Servo Controlled Time-Lapse Camera

For our HAB mission, we created a servo controlled camera running on a RasPi Zero and using xChips to control/drive a servo.

Hardware components

• Raspberry Pi Zero x 1
  Get the newer version that has a camera interface. And make sure you got a Micro-USB cable to connect the Pi to your computer
• XinaBox BR03 x 1
• XinaBox OC05 - Servo Driver x 1
• XinaBox XC10 x 1
• XinaBox MD01 x 1
  Really just a spacer to mount the servo on, so very optional.
• Raspberry Pi Camera Module x 1
  Remember to get the narrower flat cable that fits the RasPi Zero
• 3.7v LiPo battery (generic) x 1
• Servos (Tower Pro MG996R) x 1
  Any small servo with standard 2.54 mm 3 pin header cable, and mounting gear (nuts/bolts, rubber bands, cable ties, glue, or what ever is your preference)

Software apps and online services

• Raspberry Pi Raspbian Lite
• Balena Etcher
• XinaBox OC05 Servo Driver

Using the RasPi Zero with the PIcamera, a Servo and the OC05 Servo Driver/Controller, you can shoot a panning time-lapse video.

• Download Raspbian Lite and unzip
• Download Etcher and install
• Flash Raspbian Lite to a Micro-SD card using Etcher
• Open your terminal and go to the root of the SD Card

cd /Volumes/boot
echo 'dtoverlay=dwc2' >> config.txt
touch ssh
echo -n ' modules-load=dwc2,g_ether' >> cmdline.txt

The last 3 lines set up the RasPi Zero (and only the Zero) to be able to network via the USB port. Just verify that the last line has no newline before ' modules...' in cmdline.txt!

• Eject the SD Card
• Assemble everything as per this video:

• Connect USB Cable between your RasPi Zero and your computer.
• Either use a Mac or install Bonjour to SSH to your RasPi Zero: ssh pi@raspberrypi.local
• Password is raspberry
• Finally setup internet sharing on your computer allowing Broadcom Ethernet to connect to your WiFi via your computer.

sudo raspi-config nonint do_expand_rootfs
sudo raspi-config nonint do_i2c 0
sudo raspi-config nonint do_camera 0
sudo apt-get install vim python-smbus i2c-tools
sudo apt-get install python-picamera python3-picamera
sudo reboot

• The first 3 lines makes full use of your SD card, activates I2C for the servo controller and activates the PIcamera.
• Then I2C tools are getting installed and then PIcamera drivers.
• Then reboot to make the changes take effect.
• Login again.
• Test the connection to your servo controller, and if everything is fine you should see this:

pi@raspberrypi:~ $ 
    0  1  2  3  4  5  6  7  8  9  a  b  c  d  e  f
00:          -- -- -- -- -- -- -- -- -- -- -- -- --
10: -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- --
20: -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- --
30: -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- --
40: -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- --
50: -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- --
60: -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- --
70: 70 -- -- -- -- -- -- --

cd ~

git clone https://github.com/xinabox/rpOC05.git</a>
cd rpOC05

sudo python setup.py install

This will install the Servo Driver library, once installed, test by:

cd examples
python simpletest

• Copy and Paste the code below into xservo.py.
• Create a frames directory

cd ~
mkdir frames
python xservo.py

It should now start taking pictures and store them in frames.

• You can have the program run automatically by crontab -e
• And then write at the bottom of the file: @reboot python /home/pi/xservo.py
• Once your shoot is finished, you can copy the pictures to your computer. I use scp
• And then I use convert from ImageMagick, like this: convert -quality 100 frames*.jpg outputfile.mpeg

servo.py Python

from __future__ import division
import time
from datetime import datetime<br>import rpOC05
import picamera

pwm = rpOC05.PCA9685()

servo_min = 150  # Min pulse length out of 4096
servo_max = 500  # Max pulse length out of 4096
i = servo_max + 10
chan = 8
filename = 'frames/frame-%s.jpg'
pwm.set_pwm_freq(50)
# signal ready with a wave
pwm.set_pwm(chan, 0, servo_min)
time.sleep(1)
pwm.set_pwm(chan, 0, servo_max)
time.sleep(1)

print('Time-Lapse Running...')
while True:
  if i > servo_max:
    i = servo_min

  pwm.set_pwm(chan, 0, i)
  with picamera.PiCamera(resolution=(1920,1080)) as cam:
    ts = str(datetime.utcnow())
    cam.capture(filename % ts,quality=90,thumbnail=None)
  # time-lapse interval in seconds.
  time.sleep(0.1)
  i += 1