high quality

Whether we like it or not, at least once in our lives each of us has been through something like this. It’s perfectly normal – after all, we can’t know them all, and choosing the wrong product is a natural thing to do.

But things get a little complicated in the case of electronics because they have quite high prices and we do not buy them to change them monthly, but we want to use them for as long as possible. Fortunately, there are several tips that we can offer you and which, if you take them into account, will help you make the best decisions, depending on your needs.

Think about your needs

In order to have the guarantee that we have made the best decision for our needs, we need to … well, we need to know what they are. Logical, right? So, the first thing you need to do is think about what you expect from a certain product, whether we are talking about electronics or appliances. You can even write on a piece of paper the reasons why you want to buy it.

You don’t necessarily have to buy the latest appearances on the market, because all your needs can be met just as well by a product from a mid-range. Buying very expensive things without really needing them we will end up in a situation where we will not use them at their true value. So the investment is a bad one and it makes a hole in our budget.

Once you’ve done that, it’s time to move on to the actual search. Since you already have in mind a profile of the product you want to buy it will be much easier for you to find it.

 

The brand doesn’t really matter that much

We are not saying that a manufacturer that has built a name in the industry is not worth choosing. What we want to emphasize is that the brand is not everything. As in the case of clothes, for example, in terms of electronics and appliances we tend to pay more just for the sake of the company. It is wrong, because what makes the difference are the specifications, not a simple name.

The quality / price ratio is important

One last piece of advice we give you is related to the quality / price ratio that electronics and appliances can have. The most important thing you need to remember here is that very cheap and poor quality products will eventually make us take more money out of our pockets. How? Because we will replace them shortly after purchase. On the other hand, if we turn our attention to the middle range, we are much more likely to be able to use what we have bought for a much longer period of time.

Power Supply

The power supply is the most important part of a system, because nothing works without a power source. The power supply is the “heart” of any system. A power supply is a charge for the public AC network or a DC battery. Choosing a power supply is not easy, but an optimal choice can be made rationally following the 18 criteria explained below.

1. Maximum power required in continuous use at maximum temperature
2. Constant voltage source or constant current source
3. Field, real working environment and extreme limits
4. Reliability requirements (MTBF, estimated lifetime, warranty)
5. Natural or forced cooling of the source
6. Maximum current absorbed by the source at start-up
7. Range for input voltage
8. Electrical characteristics imposed by the application
9. Various inlet and outlet protections
10. Dynamic characteristics
11. Characteristics related to indications, interface and communication
12. Power supply system in which the source is included
13. Size and constructive form
14. Certifications and approvals required
15. Special requirements for source components
16. Standard product or special product
17. Preventive maintenance requirements
18. Price

1. Maximum power required in continuous use at maximum temperature. A source is chosen for the power supply of one or more known consumers (load) to which is added a power reserve of at least 30%. Inductive loads such as electric motors, transformers and relay coils may require a current greater than 2… 5 times the rated current for the first input voltage for several input voltage wave cycles. If one source supplies another source that has capacitors at the input (discharged at first) a high current pulse is required for charging (eg a 12Vdc source is supplied from the 24Vdc source). Cold resistive loads also require a higher current at start-up, until the resistance increases with heating (eg filament bulb, heating element).
Mandatory, the source must provide power peaks when starting electric motors that have their own inertia when starting at rest, but also a mechanical load (eg a water pump in a boiler). High-performance switching power supplies or power converters specify that they can provide, for a limited time, a current higher than the steady state current when starting inductive or capacitive loads.

2. Constant voltage source or constant current source. The application imposes a minimum of initial requirements for a power supply: if constant voltage or constant current is required (eg LEDs are supplied with constant current), if the output voltage or current is fixed or adjustable, if required multiple outputs, if it is required to connect the voltage sources in series to obtain a higher voltage or to connect the current sources in parallel to obtain a higher current.

3. Field, real working environment and extreme limits. Field of application (industrial, indoor or outdoor lighting schemes, LED display panels, commercial, medical, laboratory devices, surveillance and alarm systems), source for independent use or incorporated in another product or cabinet (source with / without housing), outdoor mounting with exposure to sun, moisture, rain, dust… or indoors in office environments, household, warehouses, degree of protection IP xy to the real working environment, respectively to moisture, dust, bodies foreign matter that can enter the source (metal powders, chips, pieces of wire…), abuse by extreme demands of temperature and humidity, frequent starts and stops, mechanical vibrations and shocks, disturbing electromagnetic fields, corrosive vapors, explosive environment.

4. Reliability requirements (MTBF, estimated lifetime, warranty). Ultra-safe operation requirements (especially in the fields of medical, military and surveillance systems). Cheap sources have not tested reliability under specified limit conditions.
Burn-in tested sources must be chosen (Note 1), specifying that the temperature sensitive parts (electrolytic capacitors) have high reliability (long life) and at the temperature of max. 105 ° C. The warranty should be 2 or 3 years.

5. Natural or forced cooling of the source. The source may have forced cooling with at least one fan running continuously or intermittently controlled by a temperature sensor or convection cooling (by free, natural circulation, air) or conduction cooling (by mounting on a good heat conductive metal support). It is mandatory to check in the technical specifications of the source, the decrease of the output power depending on the source temperature (power – temperature diagram), because the power given by the source decreases with increasing temperature. Quality sources give this diagram in specifications. An additional cooling device shall be provided if the rated power of the source is required at maximum working temperature. For example. at 50 ° C, the delivered power can be reduced from 100% to 70%. Depending on the maximum power required and the place of installation (plastic or metal box or in the cabinet with or without vents, on the rail, on the table, on the wall, in street lighting…) sources with outdoor cooling are chosen or forced with a fan.

6. Maximum current absorbed by the source at start-up.

 

pcb desing rules

Each PCB is different as for each design in establishing a separate set of regulations.

PCB Design – General Principles of PCB Design

How to design PCBs correctly to reach boards that are cost effective to produce and plant? What are the most important principles of PCB design? How about PCB production technology? We have prepared for you a series of articles on PCB design.

PCBs are an integral part of all electronic devices. Their basic function is to create a conductive connection between the pins of the individual components. PCBs first appeared in the 1960s, when the first design and production rules were developed – CPI standards. The standard for PCBs is the IPC-2221 “Generic Standards on Printed Design” standard.

What is the first step in PCB design?

In electronic practice, 3 types of components are used and their gluing possibilities are:
• components with “Through Hole” – TH terminals (axial, radial), can be glued manually or by wave,
• components with Surface Mount Devices – SMD, which can be glued in a reflow or wave oven,
• components without surface mounting terminals – “Surface Mount Devices” – SMD, which can be glued in the reflow oven.

With these three types of components you can create an electronic device in which these components are placed on a support – printed circuit board (PCB). The components can be planted on a PCB, either on one side (SMD, TH or a combination of the two), or on both sides (TH only on the top, SMT on both). When the PCB is designed, there must be the location of the components on the PCB and the type of soldering technology taken into account, as different rules apply to wave soldering or reflow soldering.

1. Soldering by soldering wave

If we want to solder components on the bottom of a PCB, we need to make sure that the components do not fall during the soldering process. The SMT components on top will be planted in a solder paste, then glued in an open reflow. The SMT components on the bottom of the PCB will be glued together with an adhesive and then the TH components will enter the holes in the PCB. SMT components bonded with adhesive and TH components will be bonded by a soldering wave.

Planting the components with terminals on one side of the PCB is an easy process, requiring only immersion in the solder wave and a conductive node is created. In the case of SMD components, when all components are immersed in the solder wave, they must withstand the wave temperature, which can be up to 260 ° C. On the side of the PCB, which will be soldered in a wave, only such SMT components can be planted, which have the manufacturer’s recommendation that they can be soldered in a wave and they must meet the requirement to withstand at least 10 seconds at 260 ° C. . These can be ceramic resistors, MELF, MINIMELF, monolithic capacitors, components in SOT, SOD, SOP capsules with a minimum pitch of 0.65 mm, to avoid a short circuit of the integrated circuit, because the wave covers each terminal of the parts and may involve the creation of a so-called resistive or capacitive bridge if they are designed in a way that prevents the soldering solution from entering.

We need to put down the components that can withstand the temperatures of the soldering wave and have the necessary distance between the terminals. For correct soldering it is necessary to take into account the distances between the SMT components, their orientation towards the soldering wave as well as the height of certain components. The components must be so arranged that their terminals create a right angle with the soldering wave. This will ensure proper gluing. However, this requirement can only be met if components with terminals on two opposite sides (SO, SOP, SOIC…) are used. In the case of integrated circuits with terminals on all 4 sides, it is necessary to place them on top of the PCB and glue them in a reflow oven. It is also recommended to mount brackets behind the integrated circuit to reduce the soldering point of the last pair of terminals. Short-circuiting can be prevented, but the possibilities of connecting the conductors are reduced.

2. Soldering with solder paste

Today, this is the most common way to glue. In this case, the conductive connection is created by the components placed in the solder paste, which is applied before planting the components. The connection of the components is thus created. When using a solder paste for soldering, we avoid problems with twisting the components. This soldering method increases the integration of components on a PCB. We do not have to consider the height of certain SMT components (tantalum capacitors, MELF power resistors, power transistors) and this method is also suitable for soldering SMT components with a radiator at the bottom of the capsule and also , for soldering SMT components without terminals. The soldering wave can cause some unwanted SMT components called “Tombstoning”. Under the influence of the imbalance of forces acting at both ends of a component, the component can “rise” like a “Tomb stone” (mainly to two-pin components, such as resistors, capacitors,… .. ). This effect is caused by irregular temperatures spread on a PCB during leakage. This can be removed by correctly applying the solder paste using a metal template.

General rules for the design of PCBs in terms of production technology

First, you need to know where the board is made. The basic information we should know is:
• Minimum route width – W,
• Minimum isolation difference – I,
• Minimum diameter of Via (opening in metal) – D.

These parameters determine the density of PCBs that can be produced – the so-called accuracy class. Currently, it is necessary to use a standard accuracy class of 6 or higher. This information must be applied when setting the design rules. The system does not allow the creation of a line that does not comply with these criteria.