Cheap Wireless Camera Review
In the past few months, cheap wireless video cameras have been showing up on a lot of auction and discount electronics websites. Claims of range and transmission quality vary, but there seem to be a few main types. Prices, depending on whether you order from a local distributor or direct from China, seem to range from the low $20's to the high $40's. I decided to grab one and see how well it works. The camera was purchased on eBay for about $25. I didn't expect much quality for that price. This version has audio and video transmission...many only have video.
You'll notice that the camera is not the same one pictured on this box. This was mentioned in the eBay listing, so no surprise there. Incidentally, the camera on the box is one of the other common types out there. This one has a decent quality metal enclosure for the receiver, and the camera itself is extremely small. Not pictured are two AC power adapters and a 9V to DC barrel plug for battery operation of the camera.
Here's a sample image. This is a photo of the output on my monitor, which accepts NTSC composite input. You can see the image quality is not that great, but it does work. There is a potentiometer used for adjusting the receiver, I found it to be a little too sensitive. It takes some tweaking to get the frequency adjusted correctly.
Let's take a close look at the camera. The first image shows the front with manual focus lens. This lens must be adjusted to get focus at the distance you need. Next is the back of the camera with the two screws that hold the case together.
Here's the camera internals. You can see the electret microphone off to the right in the first picture. The small piece wrapped in electrical tape is the transmitter that converts the camera NTSC and audio signals and transmits them at 1.2GHz. The second photo shows the transmitter board unwrapped. Also of note is the small trimpot in the bottom center of the photo. This controls the gain of the camera, and I found the image to improved a bit by adjusting the gain up a little (see third photo).
Next, let's take a look inside the receiver. The enclosure is really not bad, and comes apart easily. The first photo below shows the receiver without the cover. The large metal box on the right is a pretty standard type of tuner module. The board on the left decodes the tuner output and converts to NTSC video and mono audio signals. The second photo shows the tuner module detached, you can get a better view of the tuner potentiometer wiring.
Below is a close-up of the tuner internals and the converter PCB. Not too much hope for any useful hacking or modification, though there is an interesting story in what was omitted. Some tuner modules of this type came with an I2C interface for fine-tune adjustment. This would be controlled by an external microcontroller, which would monitor the baseband signal and help autotune the receiver for the best reception. That would make locking on to the transmitter signal much easier, and provide stability over small frequency shifts due to temperature or supply voltage variations. The NTSC converter PCB actually has some unused I2C headers and empty solder pads for a controller IC. Other modules out there may have these features enabled, probably at an additional price.
My rating? Sort of meh. It is actually pretty well put together for the price, and it does work well in bright enviroments, such as outdoors in the daytime. Normal house lighting is almost on the edge of usability, common with these small CMOS sensors and tiny lenses. Range is nothing to write home about, you can get maybe 75 feet in wide-open spaces, but it struggles to punch through more than a couple rooms in a house. Despite its limitations, the system is cheap, easy to use, and should be useful for simple surveillance or short range teleoperation.
On a scale of 1 to 10, I would give it a 6.
Submitted by Garrett on Sat, 03/08/2008 - 02:49.