12vdc Or 24vac Power Supplies?

[gian18778]

Hi everyone,

I just wanted to get some feedback on which power supply source is better suited for long distances (greater than 60 meters)?

[Woosh]

Probably the 24V twice the volatge half the current. If I remember correcty it was a long time ago.

[Keiko]

Probably the 24V twice the volatge half the current. If I remember correcty it was a long time ago.

If you are using standard 12vdc equipment you should stick to using DC power supplies.

To convert AC to DC a bridge rectifier and smoothing capacitor is needed. Without these two components

fitted (or 5 components if single diods are used to build a bridge rectifier) AC should not be used as it will

damage equipment designed for a dc power supply.

Using 12VDC equipment on a 24VDC supply is risky. You are assuming that the equipment will have a 12v regulator

built in else you could send 24v into a 12v system and destroy the whole lot!

Even if there is a 12v regulator in the equipment, asking the regulator to disperse of the extra 12 volts could be too much

for the regulator to cope with.

The excess 12 volts dont just disapear, its converted into heat and most heatsinks in alarm equipment

are not big enough to manage that increased power or temperature.

You will be best sticking to a 13.8 volt power supply and doubleing or even trippleing the cores or wire thickness and

so reducing the resistance in the cable run.

I originally qualified as electronics tv/video/satelite engineer to city and guild standards

and I would never put a 24v ac supply into a 12v dc rail.

[sjonley]

a dc voltage suffers from volt drop over distance unless a greater cross-sectional area is used, whether its doubling up on cores or a bigger cable. Using a mains flex, 0.75mm or 1mm cable should provide enough to ensure minimal volt drop and will also give a tidier installation and easier fault finding in the future.

Over greater distances use 24vac, again on mains flex or similar.

[CompostCORNER]

If you are using standard 12vdc equipment you should stick to using DC power supplies.

To convert AC to DC a bridge rectifier and smoothing capacitor is needed. Without these two components

fitted (or 5 components if single diods are used to build a bridge rectifier) AC should not be used as it will

damage equipment designed for a dc power supply.

Using 12VDC equipment on a 24VDC supply is risky. You are assuming that the equipment will have a 12v regulator

built in else you could send 24v into a 12v system and destroy the whole lot!

Even if there is a 12v regulator in the equipment, asking the regulator to disperse of the extra 12 volts could be too much

for the regulator to cope with.

The excess 12 volts dont just disapear, its converted into heat and most heatsinks in alarm equipment

are not big enough to manage that increased power or temperature.

You will be best sticking to a 13.8 volt power supply and doubleing or even trippleing the cores or wire thickness and

so reducing the resistance in the cable run.

I originally qualified as electronics tv/video/satelite engineer to city and guild standards

and I would never put a 24v ac supply into a 12v dc rail.

I would have thought the chap in the first post, was asking which power source was best 'prior' to him purchasing his cameras. But again, theres now a reasonable selection of CCTV cameras that offer the installer either 12vdc or 24vdc on the single same unit. Maybe it was this choice he was asking for advice on. I wouldn't have thought he was suggesting sticking a 12vdc cam onto a 24vdc or 24vac power supply.

[gian18778]

I would have thought the chap in the first post, was asking which power source was best 'prior' to him purchasing his cameras. But again, theres now a reasonable selection of CCTV cameras that offer the installer either 12vdc or 24vdc on the single same unit. Maybe it was this choice he was asking for advice on. I wouldn't have thought he was suggesting sticking a 12vdc cam onto a 24vdc or 24vac power supply.

You're right. The cameras are dual power (12VDC or 24VAC), so I was wondering which power source would be most benifical to utilize in this project where the distance of the cameras are about 100+ meters away from the DVR.

[ICEbear]

If you are using standard 12vdc equipment you should stick to using DC power supplies.

To convert AC to DC a bridge rectifier and smoothing capacitor is needed. Without these two components

fitted (or 5 components if single diods are used to build a bridge rectifier) AC should not be used as it will

damage equipment designed for a dc power supply.

Using 12VDC equipment on a 24VDC supply is risky. You are assuming that the equipment will have a 12v regulator

built in else you could send 24v into a 12v system and destroy the whole lot!

Even if there is a 12v regulator in the equipment, asking the regulator to disperse of the extra 12 volts could be too much

for the regulator to cope with.

The excess 12 volts dont just disapear, its converted into heat and most heatsinks in alarm equipment

are not big enough to manage that increased power or temperature.

You will be best sticking to a 13.8 volt power supply and doubleing or even trippleing the cores or wire thickness and

so reducing the resistance in the cable run.

I originally qualified as electronics tv/video/satelite engineer to city and guild standards

and I would never put a 24v ac supply into a 12v dc rail.

7812 voltage regulator (LM7812C) possitive (+) max input is 36v , ive never pulled to bits a baxall camera to see if theres a half or full wave rectifire/cap/7812 to support this 12v/24v input or even a simple pnp with a zenna bios Chain BUT i will report what i find eeeeeeeeeeeeeeeeeeeeeeeee you are rite tho, they do get hot

tv/video/satelite engineer to city and guild standards eeeeeeeeeeeeeeeeee lad, have you got scares you cant call yourself a tv engineer UNLESS a Lopty

has got ya at least once have you got scares to proove it

[Adi]

I would have thought the chap in the first post, was asking which power source was best 'prior' to him purchasing his cameras. But again, theres now a reasonable selection of CCTV cameras that offer the installer either 12vdc or 24vdc on the single same unit. Maybe it was this choice he was asking for advice on. I wouldn't have thought he was suggesting sticking a 12vdc cam onto a 24vdc or 24vac power supply.

snap

[TSS]

CCTV needs a regulated PSU with low ripple - usually a 13.8VDC PSU will not be specific enough for a camera.

Best engineering practice is to put the PSU as close as reasonably possible to the camera...

If you can't get power closer to the camera then i suggest you use some high quality Baluns that do power and video down a cat5 cable - please don't buy cheap ones - stick to NITEK or NVT.

If you're in the trade PM me and I'll tell you where to get them from

[spider]

24vac will do the trick.