with a good quality, and widths of 0.5… 0.4mm, but it depended a lot on the experience, the quality of the foil and the toner deposited.
Very often, this foil was used for the "top" layer, for the design of the components, taking into account the more modest quality of the deposition. It is therefore recommended for wiring with large surfaces, with thicker paths.
Folia Press'n'Pell Blue
Blue foil is a high quality, has a certain transparency, which is why they are also recommended for double layer printed circuits (with glass-textured support, which in turn is partially transparent).
The reason: ensures a good alignment (through transparency) of the two layers. The limit obtained is a copper path width of 0.4… 0.3mm guaranteed (experimental); good quality wiring is obtained, even professional.
It is ideal for small surface circuits or for surface mounted components, SMD. The deposition temperature used is approx. 10% lower compared to White foil.
In general, for the iron, the temperature is set at the lower limit for wool (no steam!). It is recommended to use only the iron with stainless steel or supergliss sole.
The raw printed circuit board (laminate) is cleaned, before use, with detergent (for dishes) for degreasing.
5. Digital stereo volume controller with electronic up / down control
Comfortable and quiet, without introducing electrical noise in the assembly, compared to an analog potentiometer, the digital potentiometer presented is made with general purpose integrated circuits (non-specialized).
The main elements are the two electronic switches of the type 4066 (for the two channels). Their order is made in BCD code (Decimal Coded Binary) by the binary counter (reversible), the module CD 40193.
Its command is made on the two inputs: for direct counting, on pin 5, and for reverse counting (descending) on pin 4. The effective command is made with the help of the two push-buttons, marked with S1-UP and S2-DOWN.
If you want to go directly to the minimum position, then press the S3-RESET button. So, the RESET command assumes the maximum attenuation of the signal.
The volume adjustment is done by the combined connection of four resistors (R6… R9 for the left channel and R9… R12 for the right channel) which achieves a relatively linear increment or decrement, in 16 steps, of the output signal, compared to the input one.
The clock generator is made with the integrated circuit LM555. It provides the signal corresponding to the speed of incrementing (decrementing) the volume. The assembly does not require any adjustment, if it is done correctly.
6. Speed variator for mini-drills
The presented speed variator, destined to supply the mini-drills for drilling or milling the wiring, offers a wide adjustment range and a high torque to the motor shaft.
It is known that if you want to adjust the speed of a mini-drill for drilling wiring (or other fine mechanics), using a direct current source, if we are interested in a strong torque at low speeds, the results will be unsatisfactory.
A speed regulator with series transistor (the drill motor is powered by a transistor whose base current is variable) presents this desideratum.
Another aspect is, at low speeds, difficult starting (due to the low current / voltage applied from the source). It thus becomes impossible to perform precision work (especially milling) with a drill at low speeds.
What happens, however, if using the same method of powering a motor (with series regulating transistor - see the role of Q1 in the diagram in figure 1 of the article), the control of the bias current based on the regulating transistor is done by a method PWM - Duration Tax Modulation.
The method involves attacking the base of the regulating transistor with rectangular pulses of constant frequency, but with variable width high and low levels.
To solve the problem we used a common oscillator with logic gates OR-NO (NOR, in English), which can be found in the capsule of a circuit type 4001 (CD4001, HEF4001, MMC4001, etc.).
- Supply voltage: 9… 12Vac or 9… 16Vdc;
- Recommended load current: 1A, without radiator on Q1;
- Speed adjustment ratio: 1/20;
- Adjustment method: PWM.
7. Voice separator for karaoke
The proposed montage is an audio preamplifier that offers the possibility (optional) to suppress the voice from a musical score. A microphone input will allow the user to mix (overlap) over the song to which the performer's voice was attenuated, his own voice.
The montage can be very useful at karaoke shows. Of course, the montage cannot compete with the more modern devices that contain digital sound processors, at which each frequency that composes a song can be attenuated, but using operational amplifiers the results will be satisfactory for non-professional purposes.
For most songs it will be noticed that the soloist's voice will be completely suppressed.
- supply voltage: 9Vdc from the battery;
- current consumption: 16mA;
- maximum input sensitivity: 400mV;
- microphone signal level: adjustable;
- RCA connectors for In / Out;
- voice attenuation switch.
8. Prescaler 1000MHz
Prescaler, attached to a digital multimeter, which offers the possibility of measuring frequencies, extends the respective measuring range up to 1000MHz.
Although it is designed to operate up to the frequency of 1000MHz, the assembly works up to at least 1100MHz. For frequencies within the limits of 50… 100MHz and above 1000MHz, a higher input signal of the order of 20… 25mVef is needed, instead of 15mVef, a value that is valid for the 100… 1000MHz range.
The specialized integrated circuit is used U813 BS, in configuration SIP-8 or SIP-6. The printed circuit board is designed so that any constructive type of U813 integrated circuit can be used.
9. A simple function generator made with CD4011
An interesting challenge for young electronics engineers who support their theme for the graduation project is the job generator.
How in such cases the cost-performance ratio is the first aspect considered, many young people will probably choose to build this installation.
- Generates sinusoidal, triangular and rectangular signals;
- Frequency: 0.01Hz… 600kHz;
- Symmetrical / asymmetrical shapes, filling factor adjustment;
- Option for modulation signal input.