Hi,

I have a schematic which calls for a bi-color diode. Here is what it looks like on paper:



As you can see, the schematic only shows one line going to the LED from the zener diodes, and one line coming off the LED on the opposite side.

My LED has, of course, 3 leads on it. So how do I hook up the LED:

Both anodes to the lead coming from the zener diode and the cathode to the lead leaving the LED?

Or some other configuration? Thanks in advance.

 

You have got the wrong type of bi-color-diode:

A bi color led is just two leds (on red, one green) inside the same container.

Three lead leds are made with a comon cathode and two independent anodes (or a common anode and independent cathodes)

Two lead leds have both individual leds in parallel, but with opposing polarities: one lead is the red cathode and green anode, the other lead is the red anode and green cathode.

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Thanks...

Live and Learn

 

Hi 0x00x0,

Try this, it might even work !

on1aag.

Attached Images

Bi-color problem.GIF (7.3 KB, 29 views)

 

Awesome! I will give this a try and report the results..

 

Hmm, the only diodes i have are zeners.. I guess I will have to order the 2 pin bicolor LED after all..

 

Hi 0x00x0,

Put the zeners in and use them as regular diodes.
All zener voltages are higher than the forward voltage
drop of a red or a green led.
It should work equally well.

on1aag.

 

The ones I have are 1N4732A , is that acceptable?

I have others but I cannot read the letters on most of them

Thanks again for the assist..

 

Zener diodes Vf are around 0.7V and do not exceed the voltage drop of LEDs. You can verify this by doing a simple diode check. But you can still use them in place of the 1N4148 diodes.

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Hi 0x00x0,

They will do fine because the forward voltage drop of both
leds is lower than the zener voltage.

on1aag.

 

When you say "zener voltage" are you refering to the zeners in series with the LEDs or the ones used as a switch to direct current? I am assuming you are referring to the series diodes since the switching diodes, in this app, are used as regular diodes.

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Excellent! I will give this a try... Thanks a bunch!

 

Hi Rezer,

I didn't mention the 18 volt zeners, I was referring
to the 1N4148's.

on1aag.

Attached Images

1N4732A's.GIF (7.0 KB, 12 views)

 

Very good. It's amazing how clear things look with the schematic in front of you instead of using memory.

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What sort of bi colour LEDs do you have?

Some are just a red and green LED connected in reverse parallel, they have only two leads and you need to reverse the polarity to change the color.

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