AUTOMATIC LIGHT EFFECTS
It is not always possible to place a large Christmas tree in a room; more often, a small branch is installed instead. In this case, it is decorated with small-sized lamps and LEDs, which can be connected to a machine made according to the diagram shown in the figure. Compared to devices that power one, two or three garlands, this machine is capable of managing seven garland loads. Moreover, it is permissible to use a single light source as garlands - a miniature incandescent lamp, for example, type SM or an LED of the AL 102, AL307 series. If desired, the load can be composed of two or three such sources connected in series. The machine is powered from a voltage source of 4.5...12 V, which uses a battery, two series-connected 3336L batteries or an AC power supply.
The machine uses two microcircuits. The DD1.1 trigger contains a pulse generator, the frequency (and duty cycle) of which can be changed using a variable resistor R1. Trigger DD1.2 is connected according to the circuit of a counting trigger - its inverse output (pin 12) is connected to input D (pin 9), and input C (pin 11) receives pulses from the overflow output P (pin 2) of the counter-decoder DD2.
The direct output of the trigger DD1.2 (pin 13) is connected to the input S (pin 6) of the counter-decoder DD2.
After the tenth pulse arrives at the input C of the counter-decoder, the state of the trigger DD1.2 changes to the opposite, which causes a change in the voltage at the outputs a-g of the counter-decoder, to which the loads are connected.
When using small-sized lamps, they are connected to the outputs of the DD2 microcircuit through a matching stage made on a transistor that allows the corresponding collector current. A limiting resistor Rog must be installed in the base circuit of the transistor, the resistance of which should ensure saturation of the transistor. If LEDs are used, each of them must be connected through a resistor Rн. Of course, you can attach both miniature lamps and LEDs to a Christmas tree branch - the lighting effect will only increase, especially with the appropriate coloring of the lamps and the selection of LEDs of different glow colors.
The duration of the glow of the garlands and the pauses between their lighting depends on the frequency of the pulses arriving at the counting input of the DD2 microcircuit. This frequency can be changed smoothly by variable resistor R1, and roughly by selecting capacitors C1 and C2.
Since the frequency of the generator depends on the total resistance of resistors R1 and R3, as well as resistor R2, connecting in parallel with them or in series with them (and possibly instead of R2 or R3) a thermistor that has thermal contact with one of the lamps of the garlands will give an interesting effect. Now the duration of the output state of the counter-decoder will change automatically and almost predictably. The same result can be achieved by switching on, instead of KD521A, diodes of the D2, D18 series or others that have a photoelectric effect, and placing them near incandescent lamp cylinders.
Instead of those indicated in the diagram, it is permissible to use K561TM2 (DD1) microcircuits. K176IEZ (DD2). Fixed resistors are MLT-0.125, their values are not critical for the normal operation of the device.
A. ROMANCHUK village. Novikovo, Sakhalin region.
SMALL TREE GARLANDS SWITCHES
Small-sized Christmas trees, including artificial ones, have become increasingly popular lately. But the choice of industrial lamp garlands for them is small, so you have to make them yourself. Moreover, one of the most important requirements for them is maximum safety, the absence of galvanic connection with the lighting network.
One of the options, in the author’s opinion, is to use the step-down transformer available to many radio amateurs to power a low-voltage, low-power radio. Typically, such a transformer on the secondary winding has an alternating voltage of 12 to 36 V, and the power of the transformer is 20...40 W. This voltage and power is quite enough to power garlands of miniature incandescent lamps of the SMN type - they can be easily painted in different colors and are easy to mount on the branches of a Christmas tree.
It should be noted that automatic switches, which use sharp and frequent switching on of garlands, and, as a rule, are not very durable due to the heavy operating conditions of the lamps and the rapid burnout of their filaments. A more reliable mode is in which the brightness of the lamps changes abruptly not from zero to maximum, but from 30...40 to 100%. It is on this principle that the switch is built, the diagram of which is shown in Fig. 2.
The switch contains three identical channels, each of which consists of a pulse generator on two logical elements and an electronic switch on a transistor. The generators are powered by a parametric voltage stabilizer R5VD1C1. Alternating voltage from the secondary winding of the transformer is supplied to garlands consisting of incandescent lamps connected in series. In this case, the current in the negative half-cycles of the voltage at the upper terminal of the secondary winding flows through all the garlands and diodes VD4, VD6, VD8. The garland lamps glow at no more than full intensity.
At the same time, voltage pulses from the generators arrive at the bases of the transistors. If the output of the generator has a high logical level (logical 1), the transistor will open and through it, as well as the diode VD3 for the first garland (VD5, VD7 for the second and third, respectively) current will flow during the positive half-cycle of the voltage at the same terminal of the secondary winding. The garland lamps will glow at full brightness.
Since the generators operate independently of each other and at different frequencies, the garlands switch independently of each other, which creates the illusion of shimmering light.
Most of the switch parts are placed on a printed circuit board made of single-sided foil fiberglass laminate. Instead of those indicated in the diagram, diodes KD102B, KD105B and similar ones are suitable, designed for pulsed current, approximately ten times the current consumption of incandescent lamps, zener diode VD1 - any low-power one with a maximum stabilization current of 20...30 mA and a voltage of 10...12 V. Constant resistors - MLT, S2-33, tuning resistors - SPZ-3, SPZ-19, SP4, SPO. Capacitor C1 is oxide K50-6, the remaining capacitors are KM, K73.
The choice of other parts largely depends on the voltage on the secondary winding of the transformer, the power and the number of incandescent lamps. If, for example, the voltage on the secondary winding is 36 V, and each garland uses 6.3 V lamps with a current consumption of 20 mA (six lamps connected in series) or 40 mA (two garlands connected in parallel, six lamps each), then diodes VD3-VD8 can be used as indicated above, and transistors - KT602A, KT602B, KT608A, KT608B, KT815B-KT815G or indicated in the diagram.
If the current consumed by the garlands is higher, you will have to add a transistor to each channel (Fig. 3) or install composite transistors in place of VT1-VT3, for example, KT829A-KT829G or similar, and also use diodes VD3-VD8, designed for the corresponding current.
With a lower voltage on the secondary winding, the resistance of resistor R5 should be proportionally reduced. Setting up the machine comes down to setting the switching frequency of the garlands using trimming resistors R2, R4, R8 (smoothly) or selecting capacitors C2-C4 (roughly).
I. NECHAYEV, Kursk
From the editor. Diodes VD3, VD5, VD7 protect the corresponding transistors from reverse voltage in the event of failure of diodes VD4, VD6, VD8. In most cases, these diodes do not need to be installed.
THREE GARLANDS SWITCH
The switch (Fig. 3) allows you to get the effects of “running lights”, “running shadow” and “accumulating” turning on and off the garlands. Repeated several times, one effect is replaced by another. The direction of switching the garlands also periodically changes to the opposite. The device uses a rarely used method to obtain the mentioned effects.
A master oscillator is assembled on the multiplexer DD1.1 and transistor VT1. The frequency of the pulses it generates can be smoothly varied by variable resistor R2 over a wide range. Building a generator on one of the multiplexers of the DD1 chip made it possible to reduce the total number of chip packages. The information inputs of the DD1.1 multiplexer are connected together, so for any signals at the address input it works as a repeater.
The signal from the output of the master oscillator is fed to a frequency divider by three, made on triggers DD2.1 and DD2.2. The duty cycle of the signal at the output of trigger DD2.1 is 3/2, and at the output of trigger DD2.2 - 3. An eight-bit counter assembled on the DD3 chip is connected to one of the outputs of the frequency divider.
A three-bit reversible shift register is built on the DD4 chip. The role of the register information input is played by the DO and D3 inputs connected together. When the logical level is low, information is shifted to the right at the EL input, and to the left when it is high. The direction of switching of the garlands depends on the voltage level at this input. The combined clock inputs C1 and C2 receive pulses from the master oscillator.
The pulse sequence arriving at the register input is generated using the DD1.2 multiplexer. If code 0 is applied to the address input, high-level pulses with a duty cycle of 3/2 are received at the input of register DD4, their frequency is three times less than the frequency of the master oscillator. In this case, the sequence of lighting the garlands corresponds to the “running lights” effect. When code 2 is present at the address input, pulses with duty cycle 3 appear at the output of the multiplexer. In this case, a “running shadow” effect is formed. If the code at the address input is 1 or 3, the signal from the output of the first digit of the counter DD3.1 passes to the output of the multiplexer. The signal has a meander shape, and the pulse frequency is six times less than the frequency of the master oscillator. Such a sequence of pulses is necessary to obtain an “accumulating” switching on and off of the garlands.
Automatic change of effects and direction of switching of garlands occurs due to the fact that the address inputs of the multiplexer DD1.2, as well as the control input EL of the DD4 register, are connected to the high-order bits of the counter on the DD3 chip.
When the power is turned on, register DD4 contains random information, but no pre-setting is required, since during the first three periods of the generator this information is “pushed out” of the register.
Transistors VT2-VT4 and trinistors VS1-VS3 are used to assemble electronic keys that control garlands plugged into sockets X2-X4.
The device's power supply includes a step-down network transformer T1, rectifier bridges VD1 and VD2 and a stabilizer on the DA1 chip.
The switch uses digital microcircuits of the K155, K555, KR1533 series. Integrated stabilizer DA1, in addition to that indicated in the diagram, can be KR142EN5V. Transistors - any of the KT315, KT3102 (VT1), KT316, KT3107 (VT2-VT4) series. In place of the VD1 bridge there may be KTs402 or KTs405 with letter indices A, B, Zh, I, and in place of VD2 - any of these series. SCRs - KU201K, KU201L, KU202L-KU202N. LED HL1 - AL307 with any letter index. Capacitors - K50-35, K50-40. Fixed resistors - MLT-0.125, variable R2 - SPZ-4AM. Step-down transformer with a voltage on the secondary winding of 7...10 V at a load current of at least 300 mA.
Most of the parts are mounted on a printed circuit board made of double-sided foil fiberglass. Since the machine has a galvanic connection to the network, the board must be placed in a housing made of insulating material, on the wall of which sockets X2-X4 must be secured for connecting garlands.
A device correctly assembled from serviceable parts does not require adjustment. If it is necessary to change the frequency of the master oscillator, you should select capacitor C1 (the frequency is smoothly adjusted with a variable resistor R2). The sequence of alternating effects and the direction of switching of garlands can be changed by appropriately connecting the outputs of the frequency divider (DD2) and counter DD3 with the information inputs of the multiplexer DD1.2 and the EL input of the DD4 register.
A. SHITOV, Ivanovo
Analogue circuits
Garland switch
Figure 1.1 - Garland switch
The diagram of the first switch is shown in Fig. 1. This device controls two garlands consisting of small-sized red and green LEDs, and is designed to decorate a small Christmas tree.
A symmetrical multivibrator is assembled on transistors VT1, VT2, the switching frequency of which is determined by the values of resistors R1 - R4 and capacitors Cl, C2. For the ratings of these elements indicated in the diagram, the frequency is about 1 Hz. The collector circuits of the transistors include two garlands of LEDs HL1 - HL32. Diodes VD1, VD2 and resistors Rl, R4 are necessary to ensure recharging of capacitors C1 and C2. The power supply for the garland switch is made according to the circuit of a half-wave rectifier using a VD3 diode using a ballast capacitor C4 to dampen the voltage. Diode VD4 is necessary to recharge the capacitor at a positive wave (relative to the lower voltage in the network wire diagram), resistor R6 limits the current pulse when the device is connected to the network when the capacitor is discharged. Through resistor R5, capacitor C4 is discharged after the device is turned off from the network. Rectified voltage ripples are smoothed out by capacitor SZ. There is no zener diode in the power supply, and the voltage on the multivibrator elements is limited by the voltage on the turned on garland of LEDs, i.e. LEDs perform the function of zener diodes. Since at any moment one of the two garlands is necessarily turned on, the voltage on the capacitor SZ cannot exceed the voltage on the luminous garland.
The advantage of the scheme: ease of implementation.
Disadvantages of the circuit: low output power, the presence of only one garland switching mode.
This scheme is quite simple, but it also implements a fairly large number of lighting effects, such as “running shadow”, “running fire”, “paired switching on”, “alternating switching on and off”, etc.
Figure 1.2 - Automatic garland switch
The basis of the device is a four-bit shift register with parallel loading K555IR16. The register control unit consists of a K555IE7 binary counter and logical elements DD1.3 and DD3.1. The effect of “running lights” is achieved in one direction by simply shifting the code in the register, and in the opposite direction by parallel writing it to the register by one bit.
The master oscillator of the machine is assembled on elements DD1.1 and DD1.2. Pulse frequency 3-4Hz. It can be changed by selecting R1 AND C1. The machine can control not only LEDs, but also lamps powered from the network. To do this, they must be connected according to the following diagram.
Figure 1.3 - Connection diagram for lamps powered from the mains
Let's look at the operating features of this device. The inverting input of comparator DA2 receives sawtooth pulses with a frequency equal to double the network frequency. The non-inverting input of the comparator receives triangular pulses of infra-low frequency, which are generated by a generator assembled on the logic elements of the DD1 microcircuit. Elements D1.1, DD1.2 and resistors R10, R11 form a Schmitt trigger, which is part of the generator. Let's say that at the output of logic element DD1.3 there is a high level voltage, and capacitor C4 is discharged. In this case, through diode VD5 and resistor R11, capacitor C4 will be charged, and the voltage across it will increase. When it reaches the upper switching threshold of the Schmitt trigger, the latter will switch to the opposite state, and a low level voltage will be established at the output of element DD1.3. Now capacitor C4 will be discharged through the opened diode VD4 and resistor R10. When the voltage decreases to the lower switching threshold, the Schmitt trigger will again switch to the opposite state, and the pulse formation process will repeat. As a result, the voltage shape on capacitor C4 will be close to triangular. The effect of this voltage on the non-inverting input of the comparator leads to the formation of current pulses of varying duty cycle at the output of the comparator; these current pulses, flowing through the circuit of the control electrode of the triac VS 1, change the brightness of the garland lamps (they are connected to the “Load” sockets) from minimum to maximum and vice versa.
Zener diode VD3 is necessary in order to “raise” the sawtooth voltage to a level corresponding to the lower switching threshold of the Schmitt trigger. As a DA2 microcircuit, you can use, in addition to the one indicated in the diagram, comparators of the K521SAZ type. When using other types of comparators, you will have to use an output stage current amplifier. Transistors VT1, VT2 can be of any n-p-n structure. Replacing the remaining radio components, it seems, will not cause any difficulties.
Setting up the device consists of regulating the ignition and extinguishing speeds of the garland lamps using trimming resistors R10 and R11.
Advantages of the scheme: More modes than the first scheme, but less than our scheme; there are modes when all the lights are on or all are off, i.e. in this case there is no running fire.
Disadvantages of the circuit: The control circuit for the output thyristors does not provide for gating control pulses with the network zero voltage signal, i.e. the switch creates interference for electrical equipment, which increases the more powerful the load.
On New Year’s Eve you always want to decorate the Christmas tree with garlands, and even make sure that the garlands don’t just burn, but shimmer, blink and please the eye. Let's look at several simple garland switch schemes, including “running lights,” for a Christmas tree or just for home decoration. None of the circuits contain scarce parts or microcircuits. All schemes are simple and tested more than once. Let's start with the simplest switch, which can be assembled from the simplest parts.
Single garland switch
This switch uses a minimum of parts; it can be assembled “on the knee”.
Switch diagram of one garland
Single garland switch
The diagram shows:
- L1 - Christmas tree garland
- S1 - starter SK-220
- C1 - MBM capacitor 0.5 µF, 500 V
Circuit operation
When the circuit is connected to the network, a glow discharge occurs between the electrodes of the starter S1, and the electrodes begin to heat up. One of the electrodes is bimetallic; when heated, it bends and closes to a hard electrode, the L1 garland lights up, and the starter electrodes cool and open, and the glow discharge begins again. Capacitor C1 serves for slower and smoother switching.
Circuit details
Garland L1 should be designed for a power of no more than 40 W, it can also be a regular 220 V incandescent lamp.
S1 is a regular starter from a fluorescent lamp. but for 220V, starters from a lamp with 2 lamps with one starter (or with 4 lamps and two starters) will not work, there are 127V starters. The imported starter is designated ST 111 4-80W.
Capacitor C1 - any non-polar for a voltage of at least 300V, with a capacity of 0.1-2.0 µF. The switching frequency of the garland depends on the capacity.
You can also assemble several such circuits with capacitors of different capacities and connect several garlands, which will create an interesting effect.
Switch of two garlands
This switch uses a thyristor as the switching element.
Switch diagram for two garlands
Switch of two garlands
The diagram shows:
- D1 - diode D226B
- L1, L2 - Christmas tree garlands for 220V
- VS1 - thyristor KU201L
- R1 - MLT-2 resistor, 2.4 kOhm
- R2 - resistor MLT-0.5, 10 kOhm
- C1 - capacitor K50-12, 20 µF, 350 V
Circuit operation
This switch is best used with garlands or lamps of different wattages. If the garlands L1 and L2 are of the same power, then when the thyristor VS1 is closed they will burn at full intensity, and when the thyristor is opened, the garland L2 will go out and L1 will light up at full power.
Therefore, one of the garlands needs to be taken with higher power or connected, for example, instead of L1, two garlands in parallel, and instead of L2 - one garland of the same power. Then, with VS1 closed, the garlands are connected in series and L2 will light up due to higher resistance.
If L2 is removed, you get a thyristor switch for one garland.
When voltage is applied to the circuit, capacitor C1 begins to charge, the voltage on it increases, at a certain value (depending on the thyristor used), the thyristor opens, and the capacitor begins to discharge through resistor R1 and the thyristor, VS1 closes and the cycle begins again.
Circuit details
With the specified details, you can connect garlands with a power of no more than 80 W each.
To increase the power, you can replace the D226D diode with D245, D246, D247, and the thyristor should be replaced with KU202L(M,N).
The capacitor can be used K50-3 or another electrolytic for a voltage of at least 300 V. By changing the capacitance of the capacitor, you can achieve the required switching frequency.
Resistors can be taken of any type with similar ratings, with a power dissipation not less than the specified one.
To smoothly adjust the switching frequency, you can replace R2 with a series-connected constant resistor of 4.7-6.8 kOhm and a variable resistor of 22-100 kOhm. The variable can be taken like SP-1.
Switch of three garlands
This circuit is similar to the previous one, only it already uses three thyristors.
Three garland switch diagram
Switch of three garlands
The diagram shows:
- D1 - diode D232
- D2-D4 - diodes D226B
- L1-L3 - Christmas tree garlands for 220V
- VS1-VS3 - thyristors KU201L
- R1-R3 - MLT-2 resistors, 10 kOhm
- R4-R6 - resistors MLT-0.5, 2 kOhm
- C1-C3 - capacitors K50-35, 100 µF, 63 V
Circuit operation
The switching principle is exactly the same as the previous circuit. Only here feedback is added between the thyristors through diodes D2-D4. Diode D1 is used to rectify the mains voltage.
Circuit details
With the specified details, you can connect garlands with a power of up to 400 W each.
Diode D232 can be replaced with D231, D231A, D232A, D233, D245, D246, D247 and the like.
You can replace the remaining parts as indicated in the previous diagram.
The switching frequency depends on the ratings of R1-R3, C1-C3.
Switch for four garlands (running lights)
This switch controls four garlands and allows you to get the effect of running lights if the garlands are correctly placed in a certain order. The circuit is more complicated than the previous ones, but it allows you to smoothly regulate the switching frequency and the direction of movement of the running lights.
Four garland switch diagram
Four garland switch
The diagram shows:
- D1-D4 - diodes D302
- D5-D8 - diodes D226B
- D9 - zener diode KS630A
- VS1, VS2 - thyristors KU201L
- VS3, VS4 - KN102V dinistors
- R1, R5 - resistors MLT-0.5, 220 Ohm
- R2 - MLT-2 resistor, 15 kOhm
- R3, R6 - resistors MLT-0.5, 39 kOhm
- R4 - variable resistor SPO-0.5, 33 kOhm
- C1 - capacitor K50-12, 5 µF, 350 V
- C2 - MBM capacitor 0.05 µF, 160 V
- C3 - capacitor MBM 0.1 µF, 160 V
- L1-L4 - Christmas tree garlands
Circuit operation
The circuit is powered by a rectified and stabilized voltage of about 130 V. This is carried out by parts D1-D4, R1, C1, R2, D9.
When voltage is applied, capacitors C2 and C3 begin to charge, they are charged to the opening voltage of dinistors VS3 and VS4. The first to open is dinistor VS3, since C2 has a smaller capacity and is charged through a smaller chain of resistance. SCR VS1 opens and garland L1 or garland L2 lights up, it depends on what half-cycle of the mains voltage this happened.
Then the dinistor VS4 opens and, accordingly, the thyristor VS2, the garland L3 or L4 lights up (also depends on the polarity of the half-cycle). At the same time, capacitor C3 is discharged through the chain VS4, VS2, R5, creating a negative pulse on R5, the pulse arrives at C2 and VS3 closes, accordingly, the trinistor VS1 also closes, the garland L1 (or L2) goes out.
The ratings of the parts are selected so that C2 is charged in about 5 ms (which corresponds to a quarter of the period of the mains voltage), and C3 is charged in about 15 ms (3/4 of the period). Due to this, the garlands will switch with the mains frequency (50Hz). And since the opening phase of the thyristors does not coincide with the phase of the mains voltage, the “running lights” effect occurs. And the direction of movement and speed are regulated by variable resistor R4 - in the middle position of its engine there will be no effect of running lights, a little to the right or left and the lights will run in the appropriate direction, with a speed corresponding to the angle of rotation from the “middle point”.
Circuit details
With the specified details, the power of each garland should not exceed 60 W. To increase the power up to 200 W, you can replace diodes D5-D8 with D302-D304 or others with a maximum rectified current of 1A and a reverse voltage of at least 300 V. To increase the brightness of the glow, you can shorten standard 220V garlands by the corresponding number of bulbs (by about 20 %), so that the total becomes at least 180 V.
Diodes D1-D4 can be replaced with a diode bridge KTs405A(B,V,D) or others with a current of at least 1A and a voltage of at least 300 V.
Capacitor C1 can be any electrolytic one with a voltage of at least 300 V.
It is better not to change the remaining parts and their values; in this case, the device may not need to be configured.
You can take any thyristors designed for a reverse voltage of at least 300 V.
You can take any dinistors with an opening voltage of 20-80 V.
Capacitors C2, C3, any paper, metal, for a voltage of at least 160 V.
Any non-wire resistors, with ratings close to those indicated and with a power not lower than specified.
Device setup
We replace each of the resistors R3 and R6 with a chain of constant 18-22 kOhm and variable 47-100 kOhm. We set R4 to the middle position, the variable resistor of the chain replacing R3 to the minimum resistance. Using a variable resistor in the chain replacing R6, we stop the running lights (only two garlands should light up). Then, by slowly changing the resistance of both chains, we achieve a slow and uniform switching of the running lights.
Then we turn off the device, unsolder and measure the resulting resistance of the chains replacing R3 and R6 and solder in their place permanent resistors of the same resistance. Composite resistors can be used.
ATTENTION! Be careful when setting up and operating ALL devices discussed; the circuits contain HAZARDOUS voltage.
http://elektricvdome.ru
To create the “running fire” effect, you need to alternately switch at least three garlands. The switch diagram (first option) that controls three garlands is shown in Fig. The basis of the device is a three-phase multivibrator, made on three inverting logic elements of the DD1 microcircuit. Timing circuits are formed by elements R1-R3, C1-SZ. At any moment, at one of the outputs of the logic elements there is a high level voltage, which opens the transistor-triristor switch. Consequently, the lamps of only one garland are lit at a time. Alternately switching the lamps of the EL1-EL3 garlands allows you to get the “running fire” effect. The multivibrator can operate inverters of microcircuits of the K555 and K155 series. In the second case, the resistance of resistors R1-R3 should not exceed 1 kOhm. You can also use CMOS microcircuits (K176, K561), while the resistance of the timing resistors can be increased by 100... 1000 times, and the capacitance of capacitors C1-SZ can be reduced by the same amount.
Changing the switching frequency of the garlands can be done by changing the resistance of resistors R1-R3. It is difficult to control them at the same time (the industry does not produce built-in variable resistors for widespread use). This is a disadvantage of this garland switch.
In Fig. A diagram of a garland switch (second option) with an adjustable speed of movement of the “running fire” is shown. A generator of rectangular pulses is assembled on logic elements DD1.1, DD1.2, the repetition rate of which is 0.2 ... 1 Hz. The pulses are supplied to the input of a counter consisting of two D-flip-flops DD2.1 and DD2.2 of the DD2 microcircuit. Due to the presence of feedback between element DD1.3 and input R of trigger DD2.1, the counter has a conversion factor of 3 and one of the transistors VT2-VT4 is closed at any time. If, for example, VT2 is closed, then positive voltage from its collector will be applied to the control electrode of the SCR VS1, the SCR will open and the lamps of the EL1 garland will light up. The switching frequency is controlled by variable resistor R3 of the generator.
In the device, K155 series microcircuits can be replaced with corresponding analogues from the K133 series. Transistors VT1-VT4 can be from the KT315, KT3117, KT603, KT608 series with any letters. SCRs VS1-VS3 can be of types KU201, KU202 with the letters K-N.
The source powering the device's microcircuits and transistors must be designed for a current of at least 200 mA.
The disadvantage of the switch is the need to use a transformer power supply. This is due to the relatively large current consumed by the K155LAZ and K155TM2 microcircuits.
The “running fire” devices described above have a common drawback: the logic of operation remains unchanged. The lamps in the garlands are switched only in the established order; you can only change the switching frequency. At the same time, it is desirable that the illumination be as varied as possible, without boring or tiring the eyesight. This means that it must be possible to change not only the duration of lamp burning, but also the order of their switching.
Literature - MRB 1202 Electronic devices for the home. Evseev A.N.
The proposed circuit was designed for use as a Christmas tree garland switch. However, this circuit can also be used for other purposes when periodic switching on of the load is required (automation systems, warning and alarm systems, etc.). This device is connected to a break in one of the wires going to the load, in this case a Christmas tree garland. Which, firstly, facilitates its operation, since only two wires are required to be connected to the device. Secondly, safety increases, since if these wires are shorted both outside and inside the device, a short circuit will not occur, the load will simply be constantly on. The proposed switch has two operating modes. The first is when the llamas of the garland periodically go out completely, the second is when the lamps do not go out completely, but their brightness decreases.
Scheme
Let's consider the operating principle of the circuit diagram of this device (Fig. 1). Using elements DD1.1 - DD1.6 of the k561ln2 microcircuit, a generator of rectangular pulses is assembled, the frequency of which is set by the value of resistor R1 and capacitor C2. In order to increase the output load capacity of the generator, its elements DD1.2 - DD1.6 are connected in parallel. When the generator output is at a high level, diode VD3 is locked, and thyristor VS1 connected to the diagonal of the bridge is open due to the current flowing through resistor R3 to its control electrode. As a result of this, the garland lamps are turned on. When the generator output goes low, diode VD3 opens and shorts the control electrode of thyristor VS1 to the cathode. The thyristor closes and the garland lamps go out.
If you close the contacts of switch SA1, then even with the thyristor VS1 closed, half-wave mains voltage will flow to the garland lamps through the diode VD8 and they will glow with a faint flickering light. That is, in this mode, the lamp circuits will not periodically go out completely, but their brightness will only decrease.
When thyristor VS1 is locked, the voltage flowing through resistor R2, stabilized by zener diode VD2 at 12 Volts, charges capacitor C1, and is used to power microcircuit DD1. And diode VD1 prevents capacitor C1 from discharging through resistor R2 when thyristor VS1 is open when the garland lamps are turned on.
Resistor R3 sets the current flowing through the control electrode of thyristor VS1; it should be selected with the highest possible resistance at which stable unlocking of thyristor VS1 is ensured in order to reduce the useless heating of this resistor. When replacing thyristor VS1 with a thyristor of another brand, for example, thyristors of the Ku202 series, which have a higher control electrode current, it may be necessary to reduce the value of resistor R3, increasing its power accordingly. It is not worth reducing the resistance of resistor R3 below 8 kOhm to avoid overloading the microcircuit.
Details
The DD1 k561ln2 microcircuit can be replaced with k562ln1 with appropriate correction of the printed circuit board, since these microcircuits do not have the same pin assignments. As diodes VD1, VD3, you can use CD102, CD103, CD521, CD522 with any letter index. Zener diode VD2 - ks191zh, ks210zh, ks212zh, ks213zh, ks508a. Diodes VD4 - VD8 - kd105, kd209 with any letter index. Capacitor C1 is k50-35 or similar imported, and C2 is type k10-17, k73-17 or similar imported. Switch SA1 of any type capable of withstanding the mains voltage and load current.
The arrangement of elements on the printed circuit board and its drawing are presented in Fig. 2 and Fig. 3, respectively. And the photo of the soldered printed circuit board is in Fig. 4.
The finished device was placed in a plastic electrical box. His photo is shown in Fig. 5. A domestically produced Christmas tree garland, consisting of 18 lamps of 13.5 Volts 0.16 Amperes, was connected to this switch. The frequency of switching on the garland can be changed by changing the value of resistor R1. The scheme was proposed by YRIT.