Re: Hopefully simple question about DC power supplies
- From: "Lord Garth" <lgarth@xxxxxxxxxxxx>
- Date: Tue, 11 Nov 2008 18:17:18 -0600
<davidburgess99@xxxxxxxxxxx> wrote in message
news:7545147f-7531-43a3-8199-1c283f2ba97a@xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx
On Nov 11, 10:07 pm, "Tom Biasi" <tombi...@xxxxxxxxxxxxx> wrote:
<davidburges...@xxxxxxxxxxx> wrote in message
news:14be4f7b-8051-4bdd-8f80-bced261c9a0d@xxxxxxxxxxxxxxxxxxxxxxxxxxxxxx
Hi,
I'm hoping that this is a simple question to answer. Although I'm not
a technical ignoramus, I know very little about power or cabling, so I
would like some advice with what I'm trying to do!
What I need is:
* PORTABLE (i.e. non-mains) 5V DC power into 'Device A'
and
* PORTABLE (i.e. non-mains) 12V DC power into 'Device B'
What I have at my disposal (so far) is:
* A mains adapter for 'Device A' that seems to output 5V at up-to 2A
via a small-ish DC power jack (3mm outside diameter, I think)
* A mains adapter (arriving in the post tomorrow) for 'Device B' that
should output 12V at up-to 500mA via a suitably-sized DC power jack
* A 'rechargeable laptop battery pack', that can output 12V DC via a
number of different jacks, and 5V DC via a USB cable. (details here:
http://www.maplin.co.uk/Module.aspx?ModuleNo=48490)
What I originally wanted to do was to power both devices from the
'rechargeable laptop battery pack'. But the only 5V output from that
is via a USB cable, which will not fit the device that needs a 5V
input.
I cannot use either of the mains adapters, so I need to get DC power
from the 'rechargeable laptop battery pack' (or some equivalent).
So what should I do? I have a few ideas, but I'm not sure if they are
any good:
(a) Could I somehow construct a USB-to-DC power jack for the 5V power?
I'm not sure such a thing exists to buy, but how difficult would it be
to construct?
(b) Could I split the 12V output to two destinations (1) 'Device B'
directly; and (2) 'Device A' via some way of converting it to 5V? How
would I do this?
I'm sure what I'm trying to do shouldn't be too difficult. But I'm
just not sure how to do it, and I don't want to damage my devices or
start a fire or electrocute myself. So any advice would be
appreciated!
Thanks,
David
P.S. In terms of getting hold of kit to do this, I'm UK-based, so
ordering from UK companies would work best for me.
Lets cut out some of the words:-)
You have a 12 volt battery that you need to power two devices, one with 12
volts the other with 5 volts.
Obviously both devices will stay with the battery and you need a means to
charge the battery.
It would help if you weren't so cryptic and named the devices and your
intent.
Tom
Hi Tom,
Thanks for your quick response.
The problem here is that I can be criticized for both providing too
much information (hence your need to "cut out some of the words") and
for providing insufficient information (i.e. being "cryptic")! I had
tried to find the right balance with describing my problem, but
obviously I didn't get it quite right. Sorry.
I'll try to distill it down to what I think the core problem/question
is.
I have a need for a 5V DC feed via a small DC jack, and a 12V DC feed
via a slightly larger DC jack. But what I have (at the moment) is a 5V
DC feed via a USB cable, an a 12V DC feed via a (hopefully suitable)
DC jack.
The problem is how to get the 5V DC feed via a jack.
Do I:
(a) Try to convert the USB connector to a DC jack? If so, how?
(b) Try to split the 12V feed into two, and somehow convert half of it
to 5V? If so, how?
(c) Do something else?
As background info, I am trying to setup surveillance of my garage,
where stuff seems to be regularly getting pilfered and generally
messed around with. So, 'Device A' is a small handheld DVR (with 5V
'charging' input), 'Device B' is a small CCD camera, which takes 12V.
Thanks,
David
Hi David,
Many CCD cameras can operate from an unregulated supply. My experience
is with the small cameras used to observe store fronts. Do check your
camera
for its power requirements as an AC input to a DC jack would prove
disastrous.
The cameras we use do not specify a polarity to the connection point on the
rear
which means the regulator circuitry is inside the camera itself. A typical
installation
is with a cable we call 'siamese' because it consists of a coax for the
video and a
two conductor 16 gauge stranded cables connected to the insulation of the
coax.
Most of the power supplies are full wave bridge with a few filter
capacitors. Some
of the cameras have been connected in reverse with respect to the others
(say the
red wire was placed on the left rather than the right). The camera operated
perfectly
this way.
You do not mention the current requirements of your equipment but that is
important
as well as the voltage (and polarity if your camera requires DC). A
voltmeter will
show the voltage drooping if your current demand is beyond the capability of
the
supply.
It is possible to supply power over the same coax as the video signal and
there are
adapters made to do this...a simple capacitor will block the DC but pass the
video.
You can also opt for an IP camera that supports PoE or Power Over Ethernet.
This
will allow the camera to be powered over the same CAT5 as the video plus you
can
view the image on any browser and most of these cameras come with a software
DVR that supports motion detection. Further, they can email you when motion
is
detected or in some cases, text your mobile phone. A Trendnet TV-201 is
such a
camera. A good price is from www.provantage.com
.
- References:
- Hopefully simple question about DC power supplies
- From: davidburgess99
- Re: Hopefully simple question about DC power supplies
- From: Tom Biasi
- Re: Hopefully simple question about DC power supplies
- From: davidburgess99
- Hopefully simple question about DC power supplies
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