Power Requirements

Application

Power requirements for an LCD display or monitor are very important. And also can be a big factor depending on the application for the monitor.

Some factors that could affect the power requirements are things like line loss. And the application where the display is going. for example if the monitor is going into a vehicle then it will need to be powered via a battery and must be able to get enough power.

AC & DC Power

AC and DC are types of current, AC is Alternating Current and DC is Direct Current, they both describe the flow of current in a circuit. In direct current the electric charge only flows in one direction. Alternating current on the other hand changes direction periodically. The voltage in an AC circuit  also periodically reverses because the current changes direction.

Most LCD monitors or displays use DC but some displays can use AC. It’s also very important that the monitor gets the right power supply. This is prevent anything from overloading and causing any damage.

If your monitor has a 12V 5A power supply for example but you can’t find the correct power supply for it then you can use other power supplies but you need to make sure it will power the monitor correctly. If you had a 24V 7A power supply then that would work fine because the monitor doesn’t need that much power but it will only ever take what it needs. Where as if you had a 12V 3A supply then that could potentially damage the monitor as it will be trying to pull more power because it can’t get enough and the internal boards could become damged.

AC & DC Circuit Diagram

To the left is a diagram of AC and DC current in a circuit, you can see that the DC current only flows in one direction where as the AC current changes directions periodically.

The load would be the LCD monitor in the diagram which is being powered by either a mains plug socket or a battery.

Most monitors use a DC power supply but some depending on the application do use an AC power supply.

Line Loss / Drop Voltage

Line loss or drop voltage refers to electrical current being lost due to inefficiencies or defects in the distribution system. The most common issue we have is running an LCD monitor on a long power cable, as the cable gets longer more current is lost due to the conversion of electricity to heat and electromagnetic energy.

If line loss is not calculated correctly in can result in the monitor becoming damaged due to it not receiving the right power requirements. We have had a few of our clients try to run a monitor using a 50+ meter cable. The cable is too long to carry all of the current and some of it is lost along the way. for example you might have a 12V 5A power supply from the mains running along a 50+ meter cable you might get half of that on the other end of the cable, maybe even less.

This leads to the monitor not getting enough power and it damages the internal components and renders the monitor useless.

Case Study for Line Loss

As you can see from the pictures to the right our client was looking to run one of our ‘Pro M19’ monitors in a swimming pool application for the lifeguard as a safety monitor which has a video feed from the pool so the lifeguard can see what is going on under the water.

The video feed and the power cable had to be long to be able to reach the monitor as the LCD display was positioned next to the lifeguards tower.

The power cable for the monitor was 50+ meters which caused line loss resulting in the monitor not getting enough power and causes board damage in the monitor.

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