My Allsky camera senses the temperature and humidity inside the housing and controls an internal fan and dew heater. A software service called temperatureMonitor.py sleeps for a minute then reads the temperature, humidity and the state of the fan and dew heater outputs. These values are written to a file which is used by the allsky software and added to the current image as part of the image overlay.
- Heater is on GPIO 17 (broadcom #) which controls a FET switch to switch on/off 12VDC to the nicrohire
- Fan is on GPIO 18 (broadcom #) which controls a FET switch to 5VDC fan
- Si7020 uses I2C bus 1 (3.3 VDC device)
| funct | Pin | Pin | funct |
|---|---|---|---|
| 3.3VDC | 1 | 2 | 5VDC |
| SDA | 3 | 4 | 5VDC |
| SCL | 5 | 6 | ... |
| ... | 7 | 8 | ... |
| GND | 9 | 10 | ... |
| HEATER | 11 | 12 | FAN |
| ... | 13 | 14 | GND |
| ... | 15 | 16 | ... |
| ... | 17 | 18 | ... |
| ... | 19 | 20 | GND |
| ... | 21 | 22 | ... |
| ... | 23 | 24 | ... |
| GND | 25 | 26 | ... |
| ... | 27 | 28 | ... |
| ... | 29 | 30 | GND |
| ... | 31 | 32 | ... |
| ... | 33 | 34 | GND |
| ... | 35 | 36 | ... |
| ... | 37 | 38 | ... |
| GND | 39 | 40 | ... |
| funct | Color |
|---|---|
| VCC | YELLOW |
| GND | ORANGE |
| SCL | RED |
| SDA | BROWN |
| funct | BCM pin# |
|---|---|
| HEATER | 17 |
| FAN | 18 |
- pigpio library https://abyz.me.uk/rpi/pigpio/
- smbus2 python module
- temperatureMonitory.py
make sure you enable the service > sudo systemctl enable pigpiod
install smbus2 which is used by temperatureMonitor.py to read the si7020 I2C chip
- pip3 install smbus2
you can install i2c-tools to debug your connections to the I2C chips
- sudo apt-get install i2c-tools
- sudo i2cdetect -y 1 # Use -y 0 for bus 0
pi@raspberrypi:~ $ sudo i2cdetect -y 1
*39 is TLS2560 *40 is si7021 *76 is BME280
| 0 | 1 | 2 | 3 | 4 | 5 | 6 | 7 | 8 | 9 | a | b | c | d | e | f |
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
| 00: | -- | -- | -- | -- | -- | -- | -- | -- | -- | -- | -- | -- | -- | -- | -- |
| 10: | -- | -- | -- | -- | -- | -- | -- | -- | -- | -- | -- | -- | -- | -- | -- |
| 20: | -- | -- | -- | -- | -- | -- | -- | -- | -- | -- | -- | -- | -- | -- | -- |
| 30: | -- | -- | -- | -- | -- | -- | -- | -- | 39 | -- | -- | -- | -- | -- | -- |
| 40: | 40 | -- | -- | -- | -- | -- | -- | -- | -- | -- | -- | -- | -- | -- | -- |
| 50: | -- | -- | -- | -- | -- | -- | -- | -- | -- | -- | -- | -- | -- | -- | -- |
| 60: | -- | -- | -- | -- | -- | -- | -- | -- | -- | -- | -- | -- | -- | -- | -- |
| 70: | -- | -- | -- | -- | -- | 76 | -- | -- | -- | -- | -- | -- | -- | -- | -- |
#Setup of the temperatureMonitory service
- copy the temperatureMonitory.service to /etc/systemd/system/
- enable the service ** sudo systemctl enable temperatureMonitor
- start the service ** sudo systemctrl start temperatureMonitor
- status the temperatureMonitor ** sudo systemctrl status temperatureMonitor #setup of additional storage for images using usb thumb drive You can permanaently add a usb thumb drive as more storage for your allsky
Plug in the device and then execut the following to get the UUID info
- lsblk -o NAME,UUID make a mount point for the thumbdrive
- sudo mkdir /mnt/myusbdrive edit the file system table
- sudo nano /etc/fstab add an entry into fstab *PARTUUID=your-usb-drive-uuid /mnt/myusbdrive ntfs-3g defaults,auto,users,rw,nofail,uid=1000,gid=1000 0 0 now mount the drive
- sudo mount -a now check that the drive is active
- df -h
It now has the following functions
- read temp and humidity from si7020 chip
- stores those data items in a json file in the overlays/extra folder of the allsky system
- plots the data onto a graph and saves the graph for the overlay
- at midnite it saves all the temp, humidity with individual time stamps to the previous day's image folder ** the intent here is that the T&H data will get archived with the images
- at midnite it restarts accumulating T&H data for the current day