To show you how to use the regular LED bulb, I've thrown together a quick fabric flower project, but there is no end to the ways you can use this technique. Here are the sewing supplies I used:
Pictured above: One pre-made fabric flower (you can make one or use whatever else you'd like), 4-ply conductive thread, needle, and two disks of fabric. One pretty, in case it peeps through the flower, one thick, to support the weight of the battery holder. If you have a thick fabric that will look nice peeking through, feel free to use only one disk!
You will also need a few small electronics pieces, of course.
Pictured above: 20mm coin cell battery, Super Bright Yellow LED (this can be any color or brightness of your choosing), 330 ohm resistor, and LilyPad coin cell battery holder.
First, you'll want to place the flower or object between the legs of the LED. This is also a good time to mark one leg, if you're not sure you'll remember which is positive and which is negative. If you look at the bottom of the LED, you should see that one side is flat - the leg on that side is negative. Feel free to mark it for reference later. If you're using a flower, or a similar piece, you'll want the positive leg on one side and the negative leg on the other. The fabric will insulate the legs from touching each other and shorting the circuit.
Next, place the disk of fabric that will go against the back of the flower- this will be the more decorative disk, as it will sometimes be partially visible. Press the center of the disk against the tips of the LED legs, then push them through the fabric. Push the fabric down until it is against the back of the flower.
Repeat this process with the second disk of fabric. If the disks line up poorly, you can trim them to match provided you have enough room left to accommodate the battery pack, resistor, and the light where it is without overlap.
Grasp one leg of the LED with a small pair of pliers. You'll want to be very gentle - the legs are delicate and can be snapped off by this process if you aren't careful. Holding the LED steady in your other hand, twist the pliers so that the leg wraps around them into a small loop. Keep twisting until the entire leg is part of this loop, and flush with your disk, then gently wiggle the pliers out of the loop.
Repeat this process with the second leg. When you have finished, both loops should lay flush against the back of the disks, and the top of the LED should still be pressed up against the flower. The LED will be holding everything together, so make sure things are secure now, and tighten if necessary.
Each LilyPad board has a tiny resistor built in. When using regular LEDs, you'll have to add your own resistors to the circuit, which means adapting them for sewing in the same manner you've adapted the LED. Grasp one end of your resistor in the pliers, and twist it, similar to the way you twisted the legs of the LED. This wire is thinner and easier to bend than the LED legs are, but are still delicate, so be careful.
Bend the second leg in the same manner, and make sure that both loops of wire are flat on the same side, so that it can be sewn down flush to the fabric.
The first thing you'll need to sew down is the battery pack. Sew both holes on the positive side down to the fabric, several stitches in each hole.
Place the resistor between the positive side of the battery pack and the positive end of the LED. When you're happy with the location, stitch from the positive side of the battery pack that you've just sewn down to the nearest end of the resistor. Knot your thread off and cut it, then restart stitching on the other side of the resistor. Connect this side to the positive leg of the LED.
Sew down the negative side of the battery pack the same way you did the positive side. Be careful - if the thread touches the tab between the two holes, it will short your circuit. Continue sewing from the battery pack to the negative side of the LED.
Your circuit should be completed. Insert your battery into the holder, and the LED should light up. If it doesn't, check your stitches to make sure that there's no point where the positive side and the negative side come into contact.
Congratulations! You can use this technique for any number of crafts that are better suited to a bulb shaped LED than a flat LilyPad LED. If you don't need to keep the LED legs out of view, you can always twist them up first, and then secure them to the fabric the way you did with the resistor.
Comments 7 comments
This is a great teaching project for circuits! I will be doing this in my classroom this year.
Oh, I'm so glad you like it! If you want to make it even a little easier and cheaper for the classroom, I've had great luck using small (4" or so) tissue paper flowers. Truthfully, in a lot of ways it works better than the fabric flower- fluffs up a little nicer and diffuses the light beautifully!
Here's a good tissue flower tutorial- http://kindawonderful.typepad.com/pink_paper_peppermints/2008/05/crafty-flowers.html
Dia, why do you need the resistor, i used some led's and i didn't add one of these and they lit up and how do i know what resistor to use when adding more LEDs? just want to learn. Thanks
Sorry I didn't see this sooner, but wm1995 is exactly right. To simplify further, your project very likely worked fine because you were working with conductive thread, which has a very high resistance compared to wire, and can often supply enough resistance all by itself. I usually use 330 ohm resistors because they are very easy to come by- I just keep one of these bags in my desk: http://www.sparkfun.com/products/10465
I apologise in advance if the following explanation is a bit simple, but I don't know what you do know and what you don't.
When using LEDs, you place a resistor in series with the LED to limit the current that can flow through the LED. This is because the LED has quite a low resistance and a maximum current. You can run LEDs without resistors, but they can get dangerously hot because you are allowing more current than the LED is designed to handle to flow. This is because the LED is dissipating more power (P = I x V, I is large therefore P will be large). If the voltage is high as well, then the power dissipation will be even larger, which could cause the LED to fail.
To calculate your own resistor for your LED, you need to know a few things first: the voltage that you are using to power the LED; the forward voltage drop of the LED (which can be found in the datasheet) and the maximum current through the LED (also found in the datasheet). You also need to know the formula R = V/I.
... Sorry, it cut me off.
For example, if the forward voltage drop of the LED is 2V, the power supply voltage is 5V, and the maximum current through the LED is 0.02A, the resistor is calculated as follows:
R = V / I
I = 0.02A (The resistor is in series with the LED and so the current through the LED will be equal to the current through the resistor)
V = 5V - 2V = 3V (The voltage across the resistor will be equal to the total voltage across the LED and the resistor less the forward voltage drop of the LED)
Therefore: R = 3V / 0.02A = 150 ohms
This means that a 150 ohm resistor is the minimum you ought to use in series with the LED. The life span of the LED may be extended if a larger value resistor is used. However, a larger value allows less current to flow, meaning that the LED is going to be dimmer.
To address your final concern about adding more LEDs: to put more LEDs in parallel with the current LEDs, put a resistor in series with each new LED.
Hope that helped.
very cool...thanks for the step by step video. I would like to try this on some ideas i have