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I need to control 12V/10W led brightness by a pwm signal. I know I can do it with an arduino and some TIP120 or another power transistor, but the question is, is there another method to generate a 95% PWM pulse without the need of an Arduino? And maybe regulate the duty cycle with a rheostat?

I'm doing this because of the big ammount heat dissipated by the led

Thanks everybody

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  • \$\begingroup\$ Welcome to superuser. While we've been jokingly referred to as the ewok site in the past, that question is clearly and explicitly off topic. Maybe, just maybe if there's a computer involved it might be on topic. I've moved it to the appropriate site I think \$\endgroup\$ – Journeyman Geek Sep 25 '15 at 12:52
  • \$\begingroup\$ There are tons of ways to do this, e.g. by using two NE555, dedicated PWM chips etc. it is not really clear what you need \$\endgroup\$ – PlasmaHH Sep 25 '15 at 12:58
  • \$\begingroup\$ How about a 555? \$\endgroup\$ – copper.hat Sep 25 '15 at 15:59
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Running the LED with pulses instead of DC won't reduce the heat the LED generates at the same brightness. In fact, it will make that a little worse.

You can run the LED dimmer than full brightness using pulses, and have the LED dissipate less power than at full brightness. However, just switching between 1/2 on and 1/2 off will give you close to 50% brightness, but will cause the LED to dissipate a little more power than if it were run steadily at 50% current. That is because the voltage drop across the LED is a bit higher at full current than at half current.

To actually do the switching controlled by a digital logic signal, the easiest is to use a "logic FET" low side switch. Something like the IRLML2502 can be driven directly from a 3.3 V or 5 V logic signal on its gate. Ground the source, and connect the LED between 12 V power and the drain.

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Assuming you were going to use an Arduino Uno - see here for details https://www.arduino.cc/en/Main/arduinoBoardUno

You could use one of the 'PWM Digital I/O Pins' to generate a signal between 0 and 5V...

Let us call this your "control signal". You could then use this control signal with a transistor to drive an LED..

What kind of LED (specifically) are you trying to drive? If you provide the datasheet for the LED I think it will be much easier to help you out.

if the LED is 12 Volt (DC) and 10 Watt that implies a 1.2 Amp current!

If you are new to electronics - this is a good basic guide about LED control: https://learn.adafruit.com/all-about-leds/forward-voltage-and-kvl

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