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Step 12: LEDs

LED stands for light emitting diode. It is basically a special type of diode that lights up when electricity passes through it. Like all diodes, the LED is polarized and electricity is only intended to pass through in one direction.

There are typically two indicators to let you know what direction electricity will pass through and LED. The first indicator that the LED will have a longer positive lead (anode) and a shorter ground lead (cathode). The other indicator is a flat notch on the side of the LED to indicate the positive (anode) lead. Keep in mind that not all LEDs have this indication notch (or that it is sometimes wrong).

Like all diodes, LEDs create a voltage drop in the circuit, but typically do not add much resistance. In order to prevent the circuit from shorting, you need to add a resistor in series. To figure out how large of a resistor you need for optimum intensity, you can use this online LED calculator to figure out how much resistance is needed for a single LED. It is often good practice to use a resistor that is slightly larger in the value than what is returned by calculator.

You may be tempted to wire LEDs in series, but keep in mind that each consecutive LED will result in a voltage drop until finally there is not enough power left to keep them lit. As such, it is ideal to light up multiple LEDs by wiring them in parallel. However, you need to make certain that all of the LEDs have the same power rating before you do this (different colors often are rated differently).

LEDs will show up in a schematic as a diode symbol with lightning bolts coming off of it, to indicate that it is a glowing diode.
I'm starting out in electronics and on a schematic when a wire seems to split off two ways on a right angle that just means it is connected to both of those components correct?
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<p>Hi !</p><p>I am vinay and I want to enlighten a 12 LED by the battery of my bajaj caliber 115 motorcycle, I want to know how can I use CD 7812 voltage regulator to get a constant 12 V DC while the bike is running ( when it will produce around 14.5 V).</p>
when you say ground do you mean negative<br>
Expertman, In early Electronics, ask about anything that you feel uncertain about. Its a &quot;grey&quot; area, an important question. In response, &quot;Ground&quot; and &quot;Negative&quot; are used with the same intent.They refer to the &quot;polarity&quot; of the power supply(Battery in this case) and where the 'pin' of a component's intended destination is(These components are usually labeled with this, if necessary) if unsure, find it online-(Not in a 'Blog', use 'DIGIKEY') Great prices, too!<br>. Good luck, hope this helped!
<p>i guess in both images,, wires are connected in parallel...</p>
i've been looking for this all over the endless fields of the internet. so, just tanks a lot
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<p>apt site for beginners</p>
<p>This was very educational and informative for me thanks</p>
<p><strong>nice site for beginners as well as professionals</strong>.</p>
<p>Michael U.</p><p>Thanks alot for this tutorial, it is so rich</p>
<p>Hi,<br><br>Thank you so much for this tutorial.<br><br>FYI , on step12 (ie LED) you mentioned that the flat notch indicator is on anode end , but its on cathode end of the LED. Please check it.<br><br>Thanks.</p>
<p>Thanks for this tutorial!<br><br>For all electronic fans, I made a site about basic stuctures used in analog electronic:<br><br><a href="http://shematronic.ddns.net" rel="nofollow">http://shematronic.ddns.net</a></p>
<p>I appreciate this tutorial. However, where can I go, not to find circuits, but more specifics on how circuits work. I can understand how the first circuit works , sort of understand how and why the second circuit works, and am more lost on the third one. I'd like more of an explanation on why resistors and capacitors are used in specific situations. Any suggestions?</p>
<p>For the &quot;Your second circuit&quot; section, is it 2N3906 PNP and 2N3904 NPN or should the PNP and NPN be switched? The parts list does not match the image of the circuit. </p><p>I'm a beginner, and I want to make sure I use the correct parts.</p><p>Thanks</p>
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thanks... good for start<br>
<p>Thanks, this was exactly what I needed. A nice improvement would have been to explain why each element was on the circuit, instead this feels like you just follow instructions without knowing what you are doing. But once again, it's a perfect introduction to ultra beginners like me.</p>
You should tell that where to put transistor, capacitor and others. Whether it will be in series or parallel and why ? Effect of adding or removing a component on the circuit And how someone can build thier own circuit?
<p>Wow! Thanks so much for this post. I am new to circuits and am taking automotive mechanics so this has really helped me understand the fundamentals of circuits in cars and in all other technology too. I look forward to putting it all together. Thanks again and keep up the good work.</p>

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Bio: My name is Randy and I founded the Instructables Design Studio. I'm also the author of the books 'Simple Bots,' and '62 Projects to ... More »
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