Hello Everyone,
"I was going to check for driver boards which exactly have high accuracy, considering that I'm shooting for a lambda of 500nm, and those stepper motors are supposed to... well step over the wafer without too much offset..."
I think it will be impossible to find or construct a stepper-driven screw with 500nm accuracy. This problem is usually solved in the way that is used in CD/DVD drives: a screw-shaft with a stepper motor provides wide-range but coarse and imprecise actuation over the entire range, while a short-range magnetic actuator (essentially a solenoid facing a permanent magnet suspended on springs) provides fine movement (resolution dependent only on the ADC, if any, driving the solenoid amplifier) over 2-3 steps distance.
In an optical drive, the analog tracking error signal is fed into the solenoid via an analog feedback loop, keeping the lens over the track. When the solenoid control signal approaches the end of its range in either direction, a comparator senses it and causes the stepper to step one forward or backward (while the movement of the lens caused by the stepping is canceled out by the feedback loop), bringing the solenoid back to the center of its range of movement.
Regards,
Ferenc
On 1/25/22 16:47, David Lanzendörfer wrote:
Hi So I kindly asked in Chinese for the schematics of those LCOS PCBs I've ordered and they were very forthcoming. I now have the schematics. When it comes to stepper electronics, I hadn't made up my mind yet, but I was going to check for driver boards which exactly have high accuracy, considering that I'm shooting for a lambda of 500nm, and those stepper motors are supposed to... well step over the wafer without too much offset... I've decided to not move the wafer, but instead moving the optics on top of the wafer, because the thing I've ordered will be so lightweight, that there won't be any vibrations, especially, considering that I'm anyway stepping VERY slow... I'll cross the bridge of what drivers to use, as soon as I'm there :-)
Cheers -lev
On Tuesday, January 25, 2022 2:49:45 PM WET lkcl wrote:
On January 25, 2022 11:55:13 AM UTC, "David Lanzendörfer"
leviathan@libresilicon.com wrote:
I'd be using some Mini PC like this one, for hooking up all the "webcams" (CMOS sensors) to, and then run all the software headless on there, as well as the Arduino(s) for the motion control: https://www.aliexpress.com/item/1005003020832871.html
do not for god's sake use RAMPS for a 3D printer controller.
consider getting a board designed by think3dprint3d adrian bowyer
they use the superb Trinamic 2.8A stepper drivers which have high accuracy and high frequency interpolation, and Adrian properly designed the PCB to actually take heat away.
you might think you are doing yourself a favour by getting a cheap china knockoff but it is a huge risk
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