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Electronic Selector Driven by Relays

2018-11-15 14:00  
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The circuit was aimed to produce an electronic selector for ten alternative sources with the means of showing the result in a 7-segment display being driven by relays.

4511 – aBCDto 7-segment decoder driver used to convert the logic states at the outputs of a binary coded decimal (BCD) into signals that will drive a 7-segment display4028 – aBCDto decimal/octal decoder with four inputs that provide a decimal decoded output while a 3-bit binary input provides a decoded octal output used for memory selection control, readout decoding, code conversion, demultiplexing, and address decoding with features such as low outputs on all illegal input combinations, positive logic design, 3V to 18V supply voltage range, and capability of driving one low-power SchottkyTTLload over the rated temperature rangeBD679 – a monolithicNPNSilicon epibase power Darlington transistor with resistors and diode in a TO 126 plastic package and is typically used for AF applications due to its high current gain

The circuit comprises of a rotating switch step selector S1 that serves as the means for mechanical selection from 1 to 10. Also included in the circuit is an electronic drive consisting of 10 relays RL1 to RL10. The relays may have a voltage of 6 V or 12 V. The use of 7-segment display DSP1 is for the visual indication of the selection. The display is made up of common cathodeLED, where the cathode is connected to the common point (ground) on the circuit and usually though a resistor that is often bypassed with a capacitor, placing it at AC ground potential.

The operation of the circuit is based on the connection of the mechanical selections into 4 bit binary-coded decimal (BCD) code.BCDis an encoding for decimal numbers in which each digit is represented by its own binary sequence with the values or digits using 0-9. TheBCDcode is being managed by the proper polarization of the diodes D1 to D10. During this time is the simultaneous gathering of decimal output by IC2 which is aBCDto decimal decoder.

IC1 is aBCDto 7-segment latch, decoder, or driver which drives the monitor. The circuit can be used for several types of combinations and selections. One way is by adding moreLEDs in parallel with the relays RL1 to RL10.

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Figure 2 

The theory used for the circuit of electronic selector is being used in packet-switched wavelength division multi-access (WDMA) networks and other analog adjustment applications. There are some circuits that utilize an electronic selector switch for telemetrical use with an impedance measuring circuit like those used in radiosondes.

Source:users.otenet.gr/~athsam/electronic_sel_10_step_d.htm


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