BCD to 7 segment decoder using IC 7447
Aim: To observe the BCD to 7 segment decoder using IC7447
1. BCD to 7 segment decoder kit
The 7447 decode the input data in the pattern indicated in the table-1 and segment identification as in fig-2. if the input data decimal Zero , a low signal applied to RBI blanks the display and causes a mutidigit display. For eg. By grounding the RBI of the highest order decoder and connecting it’s BI/RBO of the next lowest order decoder, etc, leading Zero’s will be suppressed. Similarly, by grounding RBI of the lowest order decoder and connecting it’s BI/RBO also serves as an unconditional blanking input. The internal NAND gate that generates the RBO signal has a resistive pull-up, as opposed to a totempole, and thus BI/RBO turns off all segment outputs. This
Blanking feature can be used to control display intensity by varying the duty cycle of the the blanking signal. A low signal applied to LT turns on all segment outputs provided that R1\RBO is not forced low
- Switch ON the experimental kit by connecting the power card to the AC mains
- Set up 4 bit BCD data using the toggle switches shown in fig -1.
- The binary equivalent is indicated on the input LED’s. A logic 1 is represented by glow and a logic 0 by no glow.
- Observe the corresponding decimal number on the 7 – segment display.
- Change the input switches of A1, A2, A3, & A4 through all the 16 states and observe the display output.
Three input full subtractor: X1 and X2 are two logic inputs and Bin is the borrow input to find the difference D and borrow B outputs for all combinations of X1, X2, and Bin.
- Connect X1, X2 and Bin to three data input switches.
- Connect OR gate output and EX-OR gate output to output status.
- Connect the circuit as shown in figure 4.
- Set up data in X1, X2, and Bin by means of the input switches and fill up the table 4.
- Verify the result with the theoretical values.
Result:> -b� - e �� H � ys'>
Realization of OR, AND, NOT, NOR gates by NAND gates
- Connect the trainer as shown in figures.
- Verify the working of OR gate, AND gate, NOT gate, NAND gate and NOR gate with the help of truth tables given.