(first of all sorry for bad grammar -_-)
Hello, recently i made a handmade SSD display which works with 5 LEDs in parallel for each segment.
i tried to run it with Arduino Pro Mini.
the problem was that the LEDs were not bright enough so i measured the output voltage of transistors (Emitter voltage with GND) and it was about 2 volts while i expecting 12 volts.
the transistors are 2n2222 (actually mmbt2222 the SMDpackage of that) and base resistor is 1k ohm.
can you please help me to find out why the voltage is so low in output or another way to use this SSD display?
-->The SSD is common cathode
tnx!
---> Each segment Schematic. ---> The Data + and Data - (how transistors are connected). ---> Its how the 4 SSDs are connected together.
Setrik_aZ:
the problem was that the LEDs were not bright enough so i measured the output voltage of transistors (Emitter voltage with GND) and it was about 2 volts while i expecting 12 volts.
the transistors are 2n2222 (actually mmbt2222 the SMDpackage of that) and base resistor is 1k ohm.
can you please help me to find out why the voltage is so low in output or another way to use this SSD display?
The circuit on the left in the second image is an "emitter follower". The emitter of the transistor "follows" the base with 0.7 V or so drop. So if you drive it with what you expect to be 3.3 V from an Arduino pin, the emitter will pull up to about 2.6 V.
Which is what you have measured.
You need a MAX7219 to drive 7 segment or matrix LED displays properly. You are essentially wasting your time trying to drive them just from the Arduino itself.
If you are trying to drive 5 LEDs in parallel, it is even worse. Better to put them in series and use a single TPIC6B595 to drive each digit. You can chain them so that they are all controlled by three Arduino pins and they will be giving full brightness. You may need somewhat more than 12 V for 5 LEDs in series however.
yes well sorry, i actually wanted to remove the topic thats why i didnt answered the responds but i didnt find out how to do that so i just left it alone.
Setrik_aZ:
yes well sorry, i actually wanted to remove the topic thats why i didnt answered the responds but i didnt find out how to do that so i just left it alone.
It would be nice to explain why you wanted to remove the topic?
---> The Data + and Data - (how transistors are connected).
---> Its how the 4 SSDs are connected together.
Better to put them in series and use a single 