LED Beginner Project: Part 2





Introduction: LED Beginner Project: Part 2

About: Lets make something

This project was my next step in my exploration of the world of LEDs. Here, I will show how to wire LEDs in parallel in order to make a simple bike light. Wiring LEDs in parallel is useful in that you can run multiple LEDs off of a single, low-voltage source.

Step 1: Materials and Such.

I've always been looking for a reason to use an Altoids tin as a project box, and this project seemed to be it.

- Altoids tin
- 2 AAA battery holder from Radioshack.
- three way toggle switch that I scavenged. I used a three-way switch becuase I plan on eventually adding a circuit that will make the light have a blinking mode. If you don't care to add this extra complexity to the light, just buy a simple SPST on-off switch.
- three white, 3V LEDs given to me by a friend.

In my previous Instructable, I explained how LEDs need to have resistors wired in series with them to keep them from blowing out. In this case, I didn't need resistors, because the supply voltage was exactly 3V and the requirement was 3V. If you are using LEDs with a lower voltage requirement, you will need to add in a resistor to keep them from burning up.

Step 2: Why Parallel Is Awesome.

Wiring LEDs in parallel opens up new ways of using them. In my last instructable, we saw that LEDs wired in series have their voltage requirement add up. This is acceptable if we are using a small amount of LEDs, becuase it ensures that each LED is at its maximum brightness, but as we start adding more lights on, we find a need for higher and higher voltages...imagine if you wanted to run twenty 3V LEDs in series...you would need to have 40 AA batteries to power it!! Wiring in parallel means that the voltages do not add up...the same voltage goes to all the LEDs. This means that we could run those same twenty 3V LEDs off of two AA batteries instead of 40. The trade off is that those two batteries will be drained much faster, and the LEDs will not be at their maximum brightness. But, for all practical reasons, if you want to have a portable multi-LED light, you're going to have to wire them in parallel.

Step 3: Preparing the Altoids Tin.

Plan out how you want the LED arranged. I chose a simple straight line in order to make it clearer how they are wired together, but you can do it whatever way you want to!

Step 4: Clip the LEDs

Next, we clip the legs of the LEDs shorter so that they dont stick out all over the place inside the tin. When you clip them, make the positive leg longer than the negative leg. If you dont know how to tell which LED leg is positive and which is negative, check out my last instrucable.

Step 5: Glue LEDs and Battery Pack Into Place.

Glue or otherwise affix the LEDs and battery inside the case. When arranging the LEDs, be sure to have all the positive legs facing one way, and the negative legs facing the other.

Step 6: Mount the Switch

drill a hole for the switch, and mount it wherever is most convenient for you

Step 7: Start the Wiring.

Wire the positive lead from the battery holder to one of the contacts on the switch. Now, wire the negative lead from the battery pack to the negative lead of one of the LEDs. Then, wire all of the NEGATIVE leads together. This is the difference between parallel and series. In series, the positive leg of one LED is wired to the negative lead of the next. In parallel, all the negative leads are connected to each other, and all the positive leads are connected to each other.

Step 8: Finish Up the Wiring.

wire all of the positive leads to each other, and then wire them to one of the contacts on the switch (for this particular switch, it is important that the contacts that you solder wires too are adjacent to each other.)

Step 9: Enjoy the Working Light!

The next step is to mount it on your bike somehow. Different people do this different ways, and I'll leave it up to your inventive mind to concont something!



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    Is it possible to use a, AAA battery for this and not use resistor.


    You didn't need resistances?

    Will either of these on/off switches work?

    Toggle switch single pole throw on off 125vac @5 amp


    a push button switch momentary 1 amp 250vac

    I'm looking for some VERY inexpensive ones and these are about a buck each at Jameco. If they won't, what amps/vac should I be looking for? Thanks!

    1 reply

    The first one will, the second one powers off once you let it lose. If you would like to use the last one you'd need a flipflop.

    if you had a 6V power source and 6-1V  would you need resistors is you did it in the parallel way?

    1 reply

    I think I understand what you mean. You have 6 LEDs that require 1V each and you have a 6V power supply. This is perfect for wiring in series. I did this with a 9V battery and 3 3V LEDs in my Bike Light instructable.

    You might want to add some rubber inserts on it so you don't short out your LEDs.

    1 reply

    Good point and very true about adding the rubber. I did a thin strip of black electrical tape around the inside lining of the tin.

    Incredible tutorials, I can't figure out how to make a flashing LED circuit b/c all the other instuctions aren't as thorough as yours. So if you could make an instructable on how to make those LEDs flash, that would be awesome. :)

    I am totally new to all this stuff. Could you add say a 4 AA battery box and add more LED's and use this as a flash light or as a lantern for camping or such?

    2 replies


    you could probably do it if you did the leds in the parallel way...

    Excellent hands-on follow up to your first tutorial. My Bunker Hill wireless alert signals an intruder by issuing a doorbell sound...as-well-as... three LEDs blinking together. I plan to cut the speaker wires to make the unit function in a silent mode with only the LEDs activated, but presently the LEDs blink once, when the intruder breaks the transmitter’s beam. Is there a way to keep the LEDs lit until I hit a reset switch?  

    Thanks for the Instructable. I used a 100 ohm resistor, a 9V battery, and a Momentary push button switch. a little different but I like yours better. here are some photos :D


    Wonderful Instructable. Thanks! This really showed me how to work with LEDs. But I used a 2.4 volt LEDs with a 150-ohm resistor along with a 9V battery. I also didn't clip the LED. .

    Nice job! As Jeasterlingtech mentioned I would suggest using some current limiting resistors. The Altoids tin seems to be so popular for these cool small enclosures and looks great in this project. :)

    If you are looking for some LEDs with some cheap shipping rates (starts at $3.00) please have a look at our store http://alan-parekh.vstore.ca/index.php/cPath/4

    If you are wanting to run an LED from a single AA battery here is an idea.

    Thanks for the instructable - this was my first electronic thing out of components. I went for the "cadillac" version and bought a small prototype case. It turned out more of a flashlight than bikelight:

    4 replies

    Dude, that looks awesome. I need to find a place to get cheap switches like that, theres not end to how useful they are!

    buy in bulk online for cheaper prices

    Thanks! That one is a Philmore on/on switch (only wired half of it) i picked up at Fry's for about a buck . Seems kinda expensive, though? i bet you could find it cheaper elsewhere/online.

    RadioShack has a good selection of switches, most are relatively cheap as well.