Reply With Quoteevo2 (16-10-11)
12VDC or 24VAC power for cameras - which is better
When choosing a power supply for cameras, which is the preferred choice: 12VDC or 24VAC, assuming that all cameras can be powered from either voltage? I know there can be issues with Earth loops with some installations, but is this only for 12VDC-powered systems, or does this apply to both types of voltages?
evo2 (16-10-11)
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For long runs it is better to use 24V ac. The internals of the camera still run at 12V but they have an inbuilt power supply. This gives a fairly large of leeway for losses over the power cabling & still enables the camera to get the correct voltage.
I am a massive fan of 24V....
Reason....
- Runs over 70 Metres compared to the 12V Limits
- 12V cameras only, They are polarity conscious and in my times we all work with people who can't read and don't know the difference between a + and a - Explain that to the supplier when dopes do it 3 times on the same job.....
- Also is it alternating Current and therefor you can get less problems in my experirnce.
Thanks
Jamie
As per Mega, 24v when possible.
As others have said the preference tends to lay with 24VAC although so far as image quality is concerned, you'll notice no benefit to either. The difference is purely in the installation and the distances you're able to run. Having said that, a lot of the multi output 12VDC PSUs now have adjustable output voltage so you can adjust the voltage to suit longer runs. As for ground loops, they occur on both 12 and 24v systems.Originally Posted by alarmman
G'Day Cobbers,
It seems to me that many have missed the point of the alternate input voltages for any equipment.
If they use a Bridge Rectifier for their input voltage, it is immaterial of the polarity of the input if DC.
However if using AC input, you need double the voltage.
Hence 12 V DC or 24 V AC.
So in theory there is no advantage in using either.
However I need to qualify that by saying that for an alarm system that you need a back up battery in the event of a power failure.
Alarms are not my forte, but basic electronics are.
Kindest Regards, " The Druid ".
To expand on my previous post about Bridge Rectiiers.
A diode bridge is an arrangement of four (or more) in a configuration that provides the same of output for either polarity of input. When used in its most common application, for conversion of an (AC) input into a (DC) output, it is known as a bridge . A bridge rectifier provides from a two-wire AC input, resulting in lower cost and weight as compared to a rectifier with a 3-wire input from a with a secondary winding.
The essential feature of a diode bridge is that the polarity of the output is the same regardless of the polarity at the input. The diode bridge circuit is also known as the Graetz circuit after its inventor, physicist .
Kindest Regards, " The Druid ".
Except some cheap sods use 1/2 wave diode bridges to catch out people.
Also 24v, twice the voltage half the current, need I say more :P
Last edited by Privatteer; 25-07-11 at 11:15 PM.
Sorry to raise this, but a diode bridge is emphatically Full Wave.
But can turn either polarity input to the required polarity output.
Also P=EI so makes no difference whether it's 12Vdc or 24Vac, same power consumption.
If you power the camera using 240VAC, you will get a bonus illumination feature.
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