Bicolor LED info

[wilykat]

I have a bunch of 2 leads red/green bicolor LEDs, is there a "proper" way to drive it for a fun display? Or can I just use a single inverter? There won't be an "off" state except when power is removed.

It will be single LED so current of about 20mA shouldn't exceed max per gate.

 

[bailey45]

The circuit will work if the previous stage can handle the LED current. I would start with an LED current of 5mA, most LEDs are bright at this lower current.

 

[audioguru]

The LED lights red when the supply voltage is one way and lights green when the polarity is reversed.

Your circuit has one end connected to the input of the inverter where there is no current.

 

[Hero999]

There will be current if a CMOS is connected to it though.

He hasn't said exactly what he wants to do with the bicolour LED yet.

What's the power supply voltage?

What colour is the LED: red/green or red/blue?

If it's red/blue the you might need to add an additional diode and resistor if the blue isn't bright enough.

 

[wilykat]

red/green and it would be hooked to output of CMOS 4017, which can drive LED by itself. I just wanted to make sure using a single inverter gate is "legal" way of driving a single bicolor LED.

I didn't go with red/blue or yellow/blue because blue tended to be on the bright side. Plus blue generally needs about +1v more than red/green.

 

[MrAl]

Hi,

Just one note here...you are missing two colors...one of which is 'dark'.
You have red, you have green, but no 'off', and no 'amber'.
If you drive it with a bi phase circuit like that you can never turn it off
unless the inverter is linear and has a gain of 1, or you have some way
to turn the power supply off.
If you use two drivers you can then control each LED almost independently,
so you can get red, green, dark, and by using a square wave of 50 percent
duty cycle you can also get amber. If you care to change the duty cycle
of the square wave you can get other in-between colors.