[Garrett Birkel’s] weekly ride usually features some pretty wild costumes. He wanted something to step up his own look so he make this LED mohawk bike helmet. He had an LED strip to start with and found a way to use acrylic and clear plastic tubing to fold the lights into the appropriate shape. From there he designed a PCB for some DC-DC converters to provide regulated power. The juice comes from Lithium Iron-Phosphate cells, the same kind we saw in the electric bike assist battery a few days ago. We find it a bit wild that you can pick out the PWM of the LEDs in the lens effect of that photograph.
Can someone give a brief, sensical description of PWM. How it works and its application. One paragraph like you are talking to a 2nd grader. :-)
Thanks.
I know hackaday is kind of elitist when it comes to arduino, but this is really a pretty great beginner tutorial for PWM.
http://www.arduino.cc/en/Tutorial/PWM
You can think of PWM as turning a light on and off really fast. If the light is on 50% of the time it appears half as bright. This allows you to control the brightness of an LED by varying the amount of time the LED is on relative to the amount of time it is off.
Is there any technical information in the link to the project page that makes this the slightest bit worthwhile reading? …nope
I’m pretty sure that the effect we’re seeing isn’t the PWM, but the actual animation of the leds…
Also, for Greg:
http://en.wikipedia.org/wiki/Pulse-width_modulation
That will definitely bring in the chicks…
not being able to cut plexiglass with a table saw?
it works very well. as long as you dont overheat it.
LMAO @ “Luminous unicorn ejaculation”. Classy, not too tight.
@mrgoogfan … the hot nerdy ones anyway, and it’s totally a conversation starter.
Very unsubtle. I like it. :)
the effect, why you can see the pulse width modulation of the diodes, is because of the ccd chip in the camera. the ccd shifts out all the pixels line per line to the bottom.
when there is overexposure, you often see the light casting lines to the bottom.
now that the light is PWMed you can see the speed of modulation in those lines because of the shifting.
you can easily cut plexiglass on a tablesaw… you put the blade in backwards.
I do it all the time.
IT’S A BOMB!!!
I wouldn’t wear that where the authorities can see me (also known as in public).
WTF!? Thats all I have to say wtf!
http://www.youtube.com/watch?v=3FWpDSCOOcU
two words…………Absolutely GAY!
Where can I get that LED strip for a decent price? Every place I’ve found it its been $150+ for 5m.
hundreds of years of the study of electricity has gone by and we get a light up mohawk that emulates “Unicorn Ejaculate”… Ask yourself if you have faith in humanity now.
Yes, you can cut Lexan with a table saw, but not nearly as fast as with a dremel tool, and you can’t cut a curve or a hole that way worth crap. If you wanna get fancy about it, what you should really do is what I said: Go to a local shop with a CNC laser-cutter.
Re: IT’S A BOMB!!1!!… It’s worse than you think. The light pattern is controlled by a small RF remote control, with an 8-inch retractable antenna and a few red buttons. When you take it out, it really does look like you’re about to set off a nearby IED.
Re: “Absolutely GAY”: *** MISSION ACCOMPLISHED ***
Also, the blurb author and keks^2 are correct – the notches in the vertical streaking are caused by the PWM driving the LEDs. The data in the CMOS inside the digital camera being used to take the movie is read progressively in horizontal strips, but the electrical signal is also transferred off the CMOS itself along a vertical array of wires, and too much charge above or below the region currently being read will cause interference as the desired line is shifted down for reading. It has nothing to do with the optics and everything to do with the sensor.
Also: Pete: You want technical information? I’ll do my best to provide it. What would you like to know?
From Running Man — “Clap if you Love Dynamo!”