davidbball13
Member
hey does anyone have a schematic for a 555 to pulse a LED meening to get brighter and then dimmer. i have looked around but i can find it.
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I'm not sure what you mean.
Do you want the LEDs to slowly fade on and off?
**broken link removed**
Using PWM the easyiest way of doing this is to build two schmitt trigger oscillators, 200Hz and 0.5Hz. Schmitt trigger oscillators produce a triangle waveform on the capacitor, if you connect comparator's + input to one capacito and the - input to the other, at the output you'll have a PWM waveform oscillating between 0% and 100% duty cycle at 0.5Hz.
If you wanted to use a PIC then perhaps you would have got more help if you posted this in the microcontrollers section.
the tital says "PWM with 555" not "PWM with a microcontroller"
the tital says "PWM with 555" not "PWM with a microcontroller"
Sure they are if you want to sit there with a pot doing the adjustment manually, and end up with an inaccurate, inconsistent result.
davidbbal13... Take everyone's advice and either do it with an opamp or a 12series pic... This forum is full of people who are quite knowledgeable, I myself have not reached this level yet, but don't discount their advice just because you are set on a 555.
Is this some form of assignment? That you are forced to utilise a 555 timer.
If you are set in your ways, look at **broken link removed** schematic. If you are just using 1LED you will not need the FET and related hardware down that end....
By its very nature, the 555 timer produces a pulse at its output, either astable or one-shot, depending on component structure. The voltage and current supply at the output is a function of the voltage used to power the device.
PMW (pulse width modulation) is the varying of the percent of on and off times of each pulse cycle. It has nothing to do with the original output values. Therefore, PMW in itself will have no effect on the brightness of a LED connected via current-limiting resistor to the output.
A quick way to see PMW in operation is to set up the 555 to produce a blinking LED with a frequency of some four or five flashes per second.
Then, connect the ends of a potentiometer to V+ and ground. Connect the wiper to pin 5 of the 555. You now have voltage controlled PMW. As you vary the pot, the LED will blink slower or faster, depending on the voltage supplied through the pot.
When the LED blinks slowly, it is because the high portion of the squarewave pulse is very narrow with respect to the off portion of the cycle. Conversely, the LED will blink faster when the on portion is greater (wider) than the off time.
Hope this answers some of your questions.
for the pot you can just do that with a pot for R1 or R 2 put i am sure i can do something with that.
yeah.......math
i need some new 9 volt batterys because all of my circuits are dim and quite