Rancilio Silvia Espresso Maker Water Tank Sensor

Description

This water sensor as described in the A Water Tank Sensor For Rancilio Espresso Machines measures the water tank level of the Rancilio Silva and is accurate enough to provide automatic shot volume levels as shown in the Espresso Maker that knows when you want some blog entry.  It measures 1700ml of water over the complete measurement range with an error of less than 12ml (-7ml/+5ml).

This sensor works is designed to work with the Espresso Connect project,  but is a stand alone sensor that can work with any controller.  the output of the sensor uses the robust SENT protocol and  Implementing the SENT protocol in python for the Raspberry Pi blog  shows one way to use it.  However, this sensor can be used by virtually any microcontroller.  The sensor also outputs the position using a 250Hz switching period PWM signal.

The sensor is ready to be installed out of the box with a simple one screw assembly and without any modification of the existing Rancilio Silvia water tank.    In addition, a 6 foot cable is also included so that attachment to the raspberry pi is just plug and play.  The cable is long enough to allow the tank to be removed from the machine to fill up with water or perform other machine services.

Sensor Accuracy:

When using the velocity calibration method described in the blog , The accuracy can reach 12ml (-7ml/+5ml) of error.   The graph below shows the error before and after the additional calibration.   The sensor is velocity calibrated and verified with a stock Rancilio Silvia espresso machine.

The sensor contains:

1. Float (PEG-G plastic) with copper tape, weights for proper floating and encased with food safe epoxy
2. Float Track (PET-G plastic)
3. Fully populated, assembled, programmed, and tested Linear Position Sensor PCB Rev 4 assembly
4. 6 foot cable between the sensor and Raspberry Pi or host processor
5. M3 x 5mm Flat Head Screw
6. Custom offset and velocity calibration CalSampleRaw.csv file will sent via email with order delivery.

Cable Description:

1.  Red Wire:  Sensor 5v supply
2.  Black Wire: Sensor Ground
3.  Brown Wire: Sensor IO2 output (SENT output)
4.  White Wire: Sensor IO3 output (PWM output)