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Joined: Mon Mar 25, 2019 8:01 pm

Rancilio Silvia raspberrypi PID project

Mon Mar 25, 2019 8:24 pm

Hi all,

I need some help with a DIY PID project on my espressomachine (Rancilio Silvia). For a long time I wanted to stabillize the temperature to make better shots. Of course you can buy a pre-installed PID from Auberins or else, but I wanted to do it myself so I can learn a thing or two out of it.

I started with the project that seemed best fit for my needs:

The parts that I've bought are the following:

- Solid State Relay
- Rasberry Pi Zero W
- Pt100 sensor (1/3 DIN) ... d/a-96836/
- MAX31865 amplifier

I've installed everything on my Rancilio Silvia V1, connected the SSR with the RPI and the Amplifier accordingly. Set the PI up and installed the program BryceSub wrote. After a couple of tries, i finally was able to get the webapi going. The script uploads the values to a webserver, where you can see for example which temperature the water is. See ... hboard.gif

I bought the MAX31855 amplifier, that is compatibel with the PT100 sensor. This has the following outputs:
* 3vs3
* CS

I've connected them in the following manner:
* 3v3 (green wire) to RPI physical pin #17
* GND (red wire) to RPI physical pin #25
* SO (yellow wire) to RPI physical pin #21
* SCK (blue wire) to RPI physical pin #23
* CS (black wire) to RPI physical pin #24

SSR is connected to:
* SSR + (red wire) to RPI physical pin #37
* SSR - (white) to RPI physical pin #39

Also we've measured on the amplifier the values of the PT100 in ohm. This is functioning properly.

Problem is: I don't get any values in the webapi, it only states (when i read out the values via Putty) 32 Fahrenheit, the equivalent of 0 degrees celsius (I'm European, hence the translation to celsius). The assumption is, is that the problem lies between the PT100 sensor and the RPI... but I dont' know exactly what I've done wrong. Or I didn't install the right libraries. The github repo i'm using uses the MAX31855 thermocouple amplifier, and I'm using the MAX31865 (because I use a PT100 sensor) I've added the MAX 31865 libraries via:

echo "Installing MAX31865 Thermocouple Amp library..." cd ~ git clone cd ~/Adafruit_Python_MAX31865 python install

When I turn the machine on, the boiler is heating up. The SSR is also on. The only thing it doesn't, is turning off at the right temperature. When the light of the Rancilio turns off (i.e. it should be on the right temperature) I'm getting steam out of it, instead of hot water.

Did I do something wrong with the installation? Is this the correct way to add a library? Or have I overlooked something else?

Thanks in advance for all the help!

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