In CCTV camera systems, the distance how far you can run the security cameras depends how far you can run the power cables. There are length limits for both the coax video cable and the power cable. In this article, we will discuss the differences between 12V DC and 24V AC power sources in security camera systems.
Traditionally, CCTV security cameras were 24V AC, but around 2005 the 12V DC cameras started to become popular due to their low cost. Nowadays the majority of HD analog security cameras (such as HD-TVI, HD-CVI, AHD, CVBS) require 12V DC power supply.
The analog security cameras use siamese coaxial cable which, a pair of wires consisting of coaxial cable 75OHMs and 2/18 gauge power wire. However, there are security cameras that take dual voltage 24V AC and 12V DC.
12V DC and 24V AC in CCTV systems
Let’s start by noting that neither of these two voltages affect the video transmission, only the power. However, the main difference is how these power supplies can power up a security camera.
Using a 24V AC power supply and 18/2 gauge the power can run up to 750 feet without any current drop. Using 12V DC power supply the cable can run up to 300 feet at max.
A security camera’s power consumption is usually referred to in milliamps (mA). Usually, the camera’s power consumption is generally around 200-400mA. Things like mechanical filters, infrared IR LEDs, and internal heaters will increase this number and eventually it gets closer to 1-1.5 Amps.
Trying to power a 1.2A camera with 12V DC over a long distance is unfeasible as there will be too much total resistance in the long cable run that adds up to a substantial voltage drop resulting in camera failure.
A common problem attributed to voltage drop is where the security camera works fine when there is low consumption but at night, when the IR LEDs turn on, it stops working completely. Problems can also include hum bars, video distortion, and other symptoms which are often mistaken as a bad camera
Nowadays most of the CCTV and HD over coax cameras use 12V DC. They usually come with an individual 12V DC power supply or can use a multi-camera power supply box. Many higher end commercial grade cameras come in dual voltage, which allows installers to use a 12V DC or 24V AC power supply accordingly to the installation job
The advantage of using AC vs DC is that the power cable can be run much longer distances without power drop with AC. Like DC, multi-camera 24V AC power supply boxes and individual 24V AC power transformers are available.
The power cable and the power supply (12V DC/24V AC)
It’s possible to run power longer distances if you use thicker gauge cable. For example if you increase the size of the power cable to 16 gauge instead of 18, you can run the 12V DC 380 feet with less than 10% power drop. You can run the 24 V AC up to 1,100 feet.
So the thicker the cable, the less the power drop and the farther the power can be transmitted. However, the good cables can get expensive, you need to analyse the project and find out the right balance between the cost and equipment.
The first thing to do when you start a CCTV project is to determine how far the farthest camera from the power source is. If the cable runs less than 300 feet then you can use the 12V DC powered security cameras. If you are running longer runs you might need to consider buying dual voltage cameras, buying thicker wires or higher amperage power supply.
From our experience, depending upon the installation requirements, 24V AC power is generally more flexible when it comes to medium to long cable runs. Either way, if you have any questions, you need to check with the spec sheet or contact the manufacturer to find out if the cameras are good for your CCTV project.