Anode Drive - LED Matrix

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Suraj143

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The attached picture shows an one row of my LED matrix (16 rows x 32 columns).

The 1st picture has a single led pixel & it’s working nicely with 5V.

Now I want to increase the leds in a pixel (3 leds per pixel/ in future it will be 9 LEDs per pixel) & needs to drive them from 12V.

Is my modification ok?

Can the TIP42 switch fast (62.5Hz frame rate)?
 

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You will have a problem connecting 9 LED's in series to work on 12VDC because the minimum voltage for some LED's is about 2VDC. Please post a schematic of the matrix, give the color. As I read your schematic, you want a - going pulse to light the LED's.
 
Hi thanks for the view.

My input signal is 5v logic from pic pin.
I want to control string leds from 5v signal.

Maximum series leds per string will be 3.I connect 3 strings parallel to make 9 leds per pixel.

My circuit should meet this requirement.

When 0v applied the leds should turn on.
When 5v applied the leds should turn off.
 
The base of the PNP transistor must be +11.5V or higher to turn it off. It never gets that so it never turns off.
When the input is +5V then the base is +11.3V and its base current is (11.3V - 5V)/1k= 6.3mA.
 

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