12V Seven Segment With Arduino ( I have a problem)

(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.

photo_2020-02-26_14-17-04.jpg

photo_2020-02-26_14-16-14.jpg

photo_2020-02-26_14-16-14 (2).jpg

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. :roll_eyes:

If you are trying to drive 5 LEDs in parallel, it is even worse. :astonished: 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.

Like this:
Capture.PNG

Capture.PNG

@Setrik_aZ

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ballscrewbob: @Setrik_aZ

Other post/duplicate DELETED Please do NOT cross post / duplicate as it wastes peoples time and efforts to have more than one post for a single topic.

Continued cross posting could result in a time out from the forum.

Could you take a few moments to Learn How To Use The Forum. It will help you get the best out of the forum in the future. Other general help and troubleshooting advice can be found here.

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? :roll_eyes: