RE: CCTV

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

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. Als  even if it has onboard
voltage
> > > regulation, dropping the extra voltage willl generate quite
a bit
> > > more heat.
> >
> > Is there anyway t  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 to 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 to put an extension lead with all the
> PSU's plugged
> > int  it and use an appliance module to switch the extension lead
but not
> > sure if it will all fit in the same case, heat might als  be a
problem
> > although I could fit a high-speed cooling fan, I have another
> tray t  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 als  bought a 4U case t  try and fit my Server int , but
> this needs
> a
> >lot of thinking, something I am loathe to 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 to 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 to do.
>
> I have now decided t  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 t  the sides of the lid will hold it in place in
the
> rack as the weight would be taken by the rails fixed t  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 als  learnt a LOT from past mistakes :-(
>
> Keith
>
>
>
>
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