Can't bike fast enough?

SpokePOV kit for bikes

Moderators: adafruit_support_bill, adafruit

Please be positive and constructive with your questions and comments.
Dave
 
Posts: 2
Joined: Mon Jul 19, 2010 8:38 am

Re: Can't bike fast enough?

Post by Dave »

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.

adafruit
 
Posts: 12151
Joined: Thu Apr 06, 2006 4:21 pm

Re: Can't bike fast enough?

Post by adafruit »

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

Dave
 
Posts: 2
Joined: Mon Jul 19, 2010 8:38 am

Re: Can't bike fast enough?

Post by Dave »

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

User avatar
adafruit_support_bill
 
Posts: 88088
Joined: Sat Feb 07, 2009 10:11 am

Re: Can't bike fast enough?

Post by adafruit_support_bill »

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.

adafruit
 
Posts: 12151
Joined: Thu Apr 06, 2006 4:21 pm

Re: Can't bike fast enough?

Post by adafruit »

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

flipper
 
Posts: 1
Joined: Mon Oct 25, 2010 8:59 pm

Re: Can't bike fast enough?

Post by flipper »

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+

AtomCore
 
Posts: 3
Joined: Tue Jun 08, 2010 2:28 am

Re: Can't bike fast enough?

Post by AtomCore »

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.

User avatar
adafruit_support_bill
 
Posts: 88088
Joined: Sat Feb 07, 2009 10:11 am

Re: Can't bike fast enough?

Post by adafruit_support_bill »

Can HALL SENSOR have some limit,
Make sure that the magnet is as close as possible to the sensor (without hitting it of course).

Locked
Please be positive and constructive with your questions and comments.

Return to “SpokePOV (discontinued)”