TypK to RGB Led
this little circuit reads a Typ K Thermocouple and indicates the Temperature with an RGB LED.
Read more:
The Quick Specs:
- ATmega168 with only a reset resistor and some noise blocking caps and inductors
- ISP header for programming (to upload the Arduino sketch hex file over avrdude)
- Typ K Thermocouple amplifier with LTC1050 (like here: http://code.google.com/p/multidisplay/wiki/TypKThermocouples)
- MCP9701 for the Ambient measurement directly above the Tyk P connector
- 5V Supply rugged for Automotive use (like here: http://code.google.com/p/multidisplay/wiki/Powersupply)
- 3 Transistors for the R-G-B Channels with Pulldown Resistors
Layout
The Thermocouple is attached to an LT1050 amplifier, and this Signal fed into the ATmega168.
For the Ambient Sensing a MCP9701 is used and directly fed into the ATmega168.
The ATmega168 is getting its 5V out of a rugged 7805 regulator with some protections against the Automotive environment.
3 Transistors then are used to get more switching power to the LED´s what are fed directly from the 12V.
Schematic and Layout: Target Layout
The Code
is written in the Arduino IDE (17 must be used, as the 18 does not generate the hex file, or i dont know where to get it)
Basically it reads the Thermocouple and the Ambient Temperature, adds both and then makes a big if / else if to find what colour would fit 
//d2k2 12.02.2010
//TypK RGB First Test
#include //for PROGMEN
#define ledPin 9 // STATUS LED connected to PB1
#define PinR 3 //PD3
#define PinG 5 //PD5
#define PinB 6 //PD6
#define TypK 0 //PC0
#define AmbK 1 //PC1
#define Set1 4 //PC4
#define Set2 3 //PC3
#define Set3 2 //PC2
unsigned int Temp;
//Averaging Values:
int TypKraw = 0;
int AmbiRaw = 0;
int TypKcel = 0;
int AmbiCel = 0;
int ResuCel = 0;
int DebugLed = 0;
#define tempTypKReadings 28 //how many entrys are in the Lookup Table
#define MaxTypK 1170 //over that will be seen as Open.
//Lookup Table for the TypK:
//from 0-1350�C in steps of 50�C, the list is in �V according to that Temp.
const unsigned int tempTypK[] PROGMEM =
{
0,
1922,
3891,
5831,
7731,
9645,
11599,
13578,
15577,
17590,
19612,
21637,
23660,
25674,
27673,
29652,
31611,
33547,
35460,
37348,
39212,
41050,
42863,
44645,
46396,
48112,
49790,
51431
};
void setup() {
TCCR0B = 0x01; // Timer 0: PWM 5 & 6 @ 16 kHz
TCCR1B = 0x01; // Timer 1: PWM 9 & 10 @ 16 kHz
TCCR2B = 0x01; // Timer 2: PWM 3 & 11 @ 16 kHz
// initialize the digital pin as an output:
pinMode(ledPin, OUTPUT);
pinMode(PinR, OUTPUT);
pinMode(PinG, OUTPUT);
pinMode(PinB, OUTPUT);
//Make a small LED Test:
analogWrite(ledPin,5);
for (int i=0; i <= 255; i++){
analogWrite(PinR, i);
delay(20);
}
analogWrite(PinR,0);
for (int i=0; i <= 255; i++){
analogWrite(PinG, i);
delay(20);
}
analogWrite(PinG,0);
for (int i=0; i <= 255; i++){
analogWrite(PinB, i);
delay(20);
}
}
void loop()
{
//Set the Debug Led:
analogWrite(ledPin,DebugLed);
//Get the Ambient Value into the Loop:
AmbiRaw = AmbiRaw * 0.9 + analogRead(AmbK) * 0.1;
//Get the Thermocouple Value into the Loop
TypKraw = TypKraw * 0.5 + analogRead(TypK) * 0.5;
//Convert both into usefull Temps
Temp = ((5.0*TypKraw)/1024.0)*10000; //gets the Volts and makes µV out of it (100 is already added from the Amp)
TypKcel = GetTypKTemp(Temp); //Converts the µV into °C
AmbiCel = ((((5.0*AmbiRaw)/1024.0)*1000)-400)/19.5; //Makes mV, takes off the 400mV Offset and then divides by the 19.5 coefficient (MCP9701)
ResuCel = TypKcel + AmbiCel;
//Get the Light according to the Temp:
int R = 0;
int G = 0;
int B = 0;
if (ResuCel < 100)
{
//Green when the Temp i below 100C
R = 0;
G = 255;
B = 0;
}
else if (ResuCel < 200)
{
//Yellow
R = 255;
G = 100;
B = 0;
}
else if (ResuCel >= 200)
{
//Red
R = 255;
G = 0;
B = 0;
}
//And set it:
analogWrite(PinR,R);
analogWrite(PinG,G);
analogWrite(PinB,B);
//wait a little:
delay(100);
//Switch the Debug Led from one to the other State
if(DebugLed == 5)
{
DebugLed = 0;
}
else
{
DebugLed = 5;
}
}
//This Sub converts the thermocouple µV reading into some usable °C
int GetTypKTemp(unsigned int microVolts)
{
int LookedupValue;
//This searches the 2 surrounding values, and then linear interpolates between them.
for(int i = 0; iif(microVolts >= pgm_read_word(&tempTypK[i]) && microVolts <= pgm_read_word(&tempTypK[i+1]))
{
LookedupValue = ((i)*50) + ((50L *(microVolts - pgm_read_word(&tempTypK[i]))) / ((pgm_read_word(&tempTypK[i+1]) - pgm_read_word(&tempTypK[i]))));
break;
}
}
return LookedupValue;
}
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