1. Electrical Engineering 1 WISE Investments Electrical Engineering Lab Digital Logic Laboratory Dr. Keith Holbert

2. Electrical Engineering 2 Laboratory Preview Next we will go to the lab (GWC 273) to see what these circuits look like First, let’s get a preview of what we expect to see in the lab The first thing we’ll look at is the trainer boards used to build the prototype of our digital circuits

3. Electrical Engineering 3 Trainer Board Trainer Board: An electrical device used for rapid prototyping of electrical circuits Our trainer board has: –Breadboard for making connections –Power supply –Switches –LED (light emitting diode) for signal display –Clock

4. Electrical Engineering 4 Power Supply +5 volts Ground 0 volts Connection and LED Breadboard region Clock Trainer Board Switches & connections

5. Electrical Engineering 5 Breadboard Bus: Terminals Horizontally Connected as Shown Gutter: Electrical Isolation of Vertical Columns for IC Insertion Terminals Vertically Connected Together as Shown

6. Electrical Engineering 6 Integrated Circuit (IC) Chips Notch provides a reference point Pins are numbered

7. Electrical Engineering 7 A data book gives the pin correspondence and function schematically 131211109814 1234567 +5V GND AND SN74LS08 AND

8. Electrical Engineering 8 Digital Combination Lock Using three AND gates, we can build a combination lock that requires a four-digit code, specifically: 1 1 1 1, using the particular 7408 pin connections illustrated below AND 4 5 6 8 11 9 13 12 10

9. Electrical Engineering 9 Digital Lock Circuit Construction Procedure 1)Insert the two ICs (7408 and 7404) across the gutter portion of the breadboard with notch to the left. 2)Connect the power supply (+5 V) and pin number 14 of both ICs to a bus at the top of the breadboard area. 3)Connect the ground (0 V) and pin number 7 of both ICs to a middle bus of the breadboard. 4) For the 1111 combination, connect the output from switches 1 thru 4 as inputs to pins 9, 10, 12 and 13 of the 7408. 5)Connect the outputs from pins 8 and 11 as inputs to pins 4 and 5. 6) The output from pin 6 is then connected to an LED. 7)Turn the trainer board ON. 8) Use the 4 switches to control the input values to the digital lock. When the switches are all on,the LED should be on; otherwise, the LED is off.

10. Electrical Engineering 10 7408 Digital Lock: Build a lock with combination 1111 7404

11. Electrical Engineering 11 To make the lock with a combination of 0110, we’ll use inverter gates from a hex inverter chip 131211109814 1234567 +5V GND SN74LS04

12. Electrical Engineering 12 Digital Combination Lock To build a combination lock whose input (key code) combination is 0 1 1 0, we use two NOT (inverter) gates from the 7404 using the pin connections below Are there other pin connections that could be utilized? AND 13 10 12 9 11 12 10 8 4 5 6 13 11 7408 7404

13. Electrical Engineering 13 7408 7404 Digital Lock: Build a lock with combination 0110

14. Electrical Engineering 14 For the railroad crossing signal, we will need to use an XOR gate 131211109814 1234567 +5V GND SN74LS86 XOR

15. Electrical Engineering 15 RR Crossing Circuit Construction Procedure 1)Insert the two ICs (SN74LS08 and SN74LS86) across the gutter portion of the breadboard with notch to the left 2)Connect the power supply (+5 V) and pin numbers 14 and 13 of both ICs to the bus next to the top 3)Connect the ground (0 V) and pin number 7 of both ICs to the bottom bus 4)Connect the clock to the pin number 12 of both ICs 5)Connect the output from pin number 11 of each IC to a different LED 6)Make sure the knobs on the top row of the trainer board are all turned to the far left (that is, fully counter clockwise) 7)Turn the trainer board ON. The LEDs should flash back and forth; if not, a loose connection may exist.

16. Electrical Engineering 16 7486 7408 Build the Railroad Crossing Signal

17. Electrical Engineering 17 Hardware Laboratory Now we are ready to go to the lab (GWC 273) You will construct –a digital combination lock –a railroad crossing signal