multicolour leds

[Thunderchild]

I'm designing a battery charge indicator circuit for a friends motor bike.

he wants a single led thats has 3 colours, and we need some information:

are comon anode leds available

does yellow show when the green AND red leads are powered ?

 

[colin55]

The LEDs we use in the following project have a common cathode. In other words the red and green LEDs within the package have the anodes on the outer leads and the common cathode lead is in the centre. See the following diagram where we use a bi-coloured LED in our Tic Tac Toe project and these LEDs produce a third colour of orange when the red LED and green LED are both illuminated.


**broken link removed**

<snip>

 

[fingaz]

Hi,

You should be able to get hold of common anode and common cathode LED's. I have some 'pirhana' superflux 3 colour led's that are common cathode. I have also had 5mm tricolour led's that are common anode.
The pirhana LED's I have do show yellow when the Green and Red die's are both lit (though you can also see RED and GREEN within the light of the led too)

Hope this helps
Neil

 

[Thunderchild]

ok thats seems to get me onto a good start then

 

[Hero999]

Use a common anode two die red and green LED.

It will give orange/yellow light when both the LEDs are illuminated.

You'll need two comparators (LM393 will do).

Suppose you want the following:

Red < 11V
Orange 11V to 12V
Green >12V

Connect both LEDs to the output of the comparator with suitable value series resistors.

You'll need a stable voltage reference: a 5.6V zener with a silicon diode in series and a suitable current limiting resistor will form a stable 6.2V reference.

You can set a comparator so it turns on or off at different voltages by putting the reference on one input and a potential divider run off the supply voltage on another input.

Set the comparator driving the red LED so it turns it off when the power supply voltage exceeds 12V.

Set the comparator driving the green LED so it turns it on when the power supply voltage exceeds 11V.

Here's an example of how to set up a comparator so it turns on an LED when the supply voltage drops below a certain level - just reverse the inverting and non-inverting pins to make it so it turns the LED off.
**broken link removed**

 

[colin55]

Here's a simple circuit that will show the battery condition:

The red LED will come on with the battery voltage from below 8v to 10.6v. The orange LED comes on between 10.6v and 11.5v The green LED comes on (actually the red LED goes off) when the battery is above 11.5v