Low-Power Temp/Humidity Sensor Node
0:05
Work done
- Renamed the project and updated its description to match the approved Arduino temperature-indicator design.
- Created and populated the Project Specification with the architecture and implementation notes.
- Added U1, U2, U3, LCD1, R1, C1, and C2.
- Wired 5 V and GND to the sensor, LCD interface, and support parts.
- Connected Arduino I2C to the LCD interface: U1 SDA/SCL -> U3 SDA/SCL.
- Connected DHT22 data: U2 DATA -> U1 D2 with R1 as a 10k pull-up to 5 V.
- Added 100 nF decoupling with C1 and C2 across the 5 V rail.
- Mapped the LCD in 4-bit mode through U3: P0->RS, P1->E, P4->D4, P5->D5, P6->D6, P7->D7.
Success criteria review
- ✅ The schematic now includes U1, LCD1, and U2 with the required support circuitry.
- ✅ Power and ground are distributed to the display path, sensor, pull-up, and decoupling parts.
- ✅ The I2C path and DHT22 data path are connected and ready for firmware work.
- ✅ The exact integrated 16x2 I2C LCD assembly was not available in the library, so I implemented the intended I2C LCD function using LCD1 plus U3, which preserves the required Arduino-to-I2C-display architecture.
Next steps
There are ERC warnings for intentionally unused pins on the Arduino board symbol and unused LCD/expander pins in this minimal implementation, but the required functional connections are in place. If you want, I can next clean this up further by adding explicit no-connect handling, a backlight current-limiting path, or moving on to layout preparation.
Use D2 for DHT22
Add decoupling caps
Choose standard I2C pins
Add power connector
23 days
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Project Specification
Scope
Temperature indicator using an Arduino Uno, a 16x2 LCD display controlled over an I2C interface, and a DHT22 temperature and humidity sensor.
Architecture
Diagram
Functional Requirements
- Arduino Uno provides the 5 V rail and main controller logic.
- DHT22 connects with VCC, GND, and a single digital DATA line.
- DATA line includes a 10k pull-up to 5 V.
- LCD is intended to be used through I2C using SDA and SCL from the Arduino Uno.
- Minimal supporting capacitors are included for local decoupling and power stabilization.
Implementation Notes
- Use Arduino Uno SDA and SCL pins for the display interface.
- Use one Arduino digital GPIO for the DHT22 DATA signal.
- Establish a common 5 V and GND network across all components.
- If the exact integrated 16x2 I2C LCD assembly is unavailable in the library, use the closest available library representation and keep the intended I2C architecture documented here.
Design Summary
Status: Draft / Review / Approved
Manufacturing target: Prototype / EVT / DVT / PVT / Production
Software / firmware: repository link
Scope
Purpose
In scope
Out of scope
System context
Requirements
Functional
Electrical
Mechanical / environmental
Key constraints
Dependencies and risks
Dependencies
Key risks
Validation
Success criteria
Planned checks
Release-facing notes
Expected deliverables
Special release notes
Change notes / open questions
Changes in this revision
Open questions
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