Tittle says it really..

If a camera is for example 300mA..

And you power it with a 1A power supply... will this damage the camera?

Maybe a daft question but there is many suppliers that give you a 1A power adapter as standard with cameras.. Is this safe to use ??

In Simple Terms.......

If you need $300 to buy something and you take $1000 with you, you only need $300 but you have something in reserve !

It's the same when powering Camera's, althought the Camera only draws 300ma from the 1000ma (1amp) supply leaveing 700ma spare it is always better to over engineer your power supplies.

The 1 amp won't damage the camera !

Simple !

Ok

I dont think i agree, i think over powering ANY electrical item with a larger supply is not the safe way to go in my experiance, But as were only talking about mA here i wasnt sure if the current was going to make a damagable difference!

I didn't think it would.

If a camera draws 300ma on a 500ma supply, it will draw exactly the same 300ma from a 1a supply, or a 2a supply...

A power supply that can provide more amperage will just have extra unused spare capacity compared to a equal one with a lower amperage..

Using a bigger amperage PSU will in no way 'force' more amperage into the camera.....

The only exception would be in a fault condition, such as a short, or a faulty camera, in which case the more amperage the psu can supply, the more damage can occur.....

Best bet would be to install a suitable fuse if your power supply amperage is much bigger than the needed amperage for the device, so in a fault, the fuse blows.

The amount of power your camera, PTZ, etc. draws is based upon resistance of the device . Just remember 1 amp, when dealing with 12vdc is not much VA's. Common misconception is that electricity is "pushed" into a motor, camera, etc. Not so. I myself always try to use a much larger Power Supply than is called for. One big reason is heat. When I build my own power supplies for large jobs, I normally use a 9 to 15 amp Sola (manufacturer) power supply. With my ampmeter, I can actually check on the "amp draw" of my project. "MA" or Milliamps are also sort of deceiving. One thousandth of an amp is hard to distinguish, when you have a camera (or other decvice) pulling 300 MA, and another pulling 500ma. Power supplies generate a lot of heat when rectifiing AC to DC. Also lose a little bit on the supply end, in terms of overall power supplied.

not really
heat is being generated only by drawing current :)

I also, do overspec my power supplies on jobs, if it requires 2 amps I use 5, if it requires 1 amp I use 2...
As long as its regulated power supply youll be ok,


Does not affect the camera unless its rated @ 12vdc and your giving it 13.8, check

Always FUSE your pos + connection @ the power supply, although most p/s's have internal fuse it dont hurt to fuse it, saves a possible fire.....

Heat is released in three ways: conduction, convection, and radiation and all power converters - AC/DC, DC/DC and DC/AC consume power that is dissipated internally as heat."Heat" must be removed from power-dissipating components within a converter in order to stay within a functioning temperature as well other critical components keeping to a stable constant temperature. The Arrhenius equation for reliability indicates a power device failure rate increases 3 to 5 times for a 25°C rise in temperature. Its a good idea to bench all power supplies and check their specs/rating prior to applying in the field. Most failures Ive come across are from improper wire practice cable management and power related camera malfunction due to "plug a play" attitude that some "professionals" as well DIYers have when working with circuits (all voltage)

I agree, I've always had customers get 1amp even for 300mA and 500mA applications because you're never 100% sure of the distance that customer is going to run and if there will be a power/voltage drop over the said distance.

I like to be over not under :)
We now have all of our power supplies here as regulated so now there's no problem with using something larger than necessary as the camera is only going to draw the mA it needs to function properly.

Thanks,
John

You're not suggesting extra current capacity directly accommodates longer wire runs...?!

You could make a case for that with a non-regulated supply, ie. 24VAC, since the higher current transformer would not load down quite as much.

A power supply that is not drawing current is not being used. Next time you find a working power supply, near its' rated capacity, and it is cool to the touch, please let me know. I work with DC power supplies all day long. Mostly in the 90VDC to 480VDC range. 12VDC CCTV power supplies are about the most simple I have ever installed. Always try to use a larger capacity power supply, and do your best to keep it cool.

Ok, i get i!
In my case my bosh camera is 12 Volts, but my power course is 48 volt... so i have no problem here, and still 36 volt as reserve.

Gonna plug it in now...

I think after tossing the grenade into the room, the original poster has long left...

lol, No im still here! just reading the posts. I take it i was wrong, I must be thinking of the wrong volt input being dangerous.

There's a good argument that could be made concerning this as I've seen first hand benefits from running a stronger power supply on longer runs (1000+ ft.) and have had cameras get a voltage/power drop (I know there two different things) over that long of a run which then required a larger power supply to get the camera up and functioning properly.

Maybe it's all in my head?

Thanks,
John

Well, from the theoretical point of view clearly extra current capacity is not going to help directly with voltage drop.

But as you have noticed and survtech has pointed out, 24 VAC transformers and older style (or cheaper) 12 VDC power supplies (based on line frequency transformers) tend to have poor regulation and so often output a higher voltage at lighter loads to make up for it. So that gives you a bit of extra headroom for wire losses.

Modern general purpose 12 VDC switch-mode designs have excellent regulation and normally nothing to allow for voltage drops. Over the entire current range it might not vary more than 0.1 V.

Next to ensuring voltage drops are minimized, the ideal solution is to use a supply with an adjustable voltage output if the wire voltage drop will cut the voltage supplied to the camera below its minimum allowable value.

One suggestion of mine to you, as not to confuse you any further. Do not confuse voltage , amperage, and resistance. Buy yourself a decent volt/ohmmeter and get familiar with how to use it. I use mine ( and I own several) everyday. Some of my "higher end" Fluke models, actually generate their own milliamp signals, and can check an incoming milliamp signal also ( my Fluke model 744, H.A.R.T. enabled) . Start out with a nice Fluke model, and teach yourself how to check resistance, voltage, and amperage. Will help you out many times over, in the long run. Good Luck !!

Hi all,

I've installed several dozen, or close to a hundred cameras, and now I have come to my greatest challenge.

I have installed around 12 Mini domes + 4 other cameras plus around 5-6 Audio mics for a large Sydney restaurant and I have been unable to get the Cameras to power up.

I believe at this stage the problem is I have too much current going through the cameras.

For instance, the 12 Mini domes, each dome is rated to take around 300mA to work, and the power supply is a 8amp 9 Channel and even though I double or triple up on each channels, it seems to be consistently delivering 1amp through each connection, and my cameras, through observation is not turning on. Another issue is that I have one starlight dome which does turn on when connected to this panel, and for this matter I believe which is odd, because starlights only need 190mAmps but then again, Starlights having their own power regulation circuitry, whereas the mini domes, although also using Sony Chips are unable to negotiate with 500mAmps +.

This is really an odd situation, because I have tried plug in power supplies and I have been able to switch on the devices before but now, for some reason fuses are blowing up on the panel and there seems to be a short on a few of the channels,

however,

I have used a cheap made in hong kong china Power Supply with 16 channels, with a total of 6 Amps and the cameras do turn on. With that said, this is all weird. I have had the cameras able to turn on with more than 500mA with no probs, but now, they just do not turn on when there is more than 500mA available.

Any ideas?

Cheers,

Joey
Sydney, Australia

There is no such thing as too much supply current. There can be too little, but never too much. If a device is fed the correct voltage and hooked up correctly, it will draw only as much current as it needs to operate.

You can also have too little (as well as too much) voltage. Too much or the wrong type (DC vs. AC) can cause problems, including frying cameras. Too little will cause non-operation. You should check the voltage at the camera with a good VOM.

Exactly true. Never "too much current available". Usually too small size wire, too much voltage drop. When you switch on a light in your home, the Power Plant that supplies your city with power, isn't "pushing" it to your home, you are "drawing" it from the grid. When you try to power up that many cameras, are they on the same power feed wire ? I have seen other installers try to wire their customers' cameras in series, believe it or not. The fuses in those ready-made power supplies ( assuming it is 12vdc) are probably in the 1amp range, but check this out for youself. Usually when this many devices ( in this case cameras) do not power up, it is because there are too many things drawing power on a circuit. Check voltage at the cameras, while they are in use.

now if you want to get really serrious..think about paralle & series circuits and the different effect that has on the current & resistance.

I never triple up cameras, just bouble up if last resort. I always plan one for one.

later........

How do you bouble up cameras?

I guess bouble up = double up = 2 cams per output right ...? :)

Or run a 3 conductor cable, 16/3 for example. Each camera has a fused "hot" or "positive", and use one common wire for "neutral" or "negative" , if two cameras are in the same physical location. Only for 24vac or 12vdc . I have never done it, but just a thought.

Thanks fellas for the tips. Yeah, I think I better just keep one camera per output. That could be why they won't turn on. If I double up I'm in effect making it a parallel circuit.

I'm getting a 9channel 5amp 12v dc power supply coming in soon, hopefully it will turn it on, but I'll fill you in on whether I can get this working or not.

Cheers

joey

That is not the best way to do it since power requires both a "hot" line and a return line to make a complete circuit. The advantage of running 3 conductor cable would be that each camera is on its own fuse, since most power supplies have a common ground for the outputs, but separate fuses for the "hot" wire.

The disadvantages would be that you couldn't use 3 wires if the power supply has isolated outputs for each camera and that the common wire still would have to handle the current for both cameras. That means the distance limits for the power wire would have to factor in the current draw for both cameras.

A good analogy for this power supply problem is, if you compare electrical power to a water supply.
Water pressure is voltage.
Water flow is amperage.
You can get big voltage through a small cable (high pressure through a small pipe), But the only way to transmit big amperage is through a big cable (big flow through a big pipe)
HOWEVER If you are transmitting this power over a long distance, and you are only using 12 v. its not sufficient to overcome the resistance of the small cable, so the only way to overcome this is to increase the size of the cable. You can also increase the voltage but is risky and difficult to calibrate, because the cameras use exactly 12 v.
Remember when you check the voltage at the end of a very long thin cable, you always get 12 v. When the camera is connected, the current begins to flow and you will see a voltage drop

As a general rule I try to use a power supply that is rated at least double the maximum camera draw. Don't forget cameras with IR illumination draw more current at night! In past experience if the power supply was rated at the same or close to the cameras current draw I would be out replacing power supplies within 6 months.

Maybe it is the electrician in me that makes me think this way ... but ...

I think my major concern would be a that my power supply will not trip via it's internal breaker / fuse before the current exceeds what my conductors can safely carry before becoming a fire hazard. Should the wires carrying that current get damaged and shorted.
Perhaps those who are much more "DC Savvy" can elaborate on when one might be concerned when working with common 18 gauge wire as often found with Siamese Cable.

I would fit a inline fuse in the cable, rated to blow before the cable overheats..

What I tend to do at home when I need several outputs from one DC power supply is build a small distribution board (just on veroboard) that takes the main DC output, and splits it X ways, with each way having its own fuse, rated at what the camera needs.

So a 4amp single output power supply could have 8 individual 500ma outputs. Although I tend to leave spare capacity by not using them all, so that the power supply runs cool.

Usually also, they are a mix of milliamps, I fit the fuse to the output needed, label it and forget it ;) (but keep a spare sets of all fuses).

The fuses are in fuse holders, and the inputs/outputs on terminal blocks on the board. The board then gets bolted inside the power supply box.

I also stick a label inside clearly stating max 500ma fuse per fuse holder in case I drop down dead tommorow (so if someone else gets the power supply they dont go sticking 4amp fuses in each holder and putting the cables at risk.)

Fuses, instead of circuit breakers, will always "blow" (open their filament) upon a short circuit. An "overload" can be different, depending on the design of the fuse ( i.e. slow blow) . No overcurrent device should be rated higher than the current-carrying capacity of the conductor (wire). One reason that "dual element" fuses are used in industry , mostly to protect motors. So, if your positive and negative (assuming 12vdc) come into contact, and everything is workly as designed, the fuses will "blow". But your camera might have to "draw" more than 1 amp for a little while, in order to "blow" the 1 amp fuse, especially if it is the smaller AGC style.