Metal Detector Circuit Diagram Using IC555

Description

Figure shows the circuit of the Metal Detector . Here I have used a coil and sometransistor switching and a 555 mono stable multi vibrator for making this circuit . Use a 22nH toroid coil at the L1 .Part list and applications are showing below .

Part List

Component No: Value Usage

R1 1.5k Oscillation

R2 10k Base Biasing

R3 100K Emitter Load

R4 10K Base Biasing

R5 1K Current Limiting

C1 103PF Discharging

C2 103PF Noise Grounding

C3 100PF Oscillation

C4 1MF Coupling

Q1 BC548 Switching

Q2 BC548 Switching

L1 22nH Oscillation

B1 6V Sound

U1 NE555 Mono Stable

Applications: Metal Detector

Seven Segment Counter Display Circuit

Here is the circuit diagram of a seven segment counter based on the counter IC CD 4033.Thiscircuit can be used in conjunction with various circuits where a counter to display theprogress adds some more attraction.

IC NE 555 is wired as an astable multivibrator for triggering the CD 4033.For each pulse theout put of CD 4033 advances by one count.The output of CD 4033 is displayed by the sevensegment LED display LT543.Switch S1 is used to initiate the counting.Diode D1 prevents therisk of accidental polarity reversal.

Voltage doubler circuit using NE555

Description.The circuit diagram of a very simple voltage doubler using NE555 timer is shown here. HereIC NE555 is wired as an astable mutivibrator operating at around 9KHz. The base of the twotransistors (Q1 and Q2) is shorted and output of the astable multivibrator (pin 3) is connectedto it. When the output of astable multivibrator is low, Q1 will be OFF and Q2 will be ON.The negative terminal of the capacitor C3 will be shorted to ground through T2 and it will becharged to the input supply voltage. When the output of the astable multi vibrator is high,transistor Q1 will be ON and transistor Q2 will be OFF. The capacitor C4 will be charged tothe voltage across capacitor C3 plus the input supply voltage (that is double the inputvoltage). This is how the circuit works.

This voltage doubler circuit can deliver only up to 50mA output current and above thatcurrent limit the output voltage will be dramatically reduced. The actual output voltage willbe around 19V for a 12V DC input and also the output voltage will be a bit unstable.Anyway, for low current applications this circuit is well enough.

Circuit diagram.

Notes. The circuit can be assembled on a vero board. The output current should not be allowed to exceed 70mA. IC1 must be mounted on a holder.

Remote controlled switch for Appliance

Description.

Here is a versatile remote controlled switch that can ON or OFF any appliance connected toit using a TV remote.

IR remote sensor IC TSOP 1738 is used for receiving the signal. Normally when no signal isfalling on IC3 the output of it will be high. This makes Q1 OFF.When a signal of 38 KHzfrom the TV remote falls on the IC3 its output goes low.This makes Q1 conduct and anegative pulse is obtained at pin 2 of IC 1 NE 555. Due to this IC1 wired as a monostablemultivibrator produces a 4 Sec long high signal at its out put.This high out put is the clock forIC 2 which is wired as a Flipflop and of , its two outputs pin 3goes low and pin 2 goes high. The high output at pin 2 is amplified to drive the relay. For thenext signal the outputs of IC2 toggles state. Result, we get a relay toggling on each press onthe remote. Any appliance connected to this circuit can be switched ON or OFF.

Remote Controlled Switch Circuit Diagram with Parts List

Notes:

* Before wiring the circuit make sure that the carrier frequency of the TV remote you have is38 kHz.For that wire the sensor part only ,point your remote to the TSOP1738 and press anyswitch.If out put of TSOP1738 goes low then OK, your remote is of 38Khz type.Nothing toworry almost all TV remote are of this type.

* You can use any switch of the remote because for any switch the code only changes, thecarrier frequency remains same.We need this carrier frequency only.

* Assemble the circuit on a good quality PCB or common board.

* The appliance can be connected through NO or NC and C contacts of the relay .* Use a regulated 6V power supply for the circuit.

Rain alarm circuit

Description.

Here is a simple rain alarm circuit that produces an audible alarm when ever rain falls. Therain detector circuit is based on two transistors (Q1 & Q2) and a NE555IC (IC1). The twotransistors are wired as a switch which goes on when the base of Q1 is shorted to the positiveof the supply by the rainwater falling on the sensor. When the transistors are ON powersupply is available to the IC1 which is wired as an astable multivibrator. The output of IC1drives the speaker to produce an alarm.

Notes.

Assemble the circuit on a good quality PCB or common board. For assembling the sensor cut a 2×2 inch mica or plastic sheet. Arrange two single

stranded wires (running parallel 2mm close to each other) on the sheet as shown infigure below. Remember the wires have to be non-insulated. Sensor ready.

Now you can connect the points A&B on the sensor to corresponding points A&B onthe circuit.

POT R2 can be used to adjust the sensitivity. To test the circuit, make all connections and power up.Place a drop of water on the

sensor so that two wires become shorted through water. Now the alarm startssounding. If not adjust R2 to get the alarm sounding.

Use a 9v battery or a 9V regulated DC supply for powering the circuit.

Do not connect speakers less than8 Ohm impedance as load. It will damage the IC. A piezo buzzer can be also used instead of the speaker.

Sensor schematic.

Water level controller circuit

Description.

A simple but very reliable and effective water level controller circuit diagram is shown here.The circuit uses 6 transistors, 1 NE555 timer IC, a relay and few passive components. Thecircuit is completely automatic which starts the pump motor when the water level in the overhead tank goes below a preset level and switches OFF the pump when the water level in theover head tank goes above the full level.

Probe D is positioned at the bottom level of the tank while probes A, B and C are placed atfull, half and medium levels of the tank respectively. The level sensing part of the circuit isbuilt around transistors Q1, Q2 and Q3. When water level is below the quarter level probesA, B and C are open and the transistor Q1, Q2 and Q3 remains OFF. When the water levelrises and touches the probes the corresponding transistors gets biased and switches ON.Resistors R1, R2, R3 limit the bases current of corresponding transistors while resistors R4,R5, R6 limit their collector current. LEDs D1, D2 and D3 provide a visible indication of thecurrent water level.

When the water level goes below medium, transistor Q2 gets switches OFF and its collectorgoes positive. Collector of Q2 is connected to the base of transistor Q6 and as result transistorQ6 gets switched ON. Transistor Q5 will be also ON because its base in connected to thecollector of Q4 which is presently OFF. As a result when the water level goes below mediumrelay K1 gets energized and the pump is driven. The relay is wired in the latching mode sothat even if the water level goes above medium level the pump remains ON so that the tankgets completely filled. For wiring the relay in latching mode one set of N/O contacts is used.When relay is activated these contacts close which forms a short across collector and emitterof Q6. This makes the state of Q6 irrelevant to the operation of the relay and the relayremains ON as long as the transistor Q5 is ON. The only way to make the relay OFF is byswitching OFF Q5 and it is done automatically when the water level reaches the full level.

Collector of transistor Q1 is connected to the trigger pin (pin2) of IC1. When the water levelreaches full level the transistor Q1 gets switched ON. As a result its collector goes to groundlevel which triggers the IC1 which is wired as a monostable. The output of IC1 goes high forabout 1S. This makes the transistor Q4 ON for the same time and transistor Q5 whose base isconnected to the collector of Q4 is switched OFF cutting the supply to the relay. This makesthe motor OFF and it remains OFF until the water level again goes below the medium level.

Resistor R8 is a pull up resistor for the trigger pin of the NE555. Capacitor C3 couples thecollector of Q1 to the trigger pin of NE555 and facilitates edge triggering whenever thetransistor Q1 goes ON. A monostable circuit can be made edge triggered by connecting thetrigger signal to the trigger input pin through a capacitor. The capacitor blocks DC and passessudden changes. The circuit used here is termed as negative edge triggered because themonostable is triggered when ever the trigger input signal falls. R10 and R12 limits thecollector current of Q4 and Q5 respectively while R9 and R11 limits their base current. R13limits the base current of Q6 while D4 is a freewheeling diode which protects the switchingtransistors from voltage transients.

Circuit diagram.

The probes can be arranged as shown in the diagram above. Insulated Aluminium wires canbe used as the probes. The probes can be binded on a plastic rod and should be erectedvertically inside the tank. The length of the probes wires and the supporting plastic rod mustbe chosen according to the depth of the tank. Since DC is used in the level sensing sectionelectrolysis will occur in the probes and so the probes require small maintenances in 1 or 2month intervals. Using AC in the sensing section will completely eliminates the chance ofelectrolysis and I am presently working on such a circuit. You can expect it soon.

Notes.

Use 12V DC for powering the water level controller circuit.

The relay I used was a 5V/220 ohm relay and that’s why the current limits resistor R12 wasadded in the circuit. If you use a 12V relay then the R12 can be shorted.

Do not use a relay that consumes 500mA. Maximum collector current PN2222 can handle is600mA.

Use insulated single strand aluminium wires for probe and they can be arranged in the tankas per the probe arrangement diagram.

Use a holder for mounting NE555. The circuit can be assembled on a Perf board. K1 must be a double pole relay. The load current, voltage ratings of the relay must be selected according to the ratings of the

pump motor. The type number of the transistors used here are not very critical and you can do suitable

replacements if any type number is not available. Most of the components required for this project can be found inside your scrap box.

Power supply for this circuit.

A classic 12V regulated DC supply based on 7812 is shown above. A power ON indicatorLED is also added in the circuit.Resistor R13 limits the LED current. A small aluminiumheatsink can be fitted to the 7812 for better saftey.Small Al heatsinks for TO-220 package arereadily available in the market.

Mobile incoming call indicator

Description.

This circuit can be used to escape from the nuisance of mobile phone rings when you are athome. This circuit will give a visual indication if placed near a mobile phone even if theringer is deactivated.

When a call is coming to the mobile phone, the transmitter inside it becomes activated. Thefrequency of the transmitter is around 900MHz.The coil L1 picks up these oscillations byinduction and feds it to the base of Q1. This makes the transistor Q1 activated.Since theCollector of Q1 is connected to the pin 2 of IC1 (NE555) , the IC1 is triggered to make theLED connected at its output pin (pin 3) to blink. The blinking of the LED is the indication ofincoming call.

Circuit diagram with Parts list.

Notes.

The coil L1 can be made by making 150 turns of 36 SWG enameled copper wire on a5mm dia plastic former.Or you can purchase a 10 uH coil from shop if available.

The circuit can be powered from a 6V battery. Assemble the circuit on a good quality PCB. C1 & C3 are to be polyester capacitors. The electrolytic capacitor C2 must be rated 10V.

Missing pulse detector circuit using NE555

Description.

An NE555 timer IC connected as shown here can detect a missing pulse or abnormallylong period between two consecutive pulses in a train of pulses. Such circuits can be used todetect the intermittent firing of the spark plug of an automobile or to monitor the heart beat ofa sick patient.

The signal from the pick up transducer is shaped to form a negative going pulse and isapplied to pin 2 of the IC which is connected as a mono stable. As long as the spacingbetween the pulse is less than the timing interval,the timing cycle is continuously reset by theinput pulses and the capacitor is discharged via T1. A decrease in pulse frequency or amissing pulse permits completion of time interval which causes a change in the output level.

Circuit diagram with Parts list.

Notes.

Assemble the circuit on a good quality PCB or common board. The circuit can be powered from a 9V battery or 9V DC power supply. The IC1 NE555 could be mounted on a holder.

10 Minute timer circuit.

Description.

When ever you need to get an alarm or intimation after ten minutes ,the circuit shown belowcan be used.The circuit is nothing but a monostable multivibrator based on IC NE 555.Whenever you press the reset push button the green LED D1 glows after 10 minutes.

Circuit diagram with Parts list.

Notes.

Assemble the circuit on a good quality PCB or common board. The time duration can be set by varying the POT R5. The switch S1 can be a push button switch. The IC1 must be mounted on an IC base.

Brightness controller for low power lamps

Description.

The circuit given here can be used to control the brightness of low power incandescent lamps.The circuit is based on IC NE555 which is wired as an astable multivibrator with variableduty cycle. The output of IC is connected to the base of transistor Q1.The Q1 drives the lamp.The duty cycle of the multivibrator can be varied by varying the POT R4.As a result, thebrightness of the lamp varies according to the position of the POT R4.The same circuit can bealso used for speed control of small DC motors.

Circuit diagram with Parts list.

Notes.

The lamp L1 can be a 6V / 200 mA lamp. The switch S1 can be SPST ON/OFF switch. The IC1 must be mounted on a holder. The circuit can be wired on a good quality PCB or common board.