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Milk in Fridge – Internet of Things




I think that one day, all food cupboards & fridges/freezers will be smart. All products will have an RFID or video recognisable label which will update a list of product usage. Your local supermarket will gather this information & replenish your products as required – who knows ??

Milk in Fridge – Internet of Things

So, I came up with the idea of ‘How much milk is in my fridge’. Well, now I can go on the Internet and see ! -very handy when out shopping :-). I use a load cell to weigh the milk & an oled display for status.

There are 4 parts to this project.

1) Connecting to WiFi using the ESP8266

2) Establishing and making a link to Thingspeak

3) Connecting the load cell (strain gauge)

4) Connecting a .96 oled mono display.

In brief:

I have a reed switch and magnet on my fridge door. When the door is opened, an interrupt is triggered. The Load cell value is read & converted to ‘pints’ and displayed on the Oled screen. There are 8 attempts made to update Thingspeak. If 8 updates have not been successful, after a delay of 30 seconds, retry occurs! Each time the fridge door is opened, the counter is reset to zero, thus initiating another 8 attempts. Why 8 attempts? just to give the load cell time to settle – 5 may well be enough!

Step 1: Step 1: Set up & test the individual parts.

I set up an Arduino Uno to test each of the 4 sections separately, then, when each was working, I merged the code.

My program is about as tidy as an unmade bed, but it works and is fairly readable.

I used a breadboard power supply & fed it with an old 9v psu – this gave me 5v (for the load cell) & 3.3v for the ESP8266 (which can draw up to 300mA according to the spec sheet). I took the Oled 3.3v from the Arduino board.

Pin connections as follows

// oled SDA #A4
// oled SDC #A5 NOTE Supply is 3.3v

// HX711.DOUT – pin #A1 // HX711.PD_SCK – pin #A0 NOTE Supply is 5v

//ESP8266 TX/RX to arduino RX/TX

//Ext USB to serial monitor(10, 11); // RX, TX //DO NOT FORGET TO Common GND ALL devices, power supplies & comms

// int on D2 normally Gnd – goes high when fridge door opened

Note – I was going to use a light sensor to detect when the fridge door was opened, I needed it on interrupt and was too lazy to fathom out how to use an analogue signal to achieve this – hence in the code you will see a variable ‘stilldark’.

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DISCLAIMER: This is an extremely dangerous project, and it should only be attempted by people with experience in electronics, and...

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