To understand the essence of it is useful, I think, to recall that the pulse-phase method allows to adjust the load power change that part of the half-cycle of line voltage during which triac passes current. So, for correct operation of the device it is first necessary to identify the beginning of each half-period (which corresponds to the instantaneous line voltage is equal to or close to zero), and then for 10 MS (duration of half cycle of mains voltage, 50 Hz) to generate an impulse. And the sooner we open the triac, the more power will be allocated to load.
Shaper of pulses of frequency 100 Hz is collected on the elements VT1, /T2, R3, R4, R7. With the advent of the positive half cycle on the top (the scheme) the network wire to the emitter of the transistor transition /T1 is the applied voltage “opening” polarity. The semiconductor triode is really getting open, and it IR close to Uэ. The voltage drop across the resistor R3 close to 1 In an open emitter junction of transistor VT1, so the “obretenii” emitter transition of transistor /T2 no breaks. When a negative half-cycle of the semiconductor triode switch roles.
Resistor R4 limits the base current through the transistors. And R7,being the collector load /T1 and VT2, a zero sets the potential at the input 1 of logic element DD1.1 (closed semiconductor triodes).
Electrical schematic of a homemade device (symbol ” 1 “is applied to the legend of the “common” wire, which is grounded in the proposed technical solution is strictly prohibited).
A printed circuit Board (a) and the location of parts (b) during the installation.
When Iset is close to zero, the current through the above-mentioned transistors does not flow because the voltage drop across the resistor R3 is not enough for their release. So, IR is equal to the voltage at the negative output of the power supply. The result is a short negative pulse corresponding to the beginning of each half-cycle of the network.
When enabled, input 2 DD1.1 high voltage level. Therefore, negative pulses arriving at the first input, the inverted logical element and through the emitter-follower (transistor /T5) the capacitor C8 charged almost to the voltage of the power supply.
The discharge is through a chain and R8R9 /T4. If the voltage drops to the threshold elements DD1.2, DD1.3 switch. “The decline” by doing with DD1.3, differentialsa chain С9R12 and in the form of a pulse of the duration about 12 µs includes (through the inverter DD1.4 and the transistor /T6 operate as a current amplifier) triac VS1.
Variable resistor R9 regulate the discharge duration of the capacitor C8, and thus change the moment of switching of the triac and the effective voltage at the load. The capacitance of the capacitor C9 determines the pulse duration of opening of the triac, the resistor R12 sets the potential at the input of logic element DD1.4. As for the Zener diode VD6, it ensures reliable starting of the device.
The inverter DD2.1 and the flip-flop DD3.1 assembled a host of on — off controller. From the same node are control signals to other parts of the scheme. The transistor VT4 is used to soft start the load and the elements DD2.2, DD2.3 together with VT7 and VD5 provide the backlight button.
When you first turn on the device or after a loss of voltage chain C3R2 generates a positive pulse at the R input of logic element DD3.1, setting it to the zero state in which the load is turned off. Performing the function of T-flip-flop, DD3.1 responsive to a positive differential voltage at input C. each time the emergence of such a differential the logic element changes its state to the opposite.
The chain of R1C1 suppress contact bounce, and its composition resistor R1 sets the desired potential at the input of the inverter DD2.1. Clicking on any of the buttons SB causes a positive differential voltage at the output of the element, switching the trigger DD3 in a single state. The resulting high signal goes to DD1.1, allowing his work. This creates favorable conditions for charging the capacitor C6 to 10 V through a resistor R6. The channel resistance of the transistor VT4 gradually decreases and 5-7 with reaches its minimum.
But the channel of the transistor VT4 is connected in series with a resistor R9 to the circuit discharge of the capacitor C8, and with increasing voltage to the gate of the VT4 load power will gradually increase to the level set by the resistor R9.
Resistor R10 creates a minimum negative bias on the gate to complete the locking of the regulator at zero resistance of the resistor R9. The need for such offset is due to the fact that after switching on the device must not be time for emergency situation when the load is still de-energized, and capacitor C7 performs the AC-voltage, the role of the shunt to the resistor R10, excluding it from the discharge circuit of the above C8.
Low-level inverse output of the trigger closes VT3, and prohibits switching of the inverters DD2.2, DD2.3. On baae transistor VT7 is maintained high level and the led VD5 is not lit.
Next press any of the buttons SB again switches the trigger in the zero state. A logical “0” output 13 trigger, prohibit the switching of the elements DD1.1, its output will be set high. Consequently, the transistor VT6 is permanently open, the capacitor C8 is charged and the load (e.g. light bulb) is de-energized. The same logical unit, coming from the output of the trigger 12 through current limiting resistor R6, will open the transistor VT3, via which the capacitor C6 is discharged, and provide training devices to the new inclusion.
A high level at the inputs 13 and 9 logic elements DD2.2, DD2.3 will allow them to pass negative pulses from the transistors VT1, VT2. These pulses open for a short time the transistor VT7, and the led lights up. Resistor R13 limits the average current through VD5 (to not overload the power source, otherwise issued to them the voltage starts to fall).
Almost all homemade controller (with the exception of connectors, fuse, triac and LEDs) is mounted on the PCB of one-sided foil fiberglass.
Transistors VT1, VT2, VT7 can be a low-power silicon, but not necessarily the structure of p-n-R, with a coefficient of current transfer more than 100. Almost the same requirements and to the choice of VT3, VT6, except for the structure. She’s here p-p-n. As VT5 acceptable solid state triode series КТ201 (with any alphabetic index at the end). You can use silicon low-power transistor structure n-p-n, having secured such a change enabling VD4 (figure is highlighted by a dashed outline). The diode protects the emitter transition from the breakdown reverse voltage, which appears after closing of the transistor VT5. On the spot VT4 work equally well all the FETs of the series КП305.
Not very strict criteria and the selection of other electronic components. Zener diode VT3 is no exception — you can use any voltage stabilization 10 V. the Diodes of the series КД509, KD510, KD522. Capacitors: C5, type K50 — 24, K50 – 29; C6, C7 – K53; Sz – any oxide; C4, C9 — silicon; C1, C2, C8 — metallized types K70 — К78 (and S2 rated operating voltage not less than 250V). A variable resistor may be of any type, its housing in order to connect the shielding with the “plus” wire of the power supply circuit. Fixed resistors — C2 — 33H, MLT. As for fuse FU1, it is, of course, must meet the current specific load.
The debug device is reduced to the selection of the resistor R10 according to the following procedure (paraphrased concisely).
Conclusion 2 elements DD1.1 is temporarily disconnected from the circuit and connected to the terminal 1. Installing R10 is a variable resistor 100 ohms, reduce the resistance to zero. Include a triac controller to the network and a minute or two wait when the “malaikottai” C2 will not charge to rated voltage 10V electrolytic capacitor C5.
Controlling the oscilloscope the shape of the pulses in the load, increase the resistance of the variable resistor — replacement R10 as long as the triac does not cease to open. Then a few times I turn off the load, ensuring existing controls to transistor /T4, the actuating properly, securely locked VS1. After that, a variable resistor replaced by a constant and restore the connection terminal 2 DD1.1 in accordance with the scheme.
Practice shows that installation and the selection of the resistor R11 can be achieved that the maximum resistance of the resistor R9 operating as a variable resistor, will correspond to zero load voltage. And to fully apply the load to minimize voltage drop on the triac, it is necessary to open after the start of the half cycle as quickly as possible. Hence, the pulse shaper of transition of mains voltage through zero needs to produce a sufficiently short pulses. To minimize them you should increase the resistance of the resistor R3 and R7 to pick up. Go the way of reducing the nominal value of R4 is undesirable is energiantuotanto.
And again. The establishment and practical application of the triac controller can not forget that connecting a device to the network for all, including a variable resistor, it is under high voltage. But AC 220 V is not a joke, even if the housing of the electronic handmade is made of a good insulating material.
A. RUDENKO, Kharkov
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