Hi
Have this part of my project.
Basicaly i have a 7*4 matrix.
For easy, i just made a 3*3 here.
My questions is.
1. Will the part with transistors work ?
2. Can i remove R4+R7 and connect T4 and T7 to same resistor(R1) as T1 ? ( that way save 42 resistors )
I use NPN for all, is that fail or ?

Hope u understnad what i-am trying to do,

 

You don't have any resistors on the LED's. They will get 12V when the transistors are on.

 

Resistor network RN1 - RN3, no Burning LED

 

Sorry. I didn't notice them.

 

if i have 7 transistors connected to 1 output from MCU, i would then get ( 7 * mA (turn one one transistor )) around 20-40 mA.
That is to much for the MCU, how can i fix that ?

 

Will the part with transistors work ?

Can't tell. You don't give base or current limit resistor values or MCU output voltage and drive capability.

2. Can i remove R4+R7 and connect T4 and T7 to same resistor(R1) as T1 ? ( that way save 42 resistors )

No, paralleling transistors that way isn't a good design practice.

if i have 7 transistors connected to 1 output from MCU, i would then get ( 7 * mA (turn one one transistor )) around 20-40 mA.
That is to much for the MCU, how can i fix that ?

Use MOSFETs instead of BJTs.

Do yourself and others a favor. Only use 90 degree bends in wires, move the transistor labels to a more appropriate place, don't run wires over text, and post schematics in black and white (professionals don't use color coded schematics).

 

(the mosfets part)

? why 12V to power the led's (( i know there exist power LED-s up to 48V ... and above -- but usually they range from 2 to 6 V))
? what voltage your MCU runs

 

I think you should move the LED resistors to the collector side of the transistors along with the LEDs.

Also if you switch to MOSFETs you can drive multiple gates with a single output pin without any resistors, if the speed is low enough.

I also need to question why you would use 904s to switch the 337s, I would suspect that should be the other way around considering the specs of those transistors.

 

your setup suggests , that you will be multiplexing these leds

in which case -- the current limiting should be at the T10 11 12 . . . . but then if your MCU is running at 5V dc and your LED-s have - say - a 5V forward drop the other transistor switches may become slow responding ← because then the CC-sinks.. . (or your emitter resistors at your current setup) . ..will act as emitter load and the intermediate switches would act as common collector switches ← these , in turn , are fast only at relatively high current biasing (the fastest switching is usually done from the power rails ... with sufficient drive current)

depending on your speed requirements - your current setup may work - but to make it potentially fast use CMOS OD comparators to drive pMOS and replace 2N3904 with nMOS . . . all this mostly to reduce the drive current -- the current limiting can be then done with source-resistors from either side

http://tinyurl.com/sarq6n6 example of the the ladder voltages (MOSfets are loosely matched to NDC7002N and BSS84)

"Standard/Default"

 

Some clarifying
I have 5 LED in serie and current limit resistor. 1.85v x5 and 0.7 v drop over transistor gives me a resistor around 100 ohm. 12v 5 LED And resistor
I use 20 mA
The resistor is on collector side.
The output from MCU will only be 5v.

T10-T12 will max use 7x20 mA each.

The complete setup will be to much to post

 

The complete setup will be to much to post

The file size limit is quite large these days.

 

The resistor is on collector side.

The resistors are only on the collector side of your horiz. transistors, they also need to be on the collector side of the vert. transistors.

If you leave them where they are your resistor calculations will be off because the voltage drop across those resistors will not be what you expect, due to being on the emitter side of the 337s.

 

Got a bit of my scehmatics.
Have 3 more , same but TD5 Connected to RB4-RB5-RB6
The 6 last connection SEG_B to SEG_G is conneted to RC0-RC5

RN5 Should be 100 Ohm, according to my calculations.
RD5 i think is 5 k.
RT29 -- RT35 is ??

MCU gives 5v output.

 

The relevant portion of the schematic: