Pir camper am312

PIR camper switch for Revotion

A small motion sensor board that switches the camper light through a Revotion NODE Ambient switch input. Motion closes a potential-free contact (AQY212 PhotoMOS) for an adjustable hold time of about 2 minutes, and a light sensor keeps it from triggering in daylight. It runs from the camper's 12 V supply and draws about 0.1 mA while idle.

Variants

The HC-SR505 board is the first version; it was built and measured (hold time about 3 min). The AM312 boards replace it and add the light sensor. The PDFs (also as HTML) contain the full build guides: schematic, perfboard layout with every solder path, parts list, simulation results and test steps.

How it works

12 V ── reverse-polarity diode ── 3.0/3.3 V LDO ── AM312 PIR
                                                     │ 2.3 s pulse per motion
                                       light inhibit ┤ (LDR + trimmer, Q2)
                                                     ▼
                                   off-delay: C1 + R2 → Q1 (≈ 2 min)
                                                     ▼
                                   AQY212 PhotoMOS LED (≈ 5 mA)
                                                     ▼
                         potential-free contact ── NODE Ambient switch input

• Off-delay: each motion pulse charges C1. When the pulse ends, C1 can only discharge through R2 into Q1's base, which keeps the PhotoMOS on. New motion recharges C1 and restarts the timer.
• Light inhibit: in daylight, the LDR divider turns on Q2, which shorts the sensor pulse so it cannot charge C1. A running timer is not cut off.
• Lamp-on override: the lamp's own light would otherwise block retriggering. Q3 senses the PhotoMOS LED current and, through Q4, holds Q2 off while the output is on, so motion keeps the light on.
• Output: the AQY212 contact (60 V, about 0.5 A, AC/DC, no polarity) replaces the wall switch on the Ambient input. It is meant for that signal input, not for switching lights or pumps directly.

Connecting to Revotion

Terminal J1:

Set that NODE Ambient input to switch mode ("Schalter"), not push-button mode ("Taster"). The sensor board and the Revotion system must share the same ground, which they do when both run from the camper's 12 V distribution.

Adjusting

Set the light threshold on site: in the light where the sensor should just stop reacting (for example at dusk), turn RV1 until motion no longer switches on. Without the LDR the board simply ignores daylight.

The end of the hold time is a slow fade, so real parts vary: the HC-SR505 board measured about 3 min where the simulation gave 2.3 min. The PDFs explain which part tolerances cause that.

AM312 SMD board

kicad/pir_camper_am312/ holds the KiCad 7 project:

Main parts: AM312 module, TPS70933 3.3 V LDO, AQY212S PhotoMOS (SOP-4), MMBTA14 Darlington for the timer, BC847C/BC857C, Bourns 3314 trimmers, Phoenix MC 3.81 mm terminal, and a JST XH socket for the optional LDR.

Regenerating the files

Everything is generated by the Python scripts in tools/:

For example, the AM312 perfboard guide:

pip install schemdraw
python3 tools/gen_am312_schematic.py
python3 tools/gen_ltspice.py
python3 tools/gen_am312_sim.py
python3 tools/build_am312_doc.py

Files

"Schaltplan" is German for schematic, "Lochraster" for perfboard, "mit Verzögerung" for "with delay" and "Umbau" for retrofit.

Revotion and NODE are trademarks of REVOTION GmbH. This project is not affiliated with REVOTION.

License

MIT, see LICENSE.