From smart access to smart energy billing
Custom IoT billing platform for a multi-location co-working operator. Delivered August 2019 after they saw our Smart Access work.
When a co-working operator needed meeting-room electricity billed by actual use, not estimates, we built IoT meters, Arduino firmware, a Laravel API, and custom PCBs that pushed usage into their existing management software across every branch.
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Case study · August 2019
Businesses often picture automation as apps and dashboards. Here the hard part was linking physical loads to billing software.
In August 2019, shortly after our Smart Access Control work, a multi-location co-working operator asked us to meter meeting rooms and event spaces by actual electricity use and feed the numbers into software they already ran.
The challenge
Meeting rooms and event spaces saw different customers, different air-con run times, and no link between bookings and the meter.
Capture electricity consumed during each reservation, not a flat room fee.
Send usage data into the client's management platform without replacing it.
One architecture for every co-working location they operated.
Reset, read, transmit, and bill with minimal staff intervention.
Data flow
Hardware never talked to the client app directly. The Laravel API authenticated devices, cleaned payloads, and fed the operator's existing platform.
Meter reading to invoice
Four hops from the room circuit to the operator's billing software.
Energy measurement
Wi-Fi firmware
Middleware
Billing and reports
kWh payload in transit
meter · reset · accumulate
The meter resets at booking start and accumulates kilowatt-hours through the session.
Core components
Each layer had a clear job from the wall socket to the client's ledger.
Erratum IoT Energy Meter V1.0
Measures real-time voltage, current, and accumulated energy on the room circuit.
Runs custom Arduino firmware, connects to Wi-Fi, and posts readings to our API.
Authenticates devices, validates payloads, and exposes usage to downstream software.
Pulls metered energy into invoices and reports the operator already trusted.
Switches high-current air-conditioning loads that ordinary relays cannot handle safely.
Measuring electricity
The PZEM-004T module sat inline so billing tracked physics, not estimates.
The accumulated energy register clears when a session opens.
Total energy rises as AC units and appliances run.
Firmware pulls the final register value from the PZEM module.
The ESP8266 posts the reading to the Laravel API for billing.
Bringing the device online
Arduino-based code kept the unit autonomous. No local PC required at each site.
Poll voltage, current, power, and energy registers over serial.
Monitor whether the room circuit is energized or isolated.
Reconnect after outages and retry failed API calls.
Send device ID, session markers, and meter readings to the Laravel backend.
Laravel middleware
Direct hardware-to-ERP links are brittle. A dedicated API layer bought room to grow.
Only registered units can post readings to the server.
Reject malformed or out-of-range payloads before they hit billing.
Central place to roll out fixes without visiting every branch.
Ops staff see which meters are online and when they last reported.
One backend serves every co-working location on the account.
New client tools can consume the same API without touching firmware.
Heavy electrical loads
L&T
MNX contactors
Bench tests showed standard relay boards could not reliably switch large AC loads. Production units paired control electronics with Larsen & Toubro industrial contactors so high-current equipment stayed isolated from the logic board.
From prototype to production
Field trials on hand-built units led to a custom Erratum PCB and sealed production enclosures.
Hand-built board
Erratum IoT Energy Meter V1.0
Industrial wiring
Multi-site rollout
Project timeline
From first conversation to units live in multiple branches within one month.
Client found us through Smart Access and outlined booking-linked billing needs.
IoT device, Laravel middleware, and ERP integration plan approved.
First unit assembled from PZEM-004T, ESP8266, relay, and power supply modules.
Arduino code and Laravel endpoints developed in parallel.
Industrial L&T switching added for air-conditioning loads.
Prototype tested on live circuits with real booking workflows.
Erratum IoT Energy Meter board laid out for production.
Production units built, programmed, and QA checked.
Devices registered and installed across co-working branches.
Client software consuming meter data; project closed successfully.
Engineering highlights
“The best digital solutions do not stop at the screen. They connect hardware, cloud infrastructure, and business workflows into one system your team can run every day.”
FAQ
Plain-language answers about what Co-working Space Automation does and who it is for.
The operator rented meeting rooms and event spaces to different clients, but air conditioners and appliances drew different loads. Manual calculations were slow and wrong, and their management software had no live energy data. We built meters that tied each booking to measured kilowatt-hours.
Each room runs through a PZEM-004T energy meter module. When a booking starts, the meter resets. It accumulates total energy until the session ends, then the device reads the value and sends it to the cloud for billing.
Off-the-shelf modules in early prototypes: PZEM-004T for measurement, ESP8266 for Wi-Fi, relay modules, and an AC-DC supply. Production units used a custom Erratum PCB, industrial L&T contactors for heavy AC loads, and sealed wall enclosures.
A Laravel API between the ESP8266 and the client's software handles device authentication, data validation, firmware upgrades, centralized monitoring, and multi-branch registration. The client's app pulls clean usage records without speaking to hardware directly.
Each location gets another installed unit registered on the same Laravel backend. Adding a branch means mounting the device, pairing it on the server, and pointing the client's software at the new meter ID. No separate app per site.
Early builds used breadboards, jumper wires, and module stacks inside test enclosures. After field trials we designed an Erratum IoT Energy Meter PCB that integrated the ESP8266, power supply, and relay footprints with terminal blocks for safer installs and faster rollout.
Erratum Solutions delivered the full stack in August 2019: embedded hardware, Arduino firmware, Laravel API, PCB design, and production units across multiple co-working locations.
Yes. We still design embedded controllers, cloud APIs, and integrations with existing business software for energy monitoring, access control, and field automation. Share your load types, branch count, and billing rules on the contact page.
We design the hardware, firmware, API, and integrations so your team bills from real usage data. Tell us about your sites and load types.
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