Classical application circuit principle and structure analysis commonly used in circuit design, take away

In electronic production and design, inductors with different parameters are often used. The inductance of these coils is not as easy to measure as resistors. Some digital multimeters have inductive measurement, but the measurement range is limited. The circuit measures the inductance value by the resonance method. The lower limit of measurement can reach 10nH, and the measurement range is wide. It can meet the measurement of inductance under normal conditions, the circuit structure is simple, the work is reliable and stable, and it is suitable for enthusiasts.

First, the circuit working principle The circuit principle is shown in Figure 1 (a).

Figure 1 Simple inductance measuring device circuit diagram

The core device of the circuit is the integrated voltage-controlled oscillator chip MC1648, which uses its voltage-controlled characteristic to generate a frequency signal at the output 3 pin, which can indirectly measure the LX value of the inductor to be tested, and the measurement accuracy is extremely high.

BB809 is a varactor. In the figure, potentiometer VR1 divides +15V. Adjusting the potentiometer can obtain different voltage output. This voltage can be added to varactor BB809 through R1 to obtain different capacitance. When measuring the measured inductance LX, just connect LX to the two points A and B in the figure, then adjust the potentiometer VR1 to make the circuit resonate. In the MC1648, the 3rd pin will output the oscillation signal of a certain frequency, and the frequency meter will measure the C point. The frequency value can be calculated by calculating the LX value.

Circuit resonance frequency: f0 = 1/2p

So LX = 1/4p2 f02C

In the formula, the resonant frequency f0 is the output frequency of the 3 pin of the MC1648, and C is the capacitance value of the varactor diode set by the potentiometer VR1. It can be seen that the value of LX needs to know the value of C first. To do this, it is necessary to calibrate the corresponding value of the potentiometer VR1 scale and the varactor.

In order to calibrate the capacitance between the varactor and the potentiometer, we have to make a standard square RF (radio frequency) inductor L0. As shown in Figure 6-7(b), the standard coil inductance is 0.44mH. During calibration, connect the RF coil L0 to both ends of A and B of Figure (a), adjust the potentiometer VR1 to different scale positions, measure the corresponding measured value at point C, and calculate the change according to the above resonance formula. The capacitance of the diode on different scales of the potentiometer VR1 dial. The attached table gives the corresponding relationship between the measured samples.

Second, the component selection

The integrated circuit IC can be selected from Motorola's VCO (Voltage Controlled Oscillator) chip. VR1 selects multi-turn high-precision potentiometers. Other components can be selected as shown in the circuit diagram.

Third, the production and debugging method production, you need to make a dial on the multi-turn potentiometer shaft, and bring the pointer. The RF standard coil is self-made according to the dimensions given in Figure (b). The circuit can be installed normally, and the potentiometer VR1 can adjust the corresponding relationship between multiple points of sliding and varactor diodes to ensure convenient measurement. This measurement method is an indirect measurement, but the measurement range is wide and the measurement is accurate, so it is desirable for electronic enthusiasts and laboratories to detect inductance. The device can be turned into a signal generator with an adjustable frequency if the inductor is fixed. Circuit 2 Three-digit display capacitance test table The majority of electronic enthusiasts have this experience. Although the medium and high-end digital multimeter has a capacitance test gear, the measurement range is generally only 1pF~20F, which often cannot meet the needs of users. , causing inconvenience to capacitance measurement. The three-digit display capacitance test table introduced by this circuit adopts four integrated circuits. The circuit is simple, easy to manufacture, digital display is intuitive, and the precision is high. The measurement range can reach 1nF~104F. Especially suitable for lovers and electrical maintenance personnel to make and use.

First, the circuit working principle The circuit principle is shown as in Fig. 2.

Figure 2 Three-digit display capacitance test chart circuit diagram

The capacitance meter circuit is composed of a reference pulse generator, a capacitance capacity time converter to be tested, a gate controller, a decoder, and a display.

The capacitance capacity time converter to be tested converts the capacity of the measured capacitance into a one-shot time td proportional to its capacity value. The reference pulse generator produces a standard cycle count pulse. The turn-on time of the gate controller is the one-shot time td. During the td time, the cycle count pulse is sent to the back counter through the gate, and the decoder drives the display to display the value. The period T of the counting pulse multiplied by the count value N displayed by the display is the one-shot time td. Since td is proportional to the capacity of the capacitor to be measured, the capacity of the capacitor to be measured is also known.

In Figure 2, the integrated circuit IC1B resistors R7~R9 and capacitor C3 form the reference pulse generator (essentially an unstable multivibrator), and the output pulse signal period T is related to R7~R9 and C3, fixed in C3. In the case of different selections of R7, R8, and R9 by the range switch K1b, three pulse signals having periods of 11 , 1.1 ms, and 11 ms can be obtained.

IC1A, IC2, R1~R6, buttons AN and C1 form a time-constant capacitor (substantially a one-shot circuit) to be tested. Pressing AN once, IC10B's 10 pin produces a negative narrow pulse trigger IC1A, and its 5 pin outputs a single high level signal. R3~R6 and the capacitor CX to be tested are single-stability components, and the one-shot time td=1.1 (R3~R6)CX.

IC4, IC2C, C5, C6, R10 form the gate controller and counter. IC4 is CD4553. Its 12-pin is the count pulse input terminal, and the 10-pin is the count enable terminal. CD4553 performs counting at low potential, and 13-pin is count clear. End, the rising edge is valid. When the AN is pressed, the 13 pin of IC4 gets a rising pulse, the counter is cleared, and the 4 pin of IC2C outputs a one-shot low level signal to the 10 pin of IC4, so IC4 counts the reference input from its 12-pin. The pulse is counted. When the one-shot time is over, IC4's 10 pin becomes high level, IC4 stops counting, and finally IC4 passes the counting result of one digit, ten digits, hundred digits by its 9-pin, 7-pin, 6 by time-sharing transmission. The foot and the 5 foot loop output the corresponding BCD code.

IC3 constitutes the decoder driver, which translates the BCD code sent from IC4 into a decimal digital pen segment code, and directly drives the seven-segment digital tube after R11~R17 current limit. The 15th, 1st, and 2nd pins of the integrated circuit CD4553 are digital selection outputs. The pulses are sent to the bases of the transistors T1~T3 through R18~R20 to make them turn on. The two parts are matched to complete the three-digit decimal. Digital Display.

The role of C7 is to generate a rising pulse on R10 when the power is turned on, and the counter is automatically cleared.

Second, in the component selection circuit, IC1 selects NE556; IC2 selects CD4001; IC3 selects CD4543; IC4 selects CD4553. The seven-segment digital tube can be used with a three-word common cathode digital tube. 850 (or other PNP type triode) is used for T1~T3. C1 should not be larger than 0.01F, and C3 should use small metallization capacitors. R3~R9 use 1/8W metal film resistor. There are no special requirements for other components, and you can select them according to the circuit labeling.

Third, the production and debugging method After the entire circuit is installed, it can be installed in a plastic box, and the digital tube and the range switch are mounted on the panel. In the production and debugging, the key is to call up the three standard pulse signals of 11s, 1.1ms and 11ms. When debugging, you need to adjust the resistance of three resistors, such as R7, R8 and R9, by means of an oscilloscope. These three pulse signals can be conveniently obtained. The resistance values ​​of R7, R8 and R9 in the circuit are experimental data for reference only. The rest of the circuit does not need to be debugged. As long as the good device is selected, the installation is correct, and the corresponding override is marked at the range switch, a practical, accurate and reliable digital capacitance meter can be obtained.

Fourth, the method of use

It should be noted that when using the 1pF~999pF range, the measurement result minus the distributed capacitance value is the accurate value of the measured capacitance due to the influence of the distributed capacitance. The range distribution capacitance value of the capacitance meter can be measured in this way, and the range is set in the range of 1pF to 999pF. When the measured capacitance is not connected, the AN button is pressed, and the measured result is the distributed capacitance value of the block. The value is generally about 10 pF after experimentation. The schedule lists the compositional relationships of the various ranges. Schedule

Circuit 3 Mains voltage bidirectional over-limit alarm protector The alarm protector can perform sound and light alarm when the mains voltage is higher or lower than the specified value, and automatically cut off the electrical power supply to protect the electrical appliance from damage. The device is small in size, full in function, simple in manufacture and practical.

First, the circuit working principle The circuit principle is shown in Figure 3.

Figure 3 Mains voltage bidirectional over-limit alarm protector circuit diagram Mains voltage one route C3 step-down, DW regulator, VD6, VD7, C2 rectification and filtering output 12V stable DC voltage supply circuit. Another route VD1 rectification, R1 step-down, C1 filtering, generating a voltage of about 10.5V on RP1, RP2 to detect the mains voltage change input signal. The gate IC1A and IC1B form an overvoltage detection circuit, IC1C is undervoltage detection, IC1D is a switch, IC1E, IC1F and piezoelectric ceramic piece YD constitute an audio pulse oscillator. The triode VT and the relay J constitute a protection action circuit. The red LED1 is used as the mains overvoltage indication, and the green tube LED2 is used as the mains undervoltage indication.

When the mains is normal, non-IC1A outputs a high level, IC1B, IC1C output low level, LED1, LED2 are off and no light, VT is off, J does not operate, the appliance is normally powered, B point is high, F4 output Low level, VD5 is on, C is low, the audio pulse oscillator is stopped, and YD is not sounding. When the mains is overvoltage or undervoltage, IC1B and IC1C have one output high level, which makes point A become high potential, VT saturation turns on, J energizes and pulls, disconnects the electrical power supply, and B point becomes Low potential, IC1D output high level, VD5 cut-off, reverse resistance is large, equivalent to open circuit, audio pulse oscillator starts, YD sounds alarm, and the corresponding LED emits light.

Second, the choice of components Integrated chip IC can choose CD74HC04 six inverter, diode VD1 ~ VD6 select IN4007, capacitor C1 ~ C6 select aluminum electrolytic capacitor, withstand voltage 400V, regulator tube selects 12V voltage regulator, relay J selects general 6V DC relay can be used, the resistor uses ordinary 1/8 or 1/4W carbon film resistor, the size can be as shown.

3. When debugging and debugging , use a voltage regulator to supply power, adjust the voltage to normal value (220V), use an incandescent lamp as load, make LED1 and LED2 go out, incandescent light, then adjust the regulator to Limit value or lower limit value, adjust RP1 or RP2 to make LED1 or LED2 just light, and the incandescent light is off, that is, the debugging is successful. All components can be installed in a small plastic box, two holes are fixed on the lid to fix the LED, a larger round hole is used to fix the piezoelectric ceramic piece, and a suitable cap is used to help the piezoelectric piece. The sound chamber makes it sound louder. Circuit 4 Infrared detection burglar alarm This alarm can detect the infrared rays emitted by the human body. When a person enters the monitoring area of ​​the alarm, it can sound an alarm. It is suitable for burglar alarms in important places such as home, office, warehouse, and laboratory.

First, the circuit working principle The circuit principle is shown in Figure 4. The device is composed of an infrared sensor, a signal amplifying circuit, a voltage comparator, a delay circuit and an audible alarm circuit. When the infrared detecting sensor IC1 detects the infrared signal radiated from the front human body, the weak electric signal is output from the 2 pin of the IC1, and is amplified by the first-stage amplifying circuit through the triode VT1, and then input to the operational amplifier IC2 through C2 for high gain. Low noise amplification, at this time the signal output by the IC21 pin is strong enough. IC3 is used as the voltage comparator. Its 5th pin provides the reference voltage from R10 and VD1. When the signal voltage output from IC21 pin reaches the 6th pin of IC3, the voltages of the two input terminals are compared. At this time, the 7th pin of IC3 is from the original The high level goes low. IC4 is the alarm delay circuit, and R14 and C6 form a delay circuit, which takes about 1 minute. When IC3's 7 pin goes low, C6 discharges through VD2. At this time, IC4's pin 2 goes low. It compares with IC4's 3-pin reference voltage. When it is lower than its reference voltage, IC4's The 1 pin becomes high level, VT2 turns on, and the alarm BL energizes to sound an alarm. After the infrared signal of the human body disappears,

Figure 4 Infrared detection burglar alarm circuit diagram IC3's 7 feet return to high level output, VD2 is cut off at this time. Since the voltage across C6 cannot be abrupt, it is slowly charged to C6 through R14. When the voltage across C6 is higher than its reference voltage, the 1 pin of IC4 becomes low level for about 1 minute, that is, the alarm is continued for 1 minute. . The power-on delay circuit consists of VT3, R20 and C8, and the time is also about 1 minute. Its setting is mainly to prevent the user from immediately alarming after starting the machine, so that the user has enough time to leave the monitoring site and prevent the power failure after the power failure. A false positive occurred while calling. The device is powered by 9-12V DC power supply, step-down by T, full-bridge U rectification, C10 filtering, detection circuit is powered by IC5 78L06, AC and DC, automatic and uninterrupted conversion.

Second, the component selection IC1 uses imported device Q74, the wavelength is 9-10um. IC2 uses the op amp LM358 with high gain and low power consumption. IC3 and IC4 are dual voltage comparators LM393, low power consumption and low offset voltage. In C2 and C5, it is necessary to use a tantalum capacitor with a small leakage electrode, otherwise the debugging will be affected. R12 is a key component for adjusting sensitivity, and a linear high-precision sealing type should be used. Other components can be selected as shown in the circuit diagram.

Third, the production and debugging methods are made, the Fresnel lens is installed in front of the end of the IC1 sensor, because the human body's active frequency range is 0.1-10Hz, the Fresnel lens needs to double the human activity frequency. Installation is correct, connect the power supply for debugging, let a person walk around 7-10m in front of the detector, adjust R12 in the circuit, so that the alarm can be alarmed. As long as the components are of good quality and the welding is correct, the other parts can work normally without debugging. The static working current of the machine is about 10 mA. After the power is turned on for about 1 minute, it enters the waiting state. As soon as someone enters the monitoring area, it will alarm, and the person will stop the alarm about 1 minute after leaving. If the sounder is changed to a relay to drive other devices, it is used for other control. Circuit 5 Non-Smoking Alerts The smoking ban warnings described in this example can be used in homes or in places where smoking is not appropriate (eg hospitals, conference rooms, etc.). When someone smokes, the no-smoking warning device will issue a "Please do not smoke!" language warning to remind the smoker to consciously stop smoking.

First, the circuit working principle The circuit principle is shown as in Fig. 5. The smoke-free warning circuit is composed of a smoke detector, a monostable trigger, a language generator and a power amplifying circuit, and the smoke detector is composed of a potentiometer RP1, a resistor R1 and a gas sensor. The monoflop is composed of a time base integrated circuit IC1, a resistor R2, a capacitor C1, and a potentiometer RP2. The speech generator circuit is composed of a voice integrated circuit IC2, a resistor R3-R5, a capacitor C2, and a Zener diode VS. The audio power amplifying circuit is composed of a transistor V, a boosting power amplifier module IC3, resistors R6 and R7, capacitors C3 and C4, and a speaker BL.

Fig. 5 Circuit diagram of the non-smoking warning device When the smoke sensor detects smoke at the end, the resistance of the two ends of A and B is large, the 2 pin of IC1 is high level (higher than 2Vcc/3), and the output of 3 pin is low. Ping, the voice generator circuit and the audio power amplifier circuit do not work, and the BL does not sound.

When someone smokes and the gas sensor detects smoke, the resistance values ​​of the two ends of A and B become smaller, so that the voltage of pin 2 of IC1 drops. When the voltage of the foot drops to VCC/3, the one-shot trigger Flip, IC1's 3 pin changes from low level to high level. After high level R3 current limit, C2 filtering and VS voltage regulation, 4, 2V DC voltage is generated, which is supplied to voice integrated circuit IC2 and crystal arm. After IC2 is powered on, it outputs a voice electric signal. After the electric signal is amplified by V and IC3, it pushes the BL to issue a "Please do not smoke!" voice warning sound.

Second, the component selection Rl-R7 selects 1/4W carbon membrane resistor or metal membrane resistor. Small linear potentiometers or variable resistors are available for RP1 and RP2. C1, C2 and C4 are all selected from aluminum electrolytic capacitors with a withstand voltage of l6V; C3 is a monolithic capacitor. VS selects 1/2W, 4·2V silicon Zener diode. V selects S9013 or C8050 type silicon NPN transistor for use. IC1 selects NE555 type time base integrated circuit; IC2 selects voice integrated circuit with "Please do not smoke!" voice information; lC3 selects WVH68 type boost power amplifier thick mode integrated circuit. BL uses 8Ω, 1-3W electric speakers. The gas sensor is a MQK-2 type sensor.

Third, the production and commissioning of the anti-smoking warning device, can be used as a smoke alarm to detect fire or as a detection of harmful gases, flammable gases. Adjusting the resistance of RP1 can change the heating current of the gas sensor (generally about 13OmA). Adjusting the resistance of RP2 can change the sensitivity of the monostable trigger circuit action. 6 circuit 555 uses a simple temperature controller circuit according to the circuit substrate is to use an automatic temperature controller 555 IC and a few external components thereof. Because the voltages at various points in the circuit are from the same DC power supply, there is no need for a regulated power supply with good performance, and the capacitor step-down method can work reliably. Circuit components are low in price, small in size, and easy to make in amateur conditions. The temperature automatic controller made by this circuit can be used for industrial heating and electric heating control of households with good effect.

First, the circuit working principle The circuit principle is shown in Figure 6.

Figure 6. Simple temperature controller circuit diagram with 555 time base circuit. When the temperature is low, the negative temperature coefficient thermistor Rt has a large resistance value. The 555 time base integrated circuit (IC) has 2 pin potentials lower than the Ec voltage. /3 (about 4V), the IC 3 pin outputs a high level, triggers the bidirectional thyristor V to conduct, and turns on the electric heater RL for heating, thereby starting the timing cycle. When the temperature of the thermistor Rt placed at the temperature measuring point is higher than the set value and the timing cycle has not been completed, the heater RL is cut off after the end of the timing period. When the thermistor Rt temperature drops below the set value, the triac V is turned on again, and the electric heater RL is turned on for heating. This will achieve the purpose of automatic temperature control.

Second, the component selection circuit, the thermistor Rt can use the negative temperature coefficient of the MF12 type or MF53 type, you can also choose different resistance values ​​and other models of negative temperature coefficient thermistor, as long as the temperature conditions required The relationship of Rt+VR1=2R4() can be satisfied. The larger the potentiometer VR1 can achieve a larger adjustment range, but the sensitivity will decrease. The triac V can also be selected according to the magnitude of the load current. There are no special requirements for other components, and parameters are selected according to the circuit diagram.

Third, the production and debugging methods The entire circuit can be installed on a circuit board, generally do not need to debug, the time interval is 1.1R2 × C3, should be selected smaller than the heating system's thermal time constant, but it can not be too small, otherwise it will Excessive RF interference is caused by the rapid turn-on or turn-off of the triac V. After installation and commissioning, it can be loaded into a small plastic box and the thermistor Rt can be taken out to the temperature measurement point. Circuit 7 uses an automatic temperature controller of the 555 time base circuit. This circuit can control the state of operation of the powered device by the change of temperature.

First, the circuit working principle The circuit principle is shown in Figure 7.

Figure 7: Automatic temperature controller circuit diagram using 555 time base circuit IC1 555 integrated circuit is connected to self-excited multivibrator, Rt is thermistor, when the ambient temperature changes, by resistor R1, thermistor Rt, The oscillation frequency composed of the capacitor C1 will change. The frequency change is sent to the 3 pin of the frequency decoding integrated circuit IC2 LM567 through the 3 pin of the integrated circuit IC1 555. When the input frequency falls exactly at the center frequency of the IC2 integrated circuit, 8 feet Output a low level, so that the relay K is turned on, the contacts are attracted, thereby controlling the on and off of the device to form a temperature control circuit.

Second, the choice of components IC1 selects NE555, μA555, SL555 and other time base integrated circuits; IC2 selects LM567 frequency decoding integrated circuit; VD selects IN4148 silicon switch diode; R1 selects RTX-1/4W type carbon film resistor. C1, C2, C3 select CT1 ceramic capacitor; C4, C5 select CD11-25V type electrolytic capacitor; K selects JZC-22F small medium power electromagnetic relay with working voltage 9V; Rt can use 51KΩ negative temperature coefficient thermal at normal temperature Resistor; RP can be WSW type organic solid fine-tuning variable resistor.

Third, the production and debugging methods In the production process, as long as the circuit is correct, this circuit is very easy to implement, if the component performance is good, you do not need to debug after installation. The circuit 8 adopts the CD4011 over-temperature monitoring automatic control circuit. The circuit has a simple structure and is easy to manufacture. A NAND gate and a thermistor constitute a measurement and control circuit and a siren sound circuit, and a relay is used as an execution circuit.

First, the circuit working principle The circuit principle is shown in Figure 8.

Figure 8 Using the CD4011 over-temperature monitoring automatic control circuit diagram Temperature measuring resistor RT is connected to the input terminal of the control gate D1, it and the resistors R1, R2 and RP through the RP partial pressure adjustment, so that the input level of the gate D1 is high , make D1 output low.

When in use, the thermistor RT is placed on the controlled device. When the temperature of the controlled device exceeds the maximum set temperature, the voltage of the D1 input becomes low due to the small voltage of the RT. After D1 is inverted to a high level, the high level is applied to the control terminal 8 of the multivibrator on the one hand, so that the multivibrator starts to oscillate, and after being amplified by the amplification tube, the siren sound is emitted by the speaker, and is also added to The base of VT1 is turned on, the relay is sucked, and the working power of the controlled device is disconnected through the normally closed contact of the relay; on the other hand, after the D2 is inverted to the low level, the LED of the LED is formed through the light. , LED lighting instructions.

Second, the choice of components IC1 selects CD4011; VD selects IN4001; VS is regulated voltage regulator 10V; VT1 selects 9013, VT2 selects V40AT; capacitor C is 2000P ceramic chip capacitor; relay is 4099 relay; RP selects 470K Ordinary adjustable potentiometer; resistors use 1/8 or 1/4W metal film resistors, BL selects 8Ω, 0.5W electric speakers.

Third, the production and debugging method The temperature measuring resistor RT is placed at the highest limit temperature, adjust the RP, so that the monitoring circuit emits a siren and the relay sucks and works, then the RT is cooled, the siren should stop. Otherwise, the RP should be adjusted repeatedly until it meets the requirements. Circuit 9 Digital Thermometer Circuit This circuit is a thermometer made by applying the integrated temperature sensor of AD590. It has the characteristics of simple structure, reliable use and high precision.

First, the circuit working principle The circuit principle is shown in Figure 9.

Figure 9 Digital thermometer circuit diagram 100V AC voltage through the transformer T1, rectifier bridge stack UR and capacitor C1, to obtain a DC voltage, and then through the adjustable regulator circuit μA723C to provide a stable operating voltage for the temperature sensor AD590. The AD590 temperature sensor is a new type of current output type temperature sensor consisting of multiple transistors and resistors with the same parameters. When a specific DC operating voltage is applied to both ends of the sensor, if the temperature of the temperature sensor is 1 degree Celsius, the output current of the sensor changes by 1 μA. The changing current of the sensor is converted into a voltage signal through the resistor R5 and the variable resistor RP2, and output to the digital meter, and the temperature change is displayed by a digital meter.

Second, the component selection integrated circuit IC selects the AD590 type temperature sensor. There are no special requirements for other components of this circuit, and can be selected according to the parameters given in the circuit diagram.

Third, the production and debugging methods can change the sensitivity of the output by changing the value of the resistor R5 and the variable resistor RP2. Circuit 10 Tropical fish tank water temperature automatic controller Tropical fish tank water temperature automatic controller uses a negative temperature coefficient thermistor as a temperature probe to automatically heat the fish tank through heating gas. The transient time of this circuit is small, which is beneficial to temperature control accuracy and is applicable to fish tanks of various sizes.

First, the circuit works The circuit diagram shown in Figure 10. After the diodes VD2~VD5 are rectified and the capacitor C2 is filtered, a voltage of about 12V is supplied to the control portion of the circuit. The 555 time base circuit is connected to a monostable flip-flop with a transient state of 11 s. Set the control temperature to 25oC, by adjusting the potentiometer RP so that RP + Rt = 2R1, Rt is a thermistor with a negative temperature coefficient. When the temperature is lower than 25oC, the resistance of Rt rises, and the 2 pin of the 555 time base circuit is low level, then the 3 pin changes from the low level output to the high level output, the relay K is turned on, and the contacts are attracted. The heating tube starts to heat until the temperature returns to 25oC, the resistance of Rt becomes smaller, the 2 pin of the 555 time base circuit is at a high level, the 3 pin outputs a low level, the relay K loses power, the contact is disconnected, and the heating stops.

Figure 1 0 Tropical fish tank water temperature automatic controller circuit diagram 2, component selection IC selects NE555, μA555, SL555 and other time base integrated circuits; VD1 selects IN4148 silicon switch diode; LED selects ordinary light-emitting diode; VD2~VD5 selects IN4001 type silicon rectifier Diode; Rt selects 470Ω MF51 type negative temperature coefficient thermistor at room temperature; RP selects WSW organic solid trimmer potentiometer for RW; RXT-1/8W type carbon film resistor for R1 and R2; CD11-16V type for C1 and C3 Electrolytic capacitor; C2 selects CT1 ceramic capacitor; K selects JZC-22F small medium power electromagnetic relay with working voltage 12V.

Third, the production and debugging method Temperature sensing probe with a plastic wire to connect the thermistor Rt, and then seal the solder joint with Rt with epoxy glue, so that it is not afraid of water erosion. This circuit is easy to implement as long as the circuit is correct during the manufacturing process. If the component performance is good, it can be used without debugging after installation. The circuit 11 adopts the simple long delay circuit of the 555 time base circuit. Compared with the general timing circuit, this circuit adds a diode VD1 at the 5th pin of the 555 time base circuit to make the timing time prolonged.

First, the circuit working principle The circuit principle is shown in Figure 11.

Figure 11 Simple long-delay circuit diagram using 555 time-base circuit When the button SB is pressed, the 12V power supply charges the capacitor Ct through the resistor Rt, so that the potential of the 6-pin is continuously raised, and when the potential of the 6-pin is raised to 5 feet At the potential of the circuit, the circuit reset timing ends. Since a diode VD1 is placed on the 5-pin string to increase the potential of the 5-pin, it has a longer timing than the normal connection (floating or grounding through a small capacitor).

Second, the selection of components 555 circuit selects NE555, μA555, SL555 and other time base integrated circuits; diode VT1, VT2 selects 4148 type silicon switch diode; resistor R1, Rt selects RTX-1/4W type carbon film resistor; capacitor Ct Electrolytic capacitors are selected; relay K can be selected according to the needs of the electrical equipment.

Third, the production and debugging method circuit timing can be adjusted by adjusting the parameter values ​​of the resistor Rt, capacitor Ct to change the length of the timing. The structure of the circuit is simple, as long as the welding according to the circuit diagram, the selected components are correct and can work normally. Circuit 12 Dual 555 Time Base Circuit Long Delay Circuit This circuit forms a timing circuit with a long timing time and adjustable timing by using two 555 time base circuits.

First, the circuit working principle The circuit principle is shown in Figure 12. The IC1 555 time base circuit is connected to a self-excited multivibrator with adjustable duty cycle. When the button SB is pressed, a DC voltage of 12V is applied to the circuit. Since the voltage of the capacitor C6 cannot be abruptly changed, the 2 pin of the IC2 circuit is at a low level, the IC2 circuit is in a set state, and the 3 pin outputs a high level, the relay When K is energized, contacts K-1 and K-2 are closed, K-1 contacts are closed to form a self-locking state, and K-2 contacts are connected to electrical equipment to control the function of turning on and off the electrical equipment.

At the same time, the IC1 555 time base circuit begins to oscillate, so the 3 feet alternately output high and low levels. When the 3-pin output is high, the capacitor C3 is charged through the diode VD3 and the resistor R3. When the 3 pin outputs low level, the diode VD3

Figure 12 The dual 555 time base circuit long delay circuit diagram is cut off, C3 is not charged, so C3 is charged only when pin 3 is high, so the charging time of capacitor C3 is longer. When the potential of the capacitor C3 rises to 2/3VDD, the IC2 555 time base circuit is reset, the 3 pin output is low level, the relay K is de-energized, the contacts K-1, K-2 are disconnected, and the initial state is restored. Prepare for the second time.

Second, the choice of components IC1, IC2 select NE555, μA555, SL555 and other time-based integrated circuits; VD1 ~ VD4 select IN4148 silicon-type switching diode, LED can use general LED; R1 ~ R5 select RTX - 1/4W type Carbon film resistors; capacitors C1, C2, C5, C6 select CT1 type ceramic capacitors, C4 selects CD11-16V electrolytic capacitors, C3 selects tantalum electrolytic capacitors with extremely small leakage current; RP can use WSW type organic solid fine-tuning variable resistors The relay K selects the JRX-13F type small electromagnetic relay with two sets of switching contacts.

Third, the production and debugging methods In the debugging, you can adjust the variable resistor RP to change the duty cycle of the square wave pulse output of the IC1 555 time base circuit 3, thus changing the timer timing. The structure of the circuit is simple, as long as the welding according to the circuit diagram, the selected components are correct and can work normally. Circuit 13 Accurate long delay circuit This circuit is composed of CD4060 timer base time circuit. The timing time base pulse generated by the circuit is divided by the internal frequency divider to output the time base signal. The frequency division circuit of the peripheral is divided to obtain the required timing control time.

First, the circuit working principle The circuit principle is shown in Figure 13. After power-on, the time-base oscillator oscillates and is frequency-divided to output the time base signal. IC2, which is a frequency divider, starts counting the division. When the count reaches 10, Q4 outputs a high level, and the high level is inverted to a low level by D1 to turn off VT, and the relay is powered off to cut off the operating power of the controlled circuit. At the same time, the D1 output is hungry low and is inverted to the high level by D2 and then applied to the CP terminal of IC2, so that the output high level of the output is maintained. After the circuit is energized to reset IC1 and IC2, the four output terminals of IC2 are low. The low level of the Q4 output is inverted by D1, the VT is turned on through R4, and the relay is energized and summed. This working state is the power-on state and the time-off state.

Second, the component selection IC1 selects CD4060, IC2 selects CD4518, IC3 selects CD4069; VT1 selects 9013, 9014; C1 selects

Figure 13: Accurate long-delay circuit diagram with ceramic chip capacitors, C2 and C3 select aluminum electrolytic capacitors with a withstand voltage of 15V; relays use model JZC-6F DC relays; RP selects 200K ordinary adjustable potentiometers; resistors use 1/8 or 1 /4W metal film resistors, SA1 and SA2 are small toggle openings.

Third, the production and debugging methods If you want to change the power-on disconnection, timing state, you can add a level of inverter between the output D1 and VT. The length of the timing can be adjusted by the RP, or by the connection of the output of the IC2 according to the correspondence of the second-decimal encoding. The timing range of this example circuit is: 3min~1h. Circuit 14 Digital Long Delay Circuits Generally, long delay circuits typically rely on electrolytic capacitors or high impedance circuits. The stability of such delay circuits is poor, and the accuracy of delay is not high. What is presented here is a digital long delay circuit that completely eliminates large electrolytic capacitors and high impedance circuits with high delay accuracy.

First, the circuit working principle The circuit principle is shown in Figure 14.

Figure 14 digital long delay circuit diagram

At the heart of the circuit is the integrated block MCI4521B, which is a 24-stage crossover circuit with an inverter that forms the oscillating circuit. If the trigger input is grounded or no signal is applied, the circuit enters a delay state, which is adjusted by the range switch X and 100KΩ potentiometer.

If X is connected to point A, the delay is 1 minute 40 seconds to 18 minutes 30 seconds, and X is connected to B, and the delay is 13 minutes 20 seconds to 2 hours 28 minutes. When X is connected to point C, the delay is 1 hour 47 minutes to 20 hours. The specific delay time is set by a 100KΩ potentiometer. If a longer delay is required, a large capacitor can be used instead of the 39nF capacitor. At this time, the delay can be more than one week. When a positive signal is applied to the trigger output, the divider in 4521B is reset.

Second, the component selection and production IC selects MCI4521B integrated circuit; Rl~R4 selects 1/4W metal film resistor for use; RP selects organic solid variable resistor. C1 uses ceramic chip capacitors. VD1 selects IN4004 type silicon rectifier diode for use; VD2 selects type IN4148 type silicon switch diode for use. VT selects BC337 type silicon triode; VS selects 1W, 15V silicon steady voltage diode. Connect the circuit as required, and basically work without debugging. The delay is reliable and stable. It is recommended to be powered by a 6~15V regulated power supply. Circuit 15 Cycle Operation Timing Controller This circuit can set the cycle time of the equipment and the time of each operation. It can let the equipment continuously cycle according to the set time. It can be applied to timing pumping, timing ventilation, timing ventilation, etc. Control the occasion.

First, the circuit working principle The circuit principle is shown in Figure 15.

Figure 15 Circuit diagram of the cyclic operation timing controller The circuit is stepped down by the capacitor C2 and the bleeder resistor R3. After the rectifier is rectified by the bridge IC2, the VD2 is regulated to obtain a DC voltage of about 12V to supply power to the IC1 and other circuits. IC1 is a 14-bit binary counter/divider integrated circuit that provides a clock pulse for IC1 timing by a clock oscillator of a certain frequency formed by the internal circuits of R1, R2, C1, and IC1. When the circuit is energized, it first enters the working gap waiting time of the device. IC1 internally realizes the delay by counting and dividing the clock pulse. When the timing time is up (according to the parameter in the figure, it is about 3 hours), the Q14 end of IC1 The output is high, so that the transistor V is turned on, and the relay KA gets a point to drive the controlled device to start working. At this point, IC1 starts to count the working time of the device again. When the timing time is up (about 20 minutes according to the parameters in the figure), the Q14 end of IC1 changes to low level again, so that V is cut off and the device stops working. At this time, IC1 is automatically reset, and the next timing is started again, so that the device can perform the timing cycle according to the set time. In the figure, VL is the work indicator.

Second, the component selection IC IC1 selects the 14-bit binary count/divider integrated circuit CD4066, can also use CC4066 or other digital circuit integrated blocks with the same function. IC2 selects 1A, 50V bridge stack, and can also be connected with four 1N4007 diodes. Transistor V uses NPN type triode 8050, and can also use domestic triodes such as 9013 or 3DG12. VD1 selects rectifier diode 1N4007; VD1 selects 1W, 12V silicon voltage regulator tube, such as 1N4742; VD3 ~ VD5 uses switching diode 1N4148; VL selects ordinary light-emitting diode. Resistors R1, R2, R4, R6 and R7 use 1/4W metal film resistors; R3 and R5 use 1/2W carbon film resistors. C1 selects polyester or monolithic capacitors; C2 selects polypropylene capacitors with a withstand voltage of 450V and above; C3 selects aluminum electrolytic capacitors with a withstand voltage of 16V. KA选用线圈电压为12V的微型继电器，触点容量根据受控设备的功率来确定。

三、制作与调试方法电路安装完成后，一般无需调试即能正常工作。当需要调节控制时间时，可调节R1、和C1的参数；也可改变IC1输出控制端（Q4～Q14）的位置来实现。 电路16 多级循环定时控制器该电路是一个三级定时控制器，可用于控制三台设备按照设定的时间依次循环工作，而且每台设备的工作时间可以独立调节，如果需要控制更多设备循环定时工作，只需要增加单元电路的数目即可。电路工作稳定、性能优良、性价比高、操作方便、适合个人和小型企业制作。可用于企业生产自动控制及彩灯控制，也可用于家用电器的趣味控制等。

一、电路工作原理电路原理如图16所示。

图16 多级循环定时控制器电路图电路中，由三个时基集成电路LM555组成三个单稳态电路，每个单稳态电路作为一个定时控制单元。三个单元共同完成三级循环定时控制功能。在接通电源的瞬间，由于555集成电路IC3和IC4的复位端4脚都接有时间常数较大的自动复位电路（分别由R4、C7和R7、C11组成），使IC3和IC4复位，它们的输出端3脚就输出低电平，使三极管T2、T3分别截止，继电器J2、J3释放。由于IC2复位端4脚直接接在电源正极，电源接通时电容C3上的电压不能突变，IC2触发端2脚得到触发电压，使其进入暂稳态，其3脚输出高电平，三极管T1导通，继电器J1吸合，J1触头可控制电器通电工作。同时电源经电位器VR1向电容C5充电，当C5上的电压升高到电源电压的三分之二（4V）时，IC2结束暂稳，其3脚输出低电平使三极管T1截止，继电器J1释放，其触头控制的电器断电停止工作。调节电位器VR1和电容C5的参数就可改变继电器J1的吸合时间。在IC2输出低电位的瞬间，由电容C6和电阻R3组成的微分电路，将在IC3的触发端2脚产生负尖脉冲，触发IC3进入暂稳态，其输出端3脚输出高电位，使三极管T2导通，继电器J2吸合，其触头控制的电器通电工作。调节电位器VR2和电容C9的参数就可改暂稳态时间。当第二单元暂稳态结束时，由电容C10和电阻R6组成的微分电路，将在IC4的触发端2脚产生负尖脉冲，触发IC4进入暂稳态，其输出端3脚输出高电位，使三极管T3导通，继电器J3吸合，其触头控制的电器通电工作。调节电位器VR3和电容C13的参数就可改暂稳态时间。当第三单元暂稳态结束时，经微分电路C3、R1去触发第一单元电路，这样依次循环来实现循环定时控制。

二、元器件选择电路中，IC1为三端集成稳压电路，选择MC7806型； IC2、IC3、IC4采用LM555时基集成电路；继电器J1、J2、J3要根据其控制电器的工作电流来选择，但继电器线圈额定电压应为直流6V。其他元器件没有特殊要求，按电路标注选择即可。

三、制作与调试方法整个电路检查接线无误，通电就能正常工作，电路中的VR1、C5；VR2、C9；VR3、C13的参数分别决定三个单元电路的定时时间，按电路参数定时时间约为1.1RC秒。 电路17 抗干扰定时器在运用555时基电路设计而成的定时器电路中，一般都将555时基电路连接成单稳态触发器，这样连接使得电路设计简单，只需要几个电阻器和电容器就能实现触发功能，但同时也存在外部对555时基电路2脚的干扰问题，本电路巧妙的利用了555时基电路4脚的强制复位的功能来实现抗干扰的定时器电路。

一、电路工作原理电路原理如图17所示。

图17 抗干扰定时器电路图在SB断开时，555时基电路的4脚通过电阻器R6与地相连，555时基电路被强制复位。此时，无论2脚受到多大的干扰，555时基电路都不工作。当按下按钮B后，电源通过二极管VD1加到4脚一个高电平，时基电路的强制复位功能解除，同时电源通过电阻器R1加到三极管VT1的基极上，使得VT1导通，电容器C2通过与VT1集电极相连后向IC电路的2脚输出一个低电平，IC翻转置位，3脚输出高电平，发光二极管点亮、继电器K得电，触点K-1闭合，插座对外供电，同时3脚的高电平通过VD2向4脚输出一个高电平使得电路自锁。当暂态结束后，电路翻回稳态，3脚输出低电平，继电器K失电，触头K-1断开，电路恢复到初始状态。

二、元器件的选择 IC1 555时基电路选用NE555、μA555、SL555等时基集成电路；R1~R7选用RTX—1/4W型碳膜电阻器；RP可用WSW型有机实心微调可变电阻器；C2、C4、C5、C6选用CT1型瓷介电容器，C1、C3、C7选用CD11—16V电解电容器；二极管VD1、VD2、VD3选用IN4148硅型开关二极管，VD4~VD7选用IN4001硅型普通整流二极管；继电器K可根据用电设备的需要选择；三端集成稳压器选用7809型三端集成稳压电路。

三、制作与调试方法在电路的调试阶段，电路的定时时间可以通过T=1.1（RRP＋R5）×C3估算，所以需要改变定时时间可以通过调节可变电阻器来实现。 电路18 采用555集成电路的简易光电控制器该光电控制器以555时基集成电路为核心，控制方式比较简单，使用可靠、寿命长，是一种价格低、体积小、便于自制的光电控制开关电路。可用于工业生产和家用电器等的控制。

一、电路工作原理电路原理如图18所示。无光照射时，光敏电阻RG的阻值很大（1MΩ以上），555时基集成电路的2脚、6脚电压约为电源电压的1/2（6V），3脚输出低电平，KA线圈无电，继电器释放。当有光线照射到光敏电阻RG上时，RG阻值会大幅下降（小于10KΩ），555的2脚、6

图18 采用555集成电路的简易光电控制器电路图脚电压降到电源电压的1/3（4V）以下，3脚输出高电平，KA线圈得电，继电器吸合，即使光照消失，KA仍保持吸合状态。

其后，如再有光线照射到光敏电阻RG上，则电容C1储存的电压通过RG加到555的6脚，使6脚的电压大于电源电压的2/3（8V），3脚输出低电平，KA线圈失电，继电器释放，电路恢复到原始状态。光敏电阻RG每受光照射一次，电路的开关状态就转换一次。

二、元器件选择及制作调试 IC用NE555集成电路， RG应选用亮电阻值≤10KΩ；暗电阻值≥1MΩ的光敏电阻，其他元件无特殊要求，各元件参数见电路图。该电路安装完后装入一小塑料盒内，将光敏电阻RG外露，不需要调试就可正常工作。 电路19 采用功率开关集成电路TWH8751的路灯自动控制器本例介绍的光控路灯，在白天不工作，夜晚能自动点亮，可用于街道或农村场院等场合。 一、电路工作原理电路原理如图19所示。该光控路灯电路由电源电路和光控电路组成，如图所示。电源电路由电源变压器T、整流二极管VDl-VD4和滤波电容器C组成。光控电路由光敏电阻器RG、电阻器R1、R2、可变电阻器RP、电子开关集成电路IC、继电器K和二极管VD5组成。交流220V电压经T降压、VDl-VD4整流和C滤波后，为光控电路提供+l2V工作电源。白天，RG受光照射而呈低阻状态，使IC的2脚(选通端)和4脚(输出端)均为高电平，其内部的电子开关处于截止状态，K不吸合，路灯EL不亮。夜晚，RC无光照射呈高阻状态，IC的2脚变为低电平，其内部的电子开关接通，EL点亮。调节RP的阻值，可改变光控的灵敏度。

图19 采用功率开关集成电路TWH8751的路灯自动控制器电路图二、元器件选择 Rl和R2选用1/4W金属膜电阻器或碳膜电阻器。RP选用实心可变电阻器。RG选用RG45系列的光敏电阻器。C选用耐压值为16V的铝电解电容器。VDl-VD5选用1N400l或lN4007型硅整流二极管。IC选用TWH8751型电子开关集成电路。K选用JZX-22F型(触头电流负荷为IOA)l2V直流继电器，可将其两组常开触头并联使用。T选用3-5W、二次电压为l2V的电源变压器。

三、制作与调试方法制作时可自制印刷电路板，也可使用万能印刷电路板，电路安装完成后，只要线路正确，一般无需调试即可正常使用。 电路20 采用双D触发器CD4013的路灯控制器本例介绍的光控路灯采用CD4013双D触发器集成电路，电路结构简单、容易制作、工作稳定可靠。

一、电路工作原理电路原理如图20所示。

图20 采用双D触发器CD4013的路灯控制器电路图该光控路灯电路由电源电路、光控电路和控制执行电路组成。交流220V电压经VD1~VD4整流、R1限流、C1滤波及VS稳压后，为光控电路和执行电路提供+12V工作电压。

白天，RG1和RG2受光照射而呈低阻状态，IC的S1端为低电平，R1端为高电平，1端输出低电平，VT处于截止状态，K处于释放状态，照明灯EL不亮。夜晚，RG1和RG2因无光照射或光照变弱而阻值增大，使IC的S1端变为高电平，R1端变为低电平，Q1端输出高电平，VT饱和导通，K通电吸和，其常开触头接通，EL点亮。

天亮后，RG1和RG2阻值下降，IC的Q1端又输出低电平，VT截止，K释放，EL熄灭。

二、元器件选择 IC选用CD4013或CC4013型双D触发器集成电路，VT选用8050或9014型硅NPN晶体管；RG1和RG2选用MG45系列的光敏电阻器；VD1~VD5均选用IN4007或IN4004型整流二极管。VS选用1W、12V稳压管，C1选用耐压25V的铝电解电容，C2选用耐压16V的铝电解电容，RP1和RP2选用普通电位器，R1选用2W的金属膜电阻器，R2~R4选用普通1/8或1/4W金属膜电阻器,K选用12V直流继电器，其触头电流容量视EL功率而定。

三、制作与调试方法电路元件选择正确，焊接无误后，即可使用，调节RP1和RP2的阻值，可以调节光控的灵敏度。 电路21 使用氖灯的单键触摸开关触摸式照明开关是一种非常实用的电子开关，用手触摸一下导电片，就能实现开关动作，使用方便可靠、电路简单、性能稳定、寿命长、节电效果明显。适合于爱好者自制。

一、电路工作原理电路原理如图21所示。

图21 使用氖灯的单键触摸开关电路图接通电源后，因C3、R5的微分作用，CD4017自动复位清零，插座为断电状态。当人手触摸M1后，氖灯发光，CDS的阻值减小使U1的CL端变为高电平，Q1由此输出高电平，使TRIAC导通点亮灯泡。当人手再一次触摸M1后，U17计数一次，Q1变为低电平，Q2输出高电平，依次类推，从而实现触摸开关功能。市电两输入线分别通过R8、R9接至触摸电路，因此安装时无需区分相线、零线。CDS的亮阻为20K，暗阻大于2MΩ。

二、元器件选择与调试 IC选用CD4017集成电路；可控硅选用BT13；VT选用9014，C1选用耐压值为400V的聚丙烯电容器；C2、C3均选用耐压值为25V的铝电解电容器，DW1选用1W、9V的硅稳压二极管。电阻选用1/4W或1/8W金属膜电阻器或碳膜电阻器。电路安装完成后，只要线路正确，一般无需调试即可正常使用。 电路22 双键触摸式照明灯本电路图使用两个触摸电极片，分别代替在实际生活中的开和关控制。

一、电路工作原理双触摸式照明开关电路如图22所示。VS与VD7构成了开关回路。当人触摸到M1（开）电极片时，人体通过R4、VD5整流后给IC NE555集成电路的2脚一个低电平信号（此时IC NE555集成电路接为RS触发器），输出脚3输出高电平，通过R3后触发VS的门极，VS导通，电灯点亮。当人触摸到M2（关）电极片时，人体通过R5、VD6整流后给IC NE555集成电路的6脚一个低电平信号，输出脚3输出低电平，R1提供的正向触发电压被R3通过集成电路的3脚对地短路，VS失去触发电压，当交流过零时即关断，电灯熄灭。

二、元器件选择 IC选用NE 555型集成电路；VS选用2N6565型普通塑封小型单向晶闸管；VD1~VD4选

图22 双键触摸式照明灯电路图用IN4007硅整流二极管；VD7选用6.2V、1W的2CW105硅稳压二极管；VD6、VD7选用IN4148型硅开关二极管；R1~R5均选用RTX—1/8W型碳膜电阻器；C1选用CD11—16V型电解电容；C2选用C＇I＇I型瓷介电容器。

三、制作与调试方法本电路结构简单、使用方便，只要焊接正确，选用元件正确都能正常工作。由于本电路负载的能力受到稳压管VD7的限制，所以负载的功率不宜大于60W。 电路23 触摸式延时照明灯本电路安装在家里的台灯上具有触摸自熄灭的功能，在过道或家里的卧室中，只要用手摸下台灯上的金属装饰，台灯就会自动点亮，几分钟后，它自动熄灭，对夜间照明提供了方便。

一、电路工作原理电路原理如图23所示。

图23 触摸式延时照明灯电路图在闭合SA时，台灯点亮，不受延时控制电路的控制。当断开SA时，如果触摸到电极片M时，通过R2将使得IC NE555集成电路的2脚的低电平触发端，3脚翻转为高电平，触发VS导通，台灯被点亮。此时，C3开始充电，当充电结束后，6脚变为高电平，3脚翻转为低电平，VS由于失去触发电流而处于截至状态，台灯熄灭。220V的交流电压经过C1、VD2、VD1、C2后，使得C2两端能输出12V的直流电压，供给集成电路IC。

二、元器件选择 IC集成电路选NE555；VS选用触发电流较小的小型塑封的MAC9A4A双向晶闸管；VD2选用12V、0.5W型2CW60稳压二极管；VD1选用IN4004硅整流二极管；R2选用RJ—1/4W型金属膜电阻器；R1、R3选用RTX—1/8W碳膜型电阻器；C1选用CBB/3—400V型聚丙烯电容器；C2、C3选用CD11—16V型电解电容器。

三、制作与调试方法本电路结构简单，只要焊接正确，元器件选用正确都能正常工作。通过调节R1、C3可以调节台灯发光的时间。 电路24 家用简易闪烁壁灯控制器现代家庭使用装饰性壁灯越来越普遍，但一般市售的壁灯都不会闪烁，本文所介绍的电路制作容易，用来改造一种市售的双头壁灯，可使两灯轮流发光、用于生日、节日、婚礼等喜庆场合，可增不少乐趣。

一、电路工作原理电路原理如图24所示。D1、D2、R1、C3组成简易电阻降压半波整流稳压电路，输出约12V直流电给IC供电。与非门Ⅰ、Ⅱ组成多谐振荡器，通过调节RP1、RP2可改变振荡频率。D3起隔离作用，防止调整RP1时影响RP2设定的时间。电路起振后，与非门输出端就交替输出高电平和低电平。当③脚输出高电平时，晶闸管VS1触发导通，A灯亮，此时④脚为低电平，B灯不亮；当③脚输出低电平时，晶闸管VS1关断，A灯灭，此时④脚为高电平，晶闸管VS2触发导通，B灯亮。C1、C2的作用是消除干扰，防止误触发。

二、元器件选择 IC为2输入四与非门CD4011，这里只选用其中两个门，另两个不用。VS1、VS2可用小型塑封晶闸管MCR100－8。灯A、B最好选用两种不同颜色的灯，这样闪烁起来更美观。图24 家用简易闪烁壁灯控制器电路图电阻选用1/4W或1/8W金属膜电阻器或碳膜电阻器，其它元器件均无特殊要求，可按图标示选用。三、制作与调试方法调试可根据自己的爱好先调节RP2，设定一个时间，再调节RP1使两灯闪光周期相等。取得合适的闪烁频率之后，再把线路板放在壁灯底座里即成。 电路25 自动应急灯电路本例介绍的自动应急灯，在白天或夜晚有灯光时不工作，当夜晚关灯后或停电时能自动点亮，延时一段时间后能自动熄灭。 一、电路工作原理电路原理如图25所示。

图25 自动应急灯电路图该自动应急灯电路由光控灯电路、电子开关电路和延

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