Tricolor LED driving circuit

Thread Starter

LavanyaThumati

Joined Sep 22, 2020
5
Hi
I am using a tri-color LED with 2 anodes and 1 cathode. If both anodes are high , then 3rd color will glow.
This LED must be controlled by a single GPIO or two GPIO pins of Microcontroller card.
But here in this case, the LED operating voltage is 12V DC, but MCU GPIO Pin voltage is 3.3V which cannot drive 12V LED. I used a N-channel FET , NPN transistor for driving the LED by connecting LED to emitter or source pin of transistor.
Below I attached the circuit which I have used, the problem here I have faced is the same base voltage is coming at Emitter pin which acnnot drve the 12V LED.

Can anyone suggest a circuit to drive the 12V Tricolor LED with common cathode which is controlled by a PIC controller.

For driving 12V single color LED, I have used ULN2003 IC as s driver to glow 12V LEDs. But in the case of tricolor LED with common cathode, the connections are different . where I should connect the single cathode for driving tricolor LED. The common cathode cannot be connected to 2 outs of ULN2003. Please suggest me any solution for this.
 

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ericgibbs

Joined Jan 29, 2010
11,091
hi LT
That circuit will not work.

With a 3.3V Base voltage the Emitter voltage will be approx 0.7V less. ie: around 2.6V
E
 

ericgibbs

Joined Jan 29, 2010
11,091
hi,
IMO that is an awful datasheet.

Did you see this note from the d/s for the bi-colour led.
Bi-color - The color is changed by reversing the polarity of the supply voltage.

E
AAA 570 12.18.gif
 

ericgibbs

Joined Jan 29, 2010
11,091
hi,
That left half circuit in post #6, just needs the same circuit for the right side, in order to drive the Tricolour.

What PNP transistors do you have in stock.?
E

Updated circuit.
 

Attachments

Last edited:

Ian0

Joined Aug 7, 2020
715
That's a very annoying LED. Do the manufacturers not realise that a single anode and two cathodes would be much more user-friendly? You could always take it apart and replace the LED inside by a common anode version.
 

soyez

Joined Aug 17, 2020
51
Hi
I am using a tri-color LED with 2 anodes and 1 cathode. If both anodes are high , then 3rd color will glow.
This LED must be controlled by a single GPIO or two GPIO pins of Microcontroller card.
But here in this case, the LED operating voltage is 12V DC, but MCU GPIO Pin voltage is 3.3V which cannot drive 12V LED. I used a N-channel FET , NPN transistor for driving the LED by connecting LED to emitter or source pin of transistor.
Below I attached the circuit which I have used, the problem here I have faced is the same base voltage is coming at Emitter pin which acnnot drve the 12V LED.

Can anyone suggest a circuit to drive the 12V Tricolor LED with common cathode which is controlled by a PIC controller.

For driving 12V single color LED, I have used ULN2003 IC as s driver to glow 12V LEDs. But in the case of tricolor LED with common cathode, the connections are different . where I should connect the single cathode for driving tricolor LED. The common cathode cannot be connected to 2 outs of ULN2003. Please suggest me any solution for this.
LEDs are turning into the true light source in this day and age of regularly growing applications. They offer

different preferences, for example, longer lifetime (normal life expectancy of more noteworthy than 100,000 hours), expanded

energy effectiveness and preferable shading properties over some other light source accessible today. In any case, the LEDs

can't create light all alone. The part called the LED driver involves power gadgets

circuit that changes over the accessible 220 V/110 V AC source into DC power hotspot for driving LEDs. The

driver disengages the high line voltage source alongside its variances from the LEDs consequently managing

power provided to them.
 
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