The binary-coded decimal number of the pressed key which is written down in the SVV segment arrives on the decoder which will transform it to a code of the seven-segment indicator. This code moves on the semiconductor indicator which highlights the corresponding number.
In not electric UVV working by such principle (for example in mechanical the timer active and passive states can be shown in various angles of rotation of the operating levers influencing executive mechanisms. In electric UVV the S(t) function as a rule, is shown in changes of values of tension at the exit.
If not to take that any UVV into account of a detail (including it is possible to present in the form of some black box having one entrance and one exit. On an entrance some external influence of X (t) arrives, and at the exit the S(t) function is formed.
The minimum resistance of these resistors gets out proceeding from the maximum admissible current via diodes. Thus that their resistance has to be in 5-6 times more than resistance of the restrictive resistor in the keyboard block is considered.
In the industry the first devices of endurance of time appeared and began to be used during a dotranzistorny era as alternative mechanical. Their advantages before the last were obvious – reliability, multifunctionality, simplicity and accuracy. For formation of the S(t) function the principle was chosen simple (and at that time and only accepted). It consisted in charging or a discharge of the condenser of a certain capacity through rather big resistance.
The light-emitting diode of HL1 serves for indication of inclusion of loading. In addition it, together with R1 carries out tension divider role. From an exit of this divider via the R2 resistor tension moves on base of the VT1 transistor and opens it. The R2 resistor limits current of base of the transistor and, thereby, prevents its influence on BUIU. Its resistance needs to be chosen whenever possible more. In our case it was picked up experimentally and equally in 10 kOhm. The collector chain of the transistor turns on the K1 relay which the contacts operates loading. The VD1 diode is necessary for short circuit of the currents of a self-induction arising in a relay winding when locking the transistor. Thereby it prevents breakdown of the transistor, and also emergence of hindrances on a power-supply circuit of chips. Resistance of the R1 resistor is chosen experimentally, on the acceptable light-emitting diode luminescence brightness.
To receive almost applicable device from this scheme, it is enough to connect parallel to the condenser any threshold device with two steady states which at achievement by tension of Uc of Uc1 value would change the state.
By pressing a key the contact disk nestles on metal contact platforms and closes them among themselves. As showed measurements in spite of the fact that an electroconductive layer rather thin, resistance of such contact makes about 60 Ohms that is quite acceptable for management of digital chips of TTL (TTLSh).
It consists of four specialized chips of this KR514ID On entrances of these chips moves four digit dvoichno – the decimal code and exits are connected to the corresponding categories of the indicator. Apparently from the scheme the static method is applied to control of the indicator. It allowed to simplify considerably the indication device, though use of a large number of connecting lines demanded. (28 pieces).