1) We are working on a Smart Dustbin that can Sort Waste into 3 Categories:
I) Food-Based waste like Banana Peel which can be used to make compost.
II) Metallic waste like iron, copper, steel, Aluminium.
III) Others like Paper, Rubber and Plastic...etc.
2) We are going to do this by measuring Weight, Resistance & Dielectric quality of waste.
i) We can measure the weight with the help of a strain gauge in half bridge mode and an OP-AMP in differential configuration to amplify the signal. The output of the OP-Amp is going to be connected to an ADC or Analog pin of the microcontroller to read the value.
ii) We can measure the resistance with a voltage divider circuit. It is going to have one fixed resistor & two disconnected points. Waste is going to sort these two points. Depending on the resistance of waste we will get an output voltage. Things like Paper, Rubber, Plastics are insulators; Metallic waste is generally conductive or has a low resistance; Food based waste can be an insulator or can have high resistance because of the presence of moisture.
iii) Capacitive Sensor is made up of 3 parts; two laminated copper parallel plates forming a capacitor & it is connected to the 6 & GND pin of NE555. NE555 is configured in an Astable mode.
Microcontroller to read measure Ton time of NE555.
One Plate is fixed, another plate is connected to the stepper motor (with an encoder) in such a way that it can move forward and backwards with respect to the fixed copper plate & act as a crusher.
Capacitance depends on 3 things.
A) Area of the plates which is fixed.
B) Distance between the two plates which is not fixed but the encoder will help us two know the distance between the two plates.
C) Dielectric Property which depends on the type of waste.
After crushing the waste, if we measure the Ton time, the change is going to take place due to the change in capacitance because resistor value is fixed. Change in capacitance depends on the distance between the plates and the dielectric property of waste because the area is fixed. If we are aware of the distance between the plates then we can determine the amount of change taking place due to waste. Food-based waste is going to show higher deflection due to the presence of moisture.
3) Our Dustbin consists of 3 Layers
i) Layer 1 (Top Layer). It has an IR proximity sensor and a Rotating flat LID. When waste is dumped on its IR proximity sensor will trigger, the microcontroller will measure weight through a strain gauge due to the flex in the Flat Lid. After measuring the weight the LID will rotate right, waste will fall down to a chamber in 2nd Layer.
ii) Layer 2: It is a chamber where we are going to crush the waste and measure its resistance & dielectric property through a capacitive sensor. This data will be provided to the microcontroller, it will decide the type of waste. The bottom part of the chamber can rotate like the top lid.
iii) Layer 3 consists of a rotating drum. The drum has 3 vertical partitions. Once the type of waste is decided, the correct partition will rotate & align itself with the bottom portion of the chamber. The bottom portion will rotate and waste will fall into the chamber. Every partition will have an IR proximity sensor to detect if the partition is filled or not.
The owner can monitor & control everything with the help of an app. They can see what type of waste is dumped, how much the partitions are filled.
i) We are dividing waste into 3 categories to make the dustbin small. If we increase the no. of categories we have to increase the no. of partitions which will increase the size of the dustbin.
ii) The big dustbin can have more categories.
ii) Our future goal is that we can give voice commands to the dustbin like we can tell it the type of waste if needed.