Hi
After some research about electronics projects for beginners, I decided to have a try designing a RGB LED driver circuit.
Heres my rough schematic:


https://ibb.co/dTgUtS

I would like to control the color of the LEDs and their brightness. Because the LEDs have common cathodes, i found a constant current load circuit based on LM339 OpAmp IC. My desire is to feed up to 25mA per single diode of every colour so around 750mA on full brightness on every colour.

Question 1:
Does it even have any chance to work?

Question 2:
Can it run on a 9V battery? If not on single one then on two in parallel?

Quesrtion 3 (if question 1 has a positive answer):
Would it be better to change the MOSFET on the NE555 to N-channel one and repurpose it to pull the OpAmps to ground rather than feed PWM to 5V voltage stabilizer ?

Thanks for the answers and sorry for my severe stupidity if that is the case


Mod's Note:
Please upload your circuit to our forum.

 

Short answer NO, it wont work.

You can ditch the regulator and use pwm on the Common Anode, and use current control on each Cathodes..
Also your 555 is wired wrong pins 2,6 need to be linked together.

 

From 9V battery you can light only 2 blue LED in series, not more (3.3V for each LED).
If max current for each LED is 25 mA, all LEDs will consume 75 mA from battery, not 750mA.

 

If those LEDs are RGB, they should be connected in parallel, through resistors.
3 separate PWM may be used in Blue, Green and Red lines.
See https://forum.allaboutcircuits.com/threads/rgb-led-current-question.34178/

 

Ahh i completly forgot that the forward voltage of diodes in series increases...
After considering things, i thought that it will be better to power this circuit with a 5V wall adapter.
Thanks for reminging me of these important aspects

One more question:
How to increase the frequency of the PWM singnal from the NE555? At the moment it hums quite loudly at duty cycle between 20-80%.

 

How to increase the frequency of the PWM singnal from the NE555? At the moment it hums quite loudly at duty cycle between 20-80%.

Decreasing value of capacitor, connected between pins 2,6 and pin 1 of NE555 will increase frequency of PWM.