Determining the correct power supply

So how do you determine the correct CCTV power supply for your security camera system?

There are two main selection criteria.
1. The number of cameras to be powered.
2. The total current draw.

You will need to get the power requirements of the camera from the spec sheet or from the camera itself. Typically the measurement you need to know is how many amps the camera will draw for AC or DC power. If you don’t know the amps you can divide the watts or VA by the voltage to find out. See the voltage conversion chart for which numbers need to be divided.

As an example a camera my show 5W at 24 VAC. How many amps is that? Based on the chart you would divide 5 by 24 for approximately .200 amps or 200 mA (milliamps).

When figuring the current draw remember that the total power available is not the sum of the maximum available from each of the outputs.

For example in a 8 camera output you may draw up to 1.85 Amps from any output. However, your total current (obtained by adding the draw of all the cameras) should not exceed 4 Amps. Loading each output at 1.85 Amps for a total of 14.8 Amps would clearly overload the supply!

Example 1: You have 2 domes drawing 1 Amp each and 6 cameras, drawing 150mA each. Your total current draw is 2.9 Amps, well within the total available current of 4 Amps. This is OK.

Example 2: You have 5 domes, drawing 1 Amp each and 3 cameras, drawing 150 mA each. Your total current draw is 5.45 Amps, exceeding the total available current of 4 Amps. This in not OK. Your installation will not work.