Gray Projects

Posted on Feb 5, 2014

Then I learned to drive it. Turns out my greatest enemy is inertia. What I`ve built is just so damn heavy and massive I can`t just start off the motor at full speed. Being a half-assed physicist I should know that already. But I guess experience is also needed. So to get the motor running properly - careful speedup, slowdown and backslash delay at

Gray Projects
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return need to be coded. Actually. I`m making this all up as I go, don`t have any formal education and doing inertia calculations seems like a pain. So I try and see what works. But basically I need to reduce weight. All that steel and heavy aluminium beams I`m moving along take a lot of effort. And cause excessive shaking of the whole machine resulting in some jitter at the printed page. Also the HP printer carriage is designed to slant forwards and backwards at different stages of the rail. The movement of the whole assembly though causes it to shake at the wrong places, more distorting the printed page. I added my old USB chip (FT 232RL) to the game so that I can both control and get diagnostics from the microcontroller. The MCU runs at 20MHz now and I think it wouldn`t keep up with the printer at any slower frequency. Getting diagnostics allowed me to plot the main roller/motor movement sequence: I had a lot of trouble figuring out when to turn the paper sensor on. To understand what the printer does I had to rebuild the old printer from the pieces I had. And I discovered that there`s a lever that is pushed when the printer head moves to the very right. When this lever is pushed - no paper is fetched if the roller turns. And paper fetching is actually done with roller turning backwards. But adding another sensor is a pain so I just deduced from the roller movement when it expects the paper sensor to turn on. This...

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