powering 3 meter led strips with DC
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Re: powering 3 meter led strips with DC

by mohawkpiper on Thu Nov 08, 2012 2:06 pm

thanks! i love the monovelo. currently i am also trying to reconstruct a better tire (the current one is a solid rubber tire all the way around, it has a lot of drag...) so it is tire-less. if i get the leds installed before the tire is finished i wont be able to actually ride it quite yet, so no video in motion til both parts of the project are done :(

burning man is definitely in thought....
the wheel is purchased, so i did not build it myself. the company that makes them is called monovelo, located in china. http://www.monovelo.com/ they built these things specifically for the chinese olympics in '08, then opened up their creation to the general public for a hefty charge. they have the option of buying it with, or without, leds already in it, but the leds they put in are run off a 3.7V cell phone battery and are your basic leds. they only come in one of three colors, red, white, and blue.

as for the zero-crossing sensor...
yes, this had been a thought. it would be pretty cool to do that. unfortunately this is totally my first arduino project already, so i dont know where to start. i was thinking about coming back to that some time in the future after finishing just getting the leds in. but making it appear as if the wheel wasnt rotating was exactly what i was planning on going for with that.
if you could point me in the right direction though, i can start taking a look and maybe work that into it earlier than expected.

the point of this project for me was
1. to make the bike look cool, but also
2. to learn arduino (always wanted to)

so the zero crossing thing was a thought, as well as putting on a display shield... http://adafruit.com/products/714
the idea for the shield was to have it removable for when riding, but to be able to program several different patterns into the wheel, and in the middle of a ride (if i stop of course) pop the shield on and be able to select and change the pattern to whatever my mood feels like :P
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Re: powering 3 meter led strips with DC

by pburgess on Fri Nov 09, 2012 2:00 am

There are a couple of ways to do the zero-crossing thing...

The cheapest/easiest route, and what's used by most bike wheel POVs, speedometers, etc. is a Hall effect sensor and a magnet (or multiple magnets equally spaced, for better detecting speed changes). Just count the elapsed time between triggers, and you can extrapolate the approximate speed at which the wheel is turning.

Could alternately use a gyro, but that's probably all kinds of overkill.

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Re: powering 3 meter led strips with DC

by adafruit_support_bill on Fri Nov 09, 2012 7:28 am

i am also trying to reconstruct a better tire

What are you using for tires? Back in my bike-shop days, we'd make penny-farthing tires from rubber compressor-hose. I have seen others made from spliced-together tubular tires, but those had major reliability issues.

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Re: powering 3 meter led strips with DC

by adafruit_support_rick on Fri Nov 09, 2012 12:07 pm

I've got a 25-foot black-rubber garden hose that would probably make a good tire. It's the heavy-duty "pro" kind - so the rubber is thick and resilient, with a lot of fabric reinforcement. You're not going to get thousands of miles out of one of these, but then you're probably not planning to ride cross-country, either.

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Re: powering 3 meter led strips with DC

by mohawkpiper on Fri Nov 09, 2012 1:56 pm

the gyro was what i had in mind originally, but i didnt know about anything else. the hall effect sensor sounds great. so the coding part... i can get the time between triggers straight from the arduino right? i dont need to put a crystal on the board?

for the tire...
im not really sure its the best, but this is what ive been working on right now...
ive put aluminum c-channel (bent to fit the curvature of the plastic wheel rim) inside the groove where the old solid rubber tire fell into place.
i screwed that in using the same screw holes that originally held the solid rubber tire.

i then bent some really thick pvc and laid that over the the groove, screwing it into the aluminum c-channel. i have about half the bike(monowheel) this way so far.

next is taking some regular bike tires (i think im gonna need 3...) and wrap the pvc in them.

my only real concern is the pvc might not hold up with the weight of everything (the monowheel is something like 80 or 90 lbs itself) and the random bumps and stuff in the road, but there's only one way to find out.
if it works great, if not, well a waste of $100 and some fun bending pvc.
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Re: powering 3 meter led strips with DC

by mohawkpiper on Wed Nov 14, 2012 1:24 pm

ok i have another question regarding powering the led strips....

when building the strips into the monowheel, i had the teensy connected to a breadboard temporarily until it was time to put it in. as i would put the leds in each section, i would test it to make sure i had it all right.
as i got to the points where added power sources came into play, it still seemed ok and all...

i finished the thing, and put the teensy inside the frame, and ive noticed something odd...
so there are 3 power sources, 1 runs 1 meter of leds, and the teensy, the other two power sources run 1 meter of leds each.
obviously i cant turn on all power sources at once.
ive noticed, if i turn on the power sources NOT running the teensy first, the leds on those power sources light up with whatever colors they were on when they were turned off and stay that way until i turn on power to the teensy at which point all the leds all start fresh from the beginning of the loop in the code.

if i turn on the power source connected to the teensy first, the leds on that power source start up, and run through the code (all other leds stay off, so far all seems as it should...) but now i can tell its running through the loop, but they flash lots of different colors in between really fast. this happens until i turn on the other two power sources, at which the code keeps going from where it was when i turned on the other two power sources, but now with all power sources on, it looks clean with no flashing of random colors inbetween.

i didnt notice this while testing, but maybe i just happened to turn on the other power sources before the teensy, im not sure.

the way i put the teensy into the wheel... resembles the way i had it hooked up to the breadboard. but i used jumper pins instead of a breadboard so that i could mount the jumper pins into the wheel which would ultimately make the teensy removeable if need be.

so i have 5V power from the first battery pack running into 5V jumper pin, which 5V power of led strip 1 is attached to also. header pin of teensy 5V is attached to other end of jumper pin.
the same goes for ground. (ground from battery into ground jumper pin, ground of led strip from ground jumper pin, and header pin of teensy ground into other end of ground jumper pin.)

i am also splitting the data and clock so that both sides of the wheel get the same exact code. (even though there are 96 total leds, im only programming 48 and each side gets same program.)

so same goes here, teensy header pin of clock into clock jumper. both of two leds strips of 48, get clock wired from other end of clock jumper.
same for data.

this is all the same as i had it on the breadboard, ive just replaced the breadboard with jumper pins.

all looks right, like im pretty sure i dont have anything crossing to other wires where it shouldnt be.

i can take pics (i know these things help a lot!) but its gonna have to wait til i get home from work.

any ideas why it might blink randomly + funny but that i can still tell its running through the code when the power to first led strip and teensy are on but other two sets of 32 leds are not powered yet?

thanks for the help
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