Is there a way to identify a blue LED? I only know it's bright (like a high intensity white LED), needs a higher voltage than the equivalent red bright LED, and has T1 (3mm) form factor.

Note By "identify" I mean find out what the part number is, so that I can google the datasheet. In particular to make it run as bright as possible without burning it in the long run.

  • \$\begingroup\$ What do you mean by identify? You have a bunch of leds and want to put the blue ones aside? Or... I don't really understand your question. \$\endgroup\$ – Vladimir Cravero Jun 10 '14 at 15:26
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    \$\begingroup\$ I usually go by the color when its on. \$\endgroup\$ – Scott Seidman Jun 10 '14 at 15:27
  • \$\begingroup\$ Addressing your question after your update: I think that identifying an LED part number by inspecting it is really hard if not impossible, at least for the most common LEDs out there. The best chance you have is by asking your supplier or lookink at the order invoice and hope that they keep track of that. \$\endgroup\$ – Ricardo Jun 10 '14 at 17:12

This doesn't answer your question directly, but as Scott Seidman mentioned in his comment, the best way to test any LED is to light it up. You'll want to light them up not only to discover their color, but also to check their brightness and true voltage drop under a given current.

LED tester schematic

For that purpose, I found this LED tester to be simplest and most useful tool. It's essentially a constant current power supply designed around the LM317L adjustable voltage regulator.

It may features are:

  • It lets you set defined current to test LEDs using a trimpot;
  • It has a convenient set of test points designed to let you measure voltage and current with a multimeter;
  • It also has convenient connectors for you to plug the LED under test;
  • Or you can use its pads for testing small SMD LEDs as well.

I keep my tester set for 20mA on my bench and run every new LED quickly through it right after a new batch arrives.

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    \$\begingroup\$ Just as a safety precaution, rather than using your switch to turn on power, I'd use a normally-closed switch to short the LED, then open it to test. This prevent an initial high voltage (and possible short current surge) when the LED is connected. \$\endgroup\$ – WhatRoughBeast Jun 10 '14 at 16:40
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    \$\begingroup\$ Or do what the small-scale Asian sellers do, just slap it across a CR2032. There's apparently enough internal resistance that it's okay. No guarantees it won't fry your LED, but they all do it. \$\endgroup\$ – Spehro Pefhany Jun 10 '14 at 17:18

protected by Community Jun 10 '14 at 16:08

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