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.
<p>160 in 1 manual (No copyright intended) just saying everything (well most) is very cool. </p><p>https://dl.dropboxusercontent.com/u/1687434/RadioShack%20160%20in%20One%20Electronic%20Project%20Kit.pdf</p>
<p>Link to the 60 in 1. </p><p>http://www.evg2000.com/Project%20Kit%20Manuals/60in128-256.pdf</p>
<p>This one has a LIE detector in it. It uses different types of transistors, relays, lights, etc.</p>
<p>Get the EP 130 in 1, 75 in 1, or the 60 in 1. They are very simple to understand and you learn about electronics, digitial circuits, etc.</p><p><iframe allowfullscreen="" frameborder="0" height="281" src="//www.youtube.com/embed/uz9w3rjVWqo" width="500"></iframe></p>
Is there anywhere online that helps teach how to /think/ in circuits for creating or problem solving?<br><br>Like, after someone knows what resistors and capacitors do, how does someone use that to dream up circuits?<br><br>My problem is that I can follow instructions and schematics easy, but I never have any clue how I would have come up with something like the simplest circuit on my own, much less how to come up with an original circuit purpose using a 555 timer.<br><br>And I get some of these simple circuits, and those with a 555 timer, have already been made the most efficient by Mims, etc, but how would one even get an original thought in the ballpark?<br><br>Is there anywhere that teaches how to think /in/ electronics, how to use electronics to solve simple problems? <br><br>Please and thank you!
<p>This was really helpful! I think I need to dive into a project to really grasp it though...</p><p><a href="http://amzn.to/2eefKw6" rel="nofollow">Would this be a good kit to help learn basic electronics?</a></p>
<p>so far helpful but a little cunfusing, i think ill get it</p>
<p>Is there a place where you would recommend getting a job lot of equpiment on the reasonably cheap?</p>
<p>What sort?</p>
<p>When you say ike, make this ciruit, but i dont have that many components to do any of it with. Where do you rekon that i can get a job lot from.(Young student so dont have much funds)</p>
<p>What <strong>types</strong> of components?</p>
<p>Thank you :)</p>
<p><strong>Why to reduce flow of current in circuit??</strong></p>
<p>When current flows through the circuit it carries some amount of heat that depends on its strength (i.e. amps.) Large current carries large amount of heat. Every component in the circuit carries designated limit of current that it can pass through, so that it should not burn due to excess heat causes due to current. Therefore, it is important to limit the current flowing in the circuit.</p>
<p><strong>The rate of reversal is measured in Hertz, which is the number of reversals per second. So, when they say that the US power supply is 60 Hz, what they mean is that it is reversing 120 times per second</strong></p><p><strong>How can calculate the number of reversing per second based on frequency, could you please explain it?? </strong></p>
I made the circuit but it's not giving me a high and low sound just a straight toned ring. What am I doing wrong?
<p>Nothing. You have done it right. It is the relationships between high 5V and low 0V that creates the ringing tone. The high and low voltages are not related to sound, but the shape of the electrical wave being created (on, off, on, off, etc ---__---__---__--- )<br><br> A tone is then created at the frequency of the square wave (the speed at which the signal is being turned on and off). You can increase and decrease the frequency of the tone, but you will still only have a single tone because you have only created one uniform square wave. </p>
<p>what do you mean by 'Ground'?</p>
<p>Ground is another name for the - (the opposite side of the +)</p>
<p>For any soon-to-be electronic enthusiasts, &quot;Arduino&quot; is something for you to look into.</p>
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?
<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
<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>
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>
i want to know how to design own circuit and own schematic how to choose write component and with value can u help me
&quot;by looking up their datasheets&quot;... you make it sound so simple. Lots of times I have tried to find datasheets on various components with no success. Either I can't find them at all or someone wants to charge me a fee (subscription/membership or one off extortionate charge or something) to download it. OR else there is no marking on the component to identify it, or lots of markings that can't be traced or whatever. <br> <br>To be constructive....maybe you could add some links to some suitable places to lookup datasheets if the manufacturer is no help or not available? Thanks. <br>
I do link to <a href="http://octopart.com">octopart.com</a>. I suppose I can link there more.<br /> <br /> I can't help that some components don't have easily attainable datasheets. Resolving that issue goes far beyond the scope of this Instructable.<br /> <br /> For most common components, you can find datasheets freely available in numerous locations.
<p>I know this is an old article but just now came upon it. Great info for the community! One small typo I noticed that could cause some confusion was on step 18 where you say &quot;I am using 293904 (NPN) and 2N3906 (PNP) transistors.&quot; Looks like a 9 snuck in there instead of the N :)</p><p>You mention Octopart for datasheet reference and they are a great resource... for an alternative I'd encourage you to check out USBid, we've recently combined ICPhotos and Smartdata so it's a good place to research part number, datasheets, and photos. Here is 2N3904 page -- <a href="http://www.usbid.com/parts/2N3904" rel="nofollow">http://www.usbid.com/parts/2N3904</a></p>
<p>You can also find a number of datasheets at <a href="http://componentsearch.com" rel="nofollow">componentsearch.com</a> if they can't be found on octopart.</p>
While it might go beyond basic electronics a ohm meter can be used to identify if a transistor in a NPN or PNP, and identify the leads. In the event one needs more data than that they should buy new transistors of known origin.<br><br> First make sure that in the ohms function that the leads for your multimeter have the negative on the negative lead, and the positive on the positive, there are meter that do not. In simple terms a transistor contains two diodes. Use the multimeter to map how the current flows through the transistor. In the event you have a multimeter that can test transistors you can use your new found knowledge about that transistor to test it's gain. Me I got lucky some years ago and bought a used BK precision transistor tester as a bargain. Hook up three leads and it tells me all I need to know.
Hi, yes I hadn't read the whole instructable when I posted the comment and saw your link in a later step, many thanks.
<p>I think yes, everybody should learn about basic electronics and I have <br>already learned from <a href="http://www.assignmentdone.co.uk/" rel="nofollow">assignment done</a> <br>something about the basic electronics.</p>
Very well documented and detailed.
<p>This is an excellent tutorial; it really helped me understand some basic elements of circuitry, a field which I've been hoping to take up for quite a while. Thank you! </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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