Bi-color LED help

Okay, so I bought a 2 lead bi-color led, but my application requires a
3 lead shared anode led. Is there any circuit I can build that would
detect the presence of negative to reverse the polarity automatically

 

Is this a trick question?

yes, install a 3 lead shared anode led is the simplest.

or get two standard LED's and hook them up as a standard 3 lead shared
anode.

Don...


--
Don McKenzie
E-Mail Contact Page: http://www.dontronics.com/e-mail.html

Micro,TTL,USB to 1.5" color LCD http://www.dontronics.com/micro-lcd.html
USB,RS232 or TTL to VGA Monitor http://www.dontronics.com/micro-vga.html
World's smallest USB 2 TTL Conv http://www.dontronics.com/micro-usb.html

 

this maybe.

K1 A
----|<---+----+--[330R]-----+---
| | |
\ / -+- |
-+- / \ |
K2 | | |
----|<---+----+--[330R]-----+

these two big
diodes are the LED.

The litle diodes are 1n914 or similar.

This circuit will give no light when both cathodes are low,
so you can get red or green but not yellow.

Bye.
Jasen

 

---
Please bottom post.

There's not enough information in your post to give you actual
circuit values, but here's the basic idea: (View in Courier).


| \ | \
IN>--+--| >O---O| >--+
| | / | / |
| [R]
| |
| [LED]
| | \ |
+-----------| >O-+
| /

"IN" is one of the signals used to drive the 3 lead LED.

If the LED's colors light up reversed, just swap the LED in the
circuit.

You may be able to get rid of two of the inverters depending on what
"IN" looks like. Post some more information about your circuit and
you'll get more help.

 

You could modify your circuit if both LEDs are *not* lighted at the same
time:
+--------+-----o
| | +
V red V gn
- -
| |
.-. .-.
| |Rred | |Rgn
| | | |
'-' '-'
| |
|/ |/
-| -|
|> |>
| |
=== ===
GND GND

+---------+-----o
| | +
.-. .-.
| |Rgn | |Rred
| | | |
'-'. '-'
| |
| red |
+-+-|<-+--+
| | | |
| +->|-+ |
| gn |
|/ |/
-| -|
|> |>
| |
=== ===
GND GND
(created by AACircuit v1.28 beta 10/06/04 www.tech-chat.de)

 

As so often, it depends.

Suppose the cathodes are driven by (microcontrollers) outputs that can
source and sink enough current *AND* you only need one of the colors at a
time *THEN* you can simply connect the 2 lead component between the cathode
cathode joints of the original LED. You may need to add a resistor to limit
the current. If the outputs cannot source enough current, you need buffers.
If the outputs can only sink current, you can use the upside-down circuit.
See below.


CA
|
|
C1---|<--+-->|---C2

Original 3 lead bi-color LED


+--->|---+
C1---+ +---C2
+---|<---+

2 lead bi-color LED


+--->|---+ ___
C1---+ +--|___|---C2
+---|<---+

Series resistor


+--------------+- Vcc
| |
.-. .-.
| | | |
| | | |
'-' '-'
| |
| +--->|---+ |
+--+ +--+
| +---|<---+ |
| |
R3___ |/ \| R4___
C1--|___|--| |--|___|--C2
|> <|
| |
| |
------+--------------+-----Gnd

You may need buffers. R3 and R4 may by ommitted.



-----+---------------+-----Vcc
| |
| |
R3___ |< >| R4___
C1--|___|--| |--|___|--C2
|\ /|
| |
| |
| |
| +---->|---+ |
+--+ +--+
| +----|<---+ |
| |
| |
.-. .-.
| | | |
| | | |
'-' '-'
| |
--------+---------------+-------Gnd

If the cathode connections can only sink current the voltage
should be able to raise above Vcc-0.7

All this may not be usefull if my assumptions are not correct. So provide
more detailed info now or the next time you have a question.

created by Andy´s ASCII-Circuit v1.24.140803 Beta www.tech-chat.de

petrus bitbyter