Introduction: 555 Timer Reaction Game

Target Audience

This instructable is targeted towards people that are interested in circuits (with a little background) that are looking for a simple game that you can build with just a few cheap components.

Difficulty Level

This would be difficult if you have little or no knowledge of circuit diagrams, but I try to be as helpful as I can along the way so you would not need to look at the diagram above (from 555 Timer Circuits)! No soldering will be used in this instructable, though you could solder this circuit together on your own if you wish.

Things You Will Need (links to purchase are on the names of each of these)

  1. A breadboard. This is essential for building our circuit on without any soldering required.
  2. Some wires to connect our components. Probably would be good to have a couple of different lengths from 2-6 inches
  3. 6V Voltage Source - I used this along with 4 standard AA batteries. The tinned leads make it so we can plug it into the breadboard.
  4. 555 Timer - This is an integrated circuit (IC) used in a lot of timer or oscillatory circuits. This handles our time delays.
  5. 7 Segment Display - This is the one I used, but there are many different ones that are virtually identical
  6. CD4026B Counter IC - This will connect the 7 segment display and 555 timer and tells which segments to light up at what time.
  7. 2 Small Buttons To start or stop the timer
  8. 3 10uF Capacitors
  9. A single 1nF Capacitor
  10. A single 68k ohm resistor
  11. 3 100k ohm resistors

Step 1: First Steps

First we have got to gather all of our components, lay them out nicely, and put our first few components on the breadboard. I have arranged my initial components in this way for (hopefully) the most optimal placement of other components around them. From top to bottom: 7 segment display, cd4026be, ne555, then the start and stop buttons.

Step 2: Connections to Voltage in and Ground

We will utilize the + and - connected columns on the left side of our breadboard to make the connections to the ground (black battery wire) and the Voltage In (red battery wire)

Step 3: Other Connections Between the Buttons and ICs

Okay, now we'll finish up the rest of the connections that are not to the Seven Segment Display. This includes the wires connecting the buttons to the rest of the circuit, and the connections between the 555 timer and the 4026 counter.

Step 4: Finish Connections to the 7 Segment Display

Then we just need to match up the alphabetic pins on the 4026 IC and the 7 Segment Display. Different displays can have the pins in different orders or positions, so you will need to consult your specific display's diagrams. Here are two common layouts, though. (the mapping of the letter to position on the display is always the same though, ex. "a" is always the top line, "g" is always the middle line, etc.) There is no need to attach the decimal point pin.

Step 5: Play!

When you press the start button, it will trigger the ne555 to start and clears anything that was already in the 4026 counter. The ne555 will send pulses to the 4026 counter at a frequency of 0.1 Hz which will change the number displayed on the 7 segment display.

When you press the stop button, it will freeze the display so you can see it!