LED, Strips, and Controllers: Part-4

In the previous part, we have told about a single color LED Strips.

By manner of powering them, They can be complete static – with Fixed intensity and dimmed – with a regulated intensity.

LED-Power Supply-examlpe-1-Hardwae-Pro

1.) Fixed Voltage Powered LED Strips

We just need to select the LED tape and to calculate needed power.

Is it so simple?

How to choose the right Power Supply Source?

The Power source in common case is an AC-to-DC converting electronic device, who allows transforming the Alternating Current (AC) from the Powering net (110V AC or 220V AC) to Direct Current (DC) Voltages for example: 12V DC.

When you choose the LED Strip, you need to select a proper Powering Supply to ensure a many hours un-interruptable work of the product.

It is a Good practice to select 25% more powerful Power Source.

Here an Example:

You need to power 2 meters of [14.4W / m ] – 12VDC, Single Color LED Tape.

On the first sight, The Power consumption is 28.8 Watts. But, let we add a 25% more power, as practice needed an engineering reserve.

28.8W * 1.25 = 36 W Power Source. You can check, that the variety of power supplies is enormous, with almost a watt or a few watts granularity.

Different manufacturers of Power Supplies remark on their guidelines or user’s manual not to use at 100% of the possibilities of the source. The ideal percentage from the engineering’s point of view is about 75-80% the maximal value.

Here are some reasons for that.

– First reason: In a case of temperature degradation of components into the Power Supply source, the calculated its efficiency sinks below.

If We have PS with 95% efficiency on 25 degrees, at 85 degrees, the efficiency drop at 85%. That means the estimated 15% are generating the heat into the Powering Source. That will bring new losses into the Source, and this “the avalanche effect” and will destroy the device.

– Second reason: The stability of Power Regulation line – as absolute Value.

– Third reason: Temperature of the LED Strips dependents.

2.) “Dimmed LED Strips” – LED Tapes with a regulated intensity.

That is possible by using active devices named: Dimmers. The Dimmers are “MOS-FET Transistor” based switches, using the technique PWM (Pulse Width Modulation) situated between the LED strip leads and the connected Power Source.

With the different coefficient of dimming, we could produce 0 to 100 % regulation of the tape’s emitted light. The effect is named: Dimming.

PWM-example-1-Hardwae-Pro

PIC. 1 PWM Main-Parameters

PWM-example-2-Hardwae-Pro

PIC. 2 Different Duty-Cycle templates [%]

Now you know does the effect “Dimming ” means. Is It Cool?

There are some Hi-End, sky-gliding devices with point by point single color led controlling. In common case these LED strips are 5 V – to 12 V powered and need smart controller unit (Personal Computer) to dump “the show program into the action” .

Here is an example with APA102 tape. The 144 fully addressable LEDs/per meter. See the pictures below.

PIC. 3 APA102 View

AMAZON.CO.UK Affiliate Link: APA102 LED Strip

A little zoomed the same LED Strip APA102:

PIC. 4 APA102 Best View