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Anode Drive - LED Matrix

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Suraj143

Active Member
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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k7elp60

Active Member
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.
 

Suraj143

Active Member
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.
 

audioguru

Well-Known Member
Most Helpful Member
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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k7elp60

Active Member
I didn't understand
 

k7elp60

Active Member
It is time for me to quit making comments on posts. By By!
 
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