Alternating LED Flasher Circuit Project

This is a great little project to do with your kids, grandchildren, students, etc. It is a small circuit that uses a battery to light up two alternating flashing LEDs. My kids who are five and seven loved working on it together in the garage. They enjoyed doing a project with dad, and learning about soldering and electronic circuits. They show their LED flashing circuit to everyone that comes to the house. So if you want something to do with your kids that involves some hands on ‘maker’ activity this is good for you. Also, if you have kids in a class or group of any sort such as scouts or summer camp and want a building activity, this project would be ideal for you.

If you have a technology or electronics class and need an actviity to build a lesson plan around, this might work out to be a good actvity.

The materials required are just a few electronic components. A materials list and tool list can be downloaded here:

Materials List - Excel File

Materials List - PDF File

If you don’t have a local supplier of electronic parts like A-1 Counterparts , you can order them from Actually I included all the Newark part numbers to make it easier for you. If you want to save a few bucks you can order a kit from me which includes the items as described in the materials list, and the wood block circuit template (the wood block is not included though).

Ebay Listing Link

You can make up your own circuit template based on the schematic below, or you can download mine for an extremely low price of $1. I spent a few hours making up the template which you can download immediately and print off as many copies as you need.

Push the button below to get the LED Flasher Wood Block Diagram and Instructions – this can save you a few hours.

Circuit Diagram

To get started, you will need to get some 3/4″ plywood or MDF and cut out a 4″ x 6″ rectangle. This will be the block that you glue the circuit template to.

Print the ciruit template out that you downloaded in pdf fomat at 100% scale so that the size matches the 4″ x 6″ wood block. Cut the template out and glue it onto the wood.



Drill some pilot holes to make hammering in the nails easier. While you’ve got the drill out, drill the 3/16″ holes for the battery zip ties. Hammer in the nails so that all the heads are about the same height.



You can start soldering pieces into place now. Trim the leads to the length that will allow you to lay the wire lead on top of the nail head for each component. I found that it was easier to start near the middle and work out. Also having a pair of needle nose pliers handy was useful to hold items in place while the soldering was taking place.



There are a few components that require attention to polarity. The LEDs have one lead longer than the other which indicates it is the anode or +’ve side. Make sure you take note of this before cutting the leads. The capacitor will have polarity inidicated on the body which should be matched up to the template. The transistor’s three wires should be matched to the template – just note that the circuit overall is mirrored, but the transistor leads are not mirrored. Double check that the resistors are selected correctly for the right spot – polarity doesn’t matter for the resistors though. Also take note of the crossing wires in the middle for which you should use the insulated wire to avoid a short.



Once you have it all soldered up, solder one side of the battery leads and leave the other one free so you can hook it up when you want it on and unhook it when you want it off. Attach a battery, zip tie it in place, and test it out.



comments powered by Disqus