[HATS] Re: Camera question

[Clint Turner]

Hi,

>I have a Sony Handicam CCD-TR64 that I would like to use for a tower cam =
>at my ATV repeater. This camera has a automatic focus feature that I =
>need to turn off. The camera does not have a manual / automatic focus =
>switch. Does anyone have any suggesstions on how to defeat this =
>function? My only thought has been to open the camera up, point it at a =
>distant object and disable the focus motor.
>
>Dave KC3AM
>  
>

Other than disconnect the motor, I don't have any great ideas as to how 
to kill the manual/auto focus.  If you are able to kill the focus (e.g. 
add a switch) make certain that you do your "manual" focus at night - 
with a wide-open iris!!!  Some cameras also have a LANC port that offers 
more control than is "officially" available - but you'd have to do your 
own research.  (Sony is well-known for doing this...)

Several years ago, at work, we put together a bunch of remote-controlled 
tower cameras for local TV station for traffic monitoring, tied back to 
the studio on 23 GHz microwave.  We used Sony camera modules (EVI series 
- the 310, 330 and 370 series) that are single-CCD, with serial control, 
etc.  (These cameras were also used for in-car video for law enforcement 
and if you have watched the "Cops" show, you have very likely seen one 
of the systems we put together...)  Having had quite a bit of experience 
with outdoor devices (cameras, radios, etc.) and knowing what to expect, 
we did the following:

- All power supplies were isolated.  At the base of the tower, there is 
an AC power supply and 15 VAC is sent to the camera.  In the enclosure, 
this is rectified, filtered, and then regulated for the camera.  This 
supply is not used (at the base) for anything else.  There were also 
some series resistors (a few ohms) and caps across the AC line at the 
camera for additional transient absorption.
- All camera controls were via optoisolators.  Again, there is no 
continuity between the camera controls (focus, zoom, autofocus on/off, 
etc.) to the camera.
- We used outdoor-rated camera enclosures with fans and sun shields 
(Pelco, actually...)  The fans are nice, but it's *really* the sun 
shield that keeps things from cooking.  All the sun shield is is another 
piece of metal between the top of the enclosure and the sky.  It's 
spaced 1/2 inch or so from the "real" top of the enclosure, so that heat 
won't directly transfer from the shield to the lid.  (These enclosures 
are powder-coated white.)
- Another thing that can help is a video buffer amplifier.  In some 
cases (such as our) this can take the form of a simple emitter-follower 
- but the precise circuit configuration may depend on your camera's 
output configuration.  The entire point of this device is to put one 
layer between the real world and the camera:  A transient coming along 
the video line has to get through the emitter-follower circuit before it 
can blow up the output of the camera.
- Often, "hum buckers" were added.  These are the coaxial chokes used to 
break ground loops in video lines to prevent 60 Hz hum.  All these are 
are RG-174-sized 75 ohm coax wrapped on a toroid or transformer core, 
providing typically 10-30 mH of common-mode inductance (depending on 
brand) and, thus, a few ohms at powerline frequencies.  These also did a 
good job of keeping RF currents from AM broadcast stations and 
transients from getting on the video line.

We put perhaps 8 of these cameras together and the only failure that we 
had was when the tower (most were on cell towers) on which one of them 
was mounted took a direct lightning hit:  The composite video output was 
blown up, but the S-video output was OK. - It was then that we decided 
to add the emitter-follower to the cameras when they were next serviced 
(usually using a crane and a "man-basket.)  The biggest problem, of 
course, is a dirty lens:  Every so-often someone has to climb the tower 
and clean the stupid thing - Especially after bird migration...

These camera/enclosures were mounted directly in the weather (in 1997) 
and have survived several record-breaking summers where the daily 
temperature was >100 F for many days at a time.  The only problem that 
has started creeping up is that one or two of them get sticky zoom/focus 
on very cold days.  Most of them have been removed from traffic 
monitoring service and are now mounted outside at the studio or on the 
mountaintop transmitter site and used for "beauty shots" and/or do 
time-lapse weather.  (They still look *really* good...)

As for using a consumer camcorder, I don't know how well those hold up.  
Many of them run pretty hot in normal use, being confined in their 
plastic cases, and perhaps that might be why they might not hold up in a 
sun-baked enclosure.  Some of the older ones (late 80's, early 90's) 
*will* die on their own owing to longevity problems with the 
electrolytic capacitors that were used - and a warm environment will 
certainly hasten this problem.  We put our camera blocks in a 
well-ventilated aluminum sub-enclosure within the main enclosure.

Good luck,

Clint
KA7OEI