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i want to control intensity of high brightness leds using microcontroller

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pranavshaw

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hey i want to control intensity of hb leds using pic18 with use of pwm and mosfet .......i m not getting the concept ....can anyone plz help to understand what exactly i need to do
 

To control the intensity of Light using microcontroller PWM, this is how it works. 0 to 255 means 0 to 5v, To have a PWM of 3v which is equal to 3/5 * 255 = 153 in digital so using mikroC library PWM is Function is already created.

PWM_SET_DUTY(153);
 

Simply - turn on/off LED via MOSFET using PWM. For current limit use resistor.
Advanced - make a boost converter with current backfeed connected to ADC. You will able to supply high voltage led chains with hiest efficency.
 

The concept is to run the LED at full current but for limited time. Instead of controlling the brightness by changing the current, you keep the current constant but flash the LED so rapidly that your vision can't see it, typically 200 times per second or faster. I normally use around 1,000 flashes per second for my applications. To change the brightness you keep the flash speed the same (the PWM frequency) but alter the duration of on time relative to off time (PWM duty cycle).

For example, if each PWM cycle lasted 1,000uS and it comprised 250uS with the current on and 750uS with the current off, the apparent brightness would be 25% of maximum. If it was 500uS on and 500uS off, th brightness would seem to be 50%.

Brian.
 
For controlling brightness of high voltage, PWM concept is used from the microcontroller.
If it is AC load then you have to go for triac, if it is DC load go with MOSFET.
 

thank you all ........can anyone recommend some book or link where i will be able to see how exactly pwm works for controlling intensity....n for practical purpose can anyone send me some proteus tutorial regarding this concept
 

hey thanks a lot .....can u send me some video where my i could clear my doubts abt pwm .....im using mplabide and c18compiler... i need to understand exact working of pwm ....so plz help me
 

can u send me c code for varying intensity using pwm for pic18f4550
 

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