In the last week, however, the engineering team was able to solve all the issues through the development of a new audio control system, compatible with almost every phone available today, and has even increased the resolution of some phones to as much as 10 microns, as can be seen in this video testing the accuracy of the lifting mechanism.
The original system used square waves, yet, certain phone and firmware combinations had one of two problems: some signals were too weak, and were passed over as background static, while other signals were strong enough, but had disturbances within the wave. Lowering the threshold solved the first problem and made the second worse, while raising it had the opposite effect.
After 12 unsuccessful attempts at tweaking the board, firmware, and app, the engineering team decided to approach the problem from a different direction. Through a complete overhaul of the board design, the engineers implemented an “audio conditioner,” which allowed for the use of sinusoidal waves, rather than square waves. This allowed for a much lower threshold, while making even the high output signals much cleaner. The board was now able to distinguish easily between the signal wave and the background static, solving both problems.
However, the team was not out of the woods yet. After the excitement at having what appeared to be a final solution, full printing tests disappointingly showed that the motor would occasionally turn the wrong way. After studying it across different phones and printing times, a clear correlation could not be drawn, as the error seemed completely random. Disheartened, the engineers went back to the lab and tested each individual component for hours, looking for the source.
After a day, the problem was found to be a minor one related to the CPU. The CPU did not have 100% accuracy on reading the signals at the 1 kHz frequency. It therefore would mistake fragments of longer signals as commands to stop and rotate in the opposite direction. After making the quick change of removing the 1 kHz frequencies, the system worked perfectly.
Now that everything has been tested and finalized, the team has ordered the first 100 pre-production boards in order to test the quality of the mass-produced boards and ship them for final testing and certification. After this, the boards will go into full-scale production to be installed in the 20,000 printer bodies already assembled and will be shipped to the Kickstarter backers and pre-order customers, who have been supporting the team from the very beginning, making all this possible.
Source: www.ono3d.net
