mas.500
problem set 4

in this problem set you will build an IR remote controlled LED / light sensor
thing-a-ma-bob.  the questions are organized to help walk you through an
effective programming and debugging strategy: only modify one thing at a time!
in this way, you know what changes you made and how they effect the program.
if you modify too many things at once, you wont know which parameter was the
one to mess things up.

the final circuit should:
1. sense the light level on your CDS photocell
2. transmit this light level information over an IR link
3. use the recieved light level information to modify the light
   intensity of an LED.

NOTE:  the "serial monitor" uses the same RX/TX lines as the IR link will most
likely use, so debugging can be difficult.

you can work with a partner on this project, or alone.  you can also work in a
group of 3, but in that case, you will need to use 2 CDS photocells to control
2 LEDs.

the final deliverable is showing a functioning circuit in class on thursday,
and a print out of your final code.

problem 1:  download the Arduino programming environment and install it on your
computer (https://www.arduino.cc/en/Main/Software).  download and install the
FTDI drivers for the sparkfun redboard (our arduion knock-off:
https://learn.sparkfun.com/tutorials/redboard-hookup-guide).  locate a USB
cable to use with your redboard.

problem 2:  upload the "Blink" program from the examples in the Arduino
library.  make sure that it uploads and the onboard LED blinks.  change the
rate of blinking by modifying the code, and make sure it uploads and works.

problem 3:  connect your CDS photocell to your arduino and read in the light
level via an analog in.  send this value to the serial monitor so you can see
that it is working, and what range of values you recieve when placing your
hand over the photocell.

problem 4:  either use the onboard LED, or connect an LED to your arduino.
write a program that varies the intensity of the LED.  next, use the value
you obtained from your CDS photocell to change the LEDs behaviour.  finally,
scale the values sent to the LED such that the change is more dramatic (the
photocell values will not cover a very wide range, and you can amplify/offset
this range in your code).

problem 5:  connect up your IR trasmitter and reciever to 2 arduinos (you can
transmit to yourself on 1 arduino if youre working alone).  you will need the
datasheets for the IR devices to know how to connect them up.

http://www.mouser.com/ds/2/311/FH415_Pb_free_2009_08_21-55946.pdf
https://www.vishay.com/docs/82461/tsop582.pdf

here are some possible ways of modulating the IR transmitter:
http://web.media.mit.edu/~geppetto/vids/irmod.jpg

you can also find online tutorials and accompanying libraries, which might be
easier.

transmit some data from one to the other, and read the values out on the serial
monitor to ensure its working.

problem 6:  use your CDS photocell as your data source, and send these data
across the IR link, and read the values out on the serial monitor to ensure
its working.

problem 7:  output your recieved photocell information via the LED.  your
project should now be fully functional.