Schematic Design Review Issues
Worked for 5 mins 51 sec
Completed the schematic-level review and created the full findings report here: Schematic-Level Design Review.
Key observed issues: U1 3V3 is floating, Y1 GND is floating, C46/C71 are shorted on RS485_ISOGND, and
CT10_P_RAW appears to incorrectly short many CT input channels together. I also noted cleanup items for unused ESP32 GPIOs, ADC NC pins, and floating J4 pins 21–24.
Remove or rewire C46 and C71 so they are not shorted on RS485_ISOGND.
Worked for 17 sec
I’ll correct the RS-485 isolated-side capacitors so C46 and C71 are no longer both tied to RS485_ISOGND, then re-run the electrical check to verify the short warnings are gone.
Worked for 2 mins 38 sec
Rewired C46 and C71 instead of removing them.
- C46:P1 and C71:P1 now connect to
RS485_VISOIN - C46:P2 and C71:P2 now connect to
RS485_ISOGND RS485_VISOOUTremains on U6 Visoout through FB1 toRS485_VISOIN- ERC shorted-component review now shows no C46/C71 short warnings.
Fix power pins
Review RS-485 block
Explain VISOIN wiring
Fix CT raw net
Check remaining ERC
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Project Specification
Project Overview
Design a panel-connected home energy monitoring system that identifies which parts of a house are consuming the most electricity, estimates cost impact, and integrates smart switches/outlets to pinpoint high-draw devices on specific branch circuits.
Primary Goal
Create a safe, scalable system that combines:
- Whole-home / panel-level monitoring to measure mains consumption and major branch circuits
- Circuit-level sensing to identify which breakers or branch runs carry the largest loads
- Smart endpoint devices (switches, outlets, relays, plugs) to attribute branch consumption to individual rooms or appliances
- Software analytics to convert power data into usage trends, waste alerts, and estimated cost
Recommended System Architecture
Block 1 — Panel Monitor Gateway
A dedicated low-voltage controller installed adjacent to the electrical panel.
Recommended sensing approach:
- Non-invasive current transformer (CT) clamps on mains feeders and selected branch circuits
- Isolated or properly rated AC voltage reference sensing so real power can be calculated instead of current-only estimates
- Local MCU or Linux-class gateway for sampling, aggregation, networking, and security
- Isolated power supply derived from a safe external supply or certified AC-DC module
Why this approach:
- CT clamps avoid cutting house wiring
- Branch circuit coverage can scale from a few channels to dozens
- Real power, apparent power, and power factor become measurable when voltage is sampled correctly
Block 2 — Measurement Front End
For each monitored circuit:
- CT sensor input
- Burden resistor sized for CT ratio and ADC range
- Anti-alias filter / input protection
- Analog front end or energy metering ADC
- Channel calibration constants stored in firmware
Preferred design direction:
- Use a dedicated multi-channel energy metering IC or isolated measurement front end rather than raw MCU ADC only
- Sample voltage and current synchronously when possible
Block 3 — Smart Endpoints
Smart switches and smart outlets provide finer attribution beyond the breaker level.
Recommended device classes:
- Smart receptacle / plug with internal power metering for plug-in loads
- Smart switch or relay module for lighting / fixed loads where switching is useful
- Optional DIN-rail relay or contactor monitor for large dedicated loads (water heater, EV charger, HVAC auxiliary loads)
Data role of smart endpoints:
- Confirm which device on a branch circuit is active
- Measure plug-level consumption for appliances that share a breaker
- Improve location accuracy (room / outlet / appliance mapping)
Block 4 — Communications and Data Model
Recommended topology:
- Panel monitor gateway as the authoritative data concentrator
- Smart devices communicate over Zigbee, Thread/Matter, Wi-Fi, or RS-485 depending on installation goals
- Gateway publishes data to local dashboard and optional cloud service
Good beginner-friendly architecture:
- Local gateway MCU or SBC
- Smart outlets/switches using Matter-over-Thread or Zigbee, or off-the-shelf Wi-Fi smart plugs during prototyping
- MQTT or a local message bus for unified telemetry
Block 5 — Analytics Software
Key software functions:
- Compute RMS current, RMS voltage, real power, apparent power, power factor, and energy
- Map each monitored branch to rooms/appliances
- Merge branch-level and endpoint-level data
- Estimate cost using utility tariff inputs
- Detect waste patterns such as:
- abnormal overnight baseload
- standby-heavy circuits
- HVAC overrun
- water heater or dryer running longer than expected
- devices drawing power when occupancy is low
Safety and Compliance Constraints
This project interacts with dangerous mains voltages.
Hard requirements
- Do not place non-isolated low-voltage electronics directly on mains conductors
- Use CT clamps for current sensing where possible
- Any voltage sensing path must be designed with:
- proper isolation strategy or certified metering front end
- fusing / current limiting
- creepage and clearance appropriate to mains category
- surge protection
- The product enclosure must prevent accidental contact with hazardous voltages
- Installation near the electrical panel should be reviewed by a qualified electrician
- PCB layout must observe mains isolation boundaries and regulatory spacing
Compliance targets to consider later
- UL / IEC safety requirements for mains-connected equipment
- EMC / surge immunity requirements
- Revenue-grade accuracy requirements if precise billing-level reporting is desired
Recommended Development Roadmap
Phase 1 — Proof of Concept
Goal: prove the measurement and analytics chain.
- Monitor split-phase mains plus 4 to 8 branch circuits
- Use CT clamps and a known-good energy metering front end
- Integrate 2 to 4 smart plugs to correlate branch and appliance loads
- Build dashboard showing live watts, daily kWh, and estimated cost
Phase 2 — Expand Circuit Coverage
- Increase branch channels using multiplexed or multi-channel metering hardware
- Add branch labels and appliance inference logic
- Add alerts for unusual or wasteful loads
Phase 3 — Productization
- Design isolated power supply and protected enclosure
- Add secure provisioning, OTA updates, and long-term data storage
- Evaluate certification path and installation method
Recommended First Hardware Revision
For the first custom board, target:
- 1 gateway MCU/SBC
- 6 to 12 CT channels
- 1 mains voltage reference input
- isolated or certified power input module
- Ethernet or Wi-Fi backhaul
- local debug port
- optional RS-485 / Modbus for expansion
Design Choices I Recommend
Measurement strategy
Best overall: panel CTs + mains voltage reference + smart outlets/switches
This gives three layers of visibility:
- Whole-home total usage
- Breaker/circuit usage
- Device/room usage
Networking strategy
Best for early prototype: Wi-Fi or Ethernet gateway + commercially available smart plugs
Reason:
- Faster prototype
- Lower firmware complexity
- Easier validation of analytics before building custom endpoint hardware
Smart endpoint strategy
Start with off-the-shelf metering smart plugs / smart relays during validation, then design custom endpoints only after the panel monitor and software model are working.
Open Engineering Decisions
These need to be fixed before schematic capture:
- Connectivity preference: Wi-Fi, Zigbee, Thread/Matter, Ethernet, RS-485
- Installation model: consumer DIY assist vs electrician-installed enclosure
- Accuracy target: trend monitoring vs near-billing-grade metering
Confirmed Requirements
- Service type: U.S. split-phase 120/240 V residential service
- Branch circuit capacity: up to 20 branch circuits in the first product target
- Endpoint strategy: fully custom smart outlets / switches / relays designed specifically for this monitoring ecosystem
- System intent: combine panel-level branch monitoring with endpoint-level attribution, not generic third-party smart plugs
Architecture Implication of Confirmed Scope
- The panel gateway should reserve at least 22 measurement channels minimum: 20 branch CT channels plus 2 mains channels
- The system should include a custom endpoint communications bus / protocol strategy so smart endpoints can be linked back to the gateway and correlated with branch data
- The panel gateway should be treated as the authoritative source for whole-home and breaker-level energy accounting, while endpoints provide appliance/room attribution and optional load control
Proposed Functional Blocks for Schematic Design
- Power input and isolated low-voltage supply
- Metering front end and ADC / energy metering IC
- MCU / gateway communications
- CT input connectors and protection
- Voltage reference sensing input
- Debug/programming interface
- Expansion bus for smart endpoint / external telemetry integration
Recommended Next Step
Before schematic capture, lock these product requirements:
- mains/service type
- target branch channel count
- chosen communications stack
- gateway compute platform
- whether smart endpoints are custom hardware or third-party devices in rev A
Initial Recommendation to the User
Build the system in two layers:
- Layer 1: a safe panel monitor using CT clamps and an energy metering front end
- Layer 2: smart outlets/switches to identify which appliance or room on that branch is responsible
This is the most practical way to find wasted energy without trying to instrument every appliance from the start.
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