The Travel Touch Alarm can be used to provide a audible alarm when someone touches the door knob or handle of your hotel room. The door knob or handle must be made of metal for the circuit to work. The main chip in the circuit is a 555 timer which will be triggered if a hand comes close to or touches the door knob. The circuit attaches to the door knob at the end of the 1 meg ohm resistor. Once the timer is triggered the LED will light and the UJT will output a tone to the speaker. The timer will time out in 5 seconds. The sensitivity of the trigger can be changed by changing the 1 meg ohm...

The Sun - Up Alarm can be used to provide a audible alarm for when the sun comes up or it can be used in a dark area and detect when a light comes on. It can also be used to detect a light beam, headlights etc. The circuit works as follows. The phototransistor is very sensitive to light. (Any phototransistor will work fine) The sun shining on this device will provide a high to one of the NAND gates. This will cause another NAND gate to oscillate which will drive another gate to output a 100hz tone. The transistor provides drive for the speaker. Copyright 2000...

This circuit is very basic to build. To open a the lock which is connected to the K1 Load you must press each momentary switch in the correct sequence. The sequence used in this circuit is S1,S2,S3,S4. If any of the other switches are pressed the circuit will reset and you will need to start over. Depending on how you wire the switches, you can use any 4 switch combination. Copyright 1999 [url=http://home.maine.rr.com/randylinscott/index.html]Randy Linscott[/url]...

that circuit i use.its very amazing &operating tone control....

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Many security systems use a closed loop of wires and switches arranged so that whenever a door or window is opened, the loop will be broken and the alarm will sound. An obvious problem is that someone can tamper with the system, short out the loop, and later on, come back and burglarize the premises without sounding the alarm. Hiding a known resistance in the loop can prevent this. That way, the alarm can distinguish a short circuit from a correctly functioning closed loop. The figure above shows a circuit that does the job. It’s a somewhat unusual application of a National Semiconductor...

The circuit uses a 555 timer wired as an astable oscillator and powered by the emitter current of the BC109C. Under dry conditions, the transistor will have no bias current and be fully off. However as the probes get wet the transistor will conduct and sounding the alarm. An On/Off switch is provided and remember to use a non-reactive metal for the probe contacts. Gold or silver plated contacts from an old relay may be used, however a cheap alternative is to wire alternate copper strips from a piece of veroboard. These will eventually oxidize over but as very little current is flowing in...

The digital lock shown below uses 4 common logic ICs to allow controlling a relay by entering a 4 digit number on a keypad. The first 4 outputs from the CD4017 decade counter (pins 3,2,4,7) are gated together with 4 digits from a keypad so that as the keys are depressed in the correct order, the counter will advance. As each correct key is pressed, a low level appears at the output of the dual NAND gate producing a high level at the output of the 8 input NAND at pin 13. The momentary high level from pin 13 activates a one shot circuit which applies an approximate 80 millisecond positive going...

This simple circuit is sure to have the police beating a path to your door - however, it has the added advantage of alerting you to their presence even before their footsteps fall on the doormat. The circuit transmits on Medium Wave (this is the small problem with the police). IC1a, together with a sensor (try a 20cm x 20cm sheet of tin foil) oscillates at just over 1MHz. This is modulated by an audio frequency (a continuous beep) produced by IC1b. When a hand or a foot approaches the sensor, the frequency of the transmitter (IC1a) drops appreciably. Suppose now that the circuit...

A cheap and simple Gate Alarm, that is intended to run off a small universal AC-DC power supply. IC1a is a fast oscillator, and IC1b a slow oscillator, which are combined through IC1c to emit a high pip-pip-pip warning sound when a gate (or window, etc.) is opened. The circuit is intended not so much to sound like a siren or warning device, but rather to give the impression: "You have been noticed." R1 and D1 may be omitted, and the value of R2 perhaps reduced, to make the Gate Alarm sound more like a warning device. VR1 adjusts the frequency of the sound emitted. IC1d is a...

The relay is energized by entering the first four digits of your chosen five-digit security code. Entering the full five-digit security code - will de-energize the relay. When "A, B, C & D" are pressed in the right order - and within the time set by C1 and R2 - current through R11 switches Q6 on. This energizes the relay. When "A, B, C, D, & E" are pressed in the right order - and within the time set by C1 and R2 - current through R7 switches Q5 on. This de-energizes the relay. The circuit was designed to control the Modular Burglar Alarm System - but it will have other applications....

Pressing a single key on the keypad - will energize the relay. Entering a four-digit code of your choice - will de-energize it. The circuit was designed to control the Modular Burglar Alarm System - but it will have other applications. If you require added security - A Five-Digit Version - of the circuit is also available. [b:bc1035d987]Notes[/b:bc1035d987] The relay is energized by pressing a single key. Choose the key you want to use - and connect it to terminal "E". Choose the four keys you want to use to de-energize the relay - and connect them to "A B C & D". Wire the common to...

This is a simple - easy to build - alarm circuit. For power - I used a small 9-volt battery. But the circuit itself will work from 5 to 15-volts - just choose a buzzer that's suitable for the voltage you're using. The standby current is virtually zero - so the battery life is good. It's very important that fire-doors are kept closed at all times. If they're left propped open - they're no longer doing their job. If SW1 is connected to the fire-door, the alarm circuit will allow you to open and close the door without sounding the Buzzer. However, if it's left open for more than about 30...

This is a simple - easy to build - alarm circuit. For power - I used a small 9-volt battery. But the circuit itself will work from 5 to 15-volts - just choose a buzzer that's suitable for the voltage you're using. The standby current is virtually zero - so the battery life is good. If SW1 is fitted to a door - every time the door opens the Buzzer will give a short beep. In an unattended shop - or reception area - the sound of the beep will alert you to the fact that you have a customer. How long the output lasts depends on the values of R2 and C2. With the values shown - it will last for...

This is a simple single-zone burglar alarm circuit. Its features include automatic Exit and Entry delays and a timed Bell/Siren Cut-Off. It's designed to be used with the usual types of normally-closed input devices such as - magnetic reed contacts - micro switches - foil tape - and PIRs. But it can be Easily Modified to accept normally-open triggering devices - such as pressure mats. It's easy to use. First check that the building is secure and that the green LED is lit. Then move SW1 to the "set" position. The red LED will light. You now have about 30 seconds to leave the building. When...

This circuit features automatic Exit and Entry delays - timed bell cut-off - and system reset. It has provision for normally-open and normally-closed switches - and will suit all of the usual input devices (Pressure Mats, Magnetic Reed contacts, Foil Tape, PIRs and Inertia-Sensors, see [url]http://uk.geocities.com/ronj_1217/cmos_sza.html#is[/url]). If the Green Led is not lighting - check for an open window or door etc. Once you're satisfied that the building is secure - and the Green Led is lighting - move SW1 to the "set" position. At this point - the Red Led will light - and the Exit...

This circuit features automatic Exit and Entry delays - timed bell cut-off - and system reset. It has provision for normally-open and normally-closed switches - and will suit all of the usual input devices (Pressure Mats, Magnetic Reed contacts, Foil Tape, PIRs and Inertia Sensors). If the building is not secure - when you switch the alarm on - the buzzer will sound. You should turn off the alarm - and check for an open window or door etc. If everything is secure - when you switch the alarm on - the buzzer will NOT sound - and the Exit delay will begin. You have about 30 seconds to...

The Basic Alarm Circuit has an automatic Exit/Entry Zone - an Instant Alarm Zone that will accept both normally-closed and normally-open triggering devices - and an "Always On" 24-hour Personal Attack/Tamper Zone. By using the Expansion Modules - you can add as many extra alarm zones as you require. The Alarm is armed and disarmed by SW1. Before you move the switch to the "set" position - all the green LEDs should be lighting. You then have up to about a minute to leave the building. As you do so - the Buzzer will sound. It should stop sounding when you close the door behind you. This...