Overview

The fan controller support in indi-allsky is intended to use the GPIO or PWM pins from a SBC such as a Raspberry PI to drive either a MOSFET or relay to manage the fan state.

The default functionality is to activate the fan during the day and deactivate at night, although it is possible to enable night time operation.

It is also possible to control the fan using temperature thresholds if you have an appropriate temperature sensor.

GPIO Permissions

If you receive a PermissionDenied exception when accessing GPIO pins

https://github.com/aaronwmorris/indi-allsky/wiki/GPIO-Permissions

WARNING

The pins from a SBC cannot be used to directly drive a fan. Trying to do so WILL damage your system.

Fan - Standard

This type of fan only supports two modes: ON and OFF. Any duty cycle applied to the fan will set it to FULL power. This type may use either a relay or MOSFET driver.

Fan - PWM

The PWM fan may be set to different power levels by utilizing the hardware PWM support from the SBC pins. This type requires the use of a MOSFET driver. A relay will not work.

Fan - Software PWM

PWM control is software managed by either the RPi.GPIO or gpiozero modules. The frequency is much more limited with Software PWM. The default frequency is 100Hz.

Adafruit Motor Shield/Hat

Support for the Motor Shield (various models) with the PCA9685 PWM driver is supported by the Adafruit MotorKit python driver. The Motor Shield is controlled via I2C. The default I2C address is 0x60

Possible pin values
motor1
motor2
motor3
motor4

Note about Motor Shield concurrent access

The Motor Shield may be used for both the focus controller and Dew Heater and Fan drivers, however, it will likely not be possible to utilize the focus/stepper capability while the fan and dew heater is active. The focus controller runs in the web interface, while dew heater/fan runs in the capture process. Trying to access the same i2c device across multiple processes will likely fail.

DockerPi 4 Channel Relay

The DockerPi 4 Channel Relay hat has individually controlled relays that are addressable at different i2c addresses.

Channel	Address
Relay 1	0x10
Relay 2	0x11
Relay 3	0x12
Relay 4	0x13

MQTT Fan Management

The MQTT support is for situations where the camera is remote from the indi-allsky capture instance. The fan will be controlled by a remote script that monitors the MQTT topics for the expected dew heater state.

The fan Pin in the config will be used as the MQTT topic name for publishing.

The ./misc/mqtt_remote_dew_heater_fan.py script may be used to operate the dew heater and fan on the remote system.

Monitor dew heater and fan topic manually:

mosquitto_sub -d -V mqttv5 -F %j -h localhost -p 1883 -u mqtt_username -P password123 -t "dew_heater_topic" -t "fan_topic"

Raspberry Pi 5

PWM support is not quite working yet.

PWM appears to be working as of Sept 2024.

Raspberry Pi 5 - RuntimeError: Cannot determine SOC peripheral base address

source virtualenv/indi-allsky/bin/activate

pip uninstall RPi.GPIO rpi.lgpio

pip install --upgrade rpi.lgpio

System virtualenv

If your virtualenv uses system python modules (like with indi_pylibcamera), it may be necessary to remove certain system python packages. This is not normally required.

sudo apt-get remove python3-rpi.gpio python3-lgpio python3-gpiozero python3-pigpio