This instructable will help you to make your own tiny pocket sized LED flasher which flashes a LED at a desirable speed. You can use it as decorative lighting for your cycle which by the way was the main reason I made this flasher.

Step 1: Components, Tools and Skills

You will require the following things for this project-

LED x1 Any colour, type and size would do (except the high power ones) I used a green one here.
Current limiting resistor for the LED (I used 1kΩ since I had it laying around).
555 IC x1
8 pin IC Holder x1 (Optional) You would get more space if you don’t use it.
1kΩ resistor x1
0.1µF ceramic capacitor x1
10µF electrolytic capacitor x1
10kΩ potentiometer x1 I used the one with a knob but if you use a trimmer then you could make the circuit smaller.
Slider switch x1 The smaller the better :)
9V battery x1 to power the circuit.
9V battery connector x1
Some connecting wires

I am not providing any link to the above listed parts as they are very common and could be easily found at any local electronics store.

Tools-

Soldering Iron with solder
Pliers
Wire cutters/Strong scissor
Hot Glue/Epoxy (optional) just to reinforce the circuit. But still important as I will explain it later.

Skills-

Soldering

Step 2: Schematics

This is the circuit diagram for this project(see the picture).

I have made this circuit on tinkercad where you could virtually simulate it here. Just go to the link and click on the “simulate” button near the bottom left corner then click on the “start simulation” near the top. Now turn on the slider switch then turn the potentiometer to watch the LED flicker at certain speed.

You can also see its real life test in the GIF above.

Step 3: Working

This circuit uses the 555 timer IC in its astable mode to create a pulse signal. To learn more about the 555 IC you can check this instructable.

This circuit uses the 555
timer IC in its astable mode to create a pulse signal.

To put it simply the output of the IC continuously toggles from high to low (there is no stable state hence it is called as ‘astable’) and this oscillation’s frequency depends on the resistors and the capacitor C2. This happens because the capacitor continuously charges and discharges between 1/3Vcc and 2/3Vcc.

There are many sources online which could explain you in a more detailed and better way so you might try and look for them.

Step 4: Soldering!

Soldering

So now you only have a few ways.

You can get a custom made PCB and solder the circuit. This is probably the easiest way. But it’s quite unnecessary for such a small project.
You can get a perfboard and then complete the circuit.
Or you could go the hard and smallest way by directly soldering the components in mid-air.

I have used the last way here. Here are some tips which might help-

Firstly, make sure your iron is properly heated or it could lead to cold solder joints.
Make sure that you do tin all the parts before soldering them tinning makes it much easier to solder.
Flux really helps to properly solder especially when it comes to bigger surfaces like the potentiometer’s base plate (I don’t know what to call it but see the picture to understand what I mean).
Since a lot of soldering would happen around the IC holder you should make the “IC pin to IC pin” at the start like I did here.
As you would be soldering at very close proximity to the components, you need to be quick otherwise you might overheat them and damage them. If you do make a mistake while soldering, then wait for a while for the joint to cool off then go ahead and correct it. This the exact reason why I used an IC holder as I thought I might overheat it and cause damage.
Last but not least is the most common mistake it that of accidentally shorting two pins. Well it is quite frustrating to remove the extra solder as it just doesn’t want to get off. You have to be a little patient to correct such mistakes.

Step 5: Reinforcement

Now that you have finished soldering its time to make the circuit stronger and drop resistant so that it could survive that accidental drop from your desk. You don’t want to go again and again to the soldering iron for such damage repairs. So power up your hot glue gun or start mixing your two-part epoxy to make the circuit stronger.(Epoxy preferred here for a stronger joint, but I am lazy) Just be careful not to glue the potentiometer.

Step 6: Putting It in Orbit!

I mean attaching it to the wheel of your cycle. You could attach it to the wheel by a lot of methods, it’s your choice. Whatever you do just DON’T USE RUBBER BANDS TO ATTACH THE FLASHER as the model’s centrifugal force easily overcomes the elastic pull of the rubber bands and launches the flasher straight at any direction. The 9V battery has enough mass to potentially cause enough damage to life and property. This has happened to me and I found that the 555 IC was in one direction and the main circuit in other and the battery flew around 10 meter away from the wheel.

Anyway the flashing of the LED creates some crude patterns thanks to the persistence of vision. And if you adjust your speed you may be able to make the pattern stay still instead of moving here and there. I leave it to you to think what does the speed of cycle has to do with the patterns.

Step 7: Don't Stop! There’s Always a Scope for Improvement

There are many ways to improve this project.

The light of the LED was pointing straight in front of it so I sanded the surface of the LED to make the light spread more evenly.
If instead of a single LED a LED chaser circuit with different colours is used, then the pattern which would emerge would be more colourful and interesting.
Another area for improvement is the battery, it would be more light weight and useful if a rechargeable battery is used.
I have doubt about this- does this device require a counter-weight attached to the diametrically opposite side of the wheel? And does the imbalance cause by concentration of mass on one side of the cycle wheel affects the speed and stability of the cycle? I would really appreciate a little help on this.
You also could make a full POV display to display words on the wheel of the cycle. I might try this idea later sometime. The only problem here is that the words would be visible from only side of the cycle. (Does anyone have any solution for this?)