Overview

The dew heater 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 dew heater state.

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

It is also possible to operate the dew heater using temperature thresholds if you have an appropriate temperature sensor. The default target temperature is the dew point, which will be available if you have a sensor that detects both temperature and relative humidity [RH]. If you do not, you may set a manual temperature threshold.

Note: The manual threshold does not need to be a temperature. You may select any of the user data slots, which could be a RH value.

GPIO Permissions

If you receive a PermissionDenied exception when accessing GPIO pins

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

Dew Heater - Standard

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

Dew Heater - PWM

The PWM dew heater 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.

WARNING

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

Raspberry Pi 5

PWM support is not quite working yet.

source virtualenv/indi-allsky/bin/activate

pip remove RPi.GPIO

pip install 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