Diagram Guide

This secret lock, unlike a conventional code lock, gives away no hints to the unwanted visitor as to its existence: there are no buttons, switches or keypads. No code sequence need be learnt: you simply need an inconspicuous key. The idea is based on two magnetically-operated switches which, when operated simultaneously, cause two relays to close. These in turn could actuate an electric door latch or start a garage door motor.

This would not be particularly noteworthy (and rather easy to defeat) if simple reed switches were used, since they do not depend on the polarity of the magnetic field: they react equally to the north or the south pole of a magnet. Instead we use Hall effect ICs, which only react to south poles. In this way the would-be intruder, carrying just a powerful permanent magnet in his pocket, is frustrated in his nefarious deeds: horseshoe and bar magnets do not have two south poles. And if that is not secure enough, you can always add further Hall effect ICs and relays: just like a lock with more levers.

Secret Lock Circuit Diagram:

 

The sensor used in the circuit shown in Figure 1 is smaller than a transistor, and yet contains rather more: a unipolar sensing surface for the magnetic field, Hall generator and threshold generator, amplifier, Schmitt trigger and output transistor. With a field stronger than 20 millitesla the open-collector output transistor is turned on. The series-connected contacts of the 12 V miniature relays then complete the circuit via connection L. Relays with a coil current of 50 mA or less should be used in order not to overload the ICs.

The Hall effect ICs are fitted or glued at least 5 cm apart behind a sheet of glass, plastic or aluminium (perhaps the letterbox or doorbell), at most 4 mm thick, with the component marking towards the key. In no circumstances should iron or steel be used as these screen the sensors from the magnetic field. The sensors can either be wired to directly or fitted on a piece of perforated board. The position of the sensors should be suitably marked on the outside.

The simplest way to make a key is from a piece of square section wood in which two small holes are bored for two cylindrical magnets (as used with reed switches). The two magnets should be glued in the same way round, which can easily be tested by checking that the poles repel. Alternatively, of course, the magnets can be fixed in a flat plastic box using hot-melt glue. Remember that only one side of the key will open the lock.

The secret lock can be safely used outside as long as it is fitted in a suitable watertight enclosure. It can save money compared to the services of a locksmith, and it will resist even the professional burglar. The lock is vandal-proof, operates independent of temperature, requires no battery in the key, can be cheaply extended and provided with any number of keys. The Hall effect ICs (Conrad Electronics order code 147508) are inexpensive. The operating voltage depends on the relays chosen, and should lie between 6 V and 24 V. The standby current for two ICs is about 7 mA at 12 V.

This electronic game pits a human player against the ‘machine’. The opponents use a common ‘game token’ and take turns moving along a path by one, two or three steps, and the winner is the first one to reach the goal exactly. Incredibly enough, this simple version of the ‘123’ game can be built without a microcontroller, and it’s almost impossible to beat. The electronics for this is built using only diode logic (Figure 1). The ‘ input inter face’ consists essentially of 30 miniature sockets to which a probe tip can be connected to mark the position of the ‘game token’.

To make the game more compact, the sockets are arranged in a grid so the route along the sockets follows a serpentine path (Figure 2). The starting position is at the bottom right, and the goal is in the middle of the playing area. The electronics becomes the ‘active player’ when the button is pressed.

The number of steps it wants to move is shown by three LEDs (one, two or three LEDs light up) at the top of the playing area. Naturally, the human player must move the ‘game token’ for the machine opponent. The winner is the first one to reach the goal exactly. How can such simple circuitry represent such a formidable opponent? As already mentioned, the path from the start to the goal is formed by 30 sockets. Each socket has an associated ideal next move. 

There are three possibilities, of course: 1, 2 or 3. As you can see from the schematic diagram, switch S1 closes the circuit (which means the player asks the ‘computer’ how many steps it wishes to move) if the probe is touching one of the sockets. All 30 sockets are classified into three types, represented in the schematic diagram by one socket for each type. All sockets belonging to a particular type are simply connected together electrically, which is not shown on the schematic diagram for the sake of clarity.

both zone uses a normally stopped up write to. These can ensue micro switches otherwise standard alarm contacts (frequently reed switches). right and proper switches can be bought from alarm shops and concealed fashionable gate frames, before window ledges.

Zone 1 is a timed zone which necessity be situated used in the function of the submission and exit feature of the building. Zones 2 - 5 are immediate zones, which choice trigger the alarm with veto delay. several RF invulnerability is provided pro extensive wiring runs by the input capacitors, C1-C5. C7 and R14 too form a transient suppressor. The main switch acts the same as the normal/Unset and Reset switch. For nice security this ought to subsist the metal type with a key.

by switch on, C6 choice charge via R11, this acts as the exit delay and is set to around 30 seconds. This can be altered by unstable either C6 before R11. once upon a time the timing dot has elapsed, LED6 will light, gist the regularity is armed. LED6 may perhaps transpire mounted externally (on the bell box on behalf of case) and provides visual indication with the purpose of the system has set. one time set some get in touch with that opens motivation trigger the alarm, counting Zone 1. To prevent triggering the alarm on entrance to the building, the concealed regarding-entry switch be obliged to live operated. This will discharge C6 and start the entry timer. The re-entry switch may well be a concealed reed switch, located anywhere dressed in a entry frame, but indistinguishable to the eye. The panic switch, after hard-pressed, wish trigger the alarm when backdrop. Relay contacts RLA1 provide the latch, RLA2 organize the warning otherwise buzzer.