1-button lock provides high security -  03/04/99 EDN-Design ideas (contains several designs, scroll to find this one) Figure 1 is the block diagram of an easily programmed, single-button combination lock.  You operate the lock by using a series of short and long pulses from a momentary switch that masquerades as a doorbell button.  The circuit uses inexpensive CMOS logic.  The retriggerable timer, T1, locks out entries made after the T1 code-entry window, thereby greatly enhancing security.  The circuit in Figure 2 operates as follows: The Schmitt-trigger quad NAND gate, IC 1, debounces the code-entry switch and, with the aid of simple analog circuitry, produces separate outputs for activation times of less than and more than 0.3 sec.  These outputs connect to the select gate, IC 5 Design by Maxwell Strange, Fulton,MD

1-Time-Only Burglar Alarm -  Multi-Zone Burglar Alarm Circuits:  When this alarm is activated its Siren will sound once - for up to 20-minutes.  Then it will switch off and remain off.  The basic circuit has a single zone with independently adjustable Exit and Entry delays.  This will be adequate in many situations.  However, there's also a range of Expansion Modules.  These will allow you to add any number of instant Zones, Tamper Zones and Personal Attack Zones to your system.  __ Designed by Ron J.

2 Zone Intruder Alarm -  This is a two-zone alarm - with automatic exit, entry and siren cut-off timers.  it can be triggered by the usual types of normally-closed input devices - such as magnetic reed contacts - foil tape - PiRs etc.  I'veused a 12-volt supply in the diagram - but the circuit will work at anything from 9 to 15-volts.  All you need do is select a siren, buzzer and relay to suit the voltage you want to use __ Designed by Ron J.

2-Zone Burglar Alarm -  Multi-Zone Burglar Alarm Circuits:  This two-zone alarm has automatic exit, entry and siren cut-off timers. So it has a particularly detailed circuit description.  There's an optional One-Time-Only module.  it will force the siren to switch off after the first ten minutes - and prevent the alarm from activating a second time.  __ Designed by Ron J.

3 Flashing LED Doorbells -  Battery Powered LED Circuits:  These circuits combine a buzzer with one or more LED displays.  When the push switch is operated - the buzzer will sound and the LEDs will flash.  When the switch is released - the buzzer will stop - but the LEDs will go on flashing for another 30 seconds or so. __ Designed by Ron J.

3 Zone Duress Alarm -  This is a 3 zone alarm for use in high risk areas or possible duress situations.  Typical examples being banking or betting booths.  The alarm consists of 3 normally open push button switches which can be hidden or in plain view.  Once pressed the alarm will latch and a LED will light showing which zone has pressed the alarm __ Designed by Andy Collison

4 Digit Keypad -  This is an enhanced 4 digit keypad which may be used with the Modular Alarm System __ Designed by Ron J.

4 in 1 Burglar Alarm -  in this circuit, the alarm will be switched on under the following four different conditions: 1.  When light falls on LDR1 (at the entry to the premises).2.  When light falling on LDR2 is obstructed.3.  When door switches are opened or a wire is broken.4.  When a handle is touched.  The light dependent resistor LDR1 should be placed in darkness near the door lock or handle etc.  if an intruder flashes his torch __ Designed by Radioland.nt.au

5 Digit Alarm Keypad -  This is an enhanced 5 digit keypad which may be used with the Modular Alarm System.  This switch will suit the Modular Burglar Alarm circuit.  However, it also has other applications.  The Keypad must be the kind with a common terminal and a separate connection for each key.  On a 12-key pad, look for 13 terminals.  The matrix type with 7 terminals will NOT do.  Choose the five keys __ Designed by Andy Collison

5 Zone Alarm -  This is a complete alarm system with 5 independent zones suitable for a small office or home environment.  it uses just 3 CMOS IC 's and features a timed entry / exit zone, 4 immediate zones and a panic button.  There are indicators for each zone a "system armed" indicator.   __ Designed by Andy Collinson

555 -Timer Based Motorcycle Alarm -  Motorcycle Alarm Circuits:  This circuit features an intermittent siren output and automatic reset.  it can be operated manually using a key-switch or a hidden switch; but it can also be wired to set itself automatically when you turn-off the ignition.  By adding external relays you can immobilize the bike, flash the lights etc. Now With Free SiMetrix Circuit Simulation.  __ Designed by Ron J.

6 Zone Alarm with 7 Segment Display -  This alarm system has 6 independent zones, 1 timed entry/exit zone, a 7 segment LED display and a test or walkthrough facility.  Suitable for a small office or home environment, it can also be adapted to use a combination lock or keypad to set and reset the alarm __ Designed by Andy Collison

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