My goal with this project was to make a flashing safety light for my bicycle. The main reasons for making and not buying one were mostly the reviews on websites selling them. The lights either worked really good, or really bad. The other reason was that the ones that seemed to give the best performance, were the most expensive. Since it is just some flashing lights at the core, why not make some that are efficient and are actually going to last because the electronics will be properly constructed and should a component fail, it will be easy to repair and there will be no need to throw away a unit and buy a new one. I hate the mentality that "if it breaks, just go buy a new one". Better to have something that will last, or at least be repairable.
Step 1: Step 1: the Schematic & Prototyping
I put the schematic on paper so i knew what i would build. The circuit is based on the 555 IC and uses some resistors and a capacitor to establish the timing intervals of the flashing lights.
With the main section of the circuit built, i used two LED's in series to create a voltage drop that is safe for the LED's to operate without the use of a resistor to limit the current.
A switch was added to the main line on the positive lead to turn the circuit on and off.
The entire circuit was powered by a 9v battery. I could have used different batteries however one of the goals of this project was to buy little to nothing for it. I happen to have all the electronics because i am an electronics guy and i use those components a lot, so this project proved to be very cost effective for me (total cost of finished product was $0). It may not be the case for you.
The video shows my circuit using analog electronics achieving the same result as an arduino performing the task with programming
Step 2: Step 2: Construction of the Circuit
After the schematic was designed, i began constructing the circuit on a PCB. My original design had the LED's soldered on the board with the rest of the electronics. This proved to be too bulky and awkward for me considering i wanted to have a low profile look for this project. So i later removed the LED's and put them on their own assembly. This decision allowed me to trim the PCB making it smaller and allowing it to fit in a case i later found to be perfect for the project.
Step 3: Step :3 Construction of My "Hollow" Inspired Faceplate
My "Hollow" inspired faceplate was made from plexiglass i had lying around from previous projects. I drew a design of how i wanted my mask to look like, then cut it out using a rotozip. I proceeded to drill the holes where the LED "eyes" will be and then i painted one side of it white. The black rings are the LED sockets that come in real handy for a project like this.
I then proceeded to wire my LED's in the series/parallel configuration for the rows and columns.
Step 4: Step 4: Fitting the Electronics in the Case
Im just gonna go ahead and say it. My case is a pink tampon case. I picked this one because it fit perfectly underneath my seat hidden away (mostly), and stayed very secure on its own. My wife was no longer using the case so i decided to re-purpose it.
The pictures show how the electronics will fit in the case, and in order for it to be done properly, i had to drill two holes in the case. One for the switch to be secured to, and the other hole was drilled at the opposite side to feed the positive wire fron the circuit and the output wire from the 555 timer. Those two wires will connect to the LED faceplate with + going to the anode of the LED array, and the output wire going to the cathode (-) of the LED array.
Step 5: Step 5: Faceplate Mount
I made the mount for my faceplate by cutting a strip from a 1 gallon water bottle jug. It was reinforced with a strip of weatherstripping to give it proper retension and traction when mounted to my bicycle seat post, then was fasteded together with a bolt and nut.
After getting the mount finished, I went ahead and insulated my LED leads on the faceplate with hot glue. then attached the faceplate to the mount in the desired position with a large amount of hot glue. Since both pieces are plastic, they bonded rather well.
After the faceplate was bonded to the mount, It was time to finish the soldering of the faceplate LED leads to give them life. I heat-shrinked the leads after they were soldered and gave the assembly a good reinforcement of hot glue. I doubt this design is 100% waterproof but being that it is insulated rather well, and the location of the LED faceplate and electronics box, i think it will be safe from all but a deluge.
Step 6: Step 6: Final Installation and Summary
With construction complete, the whole unit is significantly larger than something i could buy, but i know this will last and i know it was built properly, the electronics were anyways.
The unit works great and it fulfilled my requirements of being low profile, cost little to nothing, Can be repaired should some component fail, and it will work flawlessly.
This project was done over the period of a week or so, and while it was longer than i expected, im glad i put the effort into building this. Now i have a rear flashing light that is pretty powerful and completely unique. The video shows it in action fully attached to my bike and i talk a little bit about it.
Thanks for reading this and i hope you enjoyed it. This instructable was also entered in the Outdoors contest, so feel free to vote for it there.