user55041: I want to control about 20 leds with an arduino mega.
This leds works with 12v voltage.
I tried to put 20 relays but this solution is not good for me because leds will often blink 
I have also tried transistors but it needs to make a pcb.
I am looking for a solution without having to create a pcb
Any idea ?
Thanks 

user42539: Three TPIC6B595 shift registers, controlled by 3 pins from the Mega, can do this easily. Shift in 3 bytes with on/off state of the LEDs.
Can sink 150mA per output from 12V source.  The LEDs need current control, from simple resistor for 20mA loads, to a constant current driver per LED for higher current LEDs.
I used them to sink current from 12V for the LED strings in this display. The small digits needed ~ 20mA per segment, the larger digit is really 2 groups of 3 LEDs, drawing about 40mA per segment. One shift register per digit.
https://www.youtube.com/watch?v=6HZ0Mr51jUY

user50183: You can use the commonly available L298N module to drive four of your LEDs with each module. That means you would need five of them.

Those modules are suitable for driving either one stepper motor, two DC motors (in both directions), or four "unidirectional" loads such as your LEDs.
The input can be connected directly to your MEGA, but you may need additional series resistors depending on the LED you use (though this likely does not apply for LEDs specified as "12V").
There are also LED driver eval boards available which may suit your needs:
https://www.digikey.de/product-detail/de/adafruit-industries-llc/1455/1528-1019-ND/4990768

user4143: The ULN2803 is a chip with 8 darlington transistors in it designed for driving higher voltage, low-ish current, loads like this.  With 3 of them you have 24 channels to drive your LEDs.
You can get them on a breakout board quite easily, or as a DIP chip for working with breadboards.

55041: <p>I want to control about 20 leds with an arduino mega.
This leds works with 12v voltage.</p>

<p>I tried to put 20 relays but this solution is not good for me because leds will often blink </p>

<p>I have also tried transistors but it needs to make a pcb.</p>

<p>I am looking for a solution without having to create a pcb</p>

<p>Any idea ?</p>

<p>Thanks </p>
 42539: <p>Three TPIC6B595 shift registers, controlled by 3 pins from the Mega, can do this easily. Shift in 3 bytes with on/off state of the LEDs.
Can sink 150mA per output from 12V source.  The LEDs need current control, from simple resistor for 20mA loads, to a constant current driver per LED for higher current LEDs.</p>

<p>I used them to sink current from 12V for the LED strings in this display. The small digits needed ~ 20mA per segment, the larger digit is really 2 groups of 3 LEDs, drawing about 40mA per segment. One shift register per digit.</p>

<p><a href="https://www.youtube.com/watch?v=6HZ0Mr51jUY" rel="nofollow noreferrer">https://www.youtube.com/watch?v=6HZ0Mr51jUY</a></p>
 50183: <p>You can use the commonly available L298N module to drive four of your LEDs with each module. That means you would need five of them.
<a href="https://i.stack.imgur.com/15EKF.jpg" rel="nofollow noreferrer"><img src="https://i.stack.imgur.com/15EKF.jpg" alt="L298N module"></a>
Those modules are suitable for driving either one stepper motor, two DC motors (in both directions), or four "unidirectional" loads such as your LEDs.</p>

<p>The input can be connected directly to your MEGA, but you may need additional series resistors depending on the LED you use (though this likely does not apply for LEDs specified as "12V").</p>

<p>There are also LED driver eval boards available which may suit your needs:
<a href="https://www.digikey.de/product-detail/de/adafruit-industries-llc/1455/1528-1019-ND/4990768" rel="nofollow noreferrer">https://www.digikey.de/product-detail/de/adafruit-industries-llc/1455/1528-1019-ND/4990768</a></p>
 4143: <p>The ULN2803 is a chip with 8 darlington transistors in it designed for driving higher voltage, low-ish current, loads like this.  With 3 of them you have 24 channels to drive your LEDs.</p>

<p>You can get them on a breakout board quite easily, or as a DIP chip for working with breadboards.</p>
