Flying Camera Operation Detector Piece (Flying COD Piece)
A discussion of this project is here.
Lightweight, inexpensive digital cameras have allowed a resurgence of low elevation aerial photography. High quality images can be captured by low-end, consumer grade (point and shoot or P&S) cameras lofted a few dozen to several hundred meters above ground by kites and tethered helium balloons. Simple camera mounts, sometimes consisting of no more than rubber bands, string, and pieces of plastic soda bottles, reduce cost and weight, and lower the barriers to entry for communities in need of up to date information about their local geography. Vertical aerial images can be aligned into more extensive orthophoto mosaics using free, open source, online tools such as Mapknitter which was developed by the Public Laboratory for Open Technology and Science (PLOTS).
Several approaches to triggering the shutter of lofted cameras are commonly used:
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With the camera in continuous shutter mode, a rubber band is wrapped around the camera so that the shutter release button is permanently depressed. The shutter will be released every second or two until the battery is drained or the memory card is filled. All photos are taken with the focus and exposure settings of the first photo taken.
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For most Canon Powershots, an open source firmware enhancement (Canon Hack Development Kit or CHDK) allows scripts to control camera operations. Intervalometer scripts are widely available for triggering the shutter at any interval. Typically, the shutter will be released every 4 to 20 seconds until the battery is drained or the memory card is filled.
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Some cameras have an integrated intervalometer function.
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An external timing device can send a signal to the camera to release the shutter. Although most consumer-grade P&S cameras lack an electronic shutter release port, Canon Powershots with the CHDK enhancement can be triggered by a ~5v pulse to the USB port. Simple timers based on the 555 IC can provide this signal, and can be built from kits or parts for under US$7.00. External timers are required to synchronize the shutter release of multiple cameras for stereo photography or multiband imaging. Camera rigs with pan and tilt servos can be pointed with microcontrollers (e.g., AuRiCo, CamRemote) which also release the shutter at the appropriate time. The external timer or microcontroller typically has a separate power source which can also power pan and tilt servos.
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Remote triggering of camera shutters via radio signals from a ground operator allows more control of when photos are taken. Standard transmitter/receiver pairs designed for RC hobbyists can be purchased for about $100 and are commonly used to trigger aerial camera shutters. Camera rigs with pan and/or tilt servos can also be pointed with these four channel systems. The receivers require a power source, which is typically three or four AAA cells. The shutter can be released until the receiver or camera battery is depleted, or the memory card is full. The ground-based transmitter typically has a battery level indicator and the batteries could be changed during a flight.
None of the above approaches has any inherent system to monitor the operation of the airborne camera from the ground. Some kite aerial photographers attach colored flagging to parts of the camera rig so they can more easily see where the camera is pointed when it is low enough, and some have added a video feed to monitor the scene being captured by the camera. Some are experimenting with sophisticated one- or two-way communication using Arduino controllers. But most practitioners have no feedback from the camera. Ideally, each photo taken by the camera would be displayed remotely with some exif data (focus distance, shutter speed, aperture) so camera operation could be monitored. In reality, this is a lot of data to consume while one person is trying to fly a kite and possibly also point the camera and trigger the shutter remotely, and it is more than is required to detect the problem of stalled image capture.
A common failure is that the camera stops capturing images during a flight and returns to earth with far fewer images than expected. A primary cause of these failures is early depletion of the camera battery, timer battery, or receiver battery. If the batteries persist, the memory card can fill with images at which point capture ceases. Other poorly understood conditions cause cameras to stop responding to USB pulses. This is probably related to USB pulses arriving before the camera has finished processing the last image and may be most common with overly eager operators of radio control joysticks.
Regardless of cause, the photographer may be oblivious to the problem and the flight may continue for an hour or more during which no images are being captured. This loss of time and opportunity could be avoided with a simple feedback system which alerted the user if the camera was no longer capturing images.
All of the following approaches require a radio downlink to deliver information from the flying rig to the user. Required transmission distances are generally 50 to 500 m and are almost always line of sight.
Stream to user -- Cameras make noise when the trigger is released. This sound could be captured with a microphone and delivered to the user as a continuous stream for monitoring. For dual camera rigs with simultaneous shutter release, a stereo feed might be required to distinguish the cameras.
Onboard processing --The audio stream could be processed onboard and an alert sent when an anomaly is detected.
If battery level can be monitored, an alert could be sent when the level drops below a threshold. Power levels of the camera, timer, and/or RC receiver would have to be monitored. The variety of power sources used would make a universal solution unlikely. Also this approach would not detect a full memory card or camera lockup due to other causes.
If camera data could be acquired for each image captured, some of it could be delivered to the user. This could include a downsampled image and pertinent information (focus distance, shutter speed, aperture, zoom level, memory card remaining, number of images captured). Although this is more information than is required to know if the camera is still operating, it could detect other issues such as insufficient light or improper camera setup. This type of data is available to scripts running on Powershots enhanced with CHDK, and might be available for export to a USB connected device.
Video downlinks are used by advanced practitioners to monitor the scene being captured. An onboard video camera can be pointed to capture the same scene as the still camera.
Older Canon Powershots and many other P&S cameras have a standard “A/V out” port (3.5mm TRRS) which redirects the live image on the LCD display to an analog composite video signal which can be displayed on a TV (this allows viewing your photos on any old TV). Newer Powershots have no 3.5mm port, but instead have an HDMI port and a proprietary 11 pin USB port which combines USB data transfer and A/V out. On all Powershots, the A/V out composite video signal is available for wireless streaming by the appropriate hardware.
This video signal includes the “live view” of exactly what the camera is seeing with selected data overlain (data overlays are highly customizable using CHDK) and could be used to remotely frame photos. On Powershots, the LCD can “review” each photo for several seconds after it is taken. This review can be set to "detailed" to display an image thumbnail, shutter speed, aperture, ISO, focus mode, white balance mode, image size, number of images taken, and number of images expected to fit on SD card. This information is valuable for monitoring camera operation.
Streaming this video signal to the ground requires an onboard transmitter and power supply, plus a ground-based receiver and daylight readable display. This hardware is commonly used by RC airplane enthusiasts and is readily available. Monitoring both cameras on a dual rig complicates this approach.
Here is one of many more or less relevant discussions of this issue at the KAP forum.
Below is an almost plug and play solution. A 200mW 5.8Ghz transmitter/receiver pair for audio and video for $67 from HobbyKing. All it needs is power supplies (7-15v for Tx) and display. The range is 500m. Details here.
Also, the transmitter has a built in microphone, so to stream audio to the photographer just plug headphones into the receiver. To stream video, connect the camera's A/V out port to the transmitter and plug a display into the receiver, like this $75 3.5" wrist mounted LED monitor (totally Dick Tracy). An easy way to monitor two cameras might be to display video of the LCD display of one camera and stream audio of the other camera.
The radio frequency will not interfere with the 2.4Ghz RC system which might be in use to point and shoot the camera. However, I think this 5.8Ghz 200mW system requires an amateur radio license. I am not sure whether less powerful systems which are FCC approved for general use have the required range for this application.
Is there an open source solution that is better or cheaper or lighter (I think the transmitter weighs 25 or 34g) than this? Is wireless transfer using an 802.11b/g/n (WiFi) system a better approach?
Problem with newer Powershots: Using CHDK to trigger the shutter via a USB pulse requires connection to the camera's USB port. The A/V out connection on newer Powershots is part of a proprietary 11 pin USB port. To access the composite video signal while simultaneously sending USB pulses to the camera, a custom splitter cable is required. It can be purchased for about $50 (see "CR-Camera 11-pin USB+A/V Combo Cable for Canon"). Here is one approach to building this cable by modifying a $2 cable.
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Bushnell land surveillance camera, $100, 2MP/5MP High Quality Full Color Resolution 18 IR LED Night Vision Flash – 30’ Range Date, Time, Moon Phase Stamp Low and High Resolution Settings PIR Sensor is Motion Activated out to 30’ Simple to use system. Still Image and Video Modes Video length 15 seconds 32GB SD Card Capacity Trigger Speed—Less Than 1.5 second Trigger Interval – 10 sec to 10 minutes programmable Takes 4 (AA) Batteries Sleep state of .40 Milliamps 6 Month + Run-Time on one set of (4) AA Batteries 640 x 480 AVI Video (20 fps) Temperature Range 0F to 140F
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4D Systems microCAM Serial JPEG Camera Module - TTL - RB-Fds-15 - $64 - • Small size, low cost and low powered camera module • 3.3V DC Supply @62mA • OmniVision CMOS VGA colour sensor • On-board Serial interface (TTL levels) • RoHS compliant The 4D Systems microCAM Serial JPEG Camera Module - TTL is a highly integrated serial camera module which can be attached to any host system that requires a video camera or a JPEG compressed still camera for embedded imaging applications. The module uses an OmniVision CMOS VGA colour sensor along with a JPEG compression chip that provides a low cost and low powered camera system. The user commands are sent using a simple serial protocol that can instruct the camera to send low resolution (160x120 or 80x60) single frame raw images for a quick viewing or high resolution (640x480 or 320x240) JPEG images for storage or viewing. The uCAM comes in a compact form factor with a built in lens and a 4-wire connector that provides easy access to both power and serial data. Features: • On-board EEPROM provides a command-based interface to external host via TTL levels serial link • UART: up to 115.2 Kbps for transferring JPEG still pictures or 160x128 preview images with 0.75fps • On-board OmniVision OV7640/8 VGA colour sensor and JPEG CODEC for various resolutions • Built-in down sampling, clamping and windowing circuits for VGA, QVGA, 160x120 or 80x60 image resolutions • Built-in colour conversion circuits for 2-bit gray, 4-bit gray, 8-bit gray, 12-bit RGB, 16-bit RGB or standard JPEG preview images • No external DRAM required
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Vex Wireless camera kit - $80
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D-Link DCS-932L Wireless N Day/Night Home Network Camera - $95 - 1/5" CMOS Sensor Infrared LED for Night Vision Monitor via Web or Android & iPhone Apps Easy Three-Step Setup Compact Design D-Link D-ViewCam Management Software 10/100Base-TX Ethernet 802.11b/g/n Wireless Connectivity
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BADA 2.4GHz 2W Wireless Audio/Video AV Transmitter & Receiver Kit (100V~240V AC) -- $60 -- - Brand: Bada (known for professional quality wireless AV transmission) / Model: BD2-4G804-(2W) / 2 watt / 2000mW ultra high transmission power / 2.4GHz wireless frequency / 4 selectable channels via easy DIP switch / Ultra high clarity / Transmits both video and audio / Hi-gain antenna / Transmits up to 300 meters (manufacturer rated) / Supports multiple transmitter (up to 4), single receiver configuration -- receiver automatically switchs channel every 6 seconds / High powered transmission, interference resistant / Transmitter and receiver size: 10.4cm6.0cm3.0cm / 2 x 100V~240V AC adapters included / English and Chinese user's guide included
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Rig5 -- Arduino-based video send / receive for KAP. Arduino-related notes here.
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Future Hobbies -- on-board / wireless video products for R/C platforms
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Range Video -- "distributor and developer of wireless A/V equipment and accessories. We tailor to the hobbyist by designing easy to use, long range, wireless video systems and accessories."
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Draganfly.com -- wireless video systems (and quad copters)
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Lady Ada's Wireless images via an Eye-Fi card <-- this looks really promising!!
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Great tutorial by Lady Ada on setting up a TTL serial camera module with NTSC video output. Re: the $50 camera: "It was designed to be used in security systems and does two main things - it outputs NTSC video and can take snapshots of that video and transmit them over the TTL serial link. You can snap pictures at 640x480, 320x240 or 160x120 and they're pre-compressed JPEG images which makes them nice and small and easy to store on an SD card. Perfect for a data-logging, security, or photography project. One nice thing about this particular camera is all the 'extras' that come with it. For example it has manually adjustable focus, auto-white-balance, auto-brightness and auto-contrast taken care of for you as well as motion detection built in! That means you can have it alert your project when something moved in the frame. "