The idea is that the visual system retains each static image for a short time and so a rapid succession of slightly different still images will appear to be fused together into one continuous moving image.
The answer that is most often given (usually in the first chapter of film books, cinema books and animation books) is “Persistence of Vision”. But, why does a sequence of still images appear to be a continuous moving image?
#Persistence of vision 3d clock trial
We can guess or use trial and error to determine how small the differences between consecutive images should be and how quickly the sequence of images must be shown. What we do not know is how the system works. We might even know that this system works whether the images are recorded photographically, as in cinema, or hand-made by drawing or some other method, as in animation. We also know that the differences between any two consecutive images must be small and that the sequence of images must be shown quite quickly. In the cinema, we know that a sequence of still images is projected one after another onto a viewing screen. In this paper I want to demonstrate how chronophotography can be used to better understand two of its descendents: animation and cinema. This information can and has been used to answer questions about motion and mechanical efficiency. A chronophotograph contains information about interval, duration, speed and other derivatives of space and time. Now, in what many call the post-cinematic era 1, artists and researchers are beginning to return to chronophotography to continue some of its unfinished stories. At the beginning of the twentieth century chronophotography’s potential as a research tool was ignored as aspects of chronophotography were developed into cinema. To further reduce the pin count, I used a BCD to seven-segment driver.Chronophotography was developed, at the end of the nineteenth century by Marey, Demenÿ and later Gilbreth and used as a tool for investigating movement. In the video above, I used POV to create a digital clock out of six seven-segment displays and one PIC microcontroller. The limiting factor is the number of available pins for the cathode of each display. We can extend this to as many seven-segment displays as our chosen microcontroller can permit.
Now, we make this loop in a speed that is fast enough to trick the eye that they are simultaneous: Then, we make the segments display the digit three: Then, we make the segments display the digit one:Īfter this, we turn off the left digit and turn on the right digit. Now if we want to display the digit 13 on these two displays, what we do is turn on the left display and turn off the right display. The segments for both displays are connected to the same pins! We can turn on the left display if its cathode is low and turn it off if its cathode is high. Here we see that the cathodes for the displays are now connected to a pin. The concept is tricking the eye as if two displays are simultaneous although they are actually just alternating. If the wiring connection below is followed, then digit one is displayed when RB.1 and RB.2 are set while the rest are cleared (make low).ĭisplaying digits 0 to 9 is done by following the table below: Bit Sequenceīut what if we use more than one seven-segment display? This is where POV comes in handy. Numbers are displayed by setting (make high) certains segments. Each segment can be assigned to a microcontroller pin and the cathode connected to ground. To light up one segment, the anode of that segment must have a higher voltage than the cathode. Recall that a seven-segment display is wired like this: From Jameco I believe this is enough to grasp the basics of POV and lay the path for using other devices like sixteen-segment displays, dot matrices, etc. I will be using common cathode (CC) seven segment displays for this tutorial. A basic non-electronic example of POV is how a pencil seemed rubbery when wiggled. Basically, it’s a form of optical illusion wherein our perception of an object is not as fast as how the object is changing. Persistence of vision (POV) is a technique to reduce the microcontroller pins used without adding extra components. Thankfully, a software-based solution exists to solve such problem.
#Persistence of vision 3d clock drivers
Multiplexers and display drivers are great help but at an additional cost.
This is particularly true when dealing with liquid crystal or seven-segment displays.
Lack of pins to use is a common challenge in designing microcontroller-based projects.
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