This is a small project to control temperature with a heater. In case you are my boss : this is needed to heat out vacuum chambers. As this is not done that often, you may use it as well to prepare tea, or onsen eggs.

The mastermind of this design is of course the Arduino Nano Every. It handles the user input from the rotary encoder and displays the status on the 128 x 64 px oled display.




View inside the case.

The design uses a WG A5 6D 10Z solid state relay. It can handle 10 A and has a built in snubber circuit. It uses a control voltage of 3 ... 32 V and switches in the zero crossing of the line frequency. As the sourcing of components is hard these days, we use this module which has everything built in already.

The Connector to the outer world is a 6-pin KFV-60 DIN jack. The 6 pins are used as follows :

PIN	SIGNAL
1	+ 5 V
2	GND
3	Analog 0, for e.g. LM-35
4	I2C SDA
5	I2C SCL
6	variable, tbd

As it is possible to have pcb's made with an aluminium substrate, we were seduced to pack a TMP 101 (±2 °C Digital temperature sensor with I2C/SMBus interface) on it. It works only fine, if the water reaches close to the sensor itself. Heat conduction in the aluminium was not optimal.

This little adapter houses an MCP9600 (Thermocouple EMF to Temperature Converter, ±1.5 °C Maximum Accuracy) as well as an Eeprom to hold information about the sensor. After some struggling it came alive. And yes, we reduced the (I2C) "heartbeat" to 20 kHz.

A lot of different methods exist. Sophia is using that thermomix thing from china, whilst Nami adds up water of different temperatures.

But you are an engineer, tinkerer or physicist. That's why you are here.

Let's see how we can also do it. As a starting point, we use the data from Kenji's Food Lab : The Guide to Sous Vide Eggs. The Watercooker is filled with 1 liter ZH₂O, 4 eggs (Baselbiet), each approx. 60 gr. and the Ongmod is programmed for 59 minutes at 64 °C.




As you mayst see from the last graph, temperature stability has some headroom for optimization. By using a PID regulator, the ripple can be made much smaller. But the eggs tasted beatifully :-)



Temperature of Tea water, when using a PID Library to heat up.

The webmaster does not read these comments regularely. Urgent questions should be send via email. Ads or links to completely uncorrelated things will be removed.