Project idea
Build two identical Arduino Uno nodes that exchange typed messages across water using an IR LED transmitter and a TSOP1738 IR receiver, displaying text on 16x2 LCDs and sending an acknowledgement back on successful receipt.
A lab demo uses two water containers to show that modulated IR at 38 kHz can carry short messages through clear water across short distances, offering a simple alternative to wires for controlled environments.
 
Project description
Each node comprises an Arduino Uno handling keyboard input, packet framing with checksum, IR modulation/demodulation, LCD UI, and an ACK/timeout retry mechanism for reliable delivery.
Hardware includes an IR LED driver, a TSOP1738 38 kHz receiver for robust demodulation, a 16x2 LCD for status and received text, and regulated 5 V adapter power, assembled on a prototyping PCB.
 
Total list of components
Arduino Uno
IR LED’s
TSOP1738 IR Receiver
Computer keyboard
LCD’s (16x2)
Crystal Oscillator (16 MHz)
Resistors
Capacitors
Transistors
Cables & Connectors
Diodes
PCB (general purpose)
LED’s (indicator)
Transformer/Adapter (5 V, 1 A)
Push Button
 
Features
Bidirectional text messaging with ACK/timeout to confirm delivery and auto-retry on loss.
Clear user interface with 16x2 LCD for local typing status and received message display.
Modular, low-cost build using standard Arduino ecosystem and IR receiver tuned to 38 kHz.
 
Applications
Educational demo of underwater optical links, framing, error handling, and UI integration.
Short-range tank or pool experiments where wired links are inconvenient in controlled settings.
Entry-level study of optical wireless communication and signal integrity through water.
 
 Project Includes:
Fully assembled and tested circuit
Circuit diagram
Source code 
(For DIY KITs - only the components will be provided)
 
Project Types:
DIY KIT(Do IT YourSelf KIT) - We are providing only components in this kit for this project
DIY KIT with Code & Circuit Connections - Along with the components, you will get the Code and the Circuit Connections file to help you build the project easily.
Readymade Breadboard - We are providing fully assembled, tested and ready-made project using plug-n-play jumper wires and breadboard with all the other components, code & circuit diagram.
Readymade Soldered - We are providing fully assembled, tested and ready-made project soldered on a PCB with all the other components, code & circuit diagram.
 
Dimensions in cm
Approx. 12 × 10 × 5 per node enclosure, sized to accommodate Uno (6.86 × 5.34 cm PCB) and a 16x2 LCD (~8 × 4 cm).
Lab demo requires two small water barrels/containers placed line-of-sight between IR LED and TSOP modules.
 
Shipping dimensions in cm
For a two-node kit with accessories: ~30 × 20 × 10 including padding, power adapters, and cables.
Packing allows space for two PCBs, two LCDs, two adapters, and protective cushioning.
 
Weight
Approx. 0.35 kg per two-node set excluding water containers, dominated by adapters and LCDs.
Adapter ~0.10 kg each and LCD ~33 g each; remaining electronics contribute marginally.
 
Estimate project weight
Shipping weight ~0.60 kg for full two-node kit with accessories and packaging
 
Notes: All the products are made by LearnElectronics India and not for re-sale.