The TYCO VideoCam


Recently, for a project I was working on, I needed a low cost mono video camera. I came across the TYCO VideoCam, which is a toy camcorder aimed at 10 year olds. It looks like a very small camcorder, and is just a small camera module, microphone, and preamp boxed up together with a battery holder. They never really took off, at least in the UK, due to the rather high price (99 UKP when introduced early in 1996) and the complexity of connecting them to a VCR and/or TV. As a result, they rapidly fell out of favour in toyshops, and relatively few were sold. They got marked down to about 49.99 UKP around the beginning of the year, and still didn't sell.


A local shop recently acquired a large number of these and started selling them at 19.99 UKP, at which point they sold, but as security cameras, not toys! I bought a few, and I have disassembled one completely, to find out what it can be made to do. I have put the results here, for others to enjoy, and possibly use. Bear in mind that the camera I have is a PAL one, and if you live in a part of the world that inflicts NTSC on you, that is probably what the version for sale in your area will be. Click on the small picture to load the larger version, which are all around 70kB in size. Please note that the pictures are all video grabs from a camcorder, and hence are not the best possible quality. I'm sorry. Really.

What do you get for your money?


The camera comes in a fairly large box, containing the camera itself, a rather crap folding tripod, a set of cables, and the manual. The cables consist of a long 3.5mm stereo jack plug to stereo jack socket extension lead, a short 3.5mm stereo jack plug to two RCA phono plug lead, and a phono socket to SCART plug adapter. The camera has a battery box built into the side, which takes 6 AA cells, an on/off switch on the other side, a red LED on the back, and audio/video out in the back via a 3.5mm stereo jack socket. It also has a socket for an external 9V power supply on the back. The battery compartment is actually very well designed, with a lid held on by a pozidrive screw, which ensures good contact with the batteries. If it is desired to use the camera for security purposes, no modification is necessary, and you can simply mount it on the wall and plug it in. It produces standard composite video, with line-level audio, and has a standard tripod screw socket on the bottom. Here is a picture of the box contents.


Camera contents


However, if it is desired to use the guts of the thing for more interesting purposes, it can easily be disassembled. There are 4 screws at the bottom of holes on the left side, and one more hidden on the right side. The top of the camera is a removable piece, which can be gently pried up from the front with a flat-bladed screwdriver. Once this has been removed, the side screws can be taken out. At this point the camera will split in half, and the innards can be accessed. Inside the camera are two items of interest, the camera module itself, and a small pcb that has an audio preamp for the microphone on it. The camera module has two flying leads terminating in two-pin molex sockets. One is green/black, and this is the power supply. The other, yellow/black one is the video out. In both cases the black wire is, obviously, the ground connection. The green wire is the power input, which is 7-12v DC. The yellow wire carries standard 1v p-p composite video.


Camera parts


The power supply/preamp board is of relatively little interest, and will not be discussed further. The camera module is quite nice, however. It is a single chip design, using a VLSI Vision CMOS imager, which can produce PAL or NTSC monochrome composite video directly. The chip used is the VV5400C001EB, which is, I believe, no longer produced. However, the more recent VV5402 is very similar, and has the same pinout. A full datasheet for the VV5402 is available from the VVL website in PDF format. Please note that there is NO REVERSE POLARITY PROTECTION on the power input for this module. Connecting the power supply backwards will almost certainly destroy the chip, so don't do it.


Camera module


The camera module can be further disassembled, and the PCB removed. A different, and better, lens assembly could be made to replace the simple plastic fixed-focus lens that the module normally uses, which would probably produce a sharper image. The existing lens on the module is screwed into the housing, and sealed in place with a bit of thread-locking compound. With a bit of care, the lens can be loosened, and the focus adjusted.


I had to remove the 48 pin LCC from the PCB to read the part number, which is underneath, of course. I would NOT recommend this unless you have the correct equipment and experience to do it properly, otherwise you will probably break the chip and/or board getting it apart, never mind putting it back together. I won a bet with a friend of mine who said I would never be able to remove the chip and replace it successfully, and still have the module work. Some people have no faith!


Camera module in bits 1Camera module in bits 2


While I had the module in bits, I traced the circuit and made a circuit diagram for it. This corresponds to the example application circuit in the VVL data sheet in many respects. There are a few lines that can be pulled high or low to change the operation of the camera. The signal -SIN, on pin 17, resets the video logic. -RESETB, on pin 29, resets the entire camera. Both these pins are normally not connected. AEC, on pin 21, can be pulled low to disable the automatic exposure control. AGC, pin 22, is tied low, disabling the automation gain control. The track connecting it to GND can be cut, however, and it will float high, reenabling the AGC. LIN, on pin 19, is tied high. If the track connecting it to +5V is cut, it will float low, and produce a gamma-corrected output, rather than the default linear one. BKLIT, on pin 28, can be pulled high, which enables a mode that gives a longer exposure to the center of the image for backlit subjects. R5 can be fitted, or just linked across, which will put the camera into EIA (NTSC) mode, rather than CCIR (PAL), which is the default. If this is done, however, the 14.7456 MHz crystal will have to be replaced with a 12.000 MHz one, to produce the correct timings. In addition, lower speed crystals can be fitted, which will increase the sensitivity of the imager, but at the expense of nonstandard video timings. Also, the ODD signal, on pin 37, goes high during odd fields and low during even fields. Please note that I take no responsibility for people screwing up their cameras using the preceding information. Do it at your own risk, carefully.


Circuit diagram


The video output quality is fairly good. It is not as sensitive to low light levels as a cheap CCD camera is, but works quite well under normal lighting conditions. It's quite sensitive to IR illumination, but again, not as much as a CCD camera. Overall, for machine vision, robotics, security systems, or just playing around with, the camera is more than adequate for the most part. In addition, the extremely low cost makes up for a certain lack of sensitivity. The specifications of the imaging system below are from the VVL data sheet for the VV5402 chip, which is very similar to the VV5400.



Finally, here is a sample image from one of these cameras. Note that it was grabbed under less than ideal lighting conditions, and the particular camera module needs a bit better focussing, which I have not yet done.


Camera sample picture


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