Written for beginners by a beginner. This project is my first project using LEDs, and I have documented it to present it to the world. I mounted two green LEDs in a sign that I could hang in my bathroom to solve certain...ahem..."problems."

## Step 1: Materials

This is the list of parts I used in my project. All electronic parts were bought from Radioshack. If you can stand to wait, order some parts online. Radioshack has an absurd markup price. I went there because I'm an impatient teenager, and I wanted to do the project NOW. I am using a potentiometer because i wanted to be able to dim the LED, and a switch to turn it on and off.

-A two pack of green LEDs (part number 276-304)
-a SPST (single pole, single throw) toggle switch (part number 275-612)
-a 10 ohm resistor. I just had this lying around.
-3 AA batteries
-a 5K audiotaper Potentiometer (part number 271-1720)
-random pieces of wire that I had lying around.
-an "aquired" sign.
-a soldering iron

## Step 2: Drilling

Step one is to drill holes for the switch and the dimmer pot. 1/4" for the switch, and 5/16" for the pot.

## Step 3: Making the Battery Pack

I forgot to buy a battery holder, so insead of having to drive back to Radioshack to buy one, I just soldered three batteries together and duct taped them together. If you feel like it though, go ahead and buy a holder, and skip this step.

This is simple, just solder the "+" end of the battery to the "-" end of the other. It should be labeled on the battery which end is which, but if not, the flat end is the negative side, and the side with the little bump is the positive end.

## Step 4: OH NO, MATH!!!

Ok, now the boring part. LEDs are very sensitive to the amount of electicity flowing through them, and as such, we have to make sure the amount that is going into them is the specified amount. If we look on the package, we see that they require 2.1 volts, and they draw 30 milliamps. Now, because we are wiring the LEDs end to end, they are "in series," which means that their required voltage adds. SO, running two LEDs that require 2.1 volts means that you need at least 4.2 volts of power to run them. This is why we used three batteries (each battey is 1.5 volts...1.5 x 3 = 4.5 volts). Now, 4.5 volts IS pretty close to the required voltage of 4.2, but we dont want to take any chances of burning out the LEDs, so we have to use a resistor, which limits the amount of electricity going to the LEDs. So all we have to do, is figure out what kind of resistor we need. You CAN do the math to figure it out, using OHM's law, and I recommend that you a least understand the concept behind it, but luckily for us, there are tons of LED calculators on the internet. I used the one at http://metku.net/index.html?sect=view&n=1&path=mods/ledcalc/index_eng. So, in the "series" section of the page, we put in a supply voltage of 4.5 volts, a voltage drop of 2.1 (the required voltage of the LEDs) and the desired current of 30 milliamps. After hitting calculate, we find that the required resistance is 10 OHMs.

## Step 5: More LED Requirements

another little quirk about LEDs is that they are directional, meaning that they only allow electricity to go one way. So we have to be sure that the current is flowing in the right direction. When the LEDs come out of the pack, the longer leg is the positive side. But, we can also figure out which side is which by looking at the LED close up. the bigger side is "-", and the smaller side is "+". (see notes on picture)

## Step 6: Mounting the Hardware

mount the pot and the switch, and affix the battery pack to the sign (I used superglue)

## Step 7: Its All About the Connections

run the wire from the positive terminal of the battery pack to one of the metal posts on the switch (it doesnt matter which one) and solder it there.

## Step 8: More Connections

now, solder a length of wire from the other post on the switch to the middle post of the potentiometer. After that, solder the resistor to one of the other posts of the potentiometer, and to the "+" lead of the first LED.

## Step 9: Closing It Up.

next, solder a length of wire from the "-" lead of the 1st LED, to the "+" lead of the 2nd LED. Finally, solder anothe wire from the "-" lead of the 2nd LED to the "-" terminal of the battery pack. Now your done!

## Step 10: Add a Knob for Looks, and Enjoy!

Cut off part of the potentiometer shaft (I used a dremel), and throw a knob of some kind on there. You dont even have to, it just makes it look nice.
Where did you get the knob? RadioShack?
Why do you have a potentiometer?
potentiometer is used to increase or decrease the light of LED
o. :D
Guys take it easy, It's true, in Technical University they told us that is dangerous to solder on batteries. But I did it so many times I forgot the number. Iam 42 and I am doing this for 22 years. Nothing happened ever to me or any other technician I know. The secret it's one....Yes you can solder on batteries, but very quick and shortly.
Ive done it too but anyone is skeptical they can just buy a batery holder or tear one out of a broken toy.
mst u guys r lucky i cant buy LEDs
Why Not???
i checked all the hobbie shops and nothin i dont no where else to check u got any ideas
Might find some in the dump or on junk by the wayside if all else fails.
Okay,<br/>If you have a Paypal, you can order of the internet from one of the two stores:<br/><br/><a rel="nofollow" href="http://www.radioshack.com/search/index.jsp?kwCatId=&amp;kw=led&amp;origkw=LED%20&amp;sr=1">http://www.radioshack.com/search/index.jsp?kwCatId=&amp;kw=led&amp;origkw=LED%20&amp;sr=1</a><br/><br/><a rel="nofollow" href="http://www.sparkfun.com/commerce/categories.php?cPath=51_89">http://www.sparkfun.com/commerce/categories.php?cPath=51_89</a><br/><br/>If you have a Radio Shack near you, you should go there, here is a store Locater:<br/><br/><a rel="nofollow" href="http://www.radioshack.com/storeLocator3/index.jsp?clickid=rsk_header_storeLocator">http://www.radioshack.com/storeLocator3/index.jsp?clickid=rsk_header_storeLocator</a><br/><br/>I Hope I helped.<br/><br/>~Alex<br/>
Please note: soldering to a battery is an excellent way to heat up and potentially cause an explosion. It is best to use electrical tape or some other adhesive rather than solder directly to a battery terminal. Be Safe rather than Sorry and covered in an acidic mess!
w00t acidic messes :D ugh not fun to get Battery acid in your eyes o.o<br />
yeahhhh... its not really a good idea to solder to a bettery...
why would you need a pot for this circuit? I don't see a need for dimming the leds
Code for falstad circuit simulator (http://www.falstad.com/circuit/):<br/>\$ 1 5.0E-6 382.76258214399064 50 5.0 50<br/>v 336 272 336 256 0 0 40.0 1.5 0.0 0.0 0.5<br/>v 336 256 336 240 0 0 40.0 1.5 0.0 0.0 0.5<br/>v 336 240 336 224 0 0 40.0 1.5 0.0 0.0 0.5<br/>s 336 224 336 176 0 0 false<br/>174 368 160 304 160 0 5000.0 0.9950000000000001 Pot. Position<br/>r 304 160 240 160 0 10.0<br/>162 240 160 240 224 1 2.1024259 0.0 1.0 0.0<br/>162 240 224 240 288 1 2.1024259 0.0 1.0 0.0<br/>w 240 288 336 288 0<br/>w 336 288 336 272 0<br/>o 5 64 0 35 0.3125 0.025 0 -1<br/>
Yeah REALLY BAD IDEA to solder battery or any other kind of engery sources.
Thanks for making this tutorial. I didn't know where to look to start learning this and everything seems so advanced. I plan on putting some LEDs on one of my art pieces and i needed it to blink so I will go slow and keep up with your lessons. :) thanks much
either i'm now thinkin today or i'm right because i'm pretty sure there is no such thing and no reason as a 10 ohm resistor
nice im gonna try something like that
is the potentiometer is only for the look?I don't understand
Close, the knob is for looks, the pentiometer is a variable resistor that makes the LEDs brighter or dimmer.
Nice, thank you!
You're welcome.
Flushing? *Pshaw*
Why not use a pizeo transducer to pick up on the loud flush, and then shut off after that? Simple flip-flop chip should do the job!
nice idea! I think it would be mroe affective to use a switch inside the toilet on the flushing handle tho (be sure not to get it wet)
here's the new url:<br/><a rel="nofollow" href="http://metku.net/index.html?path=mods/ledcalc/index_eng">http://metku.net/index.html?path=mods/ledcalc/index_eng</a><br/>
sorry to tell you this but the link that you posted has changed and that page does not exist anymore so you should think about changing it
Very nice site!<br/><a rel="nofollow" href="http://www.eefl.cn">http://www.eefl.cn</a><br/><a rel="nofollow" href="http://www.cn-ovl.com">http://www.cn-ovl.com</a><br/><a rel="nofollow" href="http://www.slim-lightbox.com">http://www.slim-lightbox.com</a><br/><a rel="nofollow" href="http://www.rondeflower.com">http://www.rondeflower.com</a><br/>OVL-Good ccfl,eefl, ccfl ring, ccfl PC kits, sound controller, Lightbox, El-panel, Backlight materials inverter supplier<br/>
I like your LED project. May I suggest that you add aschematic diagram. As a beginner in electronics you could learn much by drawing one. Great stuff...... richjd
Personally, I think a 12v inverter (as used in a CCFL) connected to the metal urinal and step would negate the need for a LED. The audible signal could be heard for many kilometers :P 'Scuze my dry sense of humour. It's an Aussie thing ;) Great post ! - eight
Simple! But thats because you did an awesome job on the instructions. GREAT JOB. I wish only a few of the adults on the Corvette Site I belong to could explain things as clearly and completely as you have done. I really like the idea one guy had of adding a motion detector to trigger the Flush lights - now how about one for put the g---damned seat up!! and Wash your hands. The only problem I see is naming your yacht after you have made a fortune selling these things restaurants and other public bathrooms.
If the wires from the switch (each post I mean) are touching eachother will the switch become useless? If so, is it possible to completely just get rid of the switch and just use the potentiometer? I would try it myself, but I just completed the project and I basically have a crap load of electrical tape everywhere (I didn't try soldering because I suck at it) and I want to make sure it would work that way if I did it.
how come when figuring out which resistor you need and you used the led caculator you said you nedded a volate drop to 2.1 I though you only neede a voltage drop to 4.2 because there are 2 led's
Sweet sauce! I just finished making mine. This is my first soldering project. Thanks much for the directions and idea!
Thanks for the info on the calculator. I have wanted to "play" with LEDs for a while but that math piece was getting in the way. With this information in hand I think I can do it. Thanks again!
great instructable and for a beginner like me I think I can follow this one!<br/>AND you made the MAKE blog!<br/><a rel="nofollow" href="http://www.makezine.com/blog/archive/2006/04/led_beginner_project.html">http://www.makezine.com/blog/archive/2006/04/led_beginner_project.html</a><br/>Thanks for posting<br/>Cyen<br/><a rel="nofollow" href="http://cyenobite.blogspot.com">http://cyenobite.blogspot.com</a><br/>
thanks for the correction Invisible!
I'm a reeeeeel beginner at this electronics stuff. so a simple project like this helps me learn a lot. Thanx a bunch.
Put a timer and a motion detector on instead of a switch -- now that would be freaky! ;-) This is a good intro to show how to add LEDs to projects! Keep up the instructables! -Matt
SPST = Single Pole Single Throw<br/>SPDT = Single Pole Double Throw<br/>;)<br/>
THAT IS SOOOO SWEET! I mean... an LED "please flush" sign is SWEET, but with a DIMMER SWITCH?... that's freaking AWESOME! Love ya Will. -Phil