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### Author Topic: PWM led driver for 60 3mm led or 3528 smd leds 17.5 to 9v output led array  (Read 5075 times)

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#### dhandrei

• Posts: 1
##### PWM led driver for 60 3mm led or 3528 smd leds 17.5 to 9v output led array
« on: June 15, 2016, 05:19:30 AM »
Hello for all!!!

Dear,
I need to do a PWM led driver controller for a led array with 43 blue led and 13 3mm red led in the same pcb.
I found millions of circuit about this on the word wide web, but I'm not technician, I'm a electronic enthusiast, in this forum I found this led driver http://www.pcbheaven.com/circuitpages/LED_PWM_Dimmer/
The problem is that my car use 15.5v when the engine is off and 17.5v when the engine is on.
I wish make this pwm circuit for my AC Commander with and without dimmer (trimpot) in separated pcb, for this PCB I will need 43 leds 3mm, 20mA 3.3v and 13 red leds 3mm 20mA 2.2v or 3528 smd led.
In the CircuitWizard I made this circuit, but the voltage of the 555 output pin is 17.5v and this voltage are going direct to the leds array. What is the component I can replace to send 9v to the led array?

Some one can help me?

I made this circuit, is correct?

for the only PWM what I need remove and replace?

Thanks to all, for the help

#### kam

• Hero Member
• Posts: 1849
##### Re: PWM led driver for 60 3mm led or 3528 smd leds 17.5 to 9v output led array
« Reply #1 on: June 25, 2016, 13:01:29 PM »
Hello,
as far as i can tell, what you need is a way to drop your car's voltage down to 12V. the 555 cannot operate at higher than 15V.
So, I suggest that you use the 7812 IC. It can provide up to 1A of current (with a good heat sink) which is perfect for you since your LED strips will draw as much as 420mA. use this chip to get the 12V and then get all the +V of the circuit out of this chip instead of your bat.
A plus is that the brightness of the LEDs and the current will always remain stable since the chip will always provide 12V regardless of the car's voltage.
Remember to use a good heatsink for the 7812 as it may be required to dissipate as much as 3 Watts of heat

at 600mA current and 17V input voltage it is
(17-12) X 0.6 = 3Watt