Digital Selector with 8 Sources

Figure 1 

The objective of the circuit is to develop an electronic selector coming from 8 sources with an up-down motion in series.

• 4584 – a CMOS consisting of six Schmitt trigger circuits constructed with MOS P-channel and N-channel enhancement mode devices in a single monolithic structure primarily used for low power dissipation and high noise immunity applications with more features of limitless input rise and fall times and Schmitt trigger action on each input with no external components
• 74HC193 – a high speed Si-gate CMOS device with 4-bit synchronous binary up/down counters that is pin compatible with low power Schottky TTL and specified in compliance with Jedec standard no. 7A with features of asynchronous parallel load and reset, expandable without external logic, synchronous reversible 4-bit binary counting, and standard output capability
• 74HC237 – a high speed Si-gate CMOS device having 3-to-8 line decoder/demultiplexer with 3-bit address latches ideally suited for implementing non-overlapping decoders in 3-state systems and strobed applications in bus oriented systems due to its features of multiple input enable for easy expansion or independent controls, standard output capability, and active high mutually exclusive outputs
• 74HC4051 – an 8-channel analog multiplexer/demultiplexer with 3 digital select inputs, an active low enable input, eight independent inputs/outputs, and a common input/output, with features of wide analog input voltage range, low ON resistance, built in typical break before make, and non-standard output capability

There are 8 different sources by which the circuit can choose to make the electronic selector. It employs the service of only two switches where the movement of commands is in series of up-down motion with the control of push button switches S1 & S2. The activities that occur in every input of the circuit are being shown through the corresponding LEDs D1 to D8 which are connected to IC4. The LEDs are driven by the relay of the circuit for triggering the LEDs as they are attached to the SL1 connector.

If the relay will no longer be used, an 8-channel multiplexer, represented by IC3, can be made as a replacement during the operation. Two of these IC3 will be utilized if they are designed to work for stereo use. The will be positioned at each channel to cater the signals. The circuit can become an electronic variable resistor with 8 steps if the correct pairing or combination of resistors has been done during the construction.

Figure 2 

The concept used in building the electronic selector may be applied in some analog adjustment applications and in fast packet switched wavelength division multi access. Those applied in radiosondes that measure the impedance of a circuit are using the electronic selector for telemetrical puposes.

Source:users.otenet.gr/~athsam/digital_up_down_sel_8.htm