PLC · Modbus integration

Payment for machines never built to take it.

Many machines are run by a PLC with no payment interface and no path to cashless acceptance. We integrate payment directly into that PLC over Modbus — car washes, arcades, massage chairs and custom industrial automation. No mechanical redesign; the machine keeps running.

Talk to engineering See Hero Nexus, the edge layer
Modbus RTU / TCP RS-485 · TCP/IP No redesign
An Hero Nexus terminal connects over a Modbus RS-485 bus to a PLC. Hero Nexus writes a start command to the PLC after payment, and reads machine status back. The PLC in turn controls the machine's actuators and sensors. Hero Nexus Modbus master · payment WRITE start / program READ status / telemetry MODBUS · RS-485 PLC machine controller Machine motors · valves · sensors
  • MODBUS RTU
  • MODBUS TCP
  • RS-485
  • COILS
  • REGISTERS

Engineering note

Problem, protocol, integration, result

PLC payment integration is not a product you configure — it is an engineering job we do per machine. Here is how we think about it, in the order we actually work.

  1. Problem

    A machine with no way to take a cashless payment

    The machine is controlled by a PLC that runs its motors, valves and sensors. It was built to start on a coin, a token or a button — not a card. There is no MDB bus, no payment header, no obvious place for modern acceptance.

  2. Protocol

    Speak the language the PLC already speaks — Modbus

    Almost every industrial PLC exposes Modbus, over RS-485 (RTU) or Ethernet (TCP). Hero Nexus becomes a Modbus master: it reads the machine's state from input registers and writes commands to coils and holding registers — the same interface an operator panel would use.

  3. Integration

    Map real payment to real machine signals

    We map the machine's start and vend logic to specific Modbus addresses: a coil that starts a wash cycle, a register that sets a run time, an input that reports "busy" or "fault". Hero Nexus holds payment until the machine confirms it is ready, then asserts exactly the signal the PLC expects.

  4. Result

    The machine takes cards and reports telemetry

    The machine now accepts card, contactless, QR and meal cards, and streams sessions, revenue, uptime and faults to QuadC — with its mechanics and PLC program untouched. Payment sits in front of the PLC, not inside it.

How the mapping looks

A small, explicit Modbus register map

Every integration is a short, documented map between payment events and Modbus addresses. A car-wash bay is representative — a handful of coils and registers is usually all it takes.

Example — a single car-wash bay controlled over Modbus RTU:
COIL 0x0001 WRITE Start bay — asserted by Hero Nexus once payment is authorized
HREG 40002 WRITE Selected program (1 = quick, 2 = standard, 3 = premium)
HREG 40003 WRITE Paid run time in seconds
ISTS 0x0010 READ Bay busy — high while a cycle is running
ISTS 0x0011 READ Fault — high on e-stop, low water or motor trip
IREG 30020 READ Cycles completed today — read for telemetry

Hero Nexus polls the read block for state and telemetry, and writes the start block only after the terminal authorizes payment.

Where it runs

If a PLC controls it, payment can sit in front of it

The same Modbus approach fits any PLC-controlled machine. These are the ones operators bring us most.

Car wash Start a bay and set the program and run time once payment clears; read busy and fault state back.
Arcade & amusement Release credits or start a ride on payment, and report revenue and uptime per machine.
Massage chairs Per-session payment that starts a timed cycle and reports usage — malls, airports, gyms.
Industrial & custom Any custom or industrial machine with a Modbus-capable PLC: dose, dispense, run — on payment.

FAQ

What engineers ask about PLC payment

The questions that decide whether an integration is a day or a project.

Does integrating payment change my PLC program?

In most cases, no. Hero Nexus reads and writes existing Modbus addresses that already drive the machine. Where a machine has no free start signal, we agree a small, documented addition to the PLC program with your automation engineer — nothing that changes how the machine physically runs.

Modbus RTU or Modbus TCP — which do you use?

Both. Older machines usually expose Modbus RTU over RS-485; newer PLCs offer Modbus TCP over Ethernet. Hero Nexus speaks either as a master. We match whatever the PLC already provides rather than asking you to change it.

What happens if the network or the terminal goes down mid-session?

Hero Nexus is offline-first. It only asserts the start signal after payment is authorized locally, and it will not leave a bay running without a paid session. State is read back from the PLC, so a completed or interrupted cycle is recorded and reconciled to the cloud when the link returns.

Can you integrate a machine you have never seen before?

If it has a Modbus-capable PLC and its integrator can share the address map — or let us read it — yes. The work is understanding the machine's start and status signals; the payment and telemetry side is the part we already own.

Have a PLC machine that should take payment?

Send us the machine, its PLC and — if you have it — the Modbus map. We will scope the integration and tell you honestly whether it is a day or a project.

Talk to engineering See Hero Nexus