## [[Resources/mathematics/Proportional Integral Derivative|PID]] Controller for the Gaggia Baby Millenium

### Parts Used

- [ESP32]()
- [Solid State Relais]()
- [I2C LCD Screen]()
- [DS18B20 Temperature Sensor]()
- [Thick Wire](https://www.amazon.de/-/en/gp/product/B089CVRX42/ref=ewc_pr_img_2?smid=ATDBGRW2TNE4V&th=1)
- [220v to 5v converter](https://www.amazon.de/-/en/Sharplace-Constant-voltage-downward-converter-White/dp/B07CTQQMMT/ref=sr_1_3?keywords=230v+to+5v&qid=1683574853&sprefix=230v+to+%2Caps%2C87&sr=8-3)


# First Day

The first day was on Friday the 27.05.2023. I went with Kilian to the house he grew up in because he had to do some measurements for his Bachelor Thesis.

In a few hours i first checked if i could connect the relais i bought, which is this one:

![SSR-40A](Solid-State-Relais-SSR-40AA.webp)

This was my first mistake, because I did not check the input voltage and only thought about how much current it could handle. The specific SSR i bought is driven by a current of 80~250 Volts AC, which the ESP32 can’t output. I had noticed this a few days earlier and went to a local electronics store and bought a classic mechanical relais. This was the second mistake I did 😀 
![](relais-srsb-12vdc-sl-a-12v-dc-250v-ac-5a.webp)
The thing is normally you would use this sort of relais with a small circuit (octocoupler) that isolates the relais’ control circuit from the ESP32. These circuits look like this:

![](DC-12V-1-Kanal-Relais-Modul.webp)

Gladly i had a grove devkit with me, so atleast i got to try out connecting one of those relais to the esp which was very easy.

Then I also tried to connect my MAX6675 Thermocoupler to the ESP32. This was very easy to do as I found a schematic online. The MAX6675 uses SPI. 

## Second Day