sparkfun DIY Reaction Timer User Guide

DIY Reaction Timer 

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Introduction

Mental chronometry​ is the study of how fast humans react to different inputs. It takes a few hundred  milliseconds for the signal to get from your eyes, to your brain, out to your limbs to respond. The reaction  timer is a great project to demonstrate this time delay. It also makes for a fun game between friends!
According to the team at Human Benchmark , the average human reaction time is about 215 ms. How fast are you?
The principal of the reaction timer is simple: when the user sees the light turn on, press the button! A microcontroller is perfect for this because it can time milliseconds very accurately
For this project, we will use an Arduino to be the time-keeper. An Arduino is a small, low-cost, and fast  microcontroller that is capable of performing command / instructions at a rate of 16 MHz or roughly 62.5 ns  per instruction.

Wiring / Hook‐up Guide (Fritzing) 

 http://www.humanbenchmark.com/tests/reactiontime/index.php 

The wiring for this circuit is simple, it requires a single LED and a single button. Connect the LED between pin 12 and GND using the solderless breadboard. Remember that each row of 5 holes are connected  together by an internal metal clip. Make sure that the LED leg and the connecting wire are in the same row.
Also, LEDs have a polarity. Make sure that the short leg of the LED is connected to GND.
Similarly, connect the button up between pins 7 and GND.

Example Code  

https://codebender.cc/sketch:62303 

After uploading this code to your Arduino, open up the Serial Monitor.
When the LED turns on, press the button as fast as you can. You  should see your data results show up in the terminal window. This is  text that the Arduino is printing / sending back to the computer for  display.

Labs / Examples / Investigation Ideas 
You now have a reaction timer. Great, now what? Here are a few ideas of things to explore:

• Statistics:
  ○ What is your fastest reaction time?
  ○ What is your slowest reaction time?
  ○ What is the best measure of your actual reaction time? (Measures of central tendency —  mean, median, mode)
  ○ How do you identify an “outlier”? What does standard deviation mean?
• Bio / Social / Other Science:
  ○ Does reaction time vary with age?
  ○ Does reaction time vary with dominant vs. non-dominant hand?
  ○ Does the color of the light make a difference?
  ○ Do males vs. females have a difference in reaction time?
  ○ Internal Clock. How good is yours? How well can you estimate 5 seconds? How about 30  seconds?

Going Further 
See if you can add sound to your reaction timer. You’ll need a buzzer and a few extra lines of code.
Connect up a buzzer between pins 9 and GND.

In the ​setup ()​, add a line that reads:
pin Mode(9, OUTPUT);
And, to make a tone, use the command:
tone (9, 440);  // 9 indicates the OUTPUT pin, and 440 is the frequency
To stop the tone, use this command:
noTone(9);

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