Originally posted by ineedhelp@Mar 3 2006, 09:45 AM
i want to make a led fade in and out how would i do this ?
[post=14570]Quoted post[/post]
The SOURCE in the above drawing, by the previous poster, could also be a pulse width modulated (PWM)signal. With a very narrow positve going pulse, the LED would be off most of the time. As you increase the duty cycle(ratio of on time to off time) the average voltage of the on and off periods will approach the threshold of the LED and it will begin to glow dimly. As the duty cycle continues to increase the LED gets brighter until the duty cycle is 100% and the LED is on all the time. The basic frequency of the PWM should be in the 500Hz to 3kHz range, but the rate at which you increase and decrese the duty cycle will be much slower in the 0.25 to 10 Hz range.Originally posted by jatulm@Mar 3 2006, 11:00 AM
SOURCE ----> /\/\/\/\/\ - -D|------ GND
where /\/\/\ is the resistor and -D| is the LED (long life to ASCII drawing heh)
[post=14571]Quoted post[/post]
Quite correct. The original question was an open ended, "how would I do this" sort of question with no criteria for evaluating solutions. In the interest of completeness I advanced an alternative. It is up to the original questioner to evaluate the alternatives for his particular situation about which we know very little, or refine his requirements.Originally posted by Mazaag@Mar 3 2006, 03:38 PM
Bout the PWM, if you want it to happen automatically, then you need something ( like a microcontroller probably) that will change the duty cycle of the pulses automatically.
[post=14581]Quoted post[/post]
If you just want to make a LED dim at the twiddle of a knob. then here's a simple variable mark/space ratio generator built with a 555 timer.Originally posted by ineedhelp@Mar 3 2006, 02:45 PM
i want to make a led fade in and out how would i do this ?
[post=14570]Quoted post[/post]
Microcontroller????? What ever happened to the humble 555?Originally posted by Mazaag@Mar 4 2006, 06:38 AM
Bout the PWM, if you want it to happen automatically, then you need something ( like a microcontroller probably) that will change the duty cycle of the pulses automatically.
[post=14581]Quoted post[/post]
But the circuit IS an oscillator. The output is a square wave with a variable mark/space ratio - PWM if you like.Originally posted by thingmaker3@Mar 5 2006, 05:57 AM
In Pebe's drawing, one could substitute an oscillator for P1. Sawtooth or sine-wave would make for fade-in & fade-out.
[post=14676]Quoted post[/post]
Originally posted by windoze killa@Mar 3 2006, 07:17 PM
Microcontroller????? What ever happened to the humble 555?
[post=14612]Quoted post[/post]
by Duane Benson
by Duane Benson
by Duane Benson
by Jake Hertz