Comments on: Driving an LED with or without a resistor

By: ameer.chandel

ameer.chandel — Wed, 18 Jan 2012 09:05:23 +0000

i want to operate led of 1 watt, but the input voltage is 55v, so which resistance can use to operate the led of 1 watt?

By: Mike

Mike — Thu, 17 Nov 2011 17:56:56 +0000

Here is a good video tutorial for beginners:
http://www.youtube.com/watch?v=B042Ow8hPdU

By: Michael Bruce

Michael Bruce — Mon, 31 Oct 2011 16:04:33 +0000

Why do so many people want to prove you don’t need a resistor. Isn’t it proven that mA is what matters. So resistor or not, as long as the mA is correct and thermal runway doesn’t become an issue then its all good.

What is the point of proving you don’t need a resistor? @Mike M

By: vicente

vicente — Wed, 12 Oct 2011 00:12:17 +0000

very interesting to read all post, I am new to electronic, it helps’ a lot for like me as DIY .
does the data of led is given ? (watts, volts, amperes) I like to try making led light for home used

thakn you all
vicente

By: Replacing flashlight bulbs with LEDs « Tomi Engdahl’s ePanorama blog

Replacing flashlight bulbs with LEDs « Tomi Engdahl’s ePanorama blog — Sun, 02 Oct 2011 07:38:10 +0000

[...] Driving an LED with or without a resistor article on the other hand says that if you are able to run your complete circuit with the same voltage as forward voltage of the LED, perfect. No resistor needed. If you try to run run a 3.2 /3.4 volt warm white of a 3 volt power supply, you will get light but not the maximum amount. But usually enough for small flashlight application anyways. I had even used this idea on my LED light ring for macro photography project, so I was pretty comfortable with this idea. [...]

By: Alex

Alex — Wed, 15 Jun 2011 06:49:46 +0000

Having the resistor in parallel does not work. It has to be in series with the LED.

By: ali

ali — Sun, 12 Jun 2011 07:44:34 +0000

m using 40 LED’s of white color on 12V battery with 750 ohm resistors attached in parallel, its working fine. Most of people say i should use 1k resistors. M nt gud in physics n math. Wat u people suggest ?

By: Donald

Donald — Sat, 04 Jun 2011 00:28:58 +0000

Let’s say I wanted to use LED’s to illuminate a clear trackball that is in my computer. The trackball connects to the computer via USB, which is a 5V dc connection. Theoreticly, If I create a parallel path off of the USB black and red wires, and connect three 1.5 V LED’s in series, is the total 4.5V circuit I create close enough to the 5V power to not need a current limiting resistor? Do you think there is a sufficient power margin in a USB device to drive both the trackball and the installed LED’s without damage to either the trackball or the computer?

By: Alex

Alex — Wed, 06 Apr 2011 16:26:15 +0000

You would need PWM to mix the colors (red, green, blue). So e.g. 90% red + 80 % green + 0 % blue gives some yellow.

By: Millideac

Millideac — Wed, 06 Apr 2011 08:00:29 +0000

I found it interesting especially for the explanation of why do we need a limiting resistor and the need of PWM.I also have a project on Adaptive color light,which senses an object color(with RGB led) and lights a bulb of the same color for instance if i approach a yellow object to the sensor,the color of a bulb will be also yellow. So, My question is do i need a PWM, since i thought pwm is only to change the brightness of a led,not changing of a color of a light.I will use an AVR ,atmega32 .So could you help me on this things. especially the power circuit,the use of pwm with my respect and led driver. Thanks in advance

Millideac