Open Source Laser Power Meter

[epyn]

Guys,
I had a DIY LPM.
Carbonsoot absorbent on 8x8mm TEC element with a simple cold compensation electrical circuit and a specific calibration process.
It worked great and accurate .
Than i've bought a LaserBee AX(a month ago)
Literally there was only 2-3% of difference when i've measured my lasers.
Costs? Under 20€ and few hours of work. No arduino,no any hard to get part.

[buffo]

Than i've bought a LaserBee AX(a month ago)
Literally there was only 2-3% of difference when i've measured my lasers.
Costs? Under 20€ and few hours of work. No arduino,no any hard to get part.

I agree that the Laserbee line of power meters are great for hobbyists. But they top out at 10 watts for the biggest version, and most of them are only good to 3 or 5 watts. That's normally enough for your average hobbyist, but if you have a CO2 laser or a high-powered YAG, you need something bigger.

The meter Ed is talking about will go up to 150 watts. And for something that can accurately read power that high, a $25 price point is really impressive. I was expecting 3 figures, minimum.

Adam

[VDX]

Hi Adam,

you can easily "tweak" a 5W sensor to measure powers up to some Kilowatts with expanded beam and aperture plates or better perforated grid sheets

Viktor

[lasersbee]

so far i was able to measure 10 watt laser acurately +- 5%
and 15 to 100watt + - 2%
resolution is .01 watt
sensing element is anodized aluminum and carbon black coating
convection cooled, might go higher power with forced air cooling
but my most powerfull laser is 150 watt

I see that you are using a Type 'K' Thermocouple for the power
sensing element.
For $25.00 I'll take one of your LPMs for testing right now...
You can PM me and let me know where to send the PP payment.

What is the 100% response time at 1 Watt ??

Jerry

[aberry]

I took the liberty of restoring the indentation of the arduino code and adding in English translations for some of the text (Mostly for my own benefit--in the immortal words of Korben Dallas, "I only speak two languages...").

The calorimetric approach is quite nice in its simplicity. Of course the mass of the heatsink has to be taken into the calibration, and using a heatsink means that measurement accuracy will be dependent on the surrounding air flow conditions. Measuring the equilibrium temperature and examining the slope during the measurement and cooldown periods would probably allow you to largely remove the heatsink and ambient characteristics from the measurements, but that would get complicated and mathy.

But with a known mass of known material with a known absorption you can get pretty close quite easily. Neat!

// Digital Laser Power Meter// v 2.1




#include <max6675.h>
#include <LiquidCrystal.h>
#include <Wire.h>




//Max6675 CK,CS,SO
MAX6675 thermocouple(4, 3, 2);
int sense = 0;
float cal = 0.0000;
int t = 10;
int tiempo = t;
float p = 0.717;
int m = 87;
int maxt = 45;
float temperatura = 0.000;
float temperaturai = 0.000;
float temperaturaf = 0.000;
float temperaturaa = 0.000;
float w = 0.000;
//establecer conexiones LCD 16x2
// RS, E, D4, D5, D6, D7
LiquidCrystal lcd(8, 9, 10, 11, 12, 13);




void setup() {
	Serial.begin(9600);
	// use Arduino pins FORMAX6675 VCC AND GND 
	pinMode(5, OUTPUT); digitalWrite(5, HIGH);
	pinMode(6, OUTPUT); digitalWrite(6, LOW);
	pinMode(7, OUTPUT); digitalWrite(7, HIGH);
	lcd.begin(16, 2);
	sense = analogRead(A7);
	cal = sense * (2.0 / 1023.0);
	p = cal;
	// wait for MAX chip to stabilize
	delay(1000);
	lcd.clear();
	lcd.setCursor(0, 0);
	lcd.print ("Medidor Potencia");
	lcd.setCursor(0, 1);
	lcd.print (" Laser Co2");
	delay(2500);
	lcd.clear();
	lcd.setCursor(0, 0);
	lcd.print (" V 2.0 ");
	lcd.setCursor(0, 1);
	lcd.print ("521 229-419-3262");
	delay(5000);
	lcd.clear();
	lcd.setCursor(0, 0);
	lcd.print ("Cal P = ");
	lcd.print (p);
	delay (2500);
}




void loop() 
{




	//esperar temperqatura menor a tmax
	temperatura = thermocouple.readCelsius();


	while (thermocouple.readCelsius() > maxt)
	{
		lcd.clear();
		lcd.setCursor(0, 0);
		lcd.print (" Temperatura de "); // "High sensor temperature"
		lcd.setCursor(0, 1);
		lcd.print (" sensor alta");
		delay(2000);
		lcd.clear();
		lcd.setCursor(0, 0);
		lcd.print ("Porfavor Espere"); //"Please wait"
		lcd.setCursor(0, 1);
		lcd.print (" T = ");
		lcd.print (thermocouple.readCelsius());
		lcd.print (" C");
		delay(2000);
	}


	lcd.clear();
	lcd.setCursor(0, 0);
	lcd.print(" Medir Potencia "); // "Measure power"
	lcd.setCursor(0, 2);
	lcd.print(" Encender Laser "); // "Turn on the laser"
	// guardar temperatura inicial
	temperaturai = thermocouple.readCelsius();
	digitalWrite(7, LOW);
	//Serial.print ("Temperatura Inicial ");
	//Serial.println (temperaturai);
	//Serial.println ("Espera de laser");
	delay (180);


	do
	{
		temperatura = thermocouple.readCelsius();
		//Serial.println(temperatura);
		delay (180);
		//esperar a una diferencia de un grado de temperatura
		//wait for a difference of one degree of temperature


		if (temperatura < temperaturai)
		{
			temperaturai = temperatura;
		}
	} while (temperatura-temperaturai < 1);


	//Serial.println("Lecturas");
	//esperar T segundos para absorber energia
	//wait T seconds to absorb energy
	do
	{
		lcd.clear();
		lcd.setCursor(0, 0);
		lcd.print("ESPERE "); // "WAIT"
		lcd.print(tiempo);
		lcd.print("Seg"); // "Sec[onds]"
		tiempo=tiempo - 1;
		//Serial.println(thermocouple.readCelsius());
		delay (1000);
	} while (tiempo > 0);
	//Serial.println("Esperando Maximo");
	digitalWrite(7, HIGH);
	lcd.clear();
	lcd.setCursor(0, 0);
	lcd.print("PROCESANDO"); // "PROCESSING"
	temperaturaf = thermocouple.readCelsius();
	delay(180); 


	do
	{
		temperatura = thermocouple.readCelsius();


		//Serial.print (temperaturaf);
		//Serial.print (" - ");
		//Serial.println (temperatura);
		delay(200);
		if (temperaturaf < temperatura)
		{
			temperaturaf = temperatura;
		}
	} while ((temperaturaf - temperatura) < 0.75);








	w =((((m*(temperaturaf - temperaturai))*(4.18)*(p))/30));
	//w = (((m*(deltat))/1000)*4180)/(t);
	//Serial.println("calculo");
	//Serial.println(temperaturai);
	//Serial.println(temperaturaf);
	//Serial.print("Watts: ");
	//Serial.println(w);








	lcd.clear();
	lcd.setCursor(0, 0);
	lcd.print ("POTENCIA LASER"); // "LASER POWER"
	lcd.setCursor (0, 2);
	lcd.print(w);
	lcd.print(" Watts");




	delay(10000);
	tiempo = t;
	digitalWrite(7, HIGH);
}

[lasersbee]

I would still like to know...
What is the 100% response time at 1 Watt ??

Jerry

[aberry]

I would still like to know...
What is the 100% response time at 1 Watt ??

The code sinfocomp shared shows that it waits for the the temperature of the heatsink (or really, integrating mass) to increase by one degree, and then after that has a fixed integration time of ten seconds. So the 1W response time will depend on the mass of the heatsink. Aluminum has a specific heat of 0.9 J/gK, so the addition 1 degree time is going to be about a second per gram. So clearly low power applications want a smaller integrating mass.

[lasersbee]

The code sinfocomp shared shows that it waits for the the temperature of the heatsink (or really, integrating mass) to increase by one degree, and then after that has a fixed integration time of ten seconds. So the 1W response time will depend on the mass of the heatsink. Aluminum has a specific heat of 0.9 J/gK, so the addition 1 degree time is going to be about a second per gram. So clearly low power applications want a smaller integrating mass.

Thanks for the additional Code timing info.

Sorry, cant test, i dont have a 1 watt laser

No problem... Was just curious.

Jerry

[Openair]

Very well, but the device is already working, gives the necessary parameters?

[Openair]

Hello, device is working good, gives consistent results.

Clearly, I myself design various radio devices from time to time, by the way, 3D prototype model, I will soon order aluminum casting