RE: CCTV

["Brian G. Reynolds" <brian.g.reynolds@xxxxxxx>]

Thanks Keith.

B.

> -----Original Message-----
> From: Keith Doxey [mailto:ukha@xxxxxxx]
> Sent: 29 July 2001 22:57
> To: ukha_d@xxxxxxx
> Subject: RE: [ukha_d] CCTV
>
>
> If you are using a 12V supply then anything between 510R and 2K.
> (510R will
> give you about 20mA through the LED so it will be nice and bright
> if you are
> using it as a blown fuse indicator. If its going t  be "supply
> healthy" and
> on all the time then 1K or 2K would give a dimmer LED although any of
the
> resistors in that range will be fine.
>
> Keith
>
> > -----Original Message-----
> > From: Brian G. Reynolds [mailto:brian.g.reynolds@xxxxxxx]
> > Sent: 29 July 2001 22:28
> > To: ukha_d@xxxxxxx
> > Subject: RE: [ukha_d] CCTV
> >
> >
> > Keith, what rating LED and resistor should I use?
> >
> > B.
> >
> > > -----Original Message-----
> > > From: Keith Doxey [mailto:ukha@xxxxxxx]
> > > Sent: 29 July 2001 15:53
> > > To: ukha_d@xxxxxxx
> > > Subject: RE: [ukha_d] CCTV
> > >
> > >
> > > Hi Brian
> > >
> > > > > Depends on the camera. If it has onboard voltage
regulation
> > > > then it should
> > > > > be OK. If not you may kill it. Also even if it has
onboard voltage
> > > > > regulation, dropping the extra voltage willl
generate quite a bit
> > > > > more heat.
> > > >
> > > > Is there anyway to tell this? so by dropping the
voltage it
> > > generates more
> > > > heat? even just 3v?
> > > > is the opposite true as well? give it more voltage and
it
> turns int  a
> > > > fridge..............
> > > > complicated this lecky stuff........
> > > >
> > >
> > > Quick example.
> > >
> > > Although the original PSU is 12V @ 300mA, the camera is
possibly
> > > a 9V camera
> > > drawing 300ma which will have a built in voltage regulator.
> The Voltage
> > > Regulator will be dropping 3V @ 300mA which is 0.9W or 900mW
of heat
> > > disipated by the regulator. If you use a 15V power supply
then
> > > the regulator
> > > will drop 6V @ 300mA  = 1.8W Whilst the actual regulator may
be
> > rated for
> > > that power the heatsink may not be able t  dissipate enough
of
> > > the heat and
> > > the whole camera will run hotter than it should. Heat is the
> > > biggest killer
> > > of electronics.
> > >
> > > > Could I therefore take a feed from the PC PSU and feed
it t  all
> > > > the cameras
> > > > at the same time?
> > > > I was originally going t  put an extension lead with
all the
> > > PSU's plugged
> > > > int  it and use an appliance module t  switch the
extension
> > lead but not
> > > > sure if it will all fit in the same case, heat might
also
> be a problem
> > > > although I could fit a high-speed cooling fan, I have
another
> > > tray to try
> > > > just this.
> > > >
> > >
> > > A typical PC power supply can supply over 8A @ 12V. Thats
> enough for at
> > > least 24 cameras.
> > >
> > > > What is a wall wart? is it just slang for all PSU's
that plug
> > > > int  the wall
> > > > and look hideous?
> > > >
> > >
> > > You got it :-)
> > >
> > > > Would it be a good idea t  buy a PSU for this job?
> > > >
> > > > What fuse should I use? presumably in line with the
power cable in a
> > > > in-holder?
> > > >
> > >
> > > Neatest way if you are rack mounting is to fit panel mount
> > fuseholders on
> > > the front panel.
> > > If you put an LED and resistor across the fuse it light if
the
> > fuse blows
> > > indicating a fault, or you can put an LED on the outgoing
side
> > of the fuse
> > > to show the supple is present.
> > >
> > >
> > > FUSE BLOWN INDICATOR
> > >  +ve --------fuse------------------device--0V
> > >
> > > 	   --LED--Resistor---
> > >
> > > or
> > >
> > > SUPPLY HEALTHY
> > >   +ve --------fuse------------------device--- 0V
> > >
> > >                     --LED--resistor-------- 0V
> > >
> > >
> > > >I have also bought a 4U case to try and fit my Server
int , but
> > > this needs
> > > a
> > > >lot of thinking, something I am loathe t  do on a hot
day like t day.
> > >
> > > My original thoughts for doing this were get a Minitower.
Remove
> > > the cover,
> > > lay it on its side inside the 4U case. Slide the CD &
Floppy
> > forward, draw
> > > round them t  mark the rear of the front panel, cut the
holes
> > and bolt it
> > > all together. By fitting a "normal" chassis inside
it it means
> > > any PC config
> > > changes are easy t  do.
> > >
> > > I have now decided to use Desktop cases and just use
> Aluminuim angle as
> > > rails to support it in the rack. Short pieces of angle ali
as fixing
> > > brackets pop riveted to the sides of the lid will hold it in
> > place in the
> > > rack as the weight would be taken by the rails fixed to the
> sides of the
> > > rack. My Jukebox is a desktop machine and just measured
it....
> > 17.2 inches
> > > wide so it will fit snuggly between the 19" rails,
5.25" high
> so its 3U.
> > >
> > > > Sorry for all the questions but you guys are
soooooooooooo clever!
> > > >
> > >
> > > We've also learnt a LOT from past mistakes :-(
> > >
> > > Keith
> > >
> > >
> > >
> > >
> > > ____________________________________
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> > > http://www.automatedhome.co.uk
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> >
> >
> >
> >
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