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Talking about Fleabay item 262793423326 - the board mounted 3 x 5050 WS8212 leds Michi said

 

it's more I think, each of the white square leds is made up of three individual leds inside the package (ie the red, green and blue) and each draws 20 mA, so it's 60 mA for each at full white, so 180 mA for everything on full.

 

Oops, yes, thanks for pulling me up on that one! It's 60 mA for a single LED at full white, so 180 mA for all three LEDs. I need to learn how to multiply… :(

 

Michi.

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Oops, yes, thanks for pulling me up on that one! It's 60 mA for a single LED at full white, so 180 mA for all three LEDs. I need to learn how to multiply… :(

 

Michi.

 

Michi, A lot of the time you may not require the LEDs to be a full brightness. You may find this useful for cutting back LED intensity when required not to mention simply running LEDs on different supply voltages.

 

This one is for single LEDs for finding the required resistor value for the given voltage.

http://led.linear1.org/1led.wiz

 

And this one for multiple LEDs in series or parallel.

http://led.linear1.org/led.wiz

 

Most standard LEDs will handle 20mA as a guide but this can usually be dropped to 10mA with no noticeable difference in brightness. Dropping the supply voltage getting to the LED does drop the brightness.

 

The different colour LEDs also require different voltages and this needs to be taken into consideration.

 

Google LED colour voltages will give you the proper voltages for each colour.

Edited by Autosteve
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Michi, A lot of the time you may not require the LEDs to be a full brightness. You may find this useful for cutting back LED intensity when required not to mention simply running LEDs on different supply voltages.

 

Right. But, in the context of this discussion about addressable LEDs, I can just dial down each LED anyway by telling it not to shine as brightly. The 60 mA figure was simply to take into account the worst case for sizing the power supply.

 

I don't believe that I could under-power addressable LEDs the same way as ordinary RGB ones; presumably, the micro controller in each LED would stop working in short order once the supply voltage drops too much.

 

Cheers,

 

Michi.

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Yep, what Mitchi says is bang on.

 

For the WS2812 and similar serially controlled leds the colour and intensity are set by software command. You send them three 16 bit words to represent what you want in terms of red, green and blue intensity. This matches the 3 physical leds in the package.

 

Some libraries have predefined colours built in, otherwise you can define them yourself like below;

 

#define Green leds.Color(0x00, 0xff, 0x00)

#define Blue leds.Color(0x00, 0x00, 0xff)

#define Magenta leds.Color(0xff, 0x00, 0xff)

#define Yellow leds.Color(0xff, 0xff, 0x00)

#define Purple leds.Color(0xb7, 0x00, 0xff)

etc

 

where leds is the constructor you defined for the string

 

0,0,0 would be off

3f, 0, 0 would be quarter power red etc

 

and then just call that colour to the led you wish like

 

leds.setPixelColor (ledNumber, Purple);

 

where ledNumber is the position of the led in the string

 

(when you grab the library and install it you get examples to help you along)

 

For just plain leds (ie not serially controlled) used in the context we are talking about, which is control with a micro, use PWM to modulate them. Like analogWrite(pin, value) where value is 0 for off and 255 for max.

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