Anode Drive - LED Matrix

[Suraj143]

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)?

 

[k7elp60]

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.

 

[ronsimpson]

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

62.5hz is not fast.

T1 is on when the input is at 0V and also is on when the input is at 5V. It only turns off when the input is near 12V.

 

[Suraj143]

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]

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.

 

[k7elp60]

I didn't understand

 

[ronsimpson]

I didn't understand

This circuit (T1) needs a 0 to 12 volt signal to turn it on/off. Your little computer can not do 12 volts.

This next circuit (2N3904) works well with a computer. (0/5V)

 

[k7elp60]

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