This is the video of POV made by me n my friends Deepankar Singh, Rahul Sinha.
If this video doesnt work, then see the link below
To make it we used the components:
1)Microcontroller - AtMega32
2)Leds - 7.(u can use any number according to display u desire)
3) LM 7805 - 5v supply
4)TSOP - for sensing IR blinking at 38khz, to be used as external interrupt
The circuit diagram is:
The whole circuit is stuck to a fan. Then we give an external IR source blinking at 38khz at constant point, so that when the circuit rotates, it meets the ir light at a constant point always.This triggers low output in the TSOP. The TSOP is generally high in absence of 38khz IR, but goes low in the presence of IR.
This can be used to detect when it has completed an entire circle of revolution. For this purpose, we can use interrupts or simple poling i.e. checking the pin continiously.
Then the time taken by it is stored and used for displaying letters. We divide the time into total no. of sectors in which we want to display.
We have used 7x5 column to display letters, i.e. we have used 5 sectors of led positions, manipulating their on and off state, to display. We can use the BITMAP CALCULATOR which lets you draw a character and
visualise it. It can be seen in
Now, when the circuit starts rotating at a nearly constant speed, the first ir signal received indicates the start of rotation, the next signals received indicate the end of rotation and hence the rotation time value is stored and then the display starts. For display, lets suppose we want to display C, then, it must be like below
Seeing this we can say that the sequence of glowing of leds must be
This completes the display of "C". The wideness of display depends on the time alloted for the display of each line. Similarly we can diplay other characters also.