resistor for LED

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resistor for LED

Postby 1986lespaul » 01 Mar 2009, 01:39

So I am rehousing my Chicken Salad and am wondering what is a good resistor to put in series with the LED for the 3pdt switch?
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Re: resistor for LED

Postby IvIark » 01 Mar 2009, 02:46

It depends on the LED and how bright you want it. To work it out take the input voltage (9V I assume) take away the voltage drop across the LED and divide that by the current required. That'll give you a good figure to work with and you can experiment around it to get the brightness level you want.

You should be able to get the details required for the calc from the supplier.
Last edited by IvIark on 01 Mar 2009, 02:47, edited 1 time in total.
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Re: resistor for LED

Postby HydrozeenElectronics » 01 Mar 2009, 02:47

I use 4.7k's for super bright LEDS
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Re: resistor for LED

Postby 1986lespaul » 01 Mar 2009, 16:24

I did use 4.7k's but the LED burned out.
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Re: resistor for LED

Postby Fuzzer » 01 Mar 2009, 18:09

1986lespaul wrote:I did use 4.7k's but the LED burned out.


My friend, ¿Are you sure?, I find that really hard to believe.
The Freestompboxes Forum search function is soo great, use the search function..., the S E A R C H function.
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Re: resistor for LED

Postby Rocket Roll » 01 Mar 2009, 18:56

I use 22K with superbright LED's. Brings the shining down to "Boss levels" and preserves the battery.

I've tried 15K, but it's not enough. 4K7 with a 5mm LED makes for a great light show. :D
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Re: resistor for LED

Postby danielzink » 01 Mar 2009, 19:05

I've used 4k7's on all my CS rehouses - actually I use 4k7 on the majority of my builds (red and orange LED's).
Blue and white superbrights are really bright so I use 10k +....Greenand UV LED's take a lower resistance - 2k2, 2k7...

Funny - I've never had an LED burn out on any build (yet...knock on wood).

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Re: resistor for LED

Postby geiristudio » 09 Jan 2012, 22:36

I use 2k2 for all LEDs. The bright ones are pretty bright but people generally like it anyways! I might experiment with higher values.
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Re: resistor for LED

Postby Mungoo » 19 Mar 2012, 04:45

High-power LED's used for lighting (such as for the back-lighting of a cell phone display, or as replacements for standard light bulbs) are typically supplied from a switching power supply rather than regulated via resistors. The switching power supply will regulate the Connector / Power Wire LED Controllers LED Power Supplies current flow much more efficiently than a dropping resistor because it switches back and forth between full "on" and full "off" very rapidly, as in thousands of times per second. If the difference between the input voltage and the average output voltage is high, its output may go thru a small inductor to smooth the current before being applied to the LED.
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Re: resistor for LED

Postby robert8192 » 15 Apr 2012, 22:08

I was building a box for my new pedal and I thought..
what the heck- for the Led, I'll use a 1.6k resistor.
I've seen them with 220R, 820R, 2.2K and I figured .. 1.6K was average.
My pedal sounded busted, and the volume started out normal, then
faded away.

I learned you need to know the resistance of the Led, then go from there.
My led probably needed something around 5K... Oh Boy.. Be careful with
those leds.. they can mess you up man..
Can a Guru in this group provide us with some helpful tips on this?
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Re: resistor for LED

Postby PokeyPete » 16 Apr 2012, 04:42

robert8192 wrote:I was building a box for my new pedal and I thought..
what the heck- for the Led, I'll use a 1.6k resistor.
I've seen them with 220R, 820R, 2.2K and I figured .. 1.6K was average.
My pedal sounded busted, and the volume started out normal, then
faded away.

I learned you need to know the resistance of the Led, then go from there.
My led probably needed something around 5K... Oh Boy.. Be careful with
those leds.. they can mess you up man..
Can a Guru in this group provide us with some helpful tips on this?

IvIark has already told you the basics needed, but I'll try to help a little.

The primary stats on an LED datasheet that you would be interested in are the continuous forward current,
and the forward voltage. Most old time LEDs that I've seen and the newer superbright models use the same
20mA continuous forward current, while the forward voltage is typically 2V for the former and 3V - 3.4V for
the later. The 20mA continuous forward current tells us that we can safely select a resistor to control the
current to run at 20mA and not hurt the LED. Let's see how this plays out:

Regular LED, 2V at 20mA; 9V source, resistor ?
The LED drops 2V so the resistor will drop the other 7V. Using Ohm's Law:
E=IR......E/I=R......7/.020 = 350 ohms. Our resistor has to be at least 350 ohms to keep the LED within limits.

How about the superbright:
Let's assume an average forward voltage drop of 3.2V, the resistor will drop 5.8V.....
E/I=R......5.8/.020 = 290 ohms. Our resistor has to be at least 290 ohms to keep the LED within limits.

Increasing the resistance, decreases the forward current and brightness of the LED. 20mA is more than the
current consumption of many pedal circuits and is a drain on batteries, but not so much on a power supply.
Most people use higher resistance to lower the forward current so as to save the battery or to dim the light.
But as you can see, these "low" value resistors are quite adequate.

If the LEDs that you use has different specs than I've shown, just substitute the values and solve the same way.

NOTE: Some LEDs are static sensative and can be ruined by improper handling. These recommend the use
of antistatic wrist bands or other "proper" handling techniques.
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if he takes no other counsel than his own. He that is taught
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