Here is the DIY electronic cardlock security system that can be used as a lock to turn on dan turn off important electronic/electrical appliances. When card is inserted, depending upon the position of punched hole on the card, a particular appliance would be switched on. The card should be rectangular in shape with only one punched hole on it. Unused/broken card (ie expired credit card, student card etc) can be used for this circuit.

How The Cardlock Security System Works

The electronic cardlock security system circuit uses eight photo-transistors (T1 through T8) to sense the light. When there is no card in the lock, light from incandescent lamp L1 (40-watt, 230V) falls on all the photo- transistor detectors. Transistor T8 is used as enable detector for IC1 (74LS244). When light is incident on it, it conducts and its collector voltage goes low. This makes transistor T16 to cut-off, and its collector voltage goes high. This logic high on its collector terminal will inhibit IC1 as long as light is present on phototransistor T8.

IC1 will get enabled only when the card is completely inserted inside the lock mechanism. This arrangement ensures that only the selected appliance is switched on and prevents false operation of the system.

You can make these cards using a black, opaque plastic sheet. A small rectangular notch is made on this card to indicate proper direction for insertion of the card. If an attempt is made to insert the card wrongly, it will not go completely inside the mechanism and the system will not be enabled.

When card for any appliance (say appliance 1) is completely inserted in the mechanism, the light will fall only on photo-transistor T1. So only T1 will be on and other photo-transistors will be in off state. When transistor T1 is on, its collector voltage falls, making transistor T9 to cut-off. As a result, collector voltage of transistor T9 as also pin 2 of IC1 go logic high. This causes pin 18 (output Q1) also to go high, switching LED1 on. Simultaneously, output Q1 is connected to pin 1 of IC2 (ULN2003) for driving the relay corresponding to appliance 1. Similarly, if card for appliance 2 is inserted, only output pin 16 (Q2) of IC1 will go highmaking LED2 on while at the same time energising relay for appliance 2 via ULN2003. The same is true for other cases/appliances also.

The time during which card is present inside the mechanism, the system generates musical tone. This is achieved with the help of diodes D1 through D7 which provide a wired-OR connection at their common-cathode junction. When any of the outputs of IC1 is logic high, the commoncathode junction of diodes D1 through D7 also goes logic high, enabling IC3 (UM66) to generate a musical tone.

In this electronic cardlock security system circuit IC1 (74LS244) is used as buffer with Schmitt trigger. All outputs (Q1 through Q7) of this IC are connected to IC2 (ULN2003) which is used as relay driver. IC2 consists of seven high current relay drivers having integral diodes. External free-wheeling diodes are therefore not required.

When an input of this IC is made logic high, the corresponding output will go logic low and relay connected to that pin gets energised. This switches on a specific appliance and the corresponding LED.

Once a specific card is inserted to switch on a specific relay, that relay gets latched through its second pair of contacts. Thus even when the card is removed, the specific appliance remains on. The same holds true for all other relays/appliances as well. The only way to deenergise a latched relay after removal of the corresponding card is to switch off the corresponding switch (S1 through S7) which would cut-off the supply to the desired relay.

The +5V and +12V supplies can be obtained with conventional arrangement using a step-down transformer followed by rectifier, filter and regulator (using 7805 and 7812 etc), you may find the circuit design on power supply category.

This is the circuit diagram of car audio system anti theft security which can be effectively used to protect and secure your expensive car audio system from stealing. This simple circuit designed based on popular CMOS NAND chip CD4093,.

When the circuit is switched on via switch S1, the indicator LED1 will glow and the circuit state will be in the standby mode. LED inside optocoupler IC1 is lit as the cathode terminal is connected through the car audio (amplifier) body. As a result, the output at pin 3 of gate N1 goes low and disables the rest of the circuit.

Whenever an attempt is made to remove the car audio from its mounting by cutting its connecting wires, the optocoupler immediately turns off, as its LED cathode terminal is hanging. As a result, the oscillator circuit built around gates N2 and N3 is activated and it manages the “on” / “off” timings of the relay via transistor T2. (Relay contacts can be used to energize an emergency beeper, indicator, car horns, etc, if desired.)

Change the values of capacitor C2 to get different “on” / “off” timings for relay RL1 to be “On” / “Off”. With 100uF we get about 5 seconds as “on” and 5 seconds as “off” time. You may make your own experiments as needed.

Gate N4, with its associated components, forms a self-testing circuit. Normally, both of its inputs are in “high” state. However, when one switches off the ignition key, the supply to the car audio is also disconnected. Thus the output of gate N4 jumps to a “high” state and it provides a differentiated short pulse to forward bias transistor T1 for a short duration. (The combination of capacitor C1 and resistor R5 serves as the differentiating circuit.)

As a result, the buzzer in the collector terminal of T1 beeps to announce for a short duration that the safety circuit is intact. This period of “on” ring can be varied by changing the values ??of the capacitor C1 and / or resistor R5.

After construction, fix the LED and buzzer in dashboard as per your requirement and hide switch S1 in a in a convenient place. Then connect lead A to the body of car stereo (not to the body of vehicle) and lead B to its positive lead terminal. Take power supply for the circuit from the car battery directly.

Warning: This design is meant for car audios with negative ground only.

This laptop / notebook protector is powered by a 12V miniature battery used in remote control devices. IC TLO71 (IC1) is used as a voltage comparator with a potential divider comprising R2 and R3 providing half supply voltage at the non-inverting input (pin 3) of IC1. The inverting input receives a higher voltage through a water-activated tilt switch only when the probes in the tilt switch make contact with water.

When someone tries to take the laptop case, the unit takes the vertical position and the tilt switch breaks the electrical contact between the probes Immediately the output of IC1 becomes high and monostable IC2 is triggered. The low output from IC2 triggers the pnp transistor (T1) and the buzzer starts beeping. Construct the circuit as compactly as possible so as to make the unit matchbox size.

Make the tilt switch using a small (2.5cm long and 1cm wide) plastic bottle with two stainless pins as contacts. Fill two-third of the bottle with water such that the contacts never make electrical path when the tilt switch is in vertical position. Make the bottle leak-proof with adhesive or wax. Fix the tilt switch inside the enclosure of the circuit in horizontal position.

Fit the unit inside the laptop case in horizontal position using adhesive. Use a miniature buzzer and a micro switch (S1) to make the?compact gadget with this circuit. Maintain the laptop case in horizontal position and switch on the unit. Your laptop / notebookis now protected from stealing.

This is the circuit diagram of car anti-theft to protect and increase the security of your car, prevent your from stealing. This circuit is very simple, low cost and easy to built. When key-operated switch S2 of the car is turned on, 12V DC supply from the car battery is extended to the entire circuit through polarity-guard diode D5. Blinking LED1 flashes to indicate that the car protection circuit is enabled. It works off 12V power supply along with current-limiting resistor R4 in series.

When the car door is closed, door switch S1 is in “on” condition and 12V power supply is available across resistor R1. This condition will? prevent transistor T1 from conducting. In this position, anti-theft protection circuit is in sleep mode.

When someone opens the car door, switch S1 becomes “off” as shown in Image #2. As a result, transistor T1 conducts to fire relay-driver SCR1 (BT169) after a short delay introduced by capacitor C1. Electromagnetic relay RL1 energises and its N/O contact connects the power supply to piezobuzzer PZ1, which starts beeping to indicate that someone is make a try to steal your car. To reset the circuit, turn off switch S2 using car key. This will cutoff the power supply to the circuit, so the buzzer sound will be stopped.

Collect the circuit on an universal PCB and house in a little box suit to your car. Connect the switch S1 to th ecar door and keep piezobuzzer Pz1 at a suitable place in your car.

This is a easy built and very low-cost circuit purposed to protect your electronic appliances / devices, such as Personal Computer, TV, recording devices, refrigerator, and other devices during sudden tripping and resumption of home mains supply. Appliances like refrigerators and air-conditioners are more inclined to damage due to such conditions.

This electronic appliance protector circuit switches off the mains supply to the load as soon as the power trips. The electrical supply can be resumed only by manual intervention. Thus, the supply may be switched on only after it has stabilised.

The circuit involves a step-down transformer followed by a full-wave rectifier and smoothing capacitor C1 which acts as a supply source for relay RL1. Initially, when the circuit is switched on, the power supply path to the stepdown transformer X1 as well as the load is incomplete, as the relay is in de-energised state. To energise the relay, press switch S1 for a short duration. This completes the path for the supply to transformer X1 as also the load via closed contacts of switch S1. Meanwhile, the supply to relay becomes available and it gets energised to provide a parallel path for the supply to the transformer as well as the load.

If there is any interruption in the power supply, the supply to the transformer is not available and the relay de-energises. Thus, once the supply is interrupted even for a brief period, the relay is de-energised and you need to press switch S1 almost instantly (when the supply continues) to make it accessible to the load.

Very-short-duration (say, 1 to 5 milliseconds) interferences or changes won’t influence the circuit because of presence of large value capacitor which has to discharge via the relay coil. Therefore the circuit gives suitable security against flighty power supply conditions.

This easy to built circuit produces a warning beep when somebody crosses a secure area in your home or place of work. The transfer, hidden beneath the ground mat, causes the alarm whilst the individual walks over it.

The circuit makes use of a behaviorive foam because the switch. it may be? small items of behaviorive pads usually used to pack delicate ICs as antistatic cover. then again, you’ll be able to make the switch via coating conducting carbon ink on two small items of a copper-clad board.

When the circuit is in standby way of mode, transistor T1 does no longer conduct, for the reason that its base is floating. When the person walks, the switch is pressed and present flows via R1 and the transfer to provide certain bias to transistor T1. Transistor T1 behaviors and its collector voltage drops, which acts as a terrible cause input for the monostable stressed out around IC NE555 (IC1). 1 outputs a pulse of fifty-seconds period with preset values of R4 and C3. This pulse is carried out to the buzzer via transistor T2. The buzzer sounds a caution beep on unauthorised access. the pulse duration can also be modified to the required worth by changing the prices of R4 and C3.

Resistor R2 in the circuit makes the cause pin of IC1 high to stop fake causeing.

compile the circuit on a general purpose PCB and enclose in a plastic case. Use a 9V battery to power the circuit. connect the contactpad switch with the PCB and hide under the mat at the front. The PCB will also be fixed on the nearby wall.

Make the switch carefully the usage of conducting foam or copper clad lined with behavioring ink. place the two pieces with their habitsing surface going through each different. Solder moderately a skinny copper electrical wire and make sure that it makes contact while the two plates contact in combination on urgent. provide? 1cm rubber tabs between the plates to steer clear of touch in the standby mode.

This is the light fence schematic diagram uses LDR as the light sensing. The fundamental issue with the greater part of standard light sensors is that they require exact arrangement of light bar to quiet the circuit throughout standby mode. The circuit portrayed here is sensitive to the point that it will catch a moving individual at a separation of not many metres in sunshine or under electric lighting without unwieldy arrangement of light pillar. It requires essentially no set up, and may be basically put inside the viewable pathway of just about any light source incorporating encompassing sunlight or fluorescent electric light. The beep produced from the circuit will be noisy enough to locate the passage of an individual in the room or the secured region being protected.

The circuit utilizes a voltage comparator and a monostable clock to give the cautioning caution on distinguishing a moving individual. Ic uA741 (IC1) is utilized as a voltage comparator with two potential dividers in its upsetting and noninverting inputs. Resistors R1 and R2 give half-supply voltage of 4.5 volts to its transforming include (pin 2). LDR1 and preset VR1 structure an alternate potential divider to furnish a variable voltage include to the non-upsetting enter (stick 3).

In the event that Vr1 is fittingly balanced for the obliged light level, the yield of Ic1 will be high, which drives pnp transistor T1 out of conduction. This is because of the high potential at the base of T1. The emitter voltage of T1 will be high in this condition, which hinders Ic2 from wavering and Led1 from lighting. Ic2 is wired as a monostable clock. R6 and C2 give a preset time delay.

As an individual crosses the secured territory, his shadow will be sensed by LDR1 because of progress in the light power level and the voltage at the non-modifying include of IC1 will drop immediately. The yield of IC1 abruptly comes to be low, permitting T1 to direct. This triggers the monostable (IC2) and the caution sounds.

Build the circuit on a normal PCB and house in a plastic case. Keep LDR1 inside a dark tube to build its affectability. Alter preset VR1 until LED1 turns off at the specific light level. Keep LDR1 confronting the door of the room or the range to be ensured. Affectability of the circuit hinges on upon the correct change of VR1. Assuming that VR1 is effectively balanced, the circuit can locate a moving individual from a separation of around the range of three metres.

Good luck on your light fence project

Here the notebook anti theft protector circuit to secure your important netbook / notebook from stealing. Basically, this is a mini security alarm generator. Fixed inside the notebook case, it will definitely sound a noisy alarm when a person attempts to grab the notebook. This very sensitive circuit utilizes a homemade tilt switch to turn on the alarm system through tilting of the laptop computer case.

The circuit utilizes readily available parts and also can easily be constructed on a little piece of general-purpose PCB or a Vero board. This circuit is operated by a 12V miniature battery applied in remote control devices.

IC TLO71 (IC1) is utilized as a voltage comparator with a potential divider composed of R2 and R3 delivering fifty percent power supply voltage at the non-inverting input (pin 3) of IC1. The inverting input gets a higher voltage through a water-activated tilt switch only when the probes in the tilt switch make contact with water. When the tilt switch is maintained in the horizontal position, the inverting input of IC1 receives a higher voltage than its noninverting input and the output continues to be low.

The CD4538 (IC2) is utilized as a monostable multivibrator with timing factors R5 and C1. Considering the shown values, the output of IC2 continues to be low for a duration of three minutes. CD4538 is an accuracy monostable multivibrator free from incorrect triggering and also is much more reliable compared to the well-known timer IC 555. Its output comes to be high when power is turned on and it gets low when the trigger input (pin 5) receives a low to high transition pulse.

The circuit device is fixed inside the notebook case in horizontal position. In this position, water inside the tilt switch properly shorts the contacts, so the output of IC1 continues to be low. The alarm system generator stays silent in the standby mode as trigger pin 5 of IC2 is low. When a person attempts to grab the notebook case, the unit takes the vertical position and the tilt switch breaks the electrical contact between the probes. Instantly the output of IC1 comes to be high and monostable IC2 is triggered. The low output from IC2 triggers the PNP transistor (T1) and then the buzzer starts beeping.

Construct the circuit as compactly as feasible so as to make the unit matchbox dimension. Make the tilt switch working with a small (2.5 centimeters long and 1cm wide) plastic bottle with two stainless pins as contacts. Fill two-third of the bottle with water such that the contacts never make electrical path when the tilt switch is in vertical position. Make sure the bottle is leakproof with adhesive or wax.

Fix the tilt switch inside the enclosure of the circuit in horizontal position. Fit the unit inside the notebook case in horizontal position working with adhesive. Work with a miniature buzzer and a micro switch (S1) for making the device small and lightweight. Maintain the notebook case in horizontal position and turn on the circuit. Your notebook is right now secured.

The front end of the circuit carries a timer designed around the well-known binary counter IC CD4060 (IC1) to produce 15-minute time delay for the remaining circuitry to switch on. Resistors R3 and R4 and capacitor C2 will make Q9 output high right after 15 minutes. Diode D1 inhibits the clock input (pin 11) to maintain the output high till the electrical power is switched off. Blinking LED1 signifies the oscillation of IC1.

The high output from IC1 is utilized to enable reset pin 4 of IC2 so that it could function freely. Transistor T1 amplifies the piezo-sensor signal and triggers monostable IC2. The base of transistor T1 is biased working with a common piezo component that works as a small capacitor and flexes freely reacting to mechanical vibrations so that the output of IC2 is high up until the prefixed time period.

In the standby mode, the alarm circuit constructed close to IC3 stays inactive because it does not get current. Timing parts R8 and C6 produce the output of IC2 high for a period of three minutes.

When any mechanical vibration (generated by even a slight motion) affects the piezo component, trigger pin 2 of IC2 momentarily changes its condition and the output of IC2 is going high. This triggers triac 1 and the alarm circuit activates. Triac BT136 accomplishes the lamp circuit by activating its gate via resistor R9. IC UM3561 (IC4) produces a tone simulating the police siren with R11 as its oscillation controlling resistor. Zener diode ZD1 delivers stable 3.1V DC for the tone generating IC.

Construct this shutter guard circuit on a general purpose circuit board and enclose inside a appropriate, shockproof box. Connect the piezo component towards the circuit by utilizing a single-core shielded wire. Glue a circular rubber washer around the fine side of the piezo component and attach it on the shutter frame using the washer facing the frame to ensure that the piezo component is versatile to sense the vibrations. Attach the lamp and also the speaker on the outer side and the remaining components inside the box. Considering that triac is applied to the circuit, most points within the PCB will likely be at mains lethal potential. So it really is suggested not to touch any section of the circuit whilst trying out.

This is simple to build and cheap motorcycle alarm circuit which could be fitted in motorcycles to take care of them from getting stolen. The tiny circuit may be hidden anyplace, without having any difficult wiring. Practically, it fits all motorcycles as long as they’ve a electric battery. It is not going to drain out the battery though because the standby current is zero.

The hidden switch S1 could be a small push-to-on switch, or perhaps a reed switch with magnet, or any other identical simple arrangement. The circuit is made around a few lowvoltage MOSFETs configured as monostable timers. Motorcycle key S2 is an ignition switch, whilst switch S3 is a tilt switch.

Motorcycle key S2 gives power supply to the gate of MOSFET T2, when switched on. If you turn ignition off making use of key S2, you have about 15 seconds to get off the motorcycle; this function is executed by resistor R6 to discharge capacitor C3. Thereafter, if anyone tries to get on the motorcycle or move it, the alarm sounds for about 15 seconds and also disconnects the ignition circuit.

During parking, hidden switch S1 is normally open and will not permit triggering of MOSFET T1. But when somebody starts the motorcycle by using ignition switch S2, MOSFET T2 triggers through diode D1 and resistor R5. Relay RL1 (12V, 2C/O) energises to switch on the alarm (designed close to IC1) as well as to disconnect the ignition coil from the circuit. Disconnection of the ignition coil avoids generation of spark from the spark plug. Generally, you will find there’s wire running from the alternator towards the ignition coil, which needs to be routed through one of the N/C1 contacts of relay RL1 as shown in the circuit diagram.

Also, on disconnection of the coil, sound generator IC UM3561 (IC1) gets power supply through N/O2 contact of relay RL1. This drives the darlington pair built around T3 and T4 to produce the siren sound through loudspeaker LS1.

To start the vehicle, both hidden switch S1 and ignition key S2 should be switched on. Otherwise, the alarm will start sounding. Switching on S1 triggers SCR1, which, in turn, triggers MOSFET T1. MOSFET T1 is configured to disable MOSFET T2 from functioning. As a result, MOSFET T2 does not trigger and relay RL1 remains de-energised, alarm deactivated and ignition coil connected to the circuit. Connection to the ignition coil helps in generation of spark from the spark plug. Keeping hidden switch S1 accessible only to the owner avoids the motorcycle from pillaging.

Tilt switch S3 prevents attempt to move the vehicle without starting it. Glass- and metal-bodied versions of the switch offer bounce-free switching and quick break action even when tilted slowly. Unless otherwise stated, the angle by which the switch must be tilted to ensure the contact operation (operating angle), must be approximately 1.5 to 2 times the stated differential angle. The differential angle is the measure of the “just closed” position to the “just open” position.

The tilt switch has characteristics like contacts make and break with vibration, return to the open state at rest, non-position sensitivity, inert gas and hermetic sealing for protection of contacts and tin-plated steel housing. If you find difficulty in getting the tilt switch, you may replace it with a reed switch (N/O) and a piece of magnet. The magnet and the reed switch should be mounted such that the contacts of the switch close when the motorcycle stand is lifted up from rest.

Note. Please ensure that while driving, the two internal contacts of the Tilt switch don”t touch each other.

SCR BT169, MOSFET BS170 and transistor BC548 pin configurations