Application Circuit of LM158/LM258/LM2904 Dual Operational Amplifier

Photocoupler

Application Circuit of LM158/LM258/LM2904 Dual Operational Amplifier

The LM358 includes two independent, high-gain, internal-frequency-compensated dual op amps for single-supply operation with a wide supply voltage range. It is also suitable for dual-supply operation. Under recommended operating conditions, the supply current is The power supply voltage is independent. Its range of applications includes sense amplifiers, DC gain blocks, and all other single-supply op amps.

The LM358 is available in a packaged 8-lead dual in-line and patch package.

Internal frequency compensation

DC voltage gain is high (about 100dB)

Unity gain bandwidth (approximately 1MHz)

Wide supply voltage range: single supply (3-30V);

Dual power supply (±1.5±15V)

Low power current, suitable for battery power

Low input bias current

Low input offset voltage and offset current

Common mode input voltage range is wide, including ground

Differential mode input voltage range is wide, equal to the supply voltage range

Large output voltage swing (0 to Vcc-1.5V)

Infrared detection alarm

The alarm can detect the infrared rays emitted by the human body. When a person enters the monitoring area of ​​the alarm device, an alarm sound can be emitted, which is suitable for burglar alarms in important places such as homes, offices, warehouses, and laboratories.

working principle

The circuit principle of the device is shown in Figure 1. It consists 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, the 7th pin of IC3 returns to the high level output, and 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 a 9-12V DC power supply, stepped down by T, full-bridge U-rectified, C10 filtered, and the detection circuit is powered by IC5 78L06. The device is used for both AC and DC, and automatically converts without interruption.

Component selection and production

The list of components is shown in the table below.

Numbering name model Quantity Numbering name model Quantity
R1 resistance 47K 1 C10 Electrolytic capacitor 470u/25V 1
R2 resistance 1M 1 C11 Polyester capacitor 0.1u 1
R3 resistance 1K 1 VD1-VD5 rectifier diode IN4001 5
R4 resistance 4.7K 1 U Full bridge 2A/50V 1
R5, R6, R9, R12, R13, R15, resistance 100K (R12 is a linear trimming resistor) 6 VT1 Crystal triode 9014 1
R7, R10, R11, R17 resistance 10K 4 VT2 Crystal triode MPSA13 0.5A 30V 1
R8, R16 resistance 300K 2 VT3 Crystal triode 8050 1
R14 resistance 470K 1 IC1 Infrared sensor Q74 1
R18 resistance 2.4K 1 IC2 Operational Amplifier LM358 1
R19 resistance 220Ω 1 IC3 Comparators LM393 1
R20 resistance 560K 1 IC4 Three-terminal regulator 78L06 1
C1, C2, C6, C8, C9 Electrolytic capacitor 47u/16V (C2, C5 for cesium electrolysis) 5 BL Electromagnetic oscillator U=12V 1
C3, C5 Electrolytic capacitor 22u/16V 2 T Power Transformers 12V 5W 1
C4 Polyester capacitor 0.01u 1 S Toggle switch
1
C7 Electrolytic capacitor 220u/16V 1



IC1 uses imported device Q74 with a wavelength of 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.

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.

At the time of production, the Fresnel lens is installed in front of the end of the IC1 sensor. Since the human body's active frequency range is 0.1-10 Hz, it is necessary to multiply the frequency of human activity with a Fresnel lens.

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