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Led control through port

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I have written a program for pic controller. The program has two conditions. In condition 1 I power on the led continuously and in condition 2 i blink the led with some delay. I found that if i switch on continuously the intensity is very less whereas while toggling the intensity is more. Why this is happening?
 

Dr_Doggy

Well-Known Member
usually it is the other way around, I am suspicious that you are witnessing an optical illusion where your eyes arn't adjusted to the light when it turns on so it seems brighter
 
Can you just tell me is it possible that suppose i have 20 outputs can i connect 20 leds. I mean to is it possible to drive 20 leds? How to know what is the limit?
 
Yes I am using a resistor of 1K with the LED and the supply voltage is 5V. Right now i am driving 2 LEDs with two different ports.
 

Nigel Goodwin

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Can you just tell me is it possible that suppose i have 20 outputs can i connect 20 leds. I mean to is it possible to drive 20 leds? How to know what is the limit?
If you check my tutorials I feed 64 (multiplexed) LED's from a single PIC - and an earlier tutorial feeds 8, one for each pin on the port.
 

atferrari

Well-Known Member
Look for the total power the PIC in question can supply. All what I've checked have it lower than sum of all individual values for each pin.
 

atferrari

Well-Known Member
I have written a program for pic controller. The program has two conditions. In condition 1 I power on the led continuously and in condition 2 i blink the led with some delay. I found that if i switch on continuously the intensity is very less whereas while toggling the intensity is more. Why this is happening?
Sorry for the question but are you sure you aren't confusing both conditions? Just in case, double the OFF period of the blinking and check again.
 

Ian Rogers

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Yes I am using a resistor of 1K with the LED and the supply voltage is 5V. Right now i am driving 2 LEDs with two different ports.
I should imagine it's an optical illusion... 1k resistor LED and 5v rail... 3mA will just light the led, so the continuous LED will appear dim, whereas the pulsed LED (depending on frequency ) will alert your eye to the LED more..
 

ronsimpson

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Are you certain the 5V supply is stable. Not dropping down to 4V when the LEDs are on 100% of the time.
 
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