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LPD8806 strip's LED Voltage
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LPD8806 strip's LED Voltage

by philihp on Wed Dec 07, 2011 12:52 am

Hi,

Could I get the datasheets on the LEDs used in the LPD8806 strips?

I found that I was accidentally powering them with 7.4 volts, rather than the max rated 5.0 volts. They were still working and fine. When I stepped it down to 5.0 volts though, they were dimmer.

What bad things will happen if I continue to run them at 7.4 volts?
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Re: LPD8806 strip's LED Voltage

by adafruit_support_bill on Wed Dec 07, 2011 6:57 am

Customers have ruined strips with less voltage than that. Assuming that you are lucky and don't smoke one or more of the 8806 chips, your LEDs will have a much shorter lifetime.

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Re: LPD8806 strip's LED Voltage

by philihp on Fri Dec 09, 2011 5:26 pm

Could you post the datasheets or part number of the LEDs on the strip?
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Re: LPD8806 strip's LED Voltage

by pounce on Fri Dec 09, 2011 6:40 pm

They look like 5050's on my strip. Google 5050 SMD RBG LED.
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Re: LPD8806 strip's LED Voltage

by K2Joom on Thu Dec 29, 2011 8:12 pm

The LEDs are a 5050 SMD type and are manufactured by a variety of semiconductor companies around the world, mainly in the Far East and Americas.
It would be very difficult to know exactly which company produced the LED, without knowing the manufacturer of the strip.

The specification may vary slightly, but we would be mainly interested in the IF. Take a look here for an example: http://www.diluled.com/led-smd-2.html
You can see which SMD resistors are used on your strips, look for RR, RG and RB and with Ohms law, you can confirm this.

Its also worth making sure, if you do need to replace any, that the beam angles are similar, but also consider that color bining and manufacturing lot codes from different manufacturers will mean that there could be a chance of witnessing a slight colour difference.
When ever I repair strips, I make sure I replace all of them, from the same vendor.

I have even seen, from lesser "manufacturers" from china, where one colour varies across the whole 5m reel, not good.

Hope that helps a little.

Simon
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Re: LPD8806 strip's LED Voltage

by K2Joom on Thu Dec 29, 2011 8:20 pm

philihp wrote:What bad things will happen if I continue to run them at 7.4 volts?


You can easily burn them out completely or simply reducing their operating life.
The reason why they are now dimmer, when you drop to 5V, is because of the thermal strain put on the junction of the diode which in turn burns off the dopant material used to create the output colour.

Once done, its only ever going to get worse and quicker.

Simon
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Re: LPD8806 strip's LED Voltage

by cymatic on Thu Jan 05, 2012 2:05 am

I just went through a simliar issue. Received a 1M strip. I've worked with RGB shift register/pixel "controllers" like the Allegro A6281 before which has a built in voltage regulator and blindly assumed the LPD8806 might be set up in a similar fashion. I was using my adjustable bench power supply and I'm not sure the exact voltage I applied but it was somewhere between 7V-8V. The funny thing is the strip worked flawlessly except the last 4 LEDs were solid white and not responding to any code. By the time I had turned things on and off a few times and before I realized I was running at too high a voltage other LEDs in the strip turned pure white, but this time not at the end, further up the strip. Now only the first 6 LEDs or so actually work, the others, even when powered at 5V stay on as white and no shift register data seems to get past them. I think it would be really nice if the product page drew a little more attention to the fact that 5V seems to be the max, since often times products like this will accept a bit higher or have built-in voltage regulators.

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