Archive for the ‘Switching Circuits’ Category

Hall Effect switch

Description. The circuit diagram shown here is of a Hall Effect switch. Hall Effect sensor IC DN6848 from Panasonic is the heart of the circuit. The DN6848 has a built-in Hall Effect sensor, Schmitt trigger circuit, power supply regulator and temperature compensation circuits integrated to a single chip. High sensitivity, low drift and excellent temperature stability of the DN6848 makes it well suitable for a variety of position, rotation and speed sensing applications. When the south pole of a magnet is brought near to the front face (face with type number marking) of the IC its output pin (pin 3)…

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Simple electronic fuse.

Description. This is perhaps one of the simplest electronic fuse circuit one can make. The circuit uses only one transistor, one SCR, one push button switch and two resistors. The working of the circuit is very simple. Initially the load current flows through SCR and resistor R1.The value of R1 is so selected that, the maximum load current multiplied by the resistance of R1 is equal to 0.7 volts. When the load current exceeds the maximum value the voltage drop across R1 becomes more than 0.7V and switches transistor Q1 ON. Now the transistor completely bye passes the load current…

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Fuse with status indicator.

Description. Here is the circuit diagram of a fuse that has an automatic status indicator. This circuit can be added to circuit that operates from 12V DC. As long as the fuse is intact, the LED D3 will glow continuously and when the fuse blows off the LED will start and continue blinking. The first part of the circuit includes an astable multivibrator built around transistors Q1 and Q2.The output of the multivibrator is coupled to the base of Q3 via diode D2.When the fuse is intact the base of Q3 will be pulled to a positive voltage by the…

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Touch switch using CD4011.

Description. A simple touch switch circuit using CD4011 is given here. The IC CD4011 is wires as a flip flop here. The 9, 13 pins of the IC works as the set and reset contacts respectively.CMOS ICs like 4011 require requires a very low current for controlling its gates. Since the pins 9 and 13 are connected to the positive via resistors R1 and R2, the logic gates of the ICs will be in high state. When we touch through the points A, B the gates of the IC will be closed and the output becomes low. This switches ON…

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Intelligent trailing switch.

Description. This is a very simple yet effective circuit in which the equipments connected at the so called trailing sockets will run only if the equipment connected at the control socket is switched on. For example, let’s connect a motor is connected to the control socket and a lamp is connected at the trailing socket. The lamp will glow only when the motor is running. When the load connected at the control circuit is switched on, the load current flows through the diodes and as a result there will a voltage drop across the diodes. This voltage drop is sufficient…

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Sound operated flip flop.

Description. Here given is a circuit in which the status of the output pins of a Flip Flop IC can be toggled by using sound. A condenser microphone is used for picking up the sound. The first two op-amps in the IC1 LM 324 is used to amplify the sound picked by the condenser microphone. The third op-amp inside LM 324 is wired as a level detector. When ever the voltage produced due to sound have a level more than that of the reference voltage at pin 5 of the third op-amp, its output (pin 7) goes high, triggering the…

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