I need to make circuit which can convert 5v to 12v. I searched this on google and found many amplifying IC but I my requirement is a bit different.
I need to control 100 leds with arduino. I am planning to connect 3 leds in a string so a total of 33 strings would make it complete. Now arduino pin can only supply 5v. I tried connecting 3 leds in series and gave them 5v with resistor of 100 ohm but they didn't glow. I tried reducing the resistance value but no effect. This is why I am looking for a circuit which can boost 5v to 12v. But as I have to give PWM pulses to these leds to control their brightness level so using any IC which will give fixed output of 12v will not be a proper solution for this. I want some circuit whose output 12v can vary according to the PWM.
analogWrite(PWMPIN, 254) --> 4.8v //Leds brightness full analogWrite(PWMPIN, 50) --> 1v //Leds brightness low
so the output voltage should vary according to the input.
Leds forward voltage is 2.2v with 20mA of current. I am connecting leds in this fashion:
Edit: I am sorry. I posted half of the question because I thought that would solve the problem. I am actually using 555 timer to control the blinking rate of the leds. I cannot write this inside arduino code because arduino is busy in doing other things which will be increase the delay in blinking & we cannot do multitasking. So I thought using 555 timer would be a great idea. Following is the schematic :
Earlier I was giving 12v instead of arduino pwm. But because I have to control the brightness level of leds so I connected this pin to the pwm pin of arduino. But as @dim suggested in comments that arduino cannot drive 100leds, is there any other solution for it.