Rant: Electricity and me.

[rory 0]

Cool .. yeah my mother is scottish also, moved here in the 60's I think, same thing, in her twenties I believe.

[kensplace 0]

I am having difficulty figuring out what the electrician meant when he said it was because you had to many wires connected that caused extra resistance.

 

After all, that power supply is rated at 7 amps, so unless you had so many cameras you were exceeding those 7 amps, it should not matter how you load the supply. It puts out a voltage, and some is lost on the way, either too much is getting there, or not - but I cant figure out why multiple connections would make things worse (other than from a wiring/fusing/asthetic standpoint)

 

 

If anything, extra resistance would cause a drop in voltage, as least as far as I understand electricity, meaning less likelyhood of a problem, rather than the reverse!

 

As for the cams, some 12v cams can withstand more than 12v with ease, others cant. If your particular cams are rated at a max of +/- 10 % of 12v then that is likely to be the absolute max they can take, they probably have little regulation inside them, and rely on the external power supply being well regulated at 12v. Some cams have voltage regulators that can take a lot more, and step the voltage down to 9v or so, before stepping it up and down to the required voltages needed inside the cam.

 

 

If your lucky, you may be able to identify whatever component has burned out (if you have a working cam, I suggest you open it up (if you are comfortable doing so, and dont mind losing any warranty etc, make sure its disconnected from power/video etc first) then photographing in detail, close up the boards in the camera.

 

That way, you can compare a pic of a working cam to see what the burnt out component is you need to replace. It may just (and probably is) just a part of the power circuit that melted, and a local repair shop may be able to fix them real cheap, especially if you can provide them with part no's of all the burnt components. No guarantee something further down the line didnt blow, but its worth a shot possibly.

[survtech 0]

Keep in mind that this is an electrician that he's talking about, not an electronics technician. Electricians may know wiring but most don't know doodly about DC.

[scorpion 0]

I believe this "electrician" really has no clue as to why there was a failure. I believe he is just scratching his head like the rest of us.

 

It sounds like that one theory was more along the lines of how you would hook up speakers.

 

An amplifier that is rated at 4 ohms per channel can have two 8 ohm speakers hooked up to it if they are hooked up in parallel. If you hook too many speakers in parallel to the amplifier you will exceed the rating of the amplifier.

 

This is where home amplifiers get seperated from the big boys of the concert series.

 

Most home amplifiers can not take very much abuse. Many people do not realize that the at different frequencys that the ohm rating can change for that speaker. This has to be taken in to account in designing systems for nightclubs, bars, and road shows.

 

You would be surprised at how many on the road concerts run their amps down to 2 ohms!!!! Of course these amps are designed to take it.

 

As a side story I was doing a very small bar, but they brought in very large groups, and they made money hand over fist. They repeatedly had problems with the PA system they were using. Typical system on a tight budget. The owner said this was the third time she has replaced it in as many years. She wanted a bullet proof system.

 

Here comes the dog, and pony show!!!

 

I came back later with an amp, and a set of speakers. The sound was so clear at over 100 decibels that I thought the owner was going to cry from joy. She had never heard an amp, and speaker set up that could pull this off! I wanted a check right then, and there. I told her the price, and she said "NO WAY"! If you want quality, you have to pay for quality! I made her a bet! I will lay this speaker, on it's face, and you can run the volume as loud as you want. If it does not blow in two hours you buy a system from me. If it blows you will never see me again. Two hours later I got my check.

 

One amp, two speakers, and two subs at $25,000.00!! They have been so busy, and everyone is impressed with the quality of the sound that patrons have stopped going to the competition. One bar has closed, two others have called about getting new PAs installed! The one that closed was running Gemini amps, and speakers. Nothing wrong with the company. It was just the wrong design!

[Doug 0]

Whoever told you that has no idea what they are talking about.

 

Doug

 

 

 

Well the culprits were Ohms and resistance im told....

Electrician visited and told us that it was a nice job with the right type of wire and terminators etc, except there were too many wires running from the power pack.

 

Seems the volts and amps were acceptable (if slightly high), but too many cameras on these power packs creates resistance and a drop(?) of Ohms.

 

Got 2 fresh power packs with surge protection arriving tomorrow.

5 cameras winging their way from the UK.

2500 mile trip to get to me :/

 

 

 

Too few Ohms messed up my Karma.

[photys 0]

He did use a speaker analogy.......

 

Right now, he is supplying power packs and taking responsibility for the electricity.

Will speak to him again when he puts in the new power.

[scorpion 0]

Does this mean you do not have to pay for the power supply?

 

That's great!

 

Who pays for the camera?

[woodyads 0]

Why did it blow and what went!

 

Integrated circuits work on 3.5v ~ 5v, Computer power supplies are a bit different they supply 5v and 12v. 5v is for the integrated circuits which is then broken down to 3.5 and lower for the high density chipsets. The 12V is used for electric motors in the hard drives while the intelligence in the hard drive is IC at 5v. Where am I going with this? Your cameras have probably suffered little damage. Hopefully the damage has been done to the onboard power converter. Take the camera to a electronic technician (TV repair man) and there is a good chance of finding the fault.

 

Why was the power supply 13.8v? When charging a battery you require a higher voltage than the battery. Car batteries should sit between 12.8v and 13.2v but when your charging you should measure around 13.8v across the battery as the alternator will charge at 13.8v. Hence 2-way radios and other vehicle equipment is designed to take at least 13.8v. The power supply you have been supplied with is designed specifically to supply power for those devices when in a rack etc.

 

Another problem you have is the distance. You will get volt drop over 40m so you need to put individual power converters at each camera, get away from 12VDC, or install very fat power cable. Most high end PTZ units tend to use 24VAC then have a converter to change the power back to 12v for the camera and its own motors etc. The IC's will again use 5v. The rules here are the higher the voltage the smaller the cable you can use and hence the longer the cable. So 24VDC is better than 12VDC. The next rule is AC is more efficient over distance than DC. Hence 24VAC tends to be the standard for cameras for large infrastructure projects.

 

How to fix your problem.

 

Forget the fuse idea it won't work. Fuses are to stop your wiring from burning out if there is an excessive load (lack of resistance in your circuit) . The lack of resistance could come about from a short between your wiring or two many devices though too smaller main wiring. Your wiring could catch fire and set fire to the building. So you need the fuses but they won't stop the cameras from frying. Voltage that is killing your cameras fuses can't modify voltage.

 

1: (If you had to use the 13.8v power supply.) Put a battery in the circuit and install a solar controller. The battery will filter the power from spikes and the solar controller will deliver your 12 volts. Bit expensive and there are a few other issues to deal with.

 

2: Buy a 12V power supply. Problem is distance so you should run mains to each camera and then install a small 12v plug pack for each camera

 

3: Buy cameras that are fit for purpose (24VAC) or get 24VAC to 12VDC for each camera and run them all off a mains to 24VAC converter. These are common place available from lighting shops.