When the human body touches the touch panel in the drawing, the electromagnetic induction signal is also generated on the touch panel, and the signal enters the IC1 (741) high-gain operational amplifier through the capacitor C1 and the resistor R2, and is amplified from the 6-pin output. And through C2, D1 into the voltage comparator composed of Ic2 (CA3140) op amp. When the input pin 3 of IC2 receives the signal amplified by IC1, the transistor T1 is turned on. The piezoelectric buzzer PZ1 emits a sound. At the same time, the LED 1 is illuminated to remind people to pay attention. The circuit power supply is +12V and can be powered by the AC adapter.
Mount the circuit on a regular PCB. Then put the PCB into a small box. The touchpad is placed outside the small box and connected to the circuit input stage with a certain length of shielded wire. The size of the touchpad should not be too large. The circuit can still work normally.
High-sensitivity touch alarm circuit composed of uA741 and CA3140:
1. Each port of the Ethernet Switch is directly connected to the host, and generally works in full duplex mode.
2. The switch can connect to many pairs of ports at the same time, so that each pair of hosts that communicate with each other can transmit data without conflicts like an exclusive communication medium.
3. The user monopolizes the bandwidth of the transmission media. If the bandwidth from one interface to the host is 10 Mbit per second, then the total capacity of a switch with 10 interfaces is 100 Mbit per second. This is the biggest advantage of the switch.
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