Exploring logic gates

1. Exploring logic gates using logic blocks to get hands-on experience with logic gates and truth tables

2. using LOGIC Blocks in de • PROJECT sparkfun.com has them for $40 per kit • 2/19/2015 • CA PLTW Statewide conference • DATE • Client

3. The Light in your Fridge • What if we want a light to come on when a button is not depressed? • If pressing a button gives us a high signal (1) and not pressing it gives us a low (0), how do we get the light to come on? • Using your logic blocks, build this circuit

4. Into your notebook: • Once your circuit is built, create a truth table for it: • This is called an INVERTER gate. Make note of the chip number! • Build the circuit like this in Multisim and run the simulation. Does it have the same truth table? • What are some other situations where you would want to have your circuit reflect the opposite of what your input was?

5. Putting the Car in Gear • In order to shift, we need to have a foot on the brake AND do something mechanical to the shift lever • If applying the brake gives us a high signal (1) AND mechanically engaging the shifter also gives a high signal (1), how do we tell the car it’s OK to shift? • Using your logic blocks, build this circuit

6. Into your notebook: • Once your circuit is built, create a truth table for it: • This is called an AND gate. Make note of the chip number! • Build the circuit like this in Multisim and run the simulation. Does it have the same truth table? • What are some other situations where you would want to have your circuit react to only having two high inputs?

7. Going Further with AND • In most cars, the car also has to be turned on in order to be able shift gears • That gives us three high inputs that we would need in order to be able to shift • Using your logic blocks, build a three input AND circuit • Does it matter in which order you connect the inputs to the AND gates?

8. The Opposite of AND • Combining an AND gate with a NOT gate gives us the ability to invert the circuit • When we model this circuit, we will find that any combination of inputs will result in a high (1) output except for two highs (1). • Using your logic blocks, build this circuit

9. Into your notebook: • Once your circuit is built, create a truth table for it: • This is called a NAND gate (NOT AND). Make note of the chip number! • Build the circuit like this in Multisim and run the simulation. Does it have the same truth table? • What are some situations where you would want to have your circuit not react when it received two high signals?

10. Opening the Trunk • With most cars, there’s a trunk opener on the keychain OR a button inside the car • How do we tell the car to open the trunk if we send a high (1) signal from the keychain OR if we send a high (1) signal from the button inside the car? • Using your logic blocks, build this circuit

11. Into your notebook: • Once your circuit is built, create a truth table for it: • This is called an OR gate. Make note of the chip number! • Build the circuit like this in Multisim and run the simulation. Does it have the same truth table? • What are some other situations where you would want to have your circuit react when it received either of two high signals?

12. Going Further with OR • In most cars, you can still use a key to open the trunk as well • That gives us three high inputs that we could use in order to open the trunk • Using your logic blocks, build a three input OR circuit • Does it matter in which order you connect the inputs to the OR gates?

13. The Opposite of OR • Combining an OR gate with a NOT gate gives us the ability to invert the circuit • When we model this circuit, we will find that the only combination of inputs that will result in a high (1) output is to have two low (0) inputs. • Using your logic blocks, build this circuit

14. Into your notebook: • Once your circuit is built, create a truth table for it: • This is called a NOR gate (NOT OR). Make note of the chip number! • Build the circuit like this in Multisim and run the simulation. Does it have the same truth table? • What are some situations where you would want to have your circuit only react when it received two low signals?

15. Frienemies - Using the Exclusive OR • You don’t want to go to lunch by yourself. You like Jill and you like Sam, but if you all go to lunch together, they get all catty and it just becomes awkward. • Can we model a circuit where you’d prefer one or the other but not both? • Using your logic blocks, build this circuit

16. Into your notebook: • Once your circuit is built, create a truth table for it: • This is called an XOR gate (Exlusive OR). Make note of the chip number! • Build the circuit like this in Multisim and run the simulation. Does it have the same truth table? • What are some situations where you would want to have your circuit only react when it received one of two high signals?

17. Combinational Logic Design • To keep you safe, your car has a buzzer system that alerts you to certain conditions. We want to build that circuit. • We want a buzzer to go off (send a high (1)) under the following conditions: • Your seatbelt is not on but the key is in the ignition. • The key is in the ignition and the door is open. • Your seatbelt is not on, the key is in the ignition, and the door is open.

18. Into your notebook: • Establish your highs and lows • Create a truth table that would give you the correct behavior for your buzzer • Draw a circuit that would give you the results of your truth table

19. with your logic blocks: • Build the circuit that matches your design. Verify your truth table to see that it does what you intended. • Build the circuit in Multisim and run the simulation. Does it have the same truth table? • with multisim:

20. Working with a partner, each of you build one side of the equation • Complete the truth tables • Are the functions equal? Was one circuit easier to build than the other? When might you need to use these relationships? Going further with logic blocks hands-on proofs of demorgan’s theorems

21. The D-Latch • S/R-Latch • J-K going further with logic blocks State machines, latches and flip flops

22. These slides are available on my website: • If you have any questions or comments, please e-mail me at: • devansic@teh.k12.ca.us