Proa

electronic weekly timer

When we want to control the exact time of activation and function of a power consumption that is repeated every week we can use the weekly timer. Similarly there daily timer and rarely monthly timer.
A simple weekly electronic timer shown in the photo.

The minimum period you can turn depends on the individual model. in one in photograph is one minute.
There are also mechanic timer that gets its name from the programming way, with teeth that get on or off and each tooth has a specific duration eg 15 minutes.

The standard is to contain an internal battery to keep time if it drops the power supply.

Bottom right, in this photography is to provide suply at 230 volts and below left is the contact we use for control. The supply voltage varied depending on the model and is electrically isolated (galvanically isolated) from contact consumption.
If  we have high power consumption is better to put intermediate relays. The timer in this case controls the armature of the relay and the relay controls the consumption.
Necessarily need intermediate relay if consumption is three phase or consisting of more than two single-phase differential phase.
There are popular in the market timers who come directly to schuko socket and control the consumption of their own place in the socket - outlet.

Double recycle time relay

Sometimes we need to automate one electric - electronic element that makes continuous opening and closing his mark, like a flash, or something similar.
The double time doing just that.
It has, as shown in the photo, two positions for setting the time that the internal relay or transistor, is armed and the other adjust the time that the internal relay is deactivated.

Usually the range is independent for each time, e.g. may function to ON (armed) to select the region from 1 to 10 hours and for operation OFF (off) 0.1 to 1 second. In any case and for as long a duration is armed, the two times continuously rotated simultaneously with the contact.
The operating voltage of the double time is similar to that of other components used in automation. Common values ​​are 230 volts AC and 24 vollts AC or DC.
In the market there are times that can work in all standard voltages (the same) or multifunction time not only double but they and many other time functions.
The Timers that are more accurate but they are basically more expensive.
The numbers usually used for contact operation is 15 (for the common node) and 16/18 for open or closed contact, while arming them A1 and A2 (or B) depending on the manufacturer and the voltage operation.

inverter circuit

The three-phase motor, which is the first choice for many applications have their speed directly dependent on the frequency of the power supply.
Everywhere on earth, the frequency is determined and fixed by the provider and can not be selected
The only satisfactory way to test the speed is via inverter.

The inverter "reverses" (invert) the voltage, makes controlled AC rms and frequency.

The technique of creating alternating voltage constant, which is usually selected by the manufacturers of inverters,is the PWM (Phase Width Modulation)
The DC voltage they need is making from the alternating supply with single-phase or three-phase bridge rectifier.

The basic design operating an inverter shown.
As switches data, T1 to T6, used fast response power transistors. The diodes D1 to D6, which are free-flow passages are also fast response and is to protect the transistor.

Schneider-phase inverter

There are in-phase inverter market is small triphasic motors, three-phase inverter and intended for larger motors.
The characterization of single phase or three phase, indicating loading it, if we have a single-phase input voltage of 230 volts for Greece, or three-phase 400 volts. And also identify the maximum rms value of the output voltage can give, ie 230 volts to 400 volts single phase and three phase for.

The operating parameters of the inverter varies with the brand, the size of their power and capabilities and "passed" to memory by either the panel with the display having, or several models, through H / Y.
The main parameters include acceleration time (how many seconds from startup reaches the selected speed - frequency), time delay (in number of seconds the command will stop reaches the minimum allowable frequency before stopping), the minimum and maximum operating frequency , setting a maximum output current and thermal power.

Under the lid of inverter

Because of the way creating the alternating voltage, fragmentation of continuous electronic switches with large frequencies (approximately 5 to 20 KHz selected via parameter) there are unwanted harmonic frequencies as they are called, which are multiples of the frequency of fragmentation.
In motor controlled by inverter there is the disadvantage of unnecessary "movement" of these harmonic currents that generate unwanted heat pipes and can in some cases the energy waste is measurable and relatively large example in large industries.

The cable from the inverter to the motor must be grounded conductive mantle, that is, blentaz, as they say, because the frequencies of the harmonics are such as electromagnetic pulse transmitted by "parasites" in adjacent circuits and certainly not good for man .

Three-phase inverter yaskawa brand

The motor controlled by inverter must have good ventilation at low speeds because there is adequate ventilation by their own cooling fans.
If it works then at low revs must enter separate cooling fan. There are specially designed motor with higher heat dissipation surfaces specifically to be driven by inverter.

Air conditioners with inverter control the speed of the compressor motor freon according to the temperature setting and not the maximum speed of the motor, as it would be if they had the inverter, thus achieving a better result and economy.

The PLC of OMRON is generally consistent with many capabilities.It has many models with many variations that cover a variety of needs.

The main method is by programming with LADDER language , computer and program CX - programmer, series programs CX - one, sold separately.

DEMO version of the software is free for download and use.
A small model is the OMRON CP1E associated with the H / PC via a single USB cable from where the example of this suspension.

Simple example program for the Omron PLC CP1E with Ladder

The 0.00 is the word 0 bit 0 and is always input while 100.01 is bit 1 of word 100 which is always output.

In the example the logical process tells to the PLC:

((if the input I 0.00 is 1 or the input I 0.02 is 0) and the input I 0.01 is 1 then the output Q 100.01 becomes 1)

(If input I 0.03 comes 1 the output Q 100.00 becomes restraint 1 (Set))

(If input I 0.04 comes 1 the output Q 100.00 is 0 (Reset))

end of the program

relay

relays coil

The relay is actually an electromagnet, which when voltage applied to the ends of the coil attracts and retains an iron, or more properly a part of several steel parts, insulated from each other.
At the end of the movable iron part have adapted one or usually more electrical contacts, insulated from one another as well as to the electromagnet.
As the voltage across the coil exists, there is magnetism. When you stop the voltage, a spring that has meanwhile compressed is geting back the electrical contacts.

parts of one relay

relays label

If contacts are at rest, ie when there is no current in the coil of the relay the contacts is open, then when magnetized, closed and vice versa. The open marked as Normally Open (NO) and closed as Normally Close (NC).

There is great variety in the number of contacts, size and operating voltages of the coil.
There relay specially constructed to withstand more effectively in resistive (eg, resistance heating), inductive (eg motors) or capacitive load (eg compensation capacitors)


A form of relay common in industry and in control of three phase electric motors is that of photographs.

relays contact

Smal finder relays

The voltage of the coil is not usually printed on the relay label but in the body that carries the coil, which is an accessory that can be changed.
Problem dysfunction can occur after heavy use or poor choice of power or damage to load - consumption control. Usually the power contacts are those most frequently damaged.


The ends of the coil Names as A1 and A2 in the majority of manufacturers relay.

relays contact

Electronic board with relays

This relay photos marked as 5,5 KWatts relay at 24 volts AC, which means that for 400 volts three-phase network, is designed to withstand, the usual applications, three-phase motors up to 5,5 KWatts and coil built to 24 Volts alternating current (AC).
The contacts withstand current for motors 5,5 KWatts called power contacts and is three Normally Open, one for each phase.
The remaining contacts in the auxiliary relay are designed for low current and are from one to six. They also called contacts or auxiliary automation.
Usually an auxiliary NO is standard in main body of the relay, and if we want more NO or NC we must to buy separately and add them to the socket on the relay and are usually clipped

multimeter

 One of the most useful equipment for an electrician is the multimeter.
The name "Multimeter" shows that are many instruments together in the same case.

In this photo we have:

1. Voltmeter to measure voltage in volts ac and dc to dial numbers in black-choice and switch ac - dc in proper position. Measured by the voltage present in the test circuit in parallel connection.
2. Ohmmeter and diode controller to measure resistance in ohms and voltage threshold in volts for the diode in green numbers. Measuring without voltage in the concerned circuit.
3. Frequency meter to measure frequency in Hz in white numbers. In a parallel connection.
4. Ammeter to measure current in amperes in orange numbers. Measuring under voltage connected in series in the cable that we want to measure the amps.
5. Capacitance meter to measure capacity in farad at the blue numbers. No voltage. The ends of the capacitor goes into the slots with the symbol of the capacitor. If the capacitor is electrolytic correct in the write polarity.

The black connector is permanently attached to the connector COM (From the word common). The red probe goes into the slot with the same color you choose on the rotary knob.

In position control knob channels there is also the function of "pager", in which between terminals if the resistance is less than 20 ohms the buzzer sounds

In all options the rotary switch knob shows the number of the maximum value that can measure the multimeter. E.g. position 2 volt for up to two volt, if the voltage is greater displayed is displaying 1 with a dot (1.) to notify us that the voltage is greater than 2 volts and choose the next larger scale. It is best to start for an unknown expected value measure from the widest possible choice (p, e.g. for voltage 600 volts) and descending scale if needed, so we achieve the greatest possible accuracy.

triac

The thyristor (SCR Silicon-Controlled Rectifier) ​​is the silicon chip with three ends. With proper polarity and electrical command can becomes  switch  controlled.

If the anode of the thyristor is positive voltage relative to the cathode and the gate "give" small continuous instantaneous current by isolated circuit to the cathode, then the anode will be current to the cathode



Once the nihilist tendency or is negative, the thyristor "cuts" and wait again positive voltage pulse and starting to turn again.
The maximum current operation, which depends on the model and the form is on the order of thousands of amperes.
Reverse withstand voltage before destroyed (the cathode), is also in the thousands of volts.
The temperature developed during operation require the existence sink for heat dissipation.

Typically thyristor (scr). A Rising is the thread. The descent into large and small projecting portal metal right

 Name thyristor "came" from the beginning of the name thyratron and the ending of the word transistor. The thyratron was the ancestor of the thyristor as a lamp and did the same job.


The GTO thyristor (Gate Tern Off thyristor) is the thyristors, as the name suggests, can "cut" the power if we give to give the gate reverse current

thyristor

The triac (triac) is flanked by two thyristors in the same "package" so that you can control the flow in both directions. The triac is the element used in the dimmer that control the intensity of the incandescent lamp brightness.

The three-phase motors rotate clockwise or counterclockwise depending on the sequence of the three phases are provided.

The end of the three phases, which typically are named with English letters R, S, T, is clockwise and the motor to be connected in series with the U, V, W, will turn clockwise. But this is not always correct, because it depends on the manufacturer of the motor,  how has wrapped its coils and the "visual" of each. Besides, there is no right rotation for the motor; depends on the work that we want to achieve.

The change of direction is made in mutual permutation of two of the three phases. The plan change effect is accomplished by swapping the first to the third phase. The same effect can be rotating the second to the third or the first to the second.





A simple plan to control the rotation shown in the second drawing.

Design automation control direction three phase electric motor rotation

To avoid case to arm simultaneously two relays we put in a series on automation so-called latching contacts. Thus if one is armed relay can arm the other, even if pressing the START button, must necessarily be deactivated first reinforced by pressing the stop and then to activate the other. One relay that "latches" the other with a closed contact (normal close NC) to prevent the arm, hence the name of the contact.

This pattern of changing direction is not ideal because it requires the operator's attention to the actual stopping of the motor, wait some time before starting to reverse. Could someone, while the motor turns at once, press the stop and immediately after, without waiting at all, press the START of the other direction, bringing the motor and load abruptly and perhaps dangerous. This can be prevented by addition of another insurance provision.

Single and three phase bridge rectifier

When we want our application to use continuous DC voltage and as the only power source we have is alternating voltage AC then the bridge rectifier will almost certainly be part of the circuit.

The input ac voltage to the bridge can be any value as long bridge and capacitor are constructed to withstand the voltage and amperage that will work.
Of course we can build the bridge rectifier with diodes independent linking them as appropriate to the project.

The three-phase bridge rectification doing better than the single-phase, for the same frequency voltage of course.

Three-phase bridge rectifier

The capacitor stabilizes the voltage but not always with satisfactory results, however, the greater capacitance value is, the better.
Always put in parallel to the output electrolytic capacitor rather simple.

Diodes

The heat of bridge by the current is a problem so bridges must be placed in a smooth surface for this purpose, heat sink abducting heat protecting diodes. In the bridge heat sink thermal we put special silicone to avoid trapping air and for spreads heat quickly.

If we stabilized voltage, voltage without variation, must be put in the output suitable stabilizer such as for up to 1.5 amps the integrated circuit 7824 to 24 volts DC or 7812 for 12 volts DC or whatever 78 ** for another voltage.
The integrated circuit LM 317 by suitable wiring can give voltage value, by means of an adjustable potentiometer, from 1.2 to 37 volts DC.