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# LED in parallel to power? Answered

I have a project and i am wondering if you can hook up a diode to the power source (hook it up in parallel to it) would you have to hook it to ground in some way??

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## 11 Replies

Power dissipation = current x voiltage drop. Thus 2v x 0.02 A ... or 40mW.....
HTH
Steve

astroboy907 (author)2010-05-17

To All,
Here is a (simple) schematic i made of it. It is for a small dc to dc power converter (similar to mintyboost). I wanted to have an led to tell weather it was on or off. It is a 603 SMD led, with a resistor (which should be somewhere around 100 ohms) would i have to get a high wattage resistor? or because it is in parallel could it be smaller? I am also a little confused about how to wire it (see schematic)

steveastrouk (author)2010-05-17

We need to know the supply voltage, and the LED type to comment further.

Steve

astroboy907 (author)2010-05-17

The led is a 0603 SMD LED, and the resistor is also 0603. Both can be changed if necessary.

steveastrouk (author)2010-05-18

The "Or this" diagram will work. The first is completely redundant, because you have shorted out all your circuit !

astroboy907 (author)2010-05-20

k :)
Thanks! I just have 1 more question, should i get a 2.5 (or greater) wattage resistor? just in case. oh + if you were wondering i switched all my parts to non SMT :)
Also, will there be any significant power loss??

steveastrouk (author)2010-05-20

Power dissipation = current x voiltage drop. Thus 2v x 0.02 A ... or 40mW.....

Steve

astroboy907 (author)2010-05-20

can you post this as an answer?, then i will pick u as best

If you're talking about a low voltage DC power source, it needs to have a resistor in series with the LED.  There's a calculator for the value HERE.
If it's a normal LED, enter 20mA for the current, and the forward voltage should be written on the pack they came in or in the advert you bought them from - If not, use 2V.
If you want to connect to AC or to over 12V then things are a little more complicated - Let us know the details.

steveastrouk (author)2010-05-16

HAVE to have a resistor with it.

Steve

Re-design (author)2010-05-16

Ground is just another name for NEGATIVE (usually).  So just hook that led up to the pos and the neg with any required resistor and away you go.