Need clarification on power supply specs

[tegatdavis 0]

I need some help making sense of power supply specs. I plan on hooking up 6 cameras to a central power supply. Each camera uses 12VDC/24VAC and draws 1 amp with the LEDs on which makes for a total of 6 amps. I would also like to have more power for possibly more cameras later on. The camera manufacturer requires the use of a regulated power supply.

 

After searching around the internet and on this forum, I still need clarification on these:

1. What is the difference between continuous and regulated power? Is it that continuous can have huge spikes in voltage over short periods whereas regulated limits the size of any variation from the specified output?

2. When a power supply says for example: "Output fuses are rated @ 3.5 amp", does that mean that the draw on each fuse can be as high as 3.5 amps provided the total draw over all the fuses do not surpass the maximum output of the power supply? Or is the total amps on each output basically the total output of the power supply divided by the number of outputs and the 3.5 amps is talking about something else?

3. Do words like this mean that the power supply is truly regulated for CCTV camera purposes: "Filtered and electronically regulated outputs". I would assume so but too often manufacturers play with the words to mislead customers.

4. Does this mean that if too much load is put on the power supply it will trip: "Short circuit and thermal overload protection."

5. Any thoughts on using 12VDC vs. 24VAC such as when one would be more appropriate than the other? I've read that 12VDC power supplies will generally result in "cleaner" (not sure what that means in this context) power delivered to the cameras.

 

By the way, the quotes from above are taken from the specs for Altronix's ALTV615DC1016 model.

 

I think I know enough to stay away from PTC outputs. For some reason it's hard to find a supply with 8 fused outputs which is rated at 8 amps total or higher and also regulated. I guess I'll just have to go with 16 fused outputs.

[survtech 0]

I need some help making sense of power supply specs. I plan on hooking up 6 cameras to a central power supply. Each camera uses 12VDC/24VAC and draws 1 amp with the LEDs on which makes for a total of 6 amps. I would also like to have more power for possibly more cameras later on. The camera manufacturer requires the use of a regulated power supply.

 

After searching around the internet and on this forum, I still need clarification on these:

1. What is the difference between continuous and regulated power? Is it that continuous can have huge spikes in voltage over short periods whereas regulated limits the size of any variation from the specified output?

You won't find a regulated 24VAC power supply but that is not important. If you want to use 12VDC, then you should use a regulated power supply.

 

2. When a power supply says for example: "Output fuses are rated @ 3.5 amp", does that mean that the draw on each fuse can be as high as 3.5 amps provided the total draw over all the fuses do not surpass the maximum output of the power supply? Or is the total amps on each output basically the total output of the power supply divided by the number of outputs and the 3.5 amps is talking about something else?

Each output can supply up to the fuse rating, although I would not recommend exceeding 50%-75% of any fuse's rating. Then add up the draw from all cameras and it should not exceed 50% to 75% of the supply's total capacity.

 

3. Do words like this mean that the power supply is truly regulated for CCTV camera purposes: "Filtered and electronically regulated outputs". I would assume so but too often manufacturers play with the words to mislead customers.

Yes. "Electronically Regulated" should mean just that.

 

4. Does this mean that if too much load is put on the power supply it will trip: "Short circuit and thermal overload protection."

Yes.

 

5. Any thoughts on using 12VDC vs. 24VAC such as when one would be more appropriate than the other? I've read that 12VDC power supplies will generally result in "cleaner" (not sure what that means in this context) power delivered to the cameras.

You are better off using 24VAC where possible. You can get by with smaller power cables or run them farther.

 

By the way, the quotes from above are taken from the specs for Altronix's ALTV615DC1016 model.

 

I think I know enough to stay away from PTC outputs. For some reason it's hard to find a supply with 8 fused outputs which is rated at 8 amps total or higher and also regulated. I guess I'll just have to go with 16 fused outputs.

Again, you are better off using 24VAC if your cameras support that. Altronix has a number of 24VAC supplies that meet or exceed your requirements, Check out the ALTV248300 (12.5A@24VAC) or, for 16 outputs, the ALTV2416350 (14A@24VAC) or the 2416600 (25A@24VAC). If you want to meet code, use the UL Listed versions (ALTV248300UL, ALTV2416350UL and ALTV2416600UL).

[tegatdavis 0]

Thanks survtech for clearing that up; it was very helpful. Can you elaborate a little bit on why a regulated 24VAC power supply can't be found? I guess the regulation is not needed but if so how does it keep the voltage from varying too much? The cameras I was looking at (Nuvico CB-SD3895) don't say whether or not it has regulation on the camera end but maybe that's standard for 24VAC cameras? The primary reason why I wanted to stick with a regulated power supply is so I don't void my camera warranty if something was to go awry from the power supply side (however small the odds are).

 

My cable runs are all shorter than 50 feet so I don't think I have to worry about distance too much but it does sound like the 24VAC power supplies offer more flexibility. Just concerned about the regulated part so if you can elaborate on that that would be great.

[Squiffy 0]

It would be easier (and probably cheaper) to source a 12V PSU rather than a 24V AC PSU. An AC supply can be regulated (if using switched mode chopping and filtering techniques) but usually it won't be, therefore it will simply be regulated as much as the local mains voltage is.

 

A regulated supply is best when a fixed DC voltage is stipulated, because it will not (or should not) change with different loads (i.e. the current drawn, if within the limits, will not affect the voltage).

 

Note that a cheap way to provide a high current 12V DC source for general domestic use is by using an ATX computer PSU and a bit of DIY, but if you're not technically minded it's best to buy a commercial PSU.

 

http://www.instructables.com/id/Convert-an-ATX-Power-Supply-Into-a-Regular-DC-Powe/

[survtech 0]

The reasons it is rare to find a regulated AC power supply is that it is quite expensive and unnecessary. AC supplies usually consist of just a transformer and fuses, with perhaps an MOV to protect against power surges. Since voltage ratings of cameras and the like are usually +/- 10% (most allow at least +/- 20%), the supply voltage would have to surge by 12-24 volts before you would exceed the camera's rating.

 

With an AC supply, a simple surge protector would protect against power surges. Unless you are in an area that has particularly awful power, the likelihood of cameras failing due to normal power fluctuations is minimal. I've installed well over 1000 cameras and have yet to see one fail using 24VAC unless a lightning stike sent a surge down the line.

 

DC Power supplies are another issue. The tolerances are tighter in the camera so a 20% increase to 14.4 volts may not be tolerated. Since most cameras that use 24VAC have a built-in rectifier, filter and regulator, they tolerate voltage swings on the AC better. In most 12VDC cameras, the DC voltage is used to directly power the components.