Control hardware
The specifications for monitoring and control define how controllers and connected equipment fit together: the wired bus between a controller and its modules, the ports that probes plug into, the local network, the mains outlets a controller switches, and what every output does when something fails. Anyone can build equipment that fits, starting from open reference designs.
- Bus power: 24 V DC, never mains
- Modules on one bus: 32 or more
- Stage: Pre‑Draft
Five interfaces.
A controller, a module, a probe, a power module, or a network device from any maker works with the rest if it meets them.
Module BusPDF
The wired bus between a controller and its modules: CAN FD on Cyphal, in one line, with 24 V DC power. A new module is set up with nothing to set by hand.
Probe InterfacePDF
BNC ports for pH, ORP, and conductivity, each isolated from every other port, and ports for temperature. One calibration procedure for each kind of probe, on every product.
Device ProtocolPDF
Pumps, lights, dosers, and power strips on Ethernet, Wi-Fi, or Thread, found and controlled on the local network, with no cloud account.
Fail-Safe BehaviorPDF
What each output does when it stops hearing from its controller, after a timeout from 5 seconds to an hour. The device acts on its own.
Power ModulePDF
Mains outlets that any controller can switch, each with a declared state without power, and monitoring that catches a welded relay. Protection never depends on firmware.
Designed to fail safe.
Each interface says what happens when a cable, a controller, a probe, or the network is lost.
Safety lives in the device.
A module or a network device acts on its own when its controller is gone.
Off is not always safe.
Each output has its own fail-safe state: a return pump keeps running, and a heater turns off.
Never only a radio link.
Safety functions keep a wired path. A radio link is an addition, never a replacement.
No setup by hand.
A controller finds, addresses, and configures a new module without help from the owner.
Plug in while it runs.
Connecting or disconnecting a module never damages, restarts, or changes the outputs of anything else on the bus.
Probe ports are isolated.
Each pH, ORP, and conductivity port is isolated from every other port, the bus, and earth, so probes in the same water don’t interfere.
Built to survive mistakes.
A probe port survives static, a short circuit, the wrong probe, and the 24 V that some security cameras put on their BNC cables.
Low voltage on the bus.
The bus carries 24 V DC, within safety extra-low voltage. Mains is switched only by a power module that carries its maker’s safety certification.
Where it stands.
Early drafts, with tests you can run today.
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Now
Pre-Drafts, open for comment
Module Bus, Probe Interface, Device Protocol, Fail-Safe Behavior, and Power Module are early drafts. Many of their electrical values are marked provisional.
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Now
Tests without hardware
A simulated controller and module run the Module Bus and Fail-Safe Behavior test procedures on any computer. The same tests run against a real module through a USB-to-CAN adapter.
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Now
Reference designs, in progress
Open designs that implement these interfaces and show that the specifications work. They are licensed under the CERN Open Hardware Licence, so anyone can build and sell equipment from them.
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Next
The bus connector
The connector and pinout are not chosen yet. M12, small circular connectors, and RJ45 are the candidates.
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Later
Certified power modules
Products built to the Power Module specification, each safety-certified by the company that makes it. Until one exists, the reference designs stay at 24 V DC.
Test against the drafts.
Run the Module Bus test procedures against your own module, and report what you find.