© 2026 Simon Britton — simon-britton.com — original work, unauthorized reproduction prohibited
This is a small BMS/DDC control-logic sandbox, in the spirit of a controls engineer's wiresheet. Build a strategy from function blocks, wire it up, and press Run to watch the values flow.
Since there's no real plant to sense, the Inputs category gives you a clamped random generator, an up/down/triangle ramp, an on/off randomiser, a repeating time schedule, and manual value/switch blocks you can operate live while it runs.
The Combination block (Logic category) packs an AND/OR/NOT network into one block: it has 4 digital inputs and, in its properties panel, 4 rows each representing an AND-term. Select the block and click a cell in the Logic Table to cycle it unused → included → inverted, e.g. row "¬1 2" reads as "NOT Input 1 AND Input 2". The 4 rows are then OR-ed together to drive the output - each row's dot lights up live when that row is true.
The Process Response block (Control category) turns any control output into a simulated sensor reading: it scales the driving signal onto a response range, then applies a dead-time delay and a first-order lag before it settles - just like a room warming up after a valve opens. Wire a PID's output into its Drive, and its Out back into that same PID's PV, and you have a real closed loop to tune. The demo diagram that loads by default is exactly this.
Diagrams autosave to this browser as you work. Use Save As… to keep named versions, Export to download a JSON file, and Import to load one back in. While you run or step a strategy, its block parameters and wiring are processed transiently by this site's simulation service; named saves and autosaves remain in your browser.