Feb 23

Laser tag update 2/22/15

From last week, I had the following deliverables:

1. Get a larger lens/lenses 2"+ in diameter.
2. Build test set up and test 2" diameter lens (inside and outside) and record transmission distances at standard currents

So, I got a 4.5" lens from an old box of science stuff. I found its focal length by putting it under a light on the ceiling and measuring the height the light was off of the ground when it focused the light on the ground. I then built a (oh so sturdy) cardboard cut out to hold an LED at roughly the focal length away from the lens (I also learned that a hole punch is a little wider than a 5mm LED. I used that to make a hole. This is a test. Quick and dirty is the way to go. Does not need to be exact).

Now for the set up:

Basic Settings
Voltage for LED: 5 V
Resistance for LED: Three (x3) 24 Ohm resistors in parallel, resulting in 8 Ohm total resistance.
Current for LED: .6 (max is 1A)
Lens Diameter: 4.5"
Lens Focal Length: ~9.1"
Max Transmission distance: ??

Secondary components:
Voltage regulator: LM7805C
Transistor: TIP101G.

My goal for this iteration is to build a module that I can run around with and play laser tag with. I need to build a durable version that I can run around with and play laser tag. Then I can start adding things like different lenses, game types, etc.
However, before I build a durable model, I should max out the settings and get tag distances.


1. Change IR LED current to 1 A.
2. Get distance tests for 1 A with 4.5" lens and 1" lens.

Feb 16

Geocache Puzzle Box Code


For those of you who want to view it here, here it is:

/*This is my geocache box code. I used ladyada's tutorial on how to wire it, along
with the lcd display, and am using her library. This code is based on her example sketches for
the gps unit, lcd, along with other people's code and forum conversations on the topic

I have the distance calculator, destination calculator, attempts working, and check date function working.

I need to start adding the hardware modules (locking mechanism) and building the box.

#include <Adafruit_GPS.h>
#include <SoftwareSerial.h>
#include <math.h> //I need the cosine function, so I need to include math
#include <EEPROM.h>

SoftwareSerial mySerial(3, 2);
Adafruit_GPS GPS(&mySerial); // If using hardware serial (e.g. Arduino Mega), enable this line instead:
//Adafruit_GPS GPS(&Serial1);

const int serialDebug = 0; //serial debugging. 1 for active, 0 for off
const int lcdDebug = 0; //lcd debugging. 1 for active, 0 for off
#define GPSECHO false //echo GPS data to serial consol
int resetCounter = false; //this resets the number of tries you have until the box opens itself. true resets the counter to 1 (for first attempt)

int firstOn = 0; //first time I turned this thing on, I want this to be true

//GPS stuff
boolean usingInterrupt = false; //we're not using the interrupt
void useInterrupt(boolean); // Func prototype keeps Arduino 0023 happy

//lcd library too
#include LiquidCrystal lcd(7, 8, 6, 10, 11, 12); // initialize the library with the numbers of the interface pins

int address = 0; //the number of attempts is stored in address 0 in EEPROM


//I'm doing all of my calculations with the latitude and longitude in degrees, since that's what the haversine formula needs,
//therefore, I need to convert my coordinates into degrees in order to determine where I am using this formula.
//You have to put these two numbers into the function directly
//these have 6-7 decimal points of accuracy. Therefore, my code should account for that

//Santa Monica Pier, 25 miles from house
const float destinationLat = 34.007426; //latitude of destination (Santa Monica Pier) in DEGREES
const float destinationLong = 118.499823; //positive longitude of Santa Monica Pier in DEGREES
const float NemaDestinationLat = 3400.4456; //NEMA sentance latitude for Santa Monica Pier
const float NemaDestinationLong = 11829.9894; //NEMA sentance longitude for Santa Monica Pier
//NEMA sentence is degrees (2 decimals Lat, 3 decimals Long), minutes (two decimals.four decimals)

//Luxor, Las Vegas, 36.095511,-115.176033, 212.5 miles from house
const float destinationLat = 36.095511; //latitude of destination in DEGREES
const float destinationLong = 115.176033; //positive longitude in DEGREES
const float NemaDestinationLat = 3605.73066; //NEMA sentance latitude
const float NemaDestinationLong = 11510.56198; //NEMA sentance longitude
After comparing the distance between my NEMA converted distance and a location, I was .6912 miles off. I'm going to give myself a mile
just to be safe. I can also check the location directly, which was accurate, but did not give me good distance measurements
const float maxMilesAway = 1; // Max miles away for box to open (1760 yards). This is for calculating distance away.
//This is less accurate than comparing raw NEMA sentance output because of float limitations
const float maxGPSAway = .1; //this is .1 minutes away (from NEMA sentence). 1 minutes is 1 nautical mile, so this is .115 miles, or 200 yards
const int dlay = 2000; //longest delay during lcd debug

const long waitTime = 300000; //longest I'll wait for a fix before timeing out and turing off (ms)

const int maxAttempts = 50; //maximum number of attempts to open the box
const int offPin = 4; //digital pin to turn off the device
//note: digital pin 13 fluctuates during power on. I can't really use this pin.

//Servo pins
const int servoPin = 9; //servo on pin 9

//Other destinations:
/* latitude, longitude
42.999155,-71.47135 //island in the middle of a river in Manchester, NH. Approximately 3,000 miles away from house
34.160331, -118.131934 //Roscoe's House of Chicken and Waffles, 1.76 miles away from house
34.007426, -118.499823 //Stanta Monica Pier, in degrees 25 miles away
36.095511,-115.176033 //The Luxor, Las Vegas

const float destinationLat = 34.007426; //latitude of destination (Santa Monica Pier) in DEGREES
const float destinationLong = 118.499823; //positive longitude of Santa Monica Pier in DEGREES
const float NemaDestinationLat = 3400.45138 //NEMA sentance latitude for Santa Monica Pier
const float NemaDestinationLong = 11829.99178 //NEMA sentance longitude for Santa Monica Pier

void setup()
if (serialDebug == 1){
Serial.begin(115200); // connect at 115200 so we can read the GPS fast enough and echo without dropping chars
Serial.println("Grant's GPS Present Test");
lcd.begin(16, 2); //begin lcd

GPS.begin(9600); //GPS uses 9600 baud
GPS.sendCommand(PMTK_SET_NMEA_OUTPUT_RMCGGA); //RMC (recommended minimum) and GGA (fix data) including altitude
GPS.sendCommand(PMTK_SET_NMEA_UPDATE_1HZ); // 1 Hz update rate
useInterrupt(true); //see if using interrups

//set pins to output/input
pinMode(offPin, OUTPUT);
pinMode(servoPin, OUTPUT);
digitalWrite(servoPin, LOW);

//servo stuff


SIGNAL(TIMER0_COMPA_vect) { // Interrupt is called once a millisecond, looks for any new GPS data, and stores it
char c = GPS.read();
if (GPSECHO) // if you want to debug, this is a good time to do it!
if (c) UDR0 = c; // writing direct to UDR0 is much much faster than Serial.print but only one character can be written at a time.

void useInterrupt(boolean v) {
if (v) {
OCR0A = 0xAF; // Timer0 is already used for millis() - we'll just interrupt somewhere in the middle and call the "Compare A" function above
usingInterrupt = true;
} else {
TIMSK0 &= ~_BV(OCIE0A); // do not call the interrupt function COMPA anymore
usingInterrupt = false;

uint32_t timer = millis();

void loop()
//I'm using the interrupt, so I don't need the not using interrupt part here
if (GPS.newNMEAreceived()) { // if a sentence is received, we can check the checksum, parse it...
if (!GPS.parse(GPS.lastNMEA())) // this also sets the newNMEAreceived() flag to false
return; // we can fail to parse a sentence in which case we should just wait for another

if (timer > millis()) timer = millis(); // if millis() or timer wraps around, we'll just reset it

if (resetCounter){ //if I need to reset the value in EEPROM
EEPROM.write(address, 1); //set it to 1, so when you turn it on the next time, it's the first attempt
resetCounter = false; //don't reset it again though

if (millis() - timer > 2000) { // approximately every 2 seconds or so, check stuff
timer = millis(); // reset the timer

//now, I want to check to see whether or not I have a fix. If not, I want to run a piece of code
//that waits for a fix and turns off if I don't get one soon enough

if (GPS.fix){
if(lcdDebug){ //I want to know how long it took to get a fix, so I get an idea of what's going on
lcd.print("It took (s)");
long seconds = timer/1000;
delay(dlay); //wait until I can read it
//my checkDistance and checkDate functions return a distance (float) or a number of days (int). 0 means it's good, a number means I
//need to print something, because I'm not there yet
float myDistance = checkDistance(); //gives me my distance from destination
int myDate = checkDate(); //gives me the date from target date

if (myDistance == 0.0 && myDate == 0){
openBox(); //if I'm there, and it's time, open!
else{ //if not, then print the clues
turnOff(1); //turn off and increment the attempts
initialization(); //this runs until a fix is found or the unit powers down


//this code waits for a fix and turns off if I doesn't get one soon enough
void initialization( void ){
//the first thing that I need to do is print out stuff for Lily to read, then I need to wait for a fix
//and if I don't get one soon enough, just power off.
//I can use timer, which is already an unsigned long
timer = millis();
if (firstOn == 0) {

//if this is the first time I've turned on, then I need to say hello
//first, I'm going to get how many attempts she's made
byte attempts = EEPROM.read(address);
lcd.print("Hello Lily");
lcd.print("Attempt ");
lcd.print(attempts, DEC);
int attemptsLeft = maxAttempts - attempts;
lcd.print(" attempts left");
lcd.print("Go outside");
firstOn = 1;

if (firstOn == 1){ //if not, I'm calculating
lcd.print("Finding signal");
lcd.print("Please wait");

if (timer > waitTime) turnOff(0); //if I've waited to long, stop wasting battery and don't count it

//once I have a gps fix, then I can actually do the calculations. I've already got the lcd
//saying what I want, so go ahead and calculate stuff
Turns off everything
if it gets a 1, it turns off and increments the attempts. If it gets a 0, it turns off without incrementing attempts
if it gets anything else (like a 2), it will just say powering off and turn off
void turnOff(int attemptPlus){
//this will turn off my arduino. I don't know how this will happen yet, but it will happen for now,
//I'll just have it say that it's powering off

if (attemptPlus == 1){ //if I got a signal and am not in the right place, count the attempt
byte attempts = EEPROM.read(address);
attempts += attempts;
EEPROM.write(address, attempts);

if (attemptPlus == 0){
lcd.print("No signal");

lcd.print("Powering off");

//turn myself off with pololu switch
digitalWrite(offPin, HIGH);

//if I don't turn off, then I'm externally powered, and I want to open the box


Opens Box

void openBox(void){
//this will open the box. I'll write this once I have motors wired up.
lcd.print("Opening Box");
digitalWrite(servoPin, HIGH);
turnOff(2); //2 just makes it turn off


//Function to check the distance from destination
//this returns 0 for there, or the distance away in miles

float checkDistance( void ){
//I'm going to calculate the distance that I have between me and the target location using the haversine
//function. I got the function from the arduino forums
float gpsLat = NemaToDegrees(GPS.latitude);
float gpsLong = NemaToDegrees(GPS.longitude);
if (lcdDebug){

//I'm going to find the approximate distance and save it to miles away
float milesAway = calcdist( destinationLat , destinationLong , gpsLat , gpsLong);

//here I'm comparing the raw NEMA sentance instead of calculating the distance. This is more accurate, but does not
//give me how far I am away
float latCheck = abs(NemaDestinationLat - GPS.latitude);
float longCheck = abs(NemaDestinationLong - GPS.longitude);

if (lcdDebug){

if (latCheck < maxGPSAway && longCheck < maxGPSAway) return 0.0; //this checks the raw coordinates to see if I'm close enough

//now I'm going to check to see if I'm close enought to my destination using the distance
if (milesAway < maxMilesAway) return 0.0; //checks my distance to see if I'm close enough else{ //if I'm not there, return how far away I am return milesAway; } } /****************** //I'm calling these functions only if I have a fix //this is my function to check to see if I'm on the correct day //this returns 0 for I'm at/past the correct day (it can open after her birthday) //and returns the number of days to go if not *******************/ int checkDate( void ) { int gpsMonth = GPS.month; int gpsDay = GPS.day; //so, it looks like the GPS unit is on June 16, 2012 at 5:35 when I'm at June 15, at 10:37 pm //so it's either 7 hours ahead of me, or it's just a day ahead and the time is off. //I'm going to ignore this difference, and let her open the box early. Oh darn. if (lcdDebug){ lcd.clear(); lcd.setCursor(0,1); lcd.print("Month"); lcd.home(); lcd.print(gpsMonth); delay(dlay); lcd.clear(); lcd.setCursor(0,1); lcd.print("Day"); lcd.home(); lcd.print(gpsDay); delay(dlay); } if (gpsMonth > 9){ //October is month 10
//however, I'm one day ahead with this gps unit
return 0;
else{ //otherwise, I'm not there
//I need to calculate how many days I have to go
int daysLeft = 0;
//I'm giving this to her in August, so I just need to program it to count down from August to October
if (gpsMonth == 8){
if (serialDebug) Serial.println("August");
//I'm in August. I have 30 days in September, then the rest of August (31 days)
daysLeft = 30 + 31 - gpsDay + 1; //this should be the days left before October
else if ( gpsMonth == 7){
if (serialDebug) Serial.println("July");
daysLeft = 31 + 31 +30 - gpsDay + 1;
} //June = 30 days, July = 31 days, August = 31 days, September = 30 days
if (serialDebug) Serial.println("September");
daysLeft = 30 - gpsDay + 1; //if it's not August, it's September, so subtract the day I'm at
return daysLeft;

* //Function to calculate the distance between two waypoints
* //I got this from the arduino forums.
float calcdist(float flat1, float flon1, float flat2, float flon2)
float dist_calc=0;
float dist_calc2=0;
float diflat=0;
float diflon=0;

//I've to spplit all the calculation in several steps. If i try to do it in a single line the arduino will explode.

dist_calc = (sin(diflat/2.0)*sin(diflat/2.0));
dist_calc2= cos(flat1);
dist_calc +=dist_calc2;


dist_calc*=3958.76; //Converting to miles
return dist_calc;

NEMA parser
Takes in the NEMA sentance values (degree.minutes) and outputs degrees
This is off by .3 miles (per calculation) due to the constraints of floats. a.k.a, I calculated it once, and I was off by
.3 miles. It may be more for other destinations.

float NemaToDegrees( float NemaValue ){
int NemaDegrees = NemaValue/100; //this gives me degrees
if (serialDebug){
Serial.println("Nema degrees Calculated");
float NemaMinutes = (NemaValue - (float)NemaDegrees*100.0); //this gives me the minutes (positive value, since NemaValue is larger
if (serialDebug){
Serial.println("Nema Minutes Calculated");
return (float)NemaDegrees + (NemaMinutes/60); //convert Minutes to degrees, add them, and return value

Feb 15

Laser Tag Update 2/15/15

So, about two years ago, I wanted to make a course to teach laser tag. I didn't make it a habit, and it didn't get done.

Now, I've made some progress towards that laser tag. However, like the me of the past, this is still a large project, and I haven't gotten very far.

So now, I'm going to (try to) use some of the advice I've got from Extra Credits. They make videos about video games, and their advice can be translated to other projects. I'm specifically talking about their series on making video games, and their rules video. I should refer to this every once in a while when I am unsure of what to do.

Completed Work

1. Create a program to send and receive tags
2. Build a prototype that can send and receive tags
3. Build a lens setup and test adding a lens - adding lens increased tag distance
4. Build LED test setup and increase current - increasing drive current increases tag distance
(Note: requires batteries that can supply the current, and capacitors)

In Progress

1. Increase range of tag unit send/receive


In my meanderings across the internet, books and the like, I have come across information on optics. I haven't done very much with optics, so this is a lot of trial and error on my part. However, I do know that I want to collimate light. Basically, I want to take light from an LED (emanating at about 25 degrees) and turn it into a beam that travels straight. Fortunately, if you buy a lens, they tell you the focal length, or distance away that a collimated light source will be focused. Put a light source that far away, and presto, instant collimated light.

However, what assumptions are they making about that light source? In the land of physics, everything is a point source, meaning it doesn't have any height or width. I tried using a 1" diameter lens to collimate a 5mm diameter IR LED. I got it to transmit about 50 feet, but it did not work very well outside. When I checked what the beam looked like with a red LED, the beam was not a column, but focused a few inches from the lens. If I want my lens to work more like the theoretical column, I need to make my LED look more like a point source. That means a larger lens or a smaller LED. Why not try both?


1. Get a larger lens/lenses 2"+ in diameter.
2. Build test set up and test 2" diameter lens (inside and outside) and record transmission distances at standard currents

Future work

1. Add more light indication.
2. Make tag unit more sturdy.