Mobile Incoming Call Indicator
Automatic Street Light Circuit
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Mobile Incoming Call Indicator
Description :
A cheap and simple automatic night light using few transistors and NE555 timer is shown here. The circuit will automatically switch on the AC lamp when night falls and the lamp will be automatically switched off after a preset time.
A cheap and simple automatic night light using few transistors and NE555 timer is shown here. The circuit will automatically switch on the AC lamp when night falls and the lamp will be automatically switched off after a preset time.
The working of this night light circuit very simple. An LDR is used as the sensor here. At day time the resistance of the LDR will be low and so do the voltage drop across it, the transistor Q1 will be in the conducting mode. When darkness falls the resistance of LDR increases and so do the voltage across it. This makes the transistor Q1 OFF. Base of Q2 is connected to the emitter of Q1 and so Q2 is biased on which in turn powers the IC1. NE555 is wired as monostable multivibrator that is automatically triggered at power ON. This automatic triggering is achieved with the help of capacitor C2. The output of IC1 remains high for a time determined by resistor R5 and capacitor C4. When output of IC1 goes high transistor Q3 is switched ON which triggers triac T1 and the lamp glows. A 9V battery is included in the circuit in order to power the timer circuit during power failures. Resistor R1, diode D1, capacitor C1 and Zener D3 forms the power supply section of the circuit. R7 and R8 are current limiting resistors.
Circuit diagram of automatic night light :
Notes :
- The circuit can be assembled on a vero board.
- Preset R2 can be used to adjust the sensitivity of the circuit.
- Preset R5 can be used to adjust the ON time of the lamp.
- With R5 @ 4.7M the ON time will be around three hours.
- The wattage of L1 must not exceed 200W.
- Heat sink is recommended for BT136.
- IC1 must be mounted on a holder.
Simple Electronic Fuse
Description :
Many electronic circuits related to fan speed controlling have been published here and this one is just another approach. The circuit diagram shown here is of 12V DC fan speed controller using the IC LM2941CT which is a low drop out 1A voltage regulator. The IC has a dropout voltage as low as 0.5 and has also many useful features like power supply reverse protection, thermal protection, short circuit protection etc. The maximum output current the IC can source is 1A.
The 12V DC supply is connected between the Vin (pin4) and ground (pin3) of the IC. The load, which is the fan, is connected across the Vout (pin5) and ground (pin3) of the IC. The network comprising of potentiometers R1, R2 and resistor determines adjust current (Iadj) of the IC. By varying the Iadj using the POT R2 we can adjust the output voltage of the IC and hence the fan speed.
The 12V DC supply is connected between the Vin (pin4) and ground (pin3) of the IC. The load, which is the fan, is connected across the Vout (pin5) and ground (pin3) of the IC. The network comprising of potentiometers R1, R2 and resistor determines adjust current (Iadj) of the IC. By varying the Iadj using the POT R2 we can adjust the output voltage of the IC and hence the fan speed.
Circuit diagram :
Notes :
- The circuit can be powered from 12V DC.
- The maximum possible load current is 1A.
- A heat sink is recommended for the IC.
- POT R1 can be used to adjust the minimum fan speed.
- POT R2 can be used to adjust the fan speed.
Automatic Street Light Circuit
Description :
This is a simple single chip metal detector circuit based on IC CS209A from the Cherry Semiconductors. A 100uH coil is used to sense the presence of metal. The IC CS209A has a built in oscillator circuit and the coil L1 forms a part of its external LC circuit which determines the frequency of oscillation. The inductance of the coil change in the presence of metals and the resultant change in oscillation is demodulated to create an alarm. The LED gives a visual indication too. This circuit can sense metals up to a distance of few inches.
Circuit diagram with Parts list :
Notes :
- Assemble the circuit on a general purpose PCB.
- The switch S1 can be a slide type ON/OFF switch.
- The IC must be mounted on a holder.
- The POT R1 can be used to adjust the sensitivity of the circuit.
This is a simple single chip metal detector circuit based on IC CS209A from the Cherry Semiconductors. A 100uH coil is used to sense the presence of metal. The IC CS209A has a built in oscillator circuit and the coil L1 forms a part of its external LC circuit which determines the frequency of oscillation. The inductance of the coil change in the presence of metals and the resultant change in oscillation is demodulated to create an alarm. The LED gives a visual indication too. This circuit can sense metals up to a distance of few inches.
Single Chip Metal Detetector
Description :
This is a simple musical alarm circuit which produces a musical tone when water or some conducting liquid comes in contact with the two sensor wires provided. The circuit is based on four transistors and one melody generator IC (M 3482).
When water comes in contact with the sensors wires A & B, the base of Q1 gets connected with the negative and it conducts. This makes Q2 and Q3 ON. When Q3 is ON the power is available for the music generator circuit and it starts producing 12 different melodies one after another. The music continues as long as there is water between the sensor wires. The POT R12 can be used as a volume controller.
Circuit diagram with Parts list :
Notes :
- Assemble the circuit on a good quality PCB or common board.
- Two insulated aluminum wires can be used as the sensor.
- The IC1 must be mounted on an IC holder.
- The speaker can be a 8 Ohm, ½ W tweeter.
Automatic Night Light Circuit
Description :
This circuit is a simple approach for converting a loud speaker into a microphone. When the sound waves fall on the diaphragm of a speaker, there will be fluctuations in the coil and there will be a small proportional induced voltage. Usually this induced voltage is very low in magnitude and useless. Here in the circuit the low voltage is amplified using transistors to produce a reasonable output. The transistor Q1 is wired in common base mode and produces the required voltage gain. The transistor Q2 is wired as an emitter follower to produce enough current gain. The voice quality of this circuit will not be as much as a conventional microphone but quite reasonable quality can be obtained. To set up the circuit, keep the preset R2 at around 10 Ohms and connect the battery. Now adjust R2 to obtain the optimum sound quality.
Circuit diagram with Parts list :
Notes :
- Assemble the circuit on a general purpose PCB.
- Power the circuit from a 9 V PP3 battery.
- A 3 inch speaker can be used as K1.
- All capacitors must be rated at least 15V.
- An 8 Ohm speaker or head phone can be connected at the output to hear the picked sound.
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