Help with circuit advice.

[Regenerate3d]

Fair enough i shall get onto prototype and get PCB cut tomorrow.

[Regenerate3d]

Benta fantastic thank you.

[Benta]

I hope you got the point about ULN2003A and ULN2803A.
One has 7, the other 8 drivers, giving you exactly 15 outputs. You could also standardise on the ULN2803A and use the spare output for something else.

Cheers.

[tooki]

In your application, "flickering" is a human visual perception phenomenon.  Switching speed of 1kHz is more than adequate.

When you said fast switching, some might've thought 1MHz or more!

An Arduino Mega can’t do more than 490Hz PWM on most of its PWM pins, which is terrible for LEDs, but more than adequate for incandescent bulbs. One could reconfigure the PWM to 245Hz and get 16-bit PWM instead, and still be above what’s needed for flicker-free incandescent.

(Remember that mains light bulbs don’t flicker, even dimmed, and they’re pulsed at 100/120Hz effectively.)

[ledtester]

An Arduino Mega can’t do more than 490Hz PWM on most of its PWM pins, which is terrible for LEDs, but more than adequate for incandescent bulbs. ...

490 Hz is only the default value using the Arduino libraries. Faster frequencies are possible -- see for instance:

https://www.etechnophiles.com/how-to-change-pwm-frequency-of-arduino-mega/

You can get F_CLK/256 for 8-bit PWM if you want, i.e. 62.5 KHz when using a 16 MHz system clock.

[tooki]

An Arduino Mega can’t do more than 490Hz PWM on most of its PWM pins, which is terrible for LEDs, but more than adequate for incandescent bulbs. ...

490 Hz is only the default value using the Arduino libraries. Faster frequencies are possible -- see for instance:

https://www.etechnophiles.com/how-to-change-pwm-frequency-of-arduino-mega/

You can get F_CLK/256 for 8-bit PWM if you want, i.e. 62.5 KHz when using a 16 MHz system clock.

The problem is that one needs to be very careful when doing this, or else you can break all the other system timers, including the millis() and micros() functions. That’s why the Arduino libraries don’t expose any function to change the PWM frequencies. To change them, you have to go around the libraries and use bare C functions to set the timer configs.

[Regenerate3d]

Indeed you are correct. I can use a mosfett to control dimming via arduino pwm and put that in series for the bulbs and used arrays to switch bulbs on and off?

[tooki]

MOSFET not "mosfett". (It's short for Metal Oxide Semiconductor Field-Effect Transistor, that is, a FET made with MOS technology.)

You can either use N-channel MOSFETs, or individual BJTs, or a BJT array like the ULN chips shown above.

[Regenerate3d]

Excuses to spelling error. I'm currently using single sided copper pcb on cnc router but i cannot get free routing to only do single side auto routing! Any ideas?

[Benta]

0 ohm resistors. Or just a wire.