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# I recently bought something that has a color changing LED in it. That LED has only two pins. Answered

I recently bought something that has a color changing LED in it. That LED has only two pins.
When I look at radioshack, they have color changing LEDs that have two pins with mode, so three pins.
Where can I buy two pin color changing LEDs without mode. They do have that type of LED.

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## 16 Replies

These rainbow LEDs are easily available here in the UK - They fade under internal microprocessor control. Several together make and interesting display as their fade isn't synchronised so they produce a wide range of colour blends. See

https://www.instructables.com/id/Easy-Mood-light/

bassman1950 (author)2013-05-10

Ok some one explain this one to me
I took the single two wire led out of one of those dragon fly garden lights you see. with nothing but the led and a 3 volt battery it changed color from red to green to blue. No other parts are involved at all.
It appears to me that it is the 3 volt battery making it change color as the same led will not change color with the standard 2,2 volt battery garden lights use.

bassman1950 (author)2013-05-11

I take your word on it as I looked closely at it with a good magnifier
but the only thing I could see was that the anode and cathode looked bigger than the normal LED

iceng (author)2013-05-10

THAT'S ANOTHER QUESTION !!

The ignition or forward voltage of Blue LEDs needs the 3 VDC.
and don't forget the micro processor in  the LED that controls the
changing internal LED color chips..

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gruffalo child (author)2011-04-14

If there are only two 'basic' colours (green and red are quite usual)-then it should be two LEDs connected to the pins in different polarity: i.e one way is green, the other way round is red and oscillating current is yellow.
TV on-off LEDs work like that.

gruffalo child (author)2011-04-14

Also, I can prove (mathematics!!!) that you can't control three colours with two pins.

iceng (author)2011-04-21

I beg to differ, you are hung up digitally. There is an analog world too.
Here goes again,
Only two (2) wires run power to a voltage tolerant micro chip that controls three (3) LEDs.
A red, A blue and A green. A suitably biased Op-Amp watching the power pins reports the millivolt variations of the above a set supply ( like industrial current loop ) to the micro.
Based on the analog data from the Op-Amp the micro, sets the individual color LED intensity and and produces a thousand responding colors to input control over only two wires.

All these parts are embedded in a single plastic LED shape...

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gruffalo child (author)2011-04-24

I got it later on, but that's a bit of cheating... Thanks, anyway

iceng (author)2011-04-24

That kind of cheat thinking can make you \$\$\$ one day.

I once made a three LED wand that would produce seven steady colors and other affects based on how long you depressed a single digit button.

Your land line telephone converts analog voice to a digital subscriber line stream packet at a distribution center for sequential switching with other callers onto a trunk line, then back to analog at the final destination.

Even the quantum realm is not completely digital.

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frollard (author)2011-04-15

you can't control three individual diode colours, but you can produce 'visible' 3 colours with 3 power states if the diodes are reverse biased and you flash back and forth between polarities rapidly.
+/-
-/+
off/off

steveastrouk (author)2011-04-15

Which just goes to show that mathematics is no way to represent the real world.....

Steve

gruffalo child (author)2011-04-15

Actually the best thing I like about mathematics is that all those strange fields and rings actually represent something, and not only more complex fields, but also a place where I can swim in the river, eat blueberries and sing songs...(That was a bit of summer nostalgia-it's +5 and raining here).
Oh, and if I never finish the differential function analysis paper I'll never have a chance to understand why an electron can have only two spins (that is what has been thought of as my MOTIVATION).

alpe_97 (author)2011-04-14

Are you sure? I took it apart then unsoldered it and looked at it very carefully...
it has a black little box inside it. They do have it i am sure. because i inserted it into bread board. But first i took multimeter to it so i don't burn the led. Then it red then fades to green then fades to blue. It repeats over and over. I am looking at it right now.

orksecurity (author)2011-04-14

If the LED all by itself is doing the fade, they've got the control chip inside the casing. and it's controlling two or three LEDs also inside that casing. That's unusual but not unheard of; it's a cheap packaging used mostly in toys. (Actually, the control circuitry and one or more of the LEDs might all be on the same silicon chip, again reducing manufacturing costs. That chip, by the way, is the "black box" you're seeing; the rest of the unit is just connecting wires and a plastic case/lens for it..)

The more traditional/controllable multicolor LEDs either use two pins and do the forward-and-backward thing (LEDs are Diodes, after all), or use more pins. It isn't uncommon to generate intermediate colors by combining light from two (or three) LEDs; in the back-to-back configuration that's done by pulsing them with varying waveforms to adjust how much time each spends lit up and counting on persistence of vision to blend the colors.

frollard (author)2011-04-15

Two-pin colour changing leds have a microcontroller built in and just take power, the rest is up to the led to do its own colour changing.

iceng (author)2011-04-14

I have had in my hands a 2wire LED that changed colors on its own timing there was no way to control it except to interrupt power to it.

Also had in my hands a 2wire LED that responded to fractional voltage changes around an 8 or 9 vdc source to generate over thirty steady colors for as long as voltages kept stable.
I saw these put to beautiful use at Burning Man a few years ago..
I think some of the China based LED suppliers would sell these LEDs.

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