Coded lock

Coded locks are rather widely applied to restriction of access of extraneous persons to protected objects. Convenience of using such locks consists in possibility both individual, and collective access (pass to service premises, access to left-luggage offices, etc.) .

of the Fig. 1. The standard type-setting element of the coded lock the Standard type-setting element of the coded lock is shown to p by

on fig. 1. The operating procedure with the coded lock is completely identical to work with locks of automatic left-luggage offices. After a set of the internal code hidden from an extraneous look (installations of SA2 switches in the situation defined by the user), a door slam. The lock is automatically latched. Number of possible options of code combinations equally to number of positions of the SA1 and SA2 switches erected in degree, equal to number of standard type-setting elements. To open the lock, it is necessary to gather a necessary code on its type-setting elements. The sequence of elements of the lock represents the simplest circuit of coincidence. In case the correct code, an operating electrode of analog of a tiristor is gathered (transistors VT1, VT2 on fig. 2) it appears for - shunted. As a result, by pressing the SB1 button "Otkr"., interfaced to the door handle, the element of management of the lock (the electromagnetic K1 relay) appears connected to the power supply. The relay works, its contacts К1.1 include a lock electromagnet, the lock opens.

of the Fig. 2. A schematic electric circuit of the coded lock

At the wrong set of a code and pressing the SB1 button "Otkr"., tension through a winding of the K1 relay arrives on an operating electrode of analog of a tiristor, it opens, having turned on the K2 relay. Contacts of the K2.1 relay disconnect a chain of a set of a code and turn on the alarm system (HA1 call, an alarm lamp, etc.) .

the Repeated set of a code will be possible only after pressing the SB2 "Dumping" button. As the current through a K1 relay winding in case of the wrong set of a code is insignificant (is limited by the R1 resistor and other elements of the circuit), the K1 relay does not work. Thus, for opening of the lock only one attempt is provided to the user that sharply limits possibility of selection of a code to extraneous persons.

the Diodes VD1, VD2 which have been switched on parallel to windings of the relay, interfere with development of oscillatory processes when switching inductive loading. The element of a delay of operation is entered into the circuit - the high-capacity C1 condenser. It detains interlock operation for some instants and allows the user to be convinced that the door is slammed, and the lock is closed. On a case of an emergency shutdown of the power supply it is expedient to provide a reserve food of the device from the accumulator.

A bit different principle of action is used by p in the circuit of the coded lock represented on fig. 3. As well as in the previous cases, at the correct set of a code consistently included standard elements provide supply voltage giving on a K1 relay winding by pressing the SB1 button "Otkr". But at the same time with pressing this button HA1 call joins, and the sound signal displaying the fact of opening of the lock is given. Blocking thus do not occur.

of the Fig. 3. A schematic electric circuit of the coded lock

At the wrong set of a code and pressing the SB1 "Otkr" button. also the sound signal is given. As the winding of the K1 relay is consistently connected to the R1 resistor, the current through a winding of the relay is insignificant, and its operation does not occur. At the same time, the supply voltage arrives via the R2 resistor on the C2 condenser.

In an initial condition resistance of the channel a source drain of the field VT1 transistor is insignificant, the operating electrode of a tiristor "is short-circuited" on the general wire. If SB1 "Otkr" button. it is pressed over 5 with, or attempts of selection of a code with SB1 button short circuit are made, the C2 condenser is charged, the VT1 transistor will unblock a management chain tiristory VS1. Tiristor joins, the K2 relay (tiristor loading) the contacts К2.1 disconnects a chain of a set of a code and turns on sound (or other, not shown on the circuit) the alarm system. The subsequent appeals to the lock are possible after a circuit deblokirovka - SB2 "Dumping" button pressing.

the Interval of time of a delay of operation is defined by C2-R2 RC chain. For a variation of this time it is possible to use the variable R2 resistor. The VD2 diode is intended for the instant category of the C2 condenser at the "correct" set of a code and is not obligatory.

Author: M ШУСТОВ, Tomsk