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LED Fade Circuit

LEDEnthusiast

Jan 27, 2016
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Jan 27, 2016
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Hello everyone, first post here. I've been interested in this subject for a while, but have never actually built anything on a PCB. That being said I'm not 100% familiar with it all, but not exactly a noob either.
Recently, I came up with the idea to construct a fade circuit for my truck's dash lighting. Simple premise, should be easily built. The idea is, you turn the dash lighting on and it comes on smoothly until it reaches full intensity. Turn the dash lighting off and it goes from full intensity fading down to off. I have LEDs installed in my dash, so I'll have to have PWM for this.
I'm thinking an NE555 timer would be the perfect heart of this project, the PWM signal generated by the NE555 controlling a transistor or mosphet of some description. As for the timing of the fade, I'm considering a potentiometer with a capacitor, the charging time for the capacitor ultimately controlling the duty cycle, in turn switching the mosphet or transistor rapidly until full brightness or completely off is achieved.

On youtube I found a PC fan controller circuit, made by GreatScott!, complete with schematic and all the parts listed. I figure if you switch around the potentiometer and add a capacitor in such a way for the charge rate to modify the duty cycle would suit fine.
So, I suppose I should ask the million dollar question. Would this actually work?
 

duke37

Jan 9, 2011
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Jan 9, 2011
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It depends on the current that the leds take but it may be possible to use a resistor and capacitor to give a slow rise and fall then, if the current is considerable, a voltage follower could be sufficient.

Thinking again! You need to control current not voltage.
 

LEDEnthusiast

Jan 27, 2016
2
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Jan 27, 2016
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Once I get done with installing new LEDs behind the dash and in my climate control system, I estimate there to be an absolute maximum load of 9 amps.
Digging through my parts, I found I have six p60nf06 n channel mosphets. These apparently can withstand 60 volts and 60 amps, which is way overkill for my purposes but a safety margin never hurts.
Most of the LEDs faded by this little setup would be RGB strips controlled by, well, a controller. I'm sure my controller wouldn't like being pulsed like that, so I'd be pulsing the output side.
Managed to dig up a datasheet for it. http://www.mouser.com/ds/2/389/CD00002318-250241.pdf
 

chopnhack

Apr 28, 2014
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Apr 28, 2014
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9 amps of LED lights? How did you come up with a max load of 9A?
 
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