LED Fader using LM358

This is a video of a LM358 dual op-amp being used to fade an LED on and then fade it back off. The circuit creates a triangle wave that is used to turn a NPN transistor on and off which drives the LED. The circuit is running off a 9 volt battery and draws only around 10-15 ma when the LED is at full brightness. Although the LED appears in the video to flicker it reality it doesn't it's just the camera trying to adjust the brightness because of how bright the LED is.

If you want schematics first try google but if you PM me and give me your email I can also send you schematics and component values that I used.
Enjoy!

Category:

Science & Technology

Tags:

• LED
• fader
• triangle
• wave
• LM358
• lm3
• op
• amp
• op-amp
• electronics
• circuit
• fading

[slightlydrybeans]

This would be possible without the cap right? I could use a pot instead?

[Sparrow338]

@slightlydrybeans: The capacitor is necessary for this circuit to work and it could not be replaced by a resistor. It isn't actually possible to ever replace a capacitor with a resistor or potentiometer (aka variable resistor). However if you replaced the fix capacitor with a variable capacitor this would work. But variable capacitors with values high enough for this circuit would be likely big and unpractical.

[julieail]

so is this a sine wave?

[Sparrow338]

@julieail: It's actually a pure triangle wave. Although a sine wave would give a similar, if not identical, effect. This circuit setup is capable of making a sine wave though.

[julieail]

@Sparrow338 can it run off of a 9v battery?

[Sparrow338]

@julieail: Yes it can run from a 9volt (it's running from one in this video). The LM358 IC is good from around 3-35volts. I think in this set up it begins to stop oscillating around 5 volts and is good up to 35volts. Make sure you use the correct resistor in series with your LED/load.

-Sparrow

[robbe8282]

@robbe8282 i'll be running 12v, it's going to be inside a pc.

[rockervampires]

I like the video! Please sendme the schematic rockervampires@hotmail.com

[Phonexdevendra]

My email is devendra.sawant@ymail.com

please send me circuit diagram

[mat2dong]

Email is mat2dong(at)yahoo.com

[mat2dong]

Wow!! Great job:) Can you send it to me please? My son would love to do this with me!

Is there a way to randomize when the light comes on and can you hook up more then one LED and have them all come on at random times all fading in and out? Like fireflies:)

[arrosyiid]

I would like to have a copy of the circuit..and im planning to do up this circuit for my motorcycle with some led strips bought from ebay.As the strips are already installed with resistors,do i need to modify the circuit?

nur_hakam@msn.com

Thanks a million :)

[administrator1112]

How to speed up the frequency , I need it to light up more faster and turn off .. but I don't want to change the capacitor , can I just change the resister value to get a faster effect ( using a variable resister ) ? and which resister to change ... ( I need it to operate normal speed just like in your circuit to about 100 cycles / second

[dkturner10]

I would like to have a copy of your schematic as well if possible. Thanks!

turnerda@comcast.net