Here's a way to put some LED lights on a bike safety vest;
In this case it's a child-size vest, but you can of course do it for any size.
I kept the electric circuit as simple as possible, in order to focus on the LED installation;
Sorry that some intermediate steps (and photos) are missing: I'm writing this instructable about a vest that my girlfriend and me made last year.
- a bike safety vest;
- LEDs; we used white LEDs for front and red LEDs for the rear of the vest;
- a battery; we used a 3,6 Lithium rechargeable battery salvaged from a broken portable phone, but you can use any other small-sized battery; for example, 3 AAA-size batteries with their support would be fine, and you could use Ni-MH rechargeable batteries as well as alkaline 1,5V batteries; I imagine you could even use a Power Bank (supplying typically 5V) for an extra long lasting.
- some resistors; their value depends upon the tension of the battery (typically between 3,6 and 4,5 V) and the type of LED used (please see next step for details).
- a small piece of prototype electronic card (you know, the type with plenty of holes spaced 1/10 of inch);
- small electric insulated wire, 2 colours if possible, and the most flexible you can find;
- an electric switch (optional);
- some fabric for the inner lining;
- optional: some Velcro(R) band, also for the inner lining; you could also use some pressure button instead.
- all that you need to cut and sew the fabric;
- soldering iron;
- scissors for electric wire;
- small pliers to bend the LED's pins;
- optional: a drill with a thin bit, the same diameter than the electric wire;
Step 1: LED Connection
The LEDs are connected in parallel; electric wire is soldered to the LED's pins. As the vest's fabric don't stand heat, we soldered all the electrical connections BEFORE the installation in the vest.
We choose to not to install any electronic card or blinking system, just to keep it simple.
As in this type of connection they share the same voltage, it's better to use the same type of LED; as we used two types of LEDs (two different colours), we needed two different parallel connections, each one with its own resistor.
About the value of the resistor, we can calculate it with the good old Ohm's law: R = V / I.
V is the voltage across the resistor, that is the difference between the battery voltage (in our case 3,6V) and the led's voltage (white led need around 3,3V; red LEDs need around 2,0V);
I is the total current flowing through the resistor, that is the sum of the current of each LED; in our case each LED use about 20 mA, so N LEDs connected in parallel will use N x 20 mA;
As example, for 3 red LEDs R = (3,6V - 2V) / (3 x 20 mA) = 1,6 V / 60 mA = 27 ohm (approximately); you can use a different value: a higher value will give you less light but a longer battery lasting (you could quickly test it and find the value for the result you wish).
Finally, the switch will permit to switch all the LED on and off without the need to disconnect battery (good invention, isn't it?).
Step 2: A Few Electronic Components...
We choose to put all the resistors and the switch on the same piece of card (see picture); this is not really necessary, as the circuit is very simple, but we did it to get all these components gathered in the same place, in case we decided to change the value of the resistors or even to replace the card with any other blinking system one day.
* A tip about wire fixing *
I preferred to make it in a way that the wires pass through the card with their plastic insulation (see picture, indicated by red ovals): as the joining point between the wire and the card is usually the most fragile spot, the wire is most resistant because of the insulation around it; of course the insulation is removed only at the end of wire, to solder it to the card.
For the battery, I used a 1/10" JST connector, just because I had it immediately available; here, also, is not really necessary; if you wish you could even use some similar connector for the LEDs.
Step 3: Led Installation
As you can see in the pictures, LEDs were installed with the glowing part outside with its two pins traversing the fabric;
in the inner side, the pins were folded at right angle to follow the fabric, and bended in a curly way to stabilize them; ah, before to do so, maybe it's useful to mark in some way the + or - pin: when the pins are curled it's less easy to determine polarity.
We finally fixed the led to fabric with a few points of sewing; don't know whether it's necessary or not, but we preferred to do so.
Step 4: The Lining
An inner fabric lining is perhaps unnecessary but we thought that it would protect LEDs and all the circuitry, especially putting the vest on and off;
In our case the linen was made in a way that we can easily open it to reach the components (and to replace battery, if needed); we used Velcro (R) to close it in an easy and fast way;
In the lining, the battery has its own fabric pocket: in this way we don't need to sew or anyway fix the battery to the fabric. This pocket too is closed with a strip of Velcro.
Step 5: Close It Up and Ride!
That's it, it's finished; good to ride with.
*** Next time's improvements: ***
After some time, the first (and only) problem we had was that a wire broke (see picture): that's why it's better to use a very flexible wire.
I would like to thank my girlfriend Aurélie for all the sewing.
Thanks to all the readers for their kind attention;
And of course, many thanks to Instructable's website for this (free!) space.
I will submit this Instructable in the 'Make it glow' contest: thanks in advance for vote it if you like it.
* Have a good day *