eFlow
A single-line diagram editor for datacenter power. Draw the system and the power flow is simulated as you go.
The Curiosity
Two things led here.
The first was a stack question. What does it actually take, on the web, to drag a node onto a canvas, pull a connector to another node, and have that connection mean something? The answer turned out to be React Flow. Learning it opened a door much wider than one project: mind maps, flowcharts, signal chains, anything where the picture is really a graph.
The second came from the day job. I work in datacenter design, where single-line diagrams are still mostly drawn in CAD and checked by hand. The drawing knows nothing about the thing it depicts. But equipment is never connected for decoration: logic sits on the connections and calculations hang off them. I wanted to draw a system and then ask it questions. What blacks out when this UPS fails? What is this branch drawing at three in the afternoon?
The Build
eFlow is a drag-and-drop canvas built on React Flow with eleven equipment types — utility feed, generator, transformer, UPS, automatic and manual transfer switches, switchgear, circuit breaker, PDU, power meter and server — plus a load-profile node.
Power flow is recomputed on every change with a breadth-first propagation from the sources. Loads aggregate upward through the tree, transfer switches pick their live input, and a faulted device blacks out everything that depended on it.
Load profiles are 24-hour curves with IT, cooling, lighting and custom categories. Link one to a piece of equipment and the simulation follows it around the clock.
- Canvas
- React Flow with custom nodes and edges
- Simulation
- Breadth-first power-flow propagation, load aggregation, transfer-switch logic
- Storage
- Browser local storage. Autosave every 30 seconds, JSON import and export
- Runs on
- Desktop browsers. Deliberately not phones
Everything stays on your machine. Nothing is uploaded. Undo, redo, copy, paste and a full set of keyboard shortcuts are there because a diagram editor without them is a toy.
The Result
A working editor and simulator. Free, no account, nothing to install. It is the most engineering-shaped thing in the workshop.
It is also the closest thing to my professional work that I can publish. The equipment is generic and every load in it is invented, so no client drawing, no NDA and nothing internal goes anywhere near it — and the tool still does the kind of thinking the day job asks for.
What I Learned
A live simulation makes a drawing honest. Once power flow was computed continuously, topology mistakes that a static diagram would have hidden showed up immediately.
It also confirmed a small rule I keep relearning: some tools should refuse to run on a phone. Saying "desktop only" plainly is kinder than a cramped experience.