Why DomBusTracker2?

• It can be configured as dual-axis, single horizontal axis, single tilted axis mode
• It works in stand-alone mode, but also can be monitored and controlled by Home Assistant,  Domoticz, Node-RED  and other automation systems supporting Modbus or MQTT / MQTT-AD
• It uses a waterproof deep-hole light sensor that permits to optimize power production even when it's cloudy, orienting solar panels toward the brigthest portion of the sky
• Very compact, easy wiring, uses a strong industrial bus solution (RS485) that can be connected to a controller by up to 500-1000m of shielded cable (standard alarm cable)
• Very low power consumption (15mW during the night) with relays OFF
• Automatically detects limit switches inside linear actuators
• Manages additional 4 proximity sensors or limit switches, suitable for slewing gears.
• Manages a anemometer with pulsed output to put the solar panels in a safe position in case of strong wind. If a anemometer already installed on site, no need to connect additional sensors: just send wind speed value by bus (using a automation).
• Tracker status shown on the automation system. Of course it's possible to control elevation / azimuth by the automation system (smartphone).
• Optional UP/DOWN buttons to manually control elevation and azimuth, and one switch to set manual / automatic (tracking) mode.
• Buzzer output to notify the manual mode and wind safe mode (strong wind, panels in safe position).
• Night position and Wind safe position are configurable by the automation system (or Modbus registers), as like as several other parameters: default parameters are already suitable for almost any dual axis solar tracker.

Why a solar tracker?

Sun tracker is very good for photovoltaic systems because enhances the total production energy and, moreover, increases the power during the early morning and late afternoon, when energy is more expensive and less available.

The following chart shows the comparison of the energy produced in a sunny day, October 31 2024, in the Northern Italy, between a 2-axis solar tracker and a photovoltaic on the roof.

Comparing the two systems, we can say that in these conditions the 2-axis tracker performs almost 3 times over photovoltaic on the roof . Normally it performs almost twice a photovoltaic system on a roof oriented to South, with a normal tilt for italian houses (around 15 degrees). YouTube video

This controller was designed to overcome the limitations of the chinese XMYC-3 controller, using the same sun sensor, but adding some features like the automatic detection of the limit switches inside the motors (linear actuators have limit switches inside, that cut-off power) and the home automation system integration with Domoticz, Home Assistant, Node-RED, OpenHAB, ioBroker, and other systems supporting MQTT or Modbus protocols.

Features

• Configurable as dual axis, horizontal single axis and tilted single axis tracker.
• Use a standard waterproof sun sensors made by 4 photodetectors, to determine the best tilt/azimuth even in case of clouds. 
• 4x 10A relays permit to control 2 linear actuators with 800kg force (or slewing drives), supplied by a 24V (preferred) or 12V power supply unit.
• If requested, it's possible to have a version for higher power motors, 15A current limit for higher power linear actuators up to 3000kgf and higher power slewing motors.
• Current sensing to automatically detect the linear actuator internal limit switches, to find the zero and full-scale motor position.
• 4 inputs  that can be connected to external limit switches or proximity sensors (NPN type, common to GND) for the azimuth motor (useful in case that a slewing motor is used instead of linear motor). Indeed, to save energy consumption, proximity sensors are powered only when needed.
• 2 inputs that can be connected to 2 optional up/down buttons to move motors manually
• 1 input that can be connected to a optional switch to disable automatic tracking
• 1 input (IN12) that can be connected to a wind sensor (anemomenter) with pulsed (reed) output, common to GND, that can be used to move the tracker to a safe position in case of strong wind or storm
• 2x 5A additional relays for additional functions
• Internal RS485 bus terminating resistor (150 ohm) that can be enabled by a PCB jumper (with a solder iron)
• RS485 bus, that works with up to 500m of cable (using standard alarm cable: 2x0.50+2x0.22mm² + shield)
• DIN rail low-profile enclosure, 115x90x40mm
• Plugin terminal blocks for easy wiring
• Parameters configurable by RS485 bus, to work with almost any tracking system
• Available with 2 firmwares of your choice:
  • DomBus firmware, using a standard multi-master protocol working with
    • Domoticz + Creasol DomBus plugin
    • Home Assistant, Node-RED, OpenHAB, ioBroker + DomBusGateway software that realize a bridge between DomBus protocol and MQTT with AutoDiscovery
  • Modbus firmware, working with NodeRED, Home Assistant, OpenHAB and many other controllers supporting the standard Modbus protocol.
• Tracker status is exposed to the home automation system or Modbus:
  • 0: Cloudy mode (tracker moves less frequently to prevent energy consumption)
  • 1: Automatic mode
  • 2: Automatic mode, motor is moving
  • 3: Manual mode
  • 4: Manual mode, motor is moving
  • 5: Evening (tracker is going in the night position shortly)
  • 6: Night (tracker in the night position)
  • 7: Night, motor is moving (tracker is going to the night position)
  • 8: Morning (tracker is leaving the night position soon)
  • 9: Wind alert (strong wind: tracker will go to the wind safe position soon)
  • 10: Wind (tracker in the wind safe position)
  • 11: Wind, motor is moving (tracker is going in the wind safe position)
• Very low power usage: 15mW with relays OFF.
• Red/green LED showing the current status:
  

  Green LED flashing every 4s	Tracker in the night/rest position
  Green LED flashing every 2s	Tracker in cloudy mode (moves less frequently to save energy usage)
  Green LED flashing every second	Normal mode (automatic)
  Green LED flashing every 0.25s	Motor On, moving
  Red LED flashing every second	Manual mode, set by the switch input or by home automation system (MAN device)
  Red LED flashing every 0.25s	Wind gust detected (storm?), tracker in the safe position

• Optional active buzzer (with oscillator, working at 5.5V) can be soldered on the PCB to get the following alerts:
  

  1 beep	Tracker in manual mode
  2 beeps	Wind gust detected => tracker in safety mode

  The buzzer can be disabled by setting the parameter TrackerBuzzer = 0 (see table below)

Although several parameters are user configurable, default value are suitable in most cases, so the device can be used as-is for most dual axis sun trackers.

Waterproof sun light sensor already supplied, while motors and 24V power supply unit are NOT supplied.

DomBus or Modbus firmware?

The sun tracker controller is available with two firmwares of your choice:

• Modbus, suitable for all systems supporting the standard Modbus protocol, and for customized systems using that protocol
• DomBus, suitable for Domoticz (using the Creasol DomBus plugin), and for HomeAssistant, NodeRED, OpenHAB, ioBroker and other systems supporting MQTT with AutoDiscovery, by using the DomBusGateway python software that realize a bridge between DomBus protocol and MQTT-AD standard protocol. Also, building automation system supporting the MQTT with AutoDiscovery will automatically detect all entities of the sun tracker.

Connection schematic

How DomBusTracker works

1. By default, it works as a dual axis tracker controller, but it can be configured as a horizontal axis or tilted axis tracker by changing the TrackerType parameter: check the configurable parameter section below.
2. It uses a deep hole light sensor to find where the sky is brighter: this works also in case of cloudy weather, so panels will be oriented automatically to the brighter area in the sky. DomBusTracker shows the values of the light sensor for each direction, and also a % value (see ports NS and EW): when tracker is aligned to the sun, NS and EW is near 50%. If a displacement occurrs, it's compared with 50+/-TrackerLightDeviation* to determine if tracker must be moved or not.
   For example, if NS >= 50+TrackerLightDeviationNS then activate motor MS to increase tilt.
   If EW >= 50+TrackerLightDeviationEW then activate motor MW to move panels toward West.
   In case that EW<50, value is compared with 50-TrackerLightDeviationEW*2 to avoid trackers with fast motor to move to West and then return to East.
3. The following parameters must be configured: TrackerWorkingTimeNS that sets the working time of the tilt motor, TrackerWorkingTimeEW that sets the working time for the azimuth motor.
   Also, it's possible to configure TrackerHomingNS that sets the number of moving requests for tilt after which the controller moves to 0 or 100% position to keep position accuracy: the homing feature is not performed while tracking the sun, but only when a command to move to a certain fixed position (including night, morning and wind position) is requested. Similarly for TrackerHomingEW , for the azimuth position.
4. This controller measures the current fed to the motors, to detect the motor internal limit switch (normally available in the linear actuators). In case of slewing gears, normally open (default) or normally closed limit switches can be used. In case that proximity sensors are used, it's possible to set TrackerProximityEnable to 1 or 2 to provide power supply to the sensors. When TrackerProximityEnable=1, power is provided only when needed, reducing energy usage. Normally, NPN proximity sensors with NC output are used so, in case that a proximity cable is broken, motor stops working.
5. Tracker is moved every 5 minutes (TrackerPeriodicCheck) , while sunny, or every a longer time (TrackerPeriodicCheckCloudy) when cloudy (check TrackerCloudyThreshold parameter to set the light threshold to discriminate cloudy from sunny condition): parameters are shown below and may be changed by the user. The longer time is set to avoid tracker change position too often when cloudy.
6. When light decreases, in the evening, going below the TrackerSensorMin value, a counter start increasing and when it reaches the TrackerNightTime value (300 seconds, by default), panels will be oriented to the TrackerNightPositionNS (tilt) and TrackerNightPositionEW (azimuth) position.
7. When light increases, in the morning, going above the TrackerSensorMin value, panels are oriented to the TrackerMorningPositionNS (tilt) and TrackerMorningPositionEW (azimuth) position.
8. If a anemometer is connected to the Wind input, it measure the anemometer frequency comparing with the TrackerWindThreshold value: in case that wind speed stays above this threshold for TrackerWindStartTime seconds, panels position is saved and panels will be moved to a safe position set by TrackerWindPositionNS and TrackerWindPositionEW. When wind speed falls below the threshold for TrackerWindRecoveryTime seconds, panels will be moved to the previous position. 
   The system works also without a direct connection to the anemometer: the wind speed can be provided externally, by a building automation system getting this information from a weather station for example: in this case it's sufficient a simple automation to write the wind register / entity of the tracker controller, nice solution in case of a large photovoltaic farm with several trackers, or in case that a weather station is already available.

Complete information and application notes at https://www.creasol.it/DBT