FAQ
TL;DR: Build a PIC16F877A home energy meter that stays under 5 V and senses AC current safely; “use a device to step down the voltage to 5 volts.” [Elektroda, Ashesh Sharma, post #21661975]
Why it matters: It helps DIYers show live watts and monthly INR on a 16x2 LCD without unsafe mains wiring.
Quick-Facts
- PIC16F877A logic and ADC require a regulated 5 V supply; do not exceed this limit. [Elektroda, Ashesh Sharma, post #21661975]
- Target UX: 16x2 LCD shows live watts, last-day INR, and total INR since reset. [Elektroda, IMMANUVEL M, post #21661974]
- Low-cost sensing paths discussed: small series current transformer + rectifier + RC to feed ADC. [Elektroda, Frank Bushnell, post #21661977]
- Hall current transducers (e.g., Honeywell CSLH3A45/CSLT6B100) were shortlisted by the OP. [Elektroda, IMMANUVEL M, post #21661984]
- Off‑the‑shelf reference device: Kill‑A‑Watt consumer meter exists for plug-in loads. [Elektroda, Steve Lawson, post #21661985]
Quick Facts
- PIC16F877A logic and ADC require a regulated 5 V supply; do not exceed this limit. [Elektroda, Ashesh Sharma, post #21661975]
- Target UX: 16x2 LCD shows live watts, last-day INR, and total INR since reset. [Elektroda, IMMANUVEL M, post #21661974]
- Low-cost sensing paths discussed: small series current transformer + rectifier + RC to feed ADC. [Elektroda, Frank Bushnell, post #21661977]
- Hall current transducers (e.g., Honeywell CSLH3A45/CSLT6B100) were shortlisted by the OP. [Elektroda, IMMANUVEL M, post #21661984]
- Off‑the‑shelf reference device: Kill‑A‑Watt consumer meter exists for plug-in loads. [Elektroda, Steve Lawson, post #21661985]
What’s the simplest way to sense AC current for a PIC16F877A energy meter?
Use a small series current transformer. Rectify its secondary, smooth with a capacitor, add a discharge resistor, and feed the ADC. Adjust turns so full-load current maps to ~0–5 V at the ADC. This analog path is cheap and isolates mains. [Elektroda, Frank Bushnell, post #21661977]
Can I power the PIC16F877A directly from mains?
No. The PIC16F877A must run at 5 V. Use a proper low‑voltage supply (e.g., transformer or SMPS) and regulate to 5 V. Overvoltage risks permanent MCU damage and unsafe conditions. “Use a device to step down the voltage to 5 volts.” [Elektroda, Ashesh Sharma, post #21661975]
What is a current transducer and where does it fit in this build?
A current transducer converts mains current to a low‑voltage signal for your ADC. Place it on the live conductor feeding the load, then scale/condition the output for 0–5 V input range. It lets you compute kW and kWh from measured current. [Elektroda, IMMANUVEL M, post #21661976]
How do I hook up a Honeywell CSLH3A45 or CSLT6B100 Hall sensor to the ADC?
Route the live conductor through the sensor aperture, power the sensor per its spec, and level‑shift or filter the output into the 0–5 V ADC range. Calibrate with known loads to map ADC counts to amperes and watts for INR math. [Elektroda, IMMANUVEL M, post #21661984]
How do I convert amps to watts and then INR on a 16x2 LCD?
Three‑step how‑to: 1. Sense current and scale to ADC counts. 2. Compute watts from calibrated current (and voltage assumption), then integrate over time to get kWh. 3. Multiply kWh by tariff to show INR, plus daily and total. [Elektroda, IMMANUVEL M, post #21661974]
Is there an off‑the‑shelf alternative I can study or buy?
Yes. The Kill‑A‑Watt is a consumer plug‑in meter that measures and displays energy parameters. It’s a good reference for UI and features while you prototype your custom build. Availability varies by region. [Elektroda, Steve Lawson, post #21661985]
Can I add networking for automated meter reads or billing later?
Yes. You can add serial, Ethernet, modem, Wi‑Fi, or GPRS to push monthly readings to a server. This avoids manual visits and enables automated billing workflows and alerts. “Not even difficult to do.” [Elektroda, Mark Harrington, post #21661981]
Are utilities already doing automated metering (AMI), and does that affect DIY projects?
In the U.S., AMI is widely deployed using utility‑specific wireless or power‑line carriers. The aim is flexible pricing and load shaping rather than hobbyist integrations. DIY projects remain useful for home insight and learning. [Elektroda, Todd Hayden, post #21661982]
What LCD interface should I plan for with a 16x2 module?
Use a standard HD44780‑compatible 16x2 LCD. Connect data/control lines to the PIC, and display live watts, last‑day INR, and total INR per your UI plan. Keep updates readable, e.g., 1–2 Hz refresh. [Elektroda, IMMANUVEL M, post #21661974]
Any cost or scaling insights if I add remote reporting?
Thread discussion notes one phone call versus an 8‑hour meter‑reader shift at £25/hour, and SMS near 0.20 pence each. This illustrates potential OPEX savings at scale with automated retrieval. [Elektroda, Mark Harrington, post #21661981]
What’s an Arduino Nano?
Arduino Nano is a compact, breadboard‑friendly microcontroller board commonly used for prototyping control and sensing projects similar to energy meters. It offers easy USB programming and many libraries. [“Arduino Nano — Product Page”]
What is Tuya?
Tuya is a cloud‑backed IoT platform for smart devices, enabling app control, automation, and cloud connectivity across many brands and product categories. [“Tuya Smart — Platform Overview”]
What is OpenBeken?
OpenBeken is community firmware for certain IoT devices that replaces stock cloud‑dependent software with local, open control and telemetry options for makers. [“OpenBeken — Project Overview”]
What is CAN bus?
CAN bus is a robust, differential serial network used in vehicles and industry for reliable multi‑node communication with built‑in error handling and arbitration. [“CAN bus — Bosch Specification Overview”]
What safety pitfalls should I avoid when measuring mains current?
Ensure galvanic isolation between mains and MCU, keep ADC inputs within 0–5 V, and include proper discharge paths. Poor rectification or filtering skews readings; miswiring can be dangerous. Enclose mains areas and respect clearances. [Elektroda, Frank Bushnell, post #21661977]
How do I calibrate without lab equipment?
Use a known resistive load (e.g., a rated heater), record ADC counts at several currents, and build a linear map to amperes. Validate with a plug‑in reference meter if available and store the slope/offset in EEPROM. [Elektroda, IMMANUVEL M, post #21661974]