[Hidden-tech] Motion-detectors, camera suggestions, safety

ussailis at shaysnet.com ussailis at shaysnet.com
Thu Dec 31 18:56:40 EST 2009


I build security TV transmitters. To some I buy & attach cameras. Here is
some info regarding security cameras;

Most security cameras use CMOS video sensors. The reason is everything is
in the single chip. Light goes in one side, NTSC video comes out on another
pin. The manufacturer of the "camera" adds about a dozen parts, a crystal,
and a lens. Cheap!!

You add power, and a TV set.

Note NTSC video. I haven't seen a low cost "hi def" or a "digital" camera
chip yet. By digital I am referring to what is received over the air, or on
cable. There are 'digital' CMOS camera chips, they are used in cell phones,
and in "plug this camera into your computer" gadgets.

The hi def chips that are in higher-end photographer cameras are still
expensive.

I have not seen a "digital" plug-this-into-your-computer camera that was
much good. I acquired one this summer to take one picture of an electric
meter. Quality was so poor that I couldn't take the picture.

Resolution; Security cameras vary from horrid to acceptable. If anybody
advertises the "image sensor" size look for a minimum of 1/3 inch. 1/4 inch
will have a poor picture. This is a there is no free lunch issue. Larger
size equals better picture. Check out the chip size in a CMOS based Nikon
D90. Notice that the security camera at your bank is larger in size than
the one you might find at Best Buy. There is a reason for this...

Power draw; Most CMOS chips draw about 50 mA at 5 volts. Many cameras
recommend 12 volts, so they have a chip in them to reduce the voltage. Many
use a 9 volt battery, which will have a total life of about 6 to 7 hours.

Cost; I buy complete cameras, with power connector, audio & video out,
plastic body and lens for $22.50 quan 100. The folks that I get them from
are making a good profit...they try to hide where they come from. You
should pay about $50 for the same camera. 

Quality; I modify everyone that I buy to mount on my mini-transmitter. In
the process I check the circuit for errors, mostly missing solder
connections. Connections often make contact, but missing solder at a joint
causes them to fail in time. I repair about a third of them.

CCD (charged coupled device) cameras have three chips, draw buckets more
power, cost more, and usually have a better picture. Because most people
shop price, CCD is going out of this market. Quality security cameras are
CCD.

So, before buying a security camera, I would first evaluate the picture.
See if you can see what you need to see. Many look good in the store.
Outside they look terrible. On many you will not be able to ID a face.

Then, perhaps shake the stuff. If anything hiccups because of motion, look
at another brand that looks physically different. Repackaging is very
common in the industry.

Don't get hooked into a special security store. Prices will be two or three
times any where else. 

I wouldn't buy on-line, unless there is a no questions return policy.

Keep in mind that you are dealing with old video technology. You will not
get an HD picture on your spiffy plasma TV. 

Lastly, you might ask why poor quality security cameras have a market? The
recorded part of the picture is not what this is all about. Security
cameras put a measure of fear in potential thieves. Fake cameras (empty
bodies) work well also.


Jim Ussailis

Jim at nationalwireless.com







Original Message:
-----------------
From: Owen Freeman-Daniels owenfd at gmail.com
Date: Wed, 30 Dec 2009 10:01:23 -0500
To: Hidden-discuss at lists.hidden-tech.net
Subject: [Hidden-tech] Motion-detectors, camera suggestions, safety


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