After finishing the build of the oven, I drilled some holes in the tempex/wood of the box to lead the wiring through it to the outside world.

Then I connected the 5V power supply. The source is an old LabPS, but good enough for this short test. In the oven the 5V is filtered by a 100nF capacitor to keep away the most outside noise.

I measure the temperature in the oven with the TMP117, connected to a NANO via I2C, which is throwing his temperature data to the Serial port, 2 decimals.

With excel (Data Streamer) I keep track of the temp after power up. I already checked the 10MHz at the output, which is ok.

The current of the 5V in the beginning is expected high, about 600mA, but is going down pretty fast (minutes) to 150mA, and if you measure longer it will go down further, but slower and slower, until the input power is in balance with the radiated power of the wooden/tempex box.

The temperature inside the oven is going up after about 10 seconds with 0.1 C per second. And that figure is going down, and down every minute. After two hours, the temp in my oven was 42.49 C (started with 26 C). The rate was at that time +2C/hr.

After another half an hour, the rate dropped to +1.7 C/hour, and this process will go on to a temperature where the in and out going power is the same. The minimum current looks like 150mA, which makes .15A*5V= .75 Watts. This is than the radiated output power of the oven. We have to make sure that this is not warming up the GPSDO box, because there are some devices which are temperature sensitive, i.e. the D1 diode in the 1 uSec integrating puls of the phase detector, and the NGO capacitor. And certainly also the power regulators. But that is for later.

The Arduino code for this measurement is:

 

****************************************************

#include <Adafruit_TMP117.h>

#include <Adafruit_Sensor.h>
#include <math.h>
#include <Wire.h>
#include <LiquidCrystal_I2C.h>

LiquidCrystal_I2C lcd(0x27,20,4);

uint8_t ADDR_Bliley = 0x48; //adr pin to GND or open

Adafruit_TMP117 tmp117Bliley;

float Temp_Bliley = 00.00;

void setup()
{
Wire.begin();
Serial.begin(115200);
while(!Serial) delay(10);      //wait for serial port to start

Wire.setClock(1000000);    //1MHz

lcd.init();
lcd.backlight();
lcd.setCursor(1,0);
if (!tmp117Bliley.begin(ADDR_Bliley))
{
Serial.println("Failed to find the TMP117 chip (Bliley)");
while(1)
{
delay(10);
}
}
Serial.println("TMP chip (Bliley) found");

}

 

void loop()
{
read_temperatures();
write_temps_to_LCD();
write_temps_to_serial();
delay(1000);
}

void read_temperatures()
{
sensors_event_t event_Bliley;                             //create objects to be filled
tmp117Bliley.getEvent(&event_Bliley);             //fill the empty objects with the current measurements
Temp_Bliley = event_Bliley.temperature;
}

void write_temps_to_LCD()
{
lcd.setCursor(0,1);
lcd.print("Temp Bliley = ");
lcd.print(Temp_Bliley);
}

 

void write_temps_to_serial()
{
Serial.println(Temp_Bliley);
}

 

*********************************************************************************

 

Again half an hour later, the rate is dropped to 1.2 C/hour (at 43.89 C).

I have the feeling that the temperature of 45 C will be the 'end station'. I will measure it another hour, I am curious.

Good, after this hour, the rate has dropped to 0.25 C /hour. At a temp of 44.71. My guess of 45 C as the final temp is quite good, I think.

The changes in temperature of the oven will be very small and very slow from now. Tomorrow I will look what happens if the environmental temperature is changing rapidly a few degrees.

Sleeping time,.....