Project

# Title Team Members TA Documents Sponsor
43 LeafLink
 Hannah Pushparaj
Hassan Shafi
Praveen Natarajan
 Aniket Chatterjee design_document1.pdf
final_paper1.pdf
presentation1.pdf
proposal1.pdf
video1.pdf
video
LeafLink

Team Members:
Praveen Natarajan (pn17)
Hassan Shafi(hashafi2)
Hannah Pushparaj(hsp5)

PROBLEM

Plants need to be watered constantly for them to stay alive. Depending on certain scenarios, this might not always be possible for people to do (ex: going on vacation, forgetting to water, etc). We want a way to automatically water these indoor plants to make them stay alive.

SOLUTION

A standalone device that automatically senses the moisture level of the soil, and deploys a pump that supplies the plant with just the right amount of water to survive. It uses an onboard soil moisture sensor along with a water pump to supply the plant with water.
The device is designed to be reliable and easy to understand. A simple light shows what it’s doing (normal, watering, or needs attention). It also includes basic safety limits so it can’t keep running forever if something goes wrong, and it can warn the user if the water container is empty or if the device isn’t able to pump water properly. The device can store a basic history of when it watered the plant so the user can see that it’s working.
If we have time, we can add a simple companion app. The app would let the user see the current soil moisture, and it would show a log of recent watering. It would also allow the user to trigger a quick manual watering from their phone if needed (for example, after repotting or during a very hot week). The app is optional as the device should work on its own even without it.

Solution Components

Subsystem 1: Control & Processing

This subsystem serves as the central controller. An ESP32 on our custom-designed PCB reads soil moisture sensor data, executes watering logic, and controls the relay module. The PCB integrates power regulation and some basic status indication.
Components:
- ESP32
- Our Custom PCB
- 3.3 V voltage regulator
- Some LEDs and resistors


Subsystem 2: Soil Moisture Sensing
This subsystem measures soil moisture and provides an analog voltage to the ESP32 ADC pin to drive the water delivery system.
Components:
- Capacitive Soil Moisture Sensor


Subsystem 3: Water Delivery & Relay Control
This subsystem allows the ESP32 microcontroller to turn the water pump on and off by using a relay, acting as a switch between the ESP32 and higher voltage water pump. So essentially the ESP32 GPIO will drive the relay input which will switch pump power on and off.
Components:
- 6-12 V DC Water pump
- 5 V single-channel relay module
- External 5 V power supply
- Tubing and water reservoir


Subsystem 4: User Feedback & Safety
This subsystem provides basic visual feedback based on the current state of the Leaflink system and an emergency stop button
Components:
- Status LEDs (different colors for idle, watering, error).
- Red push button (emergency stop, kills power)


Subsystem 5: Wireless Monitoring
We will also have a remote monitoring feature using the ESP32’s built-in Wi-Fi. In this remote monitoring system we will display the real-time soil moisture readings (maybe even keep track of old readings over a time period), history of recent watering events, and a manual watering trigger button.
Components:
- ESP32 Wi-Fi (already part of chip)
- Simple mobile or web interface

CRITERION FOR SUCCESS

- The ESP32 on our custom PCB correctly reads soil moisture data and determines when watering is required independently (requiring no supervision)
- Ensure proper functionality of the soil moisture sensor by ensuring moisture readings are accurate (for example if we add water the moisture percentage should get higher)
- The ESP32 reliably controls the relay to turn the water pump on and off based on soil moisture thresholds.
- The water pump operates only through the relay and correctly distributes the required amount of water
- The multiple LEDs correctly indicate the current system states, including idle, watering, and error.
- Pressing the emergency stop button immediately cuts power to the water pump and halts any ongoing operation
- Remote monitoring system displays accurate real-time soil moisture data, logs watering events, and allows manual watering control.

Four Point Probe

Simon Danthinne, Ming-Yan Hsiao, Dorian Tricaud

Four Point Probe

Featured Project

# Four Point Probe

Team Members:

Simon Danthinne(simoned2)

Ming-Yan Hsiao(myhsiao2)

Dorian Tricaud (tricaud2)

# Problem:

In the manufacturing process of semiconductor wafers, numerous pieces of test equipment are essential to verify that each manufacturing step has been correctly executed. This requirement significantly raises the cost barrier for entering semiconductor manufacturing, making it challenging for students and hobbyists to gain practical experience. To address this issue, we propose developing an all-in-one four-point probe setup. This device will enable users to measure the surface resistivity of a wafer, a critical parameter that can provide insights into various properties of the wafer, such as its doping level. By offering a more accessible and cost-effective solution, we aim to lower the entry barriers and facilitate hands-on learning and experimentation in semiconductor manufacturing.

# Solution:

Our design will use an off-the-shelf four point probe head for the precision manufacturing tolerances which will be used for contact with the wafer. This wafer contact solution will then be connected to a current source precisely controlled by an IC as well as an ADC to measure the voltage. For user interface, we will have an array of buttons for user input as well as an LCD screen to provide measurement readout and parameter setup regarding wafer information. This will allow us to make better approximations for the wafer based on size and doping type.

# Solution Components:

## Subsystem 1: Measurement system

We will utilize a four-point probe head (HPS2523) with 2mm diameter gold tips to measure the sheet resistance of the silicon wafer. A DC voltage regulator (DIO6905CSH3) will be employed to force current through the two outer tips, while a 24-bit ADC (MCP3561RT-E/ST) will measure the voltage across the two inner tips, with expected measurements in the millivolt range and current operation lasting several milliseconds. Additionally, we plan to use an AC voltage regulator (TPS79633QDCQRQ1) to transiently sweep the outer tips to measure capacitances between them, which will help determine the dopants present. To accurately measure the low voltages, we will amplify the signal using an JFET op-amp (OPA140AIDGKR) to ensure it falls within the ADC’s specifications. Using these measurements, we can apply formulas with corrections for real-world factors to calculate the sheet resistance and other parameters of the wafer.

## Subsystem 2: User Input

To enable users to interact effectively with the measurement system, we will implement an array of buttons that offer various functions such as calibration, measurement setup, and measurement polling. This interface will let users configure the measurement system to ensure that the approximations are suitable for the specific properties of the wafer. The button interface will provide users with the ability to initiate calibration routines to ensure accuracy and reliability, and set up measurements by defining parameters like type, range, and size tailored to the wafer’s characteristics. Additionally, users can poll measurements to start, stop, and monitor ongoing measurements, allowing for real-time adjustments and data collection. The interface also allows users to make approximations regarding other wafer properties so the user can quickly find out more information on their wafer. This comprehensive button interface will make the measurement system user-friendly and adaptable, ensuring precise and efficient measurements tailored to the specific needs of each wafer.

## Subsystem 3: Display

To provide output to users, we will utilize a monochrome 2.4 inch 128x64 OLED LCD display driven over SPI from the MCU. This display will not only present data clearly but also serve as an interface for users to interact with the device. The monochrome LCD will be instrumental in displaying measurement results, system status, and other relevant information in a straightforward and easy-to-read format. Additionally, it will facilitate user interaction by providing visual feedback during calibration, measurement setup, and polling processes. This ensures that users can efficiently navigate and operate the device, making the overall experience intuitive and user-friendly.

# Criterion for Success:

A precise constant current can be run through the wafer for various samples

Measurement system can identify voltage (10mV range minimum) across wafer

Measurement data and calculations can be viewed on LCD

Button inputs allow us to navigate and setup measurement parameters

Total part cost per unit must be less than cheapest readily available four point probes (≤ 650 USD)

Project Videos