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Old 03-06-2010, 05:07 PM
SeeMyProfile SeeMyProfile is offline
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Question Power little LED with 110 Volt

Hello,

I'm 60 years old but never will be too old to learn.

I have a project where I'd like to use a small LED to indicate that there is power (110 volt AC).

The light and resistor would be encased in a plastic resin compound which would hinder the removal of heat from the resistor, if any. I don't want a huge resistor in the circuit, a little one would be fine.

Are there small LED's on the market designed for use at 110 Volt? If so, I can't find them.

Could I use a small resistor in line before the LED so this little 1.5 volt LED wouldn't burn out? Is that possible?

Sure could use some specific help here.

Robb in Grand Rapids, Michigan
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Old 03-06-2010, 05:51 PM
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beenthere beenthere is offline
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What is a better choice for a pilot lamp is a neon indicator - http://parts.digikey.com/1/parts/680...e-1033qd5.html

http://parts.digikey.com/1/parts/680...d-1031qd1.html

LED's are DC devices only, and used in low voltage applications.
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Old 03-07-2010, 01:39 PM
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+1 You can even get them at Radio Shack; they're replaceable if burned out, easy to wire up a socket...they have advantages over the LED.
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Old 03-07-2010, 03:59 PM
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Quote:
Originally Posted by SeeMyProfile View Post
Could I use a small resistor in line before the LED so this little 1.5 volt LED wouldn't burn out? Is that possible?
Yes, you can. But for AC usage a diode is required otherwise the LED will be damaged. Just about any diode like the 1N4148 can do.

Just use a resistor of 100KΩ in series(roughly 1KΩ per volt) with the LED and a small diode in parallel. You would need to use "high efficiency" LED for this to work.

So all together three components. As shown below.
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Last edited by bertus; 11-09-2013 at 07:57 PM. Reason: removed dangerous circuit that violates the ToS
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Old 04-08-2013, 02:06 AM
phillipbeynon phillipbeynon is offline
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The circuit can be very simple as there are several practical methods of design.

I would suggest an NPN FET in series with an LED and gated with a resistor. That is 3 components. Any led can be used here. the important part is the amperage. Most LEDs require 20mA DC. Start by using very high resistors between the gate and negative lead of the LED and work it down until your meter across the LED reads 20ma.
(Optional) Add a polar capacitor across the LED so it doesn't blink noticeably and 30hz
Two advantages of this circuit is that you are controlling the amperage not the voltage and using a FET which reduces heat and it works for nearly all LEDs.
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Old 04-08-2013, 02:10 AM
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Quote:
Originally Posted by phillipbeynon View Post
The circuit can be very simple as there are several practical methods of design.

I would suggest an NPN FET in series with an LED and gated with a resistor. That is 3 components. Any led can be used here. the important part is the amperage. Most LEDs require 20mA DC. Start by using very high resistors between the gate and negative lead of the LED and work it down until your meter across the LED reads 20ma.
(Optional) Add a polar capacitor across the LED so it doesn't blink noticeably and 30hz
Two advantages of this circuit is that you are controlling the amperage not the voltage and using a FET which reduces heat and it works for nearly all LEDs.


Why are you answering a thread that is three years old? Chances are the OP has solved the issue by now.
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Old 04-08-2013, 02:17 AM
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More importantly LED to mains is a restricted topic.
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Old 04-08-2013, 02:26 AM
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Hang on! This is a necropost, second one today.
Reported.
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Old 04-08-2013, 02:37 AM
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I have send the new user a PM, I am closing this thread since it violates our ToS.
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