Technical Info About our WebCam - The Thelen Channel

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	Sunday, February 05, 2012

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Technical Details About our WebCam

If you are curious about how our webcam works, here is a technical description of the system that puts our view on your computer. This includes the camera, enclosure, and software that we used to put it together, and how we connect it to the internet. I have also included a little bit of history about how we got to where we are now.

Camera & Lens

The camera is an Olympus Model C-4040Z 4.1 Megapixel Digital Camera. The lens is a 3X optical zoom - 7.1 ~ 21.3mm, F1.8 ~ F2.5 (Equivalent to 35 ~ 105mm lens in 35mm format). The camera has a measured angle of view of 60° horizontal, and 45° vertical.
This camera can be placed in the "PC" mode which allows all of its features to be controlled by software running on a personal computer.

The camera gets its power remotely from an AC Adaptor that is controlled by a 24 hour timer to only apply power to the camera only during the daylight hours. This also gives the camera a chance to boot up every day.

Pan & Tilt Unit

Even though I don't move the position of the camera often, I wanted to have the option of moving it to fine tune things. I located a Pan & Tilt unit on eBay. It is part of an old Pelco SB2500 ceiling enclosure that had a dome covering it. It operates from 24VAC supplied from an external controller. I modified the limit switches so the image would not go out of view when the camera was at it's limits. Here is a rear view of the unit.
I picked-up a Pan & Tilt Controller (www.CCTVProducts.com) through eBay. I then repaired and modified it to work with the Pelco Pan & Tilt unit.
I try to leave the camera pointing the same exact place but during the maintenance we may manually adjust the camera view from time to time.

Enclosure

The camera is located inside an insulated enclosure in the attic of our home and looks out through a small window. The window is located so it is protected from rain somewhat by the eaves of the house and I can raise the bottom pane to easily reach out and clean the outside of the one the camera looks out. I also put some aluminum foil on the inside of the bottom pane to reflect the sun away from the inside to keep the heat out. The inside of the enclosure is painted flat black to help minimize reflections from the sun back into the window glass. I also hung two pieces of black velvet in the enclosure to keep the reflections of the camera, tilt/pan unit, and the cables that run to the camera, out of the picture.
The attic is un-insulated, so temperatures can range from below freezing in the winter to over 130°F in the summer. The camera has an operating temperature of 32°F ~ 104°F with a storage temperature of -4°F ~ 140°F. In order to stay within the limits of the camera specifications, I needed to do something to cool the inside of this enclosure. When I built my house I put an insulated pipe that travels from the ceiling in the basement of the house up through a wall and into the bottom of the enclosure. Then a 6 inch insulated pipe that goes out of the top of the enclosure and connects to one of the house furnace cold air return ducting pipes in the attic. I put a small DC fan in the center of the 6 inch pipe with two thermostats (one for cold and one for hot) inside the enclosure to control the fan. This circulates a small amount of ambient air from the basement of the house through the enclosure and keeps the camera within its operating temperature and doesn't waste any heat or air conditioning. If the furnace fan is on, then air will circulate through this pipe. If the furnace fan is off, the thermostats will do the job.
During a heavy rain, raindrops can sometimes be seen on the glass. The lens is close enough to the window (6 1/2") that spots left behind from the rain are out of focus and cause no problems.

Moving the Images from the Camera to the Server

The Camera is connected with a USB connection to a dedicated PC running Windows XP Pro about 75 feet away in the basement. The maximum length for USB is 8 feet so I used an "active USB Extender" from Cables to Go which will extend the signal to 150 feet over standard 4 pair CAT-5 cable.
The software that I use to control the camera is VM95 from Erdman Video Systems . It runs under Windows XP and provides complete control of the camera. Every 5 minutes the software will capture a new 1024x768 JPEG image, add the overlay text and the date-time stamp to the image, copy a serialized image to the hard drive of the PC and upload another compressed image (view.jpg) by secure FTP to the web server. One of the features of this software is that it starts when the computer is turned on. I modified my computer CMOS Setup (Power Management) (PWRON After PWR Fail) from "Off" to "On". Now when the computer comes back on after a power outage, the computer will start, the camera will boot up, the software will start, and the system will start taking pictures and uploading them automatically.

Our computer is connected to the internet with a Motorola Canopy 5.3 GHz wireless networking system. The providers antenna is located about 8 miles away and the connection to the internet is typically 256 Kbps upload and download.

Current Problems

CCD Damage: Because the camera is pointing directly South, it is exposed to the winter sun. The camera CCD has been damaged by the sun as it travels from left to right across the winter sky. The path of the sun can be seen in the results of this damage as pink arcs at the top of the image. During the winter, the sun gets lower on the horizon with its lowest point occurring on the winter solstice which is December 21st. At this location, that is about 20°. During this time the sun shines directly into the lens and burns the CCD. This problem starts in late October and runs about four months. I could fix this problem by pointing the camera down but there would be more of our field showing than view and sky. As a "fast fix" I am thinking about just croping off the top damaged portion of the image leaving a size of 1024 X 590. After I replace the camera, a long term fix might be to point the new camera down and crop off the bottom leaving a 1024 X 590 image. If I cut off the bottom of the image, the CCD will never get damaged again.

Here is a Solar Azimuth plot of the sun at our locaton and the program from the University of Oregon showing the Solar Azimuth at any location.

Rain on the Window: At this location, when the wind blows hard from the south the rain is almost horizontal. With an average rainfall of 45.7 inches, it rains quite often. If the wind is blowing while it is raining there will be rain on the glass. I have been working on a rain sensing window wiper to hopefully help this problem.

Dew on the Inside of the Window: Water vapor (Dew) condenses on the inside of the cold webcam window surface obscuring the view. This happens when the temperature of the window is cooler than the temperature of the water vapor inside the enclosure. I have set a "Dri-Z-Air" Dehumidifier inside the enclosure and it does help but not completely.

Camera Dynamic Range: This is really an ongoing problem but the next generation cameras will have better sensors and software to solve this problem.

What I am working on now

There are several things that I would like to do in the software area to finish this project. Our web server uses Linux for it's operating system and they have programs installed that we will use in the processing of our images. So our scripts must be written to be processed in Linux. I have set up a local Linux system to emulate the web server and try out my shell scripts more conveniently. I have been writing scripts and HTML to build a photo archive, photo album, add temperature information, and convert the JPG files into movies on the web server.
I plan to use Image Magick to edit the images, add text, date, time, and to make thumbnail images.

Ramblings about what I went through to do this project

I have had several webcams up at this site. The first one was a Logitec USB Cam. It was comparatively easy to setup but it had really poor quality for the large view that we have here.
Then I got a Kodak DC120 and bought a copy of WebCam 32 software. I had configuration problems and had VERY POOR to no support from that software company. I would not recommend them at all. I threw their software away.
Next I tried a Sony security camera with a video capture card but the CCD sensor size was only 1/4" and the image was blurred at a distance and it also appeared "washed out. Then I tried a Sony Video HandyCam with the same video capture card. The results were similar to the other video camera.
Then I set up a Olympus C-700 Ultra Zoom 2.1 Megapixel Snapshot camera using Pine Tree Software "Camera Controller" software. The image was great but I was worried about the sun contacting the CCD sensor and damaging it so I abandoned that idea. The Camera Controller software worked very good.
I was getting tired of tinkering and I bought a Axis 223M 2.0 Megapixel Network Camera. It was easy to get running but the quality was not what I expected for the price so I sent it back. Then I spent a lot of money and got a more expensive Megapixel network camera. It was a StarDot NetCam XL - 3.1 Megapixel CMOS network (IP) camera with a 8mm fixed lens. It had a built-in Linux operating system, was easy to program, and I got it on line quickly. The problem with that camera was that it could not determine the correct exposure for high dynamic range situations. It probably worked excellent as a security camera but, I found that it did not do a good job of capturing landscapes with much quality or detail because on bright, cloudy days when the exposure was set correctly on the dark part of the picture (i.e. trees), the clouds were over-exposed. And when the clouds had correct exposure, the dark part of the picture was really dark. They just have trouble with the high contrast of the outdoors. I even bought a auto-iris lens thinking that it would help the problem. It just made the image "softer". Fortunately, the camera manufacturer was great to work with and they offered to take it back and refund my money.
When I was having all these problems with this high end camera, I remembered the great image from the old Olympus and I picked it up and snapped a picture of the same image I was viewing. There was no comparison - the old C-700UZ image was a lot better because it handled the dynamic range problem better. I picked up the present camera (an Olympus C-4040Z) and that is where I am using today and if the sensor goes bad, I can just get another used camera from eBay or CraigsList.

Overall, I have put in a lot of time on this project and had many disappointments, but being that I am a retired engineer with a need to do some nerdy tinkering, this has really been a fun project.

If you have any questions or suggestions about our WebCam, please feel free to contact us!