LightScythe v3

Credits

This project could not exist were it not for the work of The Mechatronics Guy, and his update. The work I am doing here is largely based on his list of improvements. Credit also has to be given to Adafruit for their code and components - together, you guys have saved me a lot of hard work!

Hardware

Raspberry Pi

We use a Raspberry Pi Zero W - the linked one includes a full GPIO header but this is not the default, make sure the header exists or that you purchase a kit for attaching this yourself.

To protect the device, I also bought a Pibow case.

LCD Plate

As I didn't want to get involved with wiring buttons directly to the GPIO pins on my Pi and it seemed that for real control some form of display would be needed, I opted for the Adafruit 16x2 LCD plate with built in buttons. Assembly was simple but it does require a certain level of dexterity with a soldering iron.

Once assembled insert two thin wires into the MOSI (BCOM 10 / 19) and SCLK (BCOM 11 / 23) SPI sockets.

Then attach the LCD plate to the Pi taking care to ensure that nothing is forced excessively or unevenly.

Scythe

For the Scythe itself, I am using 2 x 1m lengths of OpenBeam that are held together with the handle template provided by the Mechatronics guy. I have then used velcro to attach the Adafruit Digital LED Strip to the beam.

To power the lights, you need a theoretical maximum of 2A per meter of lights, and then another amp or so to power the Pi, so I chose this 5v 5800mAh battery from eBay which looks like it will have plenty of power for the job. I am putting the power from this on to a veroboard that is linked at both the top and bottom of the beam to the LED chain. From this there is also a micro USB to power the Raspberry Pi. North of the Pi there are 4 lanes of board and the central 2 are used to carry the light data.

Software

Raspberry Pi

These are instructions to get your Pi up and running. They are for a Mac and may skip some details if I have assumed they are too trivial, please raise an issue if something needs explaining.

1. Write Raspbian to SD card with Etcher
2. touch /Volumes/boot/ssh
3. Create /Volumes/boot/wpa_supplicant.conf and add the following contents:

   ctrl_interface=DIR=/var/run/wpa_supplicant GROUP=netdev
   update_config=1
   country=US
   
   network={
       ssid="your-network-service-set-identifier"
       psk="your-network-WPA/WPA2-security-passphrase"
       key_mgmt=WPA-PSK
   }
   

4. Unmount the SD card and insert it into your Pi, add power and wait for it to boot.
5. Get the IP of the Pi and SSH into it: ssh pi@192.168.1.22
6. Enable I2C (for the display and buttons) and SPI (for the light strip). sudo sudo raspi-config and select 5 Interfacing Options > P4 SPI and enabled it then P5 I2C and enable.
7. Update APT: sudo apt update && sudo apt upgrade -y
8. Install the Hotspot packages: sudo apt install dnsmasq hostapd -y
9. Configure a static IP address for the Pi (/etc/dhcpcd.conf):

   interface wlan0
       static ip_address=192.168.4.1/24
       nohook wpa_supplicant
   

10. Move the old dnsmasq config out of the way: sudo mv /etc/dnsmasq.conf /etc/dnsmasq.conf.orig
11. Create the new DHCP server configuration file (/etc/dnsmasq.conf) as root and add:

    interface=wlan0
      dhcp-range=192.168.4.2,192.168.4.20,255.255.255.0,24h
    

    (for wlan0, we are going to provide IP addresses between 192.168.4.2 and 192.168.4.20, with a lease time of 24 hours)
12. Edit the access point config (/etc/hostapd/hostapd.conf) and add this config:

    interface=wlan0
    driver=nl80211
    ssid=LightScythe
    hw_mode=g
    channel=7
    wmm_enabled=0
    macaddr_acl=0
    auth_algs=1
    ignore_broadcast_ssid=0
    wpa=2
    wpa_passphrase=RustyBulletHole
    wpa_key_mgmt=WPA-PSK
    wpa_pairwise=TKIP
    rsn_pairwise=CCMP
    

13. Tell the system where to find this config, edit /etc/default/hostapd to have:

    DAEMON_CONF="/etc/hostapd/hostapd.conf"
    

14. Enable IP forwarding by editing /etc/sysctl.conf and uncommenting the line net.ipv4.ip_forward=1
15. Reboot (sudo reboot) and scan your WiFi for the access point when the Pi boots back up. You should be able to connect to the access point and SSH into your Pi with ssh pi@192.168.4.1

Scythe Code

1. Install Python dependencies: pip3 install adafruit-circuitpython-charlcd Pillow
2. Install the code: git clone https://github.com/frak/LightScythe.git

Once you have everything setup, you just need to run the following from the project root.

scythe/Scythe.py

On the first run, it will create a settings.ini file in the project root. You can override this process by manually supplying a settings.ini file yourself. Here are the default values to use as a template:

[Display]
colour = VIOLET
timeout = 15
delay = 0.05

[Images]
dir = /home/pi/images
current = 0

This will expect the images to be found in /home/pi/images - if it cannot find either the directory or any images the script will terminate. When it loads, any images found in that directly will be automatically resized to the correct height, and the resized image will be saved in a "preocessed" sub-directory. You can also set the display colour and timeout here, using the following colour constants: RED, GREEN, BLUE, VIOLET, TEAL, WHITE, BLACK (off).

There are many ways to get your Pi to run this script automatically on boot which you will need out in the field, however, the simplest option I found was to use crontab. Just run crontab -e and add the following:

@reboot /home/pi/LightScythe/scythe/Scythe.py &