Print PDF
Favorite
Email
What could be cooler then LEDs, Bicycles and Safety? Just when it is combined together in a cool looking project!
The Idea is to take a basic cheap bike helmet and make it interesting and safer. I did this by adding 4 Superbright LED's and some reflective material. This Instructable is a very good one to attempt if you are just getting started in electronics and soldering. This is because it is not a very costly instructable (as far as electronics go) and the skills needed are very basic. It is also a great application of Ohms law!
The Idea is to take a basic cheap bike helmet and make it interesting and safer. I did this by adding 4 Superbright LED's and some reflective material. This Instructable is a very good one to attempt if you are just getting started in electronics and soldering. This is because it is not a very costly instructable (as far as electronics go) and the skills needed are very basic. It is also a great application of Ohms law!
Remove these ads by
Signing UpStep 1The Theory
This Step is all about basic LED wiring and Ohms Law. Some of you may not need to read this and will just jump past it. However, I recommend those new to electronics to read this first.
Ohms Law states that I = V / R . In this, I is Current in amps (or mA as it is in LED's), V is Potential Difference in Volts, and R is Resistance in Ohms
Since this equation is used for the whole circuit, it isn't very useful to us the way it is now. We have to change it so it will give us the resister value we need. This Equation is:
R= ( Vs-Vl ) / I
Vs is the supply voltage; what come out of the battery. In this project it is 9 Volts.
VI is the LED voltage. It is the voltage the LED should have. It is stated on Data sheets you can find usually at the web site you bought your LED's from. In my case, the white LED's I have were 3.5 Volts.
I is the Amperage the LED operates at. It is usually 20 to 30 mA ( 0.02- 0.03 Amps). It can also be found on the data sheet for your LED. Mine was 20 mA.
So if I was to attach 1 White LED to the battery I would have
R= ( 9 - 3.5)/ 0.02
R= 275 Ohm
This means that you want to have at a minimum a 275 Ohm Resister, however to sustain battery life it would be smarter to use 300 to 330 Ohm Resister
Now, because one LED is kinda wimpy for a head light we will put the LEDs in not only in series but in series and parallel!
The math gets a little more complicated from here on.
If we put 2 of these white LEDs in series we have to use the equation
Vl = Number of LEDs x LED Voltage
Vl = 2x3.5
Vl = 7
R= (9-7)/0.2 *IMPORTANT* Number of LEDs does not change the Amperage in the equation*
R = 100
ok, so we can do 2 LED's in series, but can we do 3?
Vl = 3 x 3.5
Vl=10.5
R= ( 9 - 10.5 ) / 0.02
R= -75
We cannot have a negative resistor so we have to keep with 2 in series, but we want to have 4 LED's. The way to do this is to have two sets of two LEDs series in parallel. Okay, that is really badly worded, but the picture below should clarify it a lot.
Now that you understand the process go and try it out with your LEDs.
If you are not good at all this math stuff you could just enter your info onto
This Site
However if you know how and why your circuits work it makes everything much easier when you get into more complicated electronics.
The Illustrations were created on Yenka and edited on Photoshop Elements
Ohms Law states that I = V / R . In this, I is Current in amps (or mA as it is in LED's), V is Potential Difference in Volts, and R is Resistance in Ohms
Since this equation is used for the whole circuit, it isn't very useful to us the way it is now. We have to change it so it will give us the resister value we need. This Equation is:
R= ( Vs-Vl ) / I
Vs is the supply voltage; what come out of the battery. In this project it is 9 Volts.
VI is the LED voltage. It is the voltage the LED should have. It is stated on Data sheets you can find usually at the web site you bought your LED's from. In my case, the white LED's I have were 3.5 Volts.
I is the Amperage the LED operates at. It is usually 20 to 30 mA ( 0.02- 0.03 Amps). It can also be found on the data sheet for your LED. Mine was 20 mA.
So if I was to attach 1 White LED to the battery I would have
R= ( 9 - 3.5)/ 0.02
R= 275 Ohm
This means that you want to have at a minimum a 275 Ohm Resister, however to sustain battery life it would be smarter to use 300 to 330 Ohm Resister
Now, because one LED is kinda wimpy for a head light we will put the LEDs in not only in series but in series and parallel!
The math gets a little more complicated from here on.
If we put 2 of these white LEDs in series we have to use the equation
Vl = Number of LEDs x LED Voltage
Vl = 2x3.5
Vl = 7
R= (9-7)/0.2 *IMPORTANT* Number of LEDs does not change the Amperage in the equation*
R = 100
ok, so we can do 2 LED's in series, but can we do 3?
Vl = 3 x 3.5
Vl=10.5
R= ( 9 - 10.5 ) / 0.02
R= -75
We cannot have a negative resistor so we have to keep with 2 in series, but we want to have 4 LED's. The way to do this is to have two sets of two LEDs series in parallel. Okay, that is really badly worded, but the picture below should clarify it a lot.
Now that you understand the process go and try it out with your LEDs.
If you are not good at all this math stuff you could just enter your info onto
This Site
However if you know how and why your circuits work it makes everything much easier when you get into more complicated electronics.
The Illustrations were created on Yenka and edited on Photoshop Elements
| « Previous Step | Download PDFView All Steps | Next Step » |
Nice idea and explanation, but you shouldn't modify your helmet structurally like that. In fact that would be illegal here in Australia, I wouldn't be suprised if it was too in your area.
The manufacturers don't put that foam in for no reason - they put the minimum in to provide the required amount of protection. If you take some away, there isn't the required level of protection anymore.
Maybe a re-think and come up with another solution? You could use some self-adhesive velcro to "stick" the battery on the outside.