controlsfreak.dev /// FIELD REFERENCE LIVE
Jump to Signal Scaling BACnet/IP Hex Thermistor Psych Chart All tools →

Tools for those in controls, built by someone in controls.

The math you don't want to redo at the panel — signal scaling, BACnet/IP, Modbus, psychrometrics, thermistors — plus explainers that walk a whole system end-to-end. No login, no ads, no tracking; view-source still works, and these pages will still run ten years from now.

Browse tools → Start with the explainers →

Latest · BACnet MS/TP explainer →

Live · AHU-1 supply-air temperature loop RUN
55.0 °F supply air 55.1 °F · valve 62 % Open the full PID Tuner →

The supervisor reads the supply-air sensor; the controller holds it at setpoint by modulating the cooling valve. Drag the setpoint and watch the loop chase it — then open the full PID Tuner to tune one yourself.

LIVE AHU-1 · holding setpoint v3.16.1 ·

Tools by Category

TOOL :: HVAC LIVE
HVAC tools →
Psychrometric chart, economizer ratio, air mixing, coil sizing, dew point, and refrigerant P-T — the airside and refrigerant math on one filtered view.
PsychrometricsCoilsEconomizer6 tools
TOOL :: PROTOCOLS LIVE
Protocol tools →
Modbus register decoding and function codes, BACnet/IP hex addressing, and the BACnet object reference — the bus-level conversions you hit mid-integration.
ModbusBACnet4 tools
TOOL :: SIGNALS LIVE
Signal tools →
Analog signal scaling (mA / V ↔ engineering units) and thermistor / RTD curves — the field-wiring math for getting a real number off a point.
Analog I/OSensors2 tools
TOOL :: HYDRONICS LIVE
Hydronic tools →
Valve Cv sizing and pump / fan affinity laws — sizing the wet side and predicting what speed changes do to flow, head, and power.
ValvesPumps2 tools

Browse

SECTION :: TOOLS OK
Calculators & lookups →
Calculators and lookups for the parts of the job that come up over and over — psychrometric staging, signal scaling, register and address conversions, thermistor curves. Open one, get an answer, get back to work.
CalculatorsLookupsConverters14 Tools
SECTION :: SIMULATORS OK
Practice on the model →
Running models you can poke at in the browser — a PID step-response loop, a mock drive keypad, a function-block wiresheet, an equipment-staging plant, and a controller-wiring rig. Practice on the controls before you're standing in front of the real thing.
PracticeSandboxesLive Models5 Simulators
SECTION :: EDUCATION OK
Learn the fundamentals →
A connected set of explainers, not a glossary. The current arc: PID control → hydronic loops → load piping → VFDs → pump control, each page asking one question and answering it with diagrams, worked examples, and the occasional interactive widget.
ExplainersDiagramsWidgets17 Lessons

About

Role Controls Programmer
Industry BAS / Building Automation
Location Northeast U.S.
REV 2026-05-24
Status Active

Hi, I'm a controls programmer based in the Northeast U.S. This is a side project I'm working on while exploring vibe coding. There's a genuine gap in easy reference websites and educational resources for this trade. This site started as just a way to have some easy reference tools in one place, but has expanded to include much more. Teaching those in the trade has been a passion of mine since I began to grow my own knowledge. With this project I aim to do that with a broader audience. I try to verify the accuracy of everything on this site the best that I can, but if anything is incorrect, please contact me and I will ensure I fix the accuracy issue. If there are any specific tools or topics you want to see covered, I want to hear about it!

The path here was a little roundabout. I started college for electrical engineering, and pretty quickly realized that learning the theory without getting my hands on it didn't sit right — I wanted to be doing the work, not just reading about it. Between electronics, electrical, and mechanical tinkering going back to when I was a kid, controls turned out to be the place where all of that overlapped. I left school to find a controls role, and the field's been the right fit since.

Day-to-day, the work splits between new-construction programming, retro-commissioning on existing systems, and the troubleshooting calls that always seem to pile up alongside. Most of it lands on institutional and education buildings — schools, universities — and light industrial sites. The teaching impulse that ended up shaping this site started kicking in once new hires began showing up on jobs alongside me; walking somebody through their first sequence of operations, or just showing them what a real panel actually looks like behind the door, turned out to be some of the more satisfying parts of the trade.

Bug reports, tool requests, or feedback — get in touch.