Micro CAN

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Introduction

The micro CAN is a small PCB (3cm x 3cm) that will be installed behind every switch and has the possibility to connect 6 switches and 6 LEDs, and measure temperature and humidity.

Features

The micro CAN has following features:

  • CAN bus connection: Typically, an UTP kabel is used that runs through the house. The micro CAN supports up to 24VDC. 4 connections:
    • 12 to 24VDC (switched power supply embedded)
    • GND
    • CAN-H
    • CAN-L
  • Switch connection: The micro CAN supports up to 6 switches.
  • LED connections: The micro CAN supports an LED for every switch being used so 6 LEDs in total. On the micro CAN, an open-collector output is used (ULN2803) which supports many types of LEDs (common anode LEDs). Typical switches already have built-in resistors. In case a seperate LED is attached, the appropriate resistor needs to be installed. The LEDs have multiple functions that can be programmed like blinking (fast, medium and slow) as well as dimming so the LEDs can be less bright for example during the night.
  • Multicolor status LED, see Micro CAN LED Functionality
  • Optional onboard temperature and humidity sensor: This is possible however, since the PCB slightly heats up due to the processor and the switched power supply, we recommend to use an external sensor.
  • External sensors: The micro CAN supports 2 external temperature sensors or 1 external temperature/humidity sensor
    • 2x DS1820/DS18S20 temperature sensor (1wire) OR
    • 1x Honeywell HIH8121-021-001 temperature and humidity sensor (I2C)
    • Automatically detect which kind of temperature sensor is connected
    • External 5V for the sensors
  • Current and short circuit protection for the external 5V
  • External 12-24VDC voltage measurement so the user knows the voltage drop on the bus - under development
  • For wiring diagram see micro CAN Connections

Note:

  • The Honeywell sensor exists in 2 versions:
    • HIH8121-021-001: default product with 1 sensor, costs approx. 12 EUR
    • HIH8121-021-001S: sample with 5 sensors, costs approx. 60 EUR
  • The micro CAN supports the DS1820, DS18S20 and DS18B20. Please make sure NOT to use the "PAR" or "P" version (parasite power) since this will not work

Installation

The micro CAN is typically installed behind a light switches or other wall mounted component. When it is equipped with a temperature or humidity sensor it is necessary to allow the free flow of external air around the sensor component. One of the possible ways to accomplish this is by using a Niko 100-76000 cover plate which features an opening at the bottom to house the sensor and allows proper airflow:

MicroCANcover1.jpg MicroCANcover2.jpg MicroCANcover3.jpg