Guys
Do any of you know a source for Bi-colour LEDs that are series configured, rather than CA or CC?
Fof
How do you imagine that being possible in the first place?
There are two-pin bicolour LEDs (basically two LEDs in parallel, opposite polarity, in one housing). Maybe that suits whatever you intend to do with them.
@wvmarle
I need to monitor an open drain pin.
I can do it with the first cct (see attached), but the second is more elegant.
I know I can get Common Anode (as per 1st) or Common Cathode, but why not Series?
I can easily get diodes in CC, CA or Series.
Fof
Document1.pdf (4.86 KB)
the second is more elegant
Except that it won't work, and the LEDs will burn out for lack of current limiting resistors (assuming the green LED is grounded).
A two-pin, bicolour LED can do this. One side connected to your inverter output; two current limiting resistors on the other side: one to GND, one to Vcc. You of course do have some current leakage through the two resistors, so don't pick too small values. 1k will do fine, unless you need very high brightness.
Just thinking: another option is to use a second inverter (there are six in that IC) for the other colour, and you can use your CA or CC three-pin LED.
Your signal as you sketched to the input of one inverter, the output of that inverter to one side of the LED and to the input of a second inverter, the output of that second inverter to the other side of the LED.
Guys
Apologies. The pic was just quickly thrown together. The resistors (2x330R) in the second should be in series with both, leds, not to the inverter OP. Whoops. see pdf.
@wvmarle. Your suggestion re another gate would have required another chip. No spares left. Using the back-back LEDs, I hadn't actually considered. Good call.
Still, my question remains, why can't I find series connected?
tCad1.pdf (6.38 KB)
If you connect two LEDs in series, one cathode to the other anode, they both light up
when forward biased. If you connect them any other way in series, neither one will light up.
@herbschwarz
In this configuration, the gate driving the junction, would effectivly "short out" one LED/resistor, as the active Hi/Lo of the HC02 would pull the junction Hi/Lo. Am I missing something?
Fof
why can't I find series connected?
No one else has a use for them.
If you want to post pictures/ graphics, do not use the pdf format.
@Paul__B
Apologies. Momentary "Brain" fade