## Can't bike fast enough?

SpokePOV kit for bikes

### Re: Can't bike fast enough?

Hi,
I just can't understand why this SpokePOV should work at a normal speed.
Granted, that we have a bike with 26 inches(66,04cm). So the circumference is 66,04cm*pi = 207cm. For the whole circle you need about 20 Hz.
That means the bike has to move with (2,07m*20) per second which is equivalent to 150km/h.
Dave

Posts: 2
Joined: Mon Jul 19, 2010 7:38 am

### Re: Can't bike fast enough?

we put spokepovs on a bicycle with a odometer, and pedaled

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Joined: Thu Apr 06, 2006 3:21 pm
Location: nyc

### Re: Can't bike fast enough?

I still don't understand.
Can you just tell me what's wrong with the thoughts and calculations I did ?
Dave

Posts: 2
Joined: Mon Jul 19, 2010 7:38 am

### Re: Can't bike fast enough?

For the whole circle you need about 20 Hz.

Not sure where this number comes from. Many 8mm movies were made at 16 fps. And you don't need even that rate for a static image.

The persistance of vision effect is subject to many variables ranging from image contrast and ambient lighting to the viewer.

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Joined: Sat Feb 07, 2009 9:11 am

### Re: Can't bike fast enough?

Dave wrote:I still don't understand.
Can you just tell me what's wrong with the thoughts and calculations I did ?

Since it has been tested to work at ~10mph, that would imply that your assumptions are wrong...you might be better off back-calculating from the known working speeds

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Joined: Thu Apr 06, 2006 3:21 pm
Location: nyc

### Re: Can't bike fast enough?

Dave calculations are correct

after tests, manually spinning a front mtb(26in) wheel will reach around 25km/h max, which around 3.3hz.
about as fast as someone cycling.

but the one thing special about LED pov is that they have a lot of "flash" power, and probably "burn" the pulse they send in human eyes.
Effect is pretty much like looking at the sun.

this add POV effect and enable us to see the whole picture. but cameras will obviously struggle capturing this, as they run at 24hz+
flipper

Posts: 1
Joined: Mon Oct 25, 2010 7:59 pm

### Re: Can't bike fast enough?

I have blur image on speed over 23km/h. Can HALL SENSOR have some limit, or send wrong signal to uC, or EEPROM is with high latency. My LED is Green High bright, maybe have voltage drop in high speed.
AtomCore

Posts: 3
Joined: Tue Jun 08, 2010 1:28 am

### Re: Can't bike fast enough?

Can HALL SENSOR have some limit,

Make sure that the magnet is as close as possible to the sensor (without hitting it of course).