controlsfreak.dev /// FIELD REFERENCE OK
BMS Field Reference

Tools for those in controls,
built for the field.

A reference site for building-controls people. Open calculators and lookups for the math you don't want to redo at the panel — BACnet/IP, Modbus registers, signal scaling, psychrometrics, thermistors. Alongside, a growing set of explainers that walk through hydronic loops, load piping, VFDs, and pump control end-to-end. No login, no ads, no tracking — view-source still works, and the same pages run ten years from now.

New to building controls? Start with the explainers →

AI / AO Scaling Modbus Register Viewer PID Tuning BACnet/IP Hex Psychrometric Chart Thermistor / RTD Lookup Latest: Practice — quizzes & drills
OK VERSION v2.16.4 LAST BUILT

Most-Reached-For Tools

TOOL :: SIGNAL SCALING LIVE
Signal Scaling Calculator
mA / V signal ↔ engineering units, with % of span and a 2-point → slope/offset tab ready to paste into Niagara's ProxyExt.
Analog I/O4-20 mA0-10 VSlope / Offset
TOOL :: BACNET/IP HEX LIVE
BACnet/IP Hex Converter
The hex address strings EBO shows for BACnet/IP devices ↔ dotted-decimal IP and UDP port, both directions.
BACnet/IPUDP 47808Hex ↔ Dec
TOOL :: THERMISTOR LIVE
Thermistor / RTD Calculator
Temperature ↔ resistance for the common HVAC sensors — 10K Type II / III, Johnson 8.7K, Schneider Type 5, 20K, 3K, 1K Balco, Pt100, Pt1000 — looked up both ways, or identify an unknown sensor from measured readings.
SensorsNTC / RTDT ↔ RID Unknown
TOOL :: PSYCH CHART LIVE
Psychrometric Chart
Walk an AHU through its processes — mix outdoor + return air, then cool, heat, and humidify — on an interactive ASHRAE psychrometric chart that follows the header's US / Metric toggle. Drag OA and RA, or type leaving conditions; coil capacities appear when you set the airflow.
HVACPsychrometricsASHRAEUS / Metric

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.
CalculatorsLookupsConverters9 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. Practice on the controls before you're standing in front of the real thing.
PracticeSandboxesLive Models3 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.
ExplainersDiagramsWidgets13 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.