Game Show Buttons

By Steve Hobley
Category: Electronics
Time Required: 1 - 2 hours
Difficulty: Difficult

In this project, taken from Charles Platt’s book Make: Electronics, we’re going to breadboard a fairly complex circuit using 555 timers and an OR logic gate.

Using these and some other, common components, we’ll build a game show button system. When one button is pressed, it automatically locks the other one out, until the quizmaster flips a reset switch.

"OR gates" are one of several types of basic logic gates. The logic of ORs are, as the name suggests, if input A or B is true (on), output X is true (on); thus, in this design, if either player presses his or her push button, the circuit will go true (on), locking out the other player’s button, and can only be reset via the toggle switch. This circuit is ideal for two-person quiz contests!

"I’ll take ‘Cool Projects’ for 100, Alex!"

Steps

Step #1: Gather Your Parts, Install ICs and Hookup Wire

Gather together the required parts along with the breadboard.
Breadboards have positive and negative power rails running along the top and bottom. They are typically marked with a red line for positive (+) and blue (or black) line for negative (-). When you power the board, you can connect a 5-6v battery (or DC power supply) with positive and negative connected to the respective rails.
Our first task is to place the 3 ICs (integrated circuits) in line, and be sure they're in the correct orientation. Using the 22AWG jumper wire, connect power (- is black, + is red). You can see that I've connected to the two power rails on either side of the breadboard.
The next step is to add the additional lines to power and ground (third image), again using red for positive, and black for negative.

Conclusion

This project demonstrates that it's possible to implement complex time-dependent circuitry without relying on a microcontroller or computer.

The 555 timer IC is one of the most useful components available, and here we've used it in a latching configuration.

2 Responses to Game Show Buttons

noob007 on April 7th, 2012 at 12:45 pm said:

You can build it just with 2 555 timer chips

Reply ↓
Josiah Ritchie on April 9th, 2012 at 2:32 pm said:

Agreed, a schematic would be a lot easier than going cross-eyed trying to see which what’s going where on that breadboard. Could we get one?

Reply ↓