4 x 7 segment common anode

[Rajinder]

Hi
I have a 4 x 7 segment common anode display, which i will be driving from a PIC micro.
I need some help in calculating resistor values and selecting the correct PNP transistors.
Can anyone help?
Thanks in advance.

 

[Harald Kapp]

Got a question about driving LEDs?

 

[Rajinder]

Got a question about driving LEDs?

Thank you.

 

[Rajinder]

Are there any considerations required for the transistors? Also if i light up segments to say display the number '8'. Do i calculate each segments current to get the overall current?

 

[Harald Kapp]

Are there any considerations required for the transistors?

The transistors are used in on/off operation only. You need to match max. current and voltage, that's more or less all.

Do i calculate each segments current to get the overall current?

Each transistor drives one segment only.
The total current (per complete display) is relevant for the power supply.
Plus you'll have to consider total current (per digit) when multiplexing the display for the transistors (per digit) that drive the common anode of each digit.

See for example here. Post your own schematic for us to cross-check.

 

[Mark2019]

Halfway down the page is the maths you need to work this out
https://electronicsclub.info/transistorcircuits.htm

 

[Rajinder]

Thankyou.