<Noxz>
so, curious if anyone has looked into inductive proximity sensors before? especially PCB based ones? looking for good tracking, cheaply?, for my piezo stages (AG-LS25)
<SpeedEvil>
Have you looked at capacitive too? The TI and AD range of capacitive sensor chips are interesting. Meant for fingers, but they are quite flexible.
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<Noxz>
I somewhat have.. I like the no-contact method of inductive
<Noxz>
there's also the option of standard DRO tracking
<Noxz>
weird in my head, because there are two projects
<Noxz>
one is just a force gauge, the other is the piezo stage position tracking
<john_cephalopoda>
How exact can you measure? And can you move as exact as you can measure?
<john_cephalopoda>
If you can only move with mm accuracy, it won't make sense to measure in nm :þ
<Noxz>
well, the mvoement isnt so exact, hence the need for the DRO or similar
<Noxz>
and it does far better than mm movements
<Noxz>
I think the minimum step is 50nm
<Noxz>
0.05um, yup
<Noxz>
but, it may do more than that, and every step is not garunteed
<Noxz>
it's basically just a piezo on a compliant push/pull system
<Noxz>
oh, it's range is only 12mm total, I thought it was 25, hence the name AG-LS25
<Noxz>
I love how simple the system is, but no positional readings beyond limits
<Noxz>
oh, max speed of 0.5mm/s is incredible as well :P
<john_cephalopoda>
You might be able to do something with that and masks, I doubt that it will work well for direct-write litho though.
<Noxz>
from what I understand, the stages is just to move over a little bit for another exposure, but it could work for writes, just very slow
<Noxz>
I have quite a few of them so gotta figure out a use
<Noxz>
positioning in a SEM or similar was the primary goal iirc
<Noxz>
the SEM itself can be used for litho, e-beam with PMMA PR
<john_cephalopoda>
With direct-write, you don't only have to be able to position it correctly, you also have to be able to move it without overshooting your target.
<Noxz>
well, upon reading position, if it goes out of tolerance, you turn off the laser or whatever
<john_cephalopoda>
When you got a mask, you only have to expose, move it to a position (which can take a second or a day, doesn't matter), then expose it again and repeat.
<john_cephalopoda>
So you'd basically draw short line segments?
<john_cephalopoda>
You could maybe even do it line printer style.
<Noxz>
that is one method
<Noxz>
no different than a printer
<Noxz>
heh, maybe
<Noxz>
the other is more of a CNC router style
<Noxz>
best path sort of thing, but the issue is your going to be turning the expsoure on/off somehow
<Noxz>
anyways
<john_cephalopoda>
Noxz: Just turn the laser on and off.
<john_cephalopoda>
You could be able to do that with a Raspi or an Arduino.
<Noxz>
well, yes, but the point is if you are doing that in the first place, then line by line vs an actual path is simple to figure out
<Noxz>
also, no need to run it with an embedded board.. I dont understand people's infatuation with trying to use them for everything, especially if a computer/laptop is nearby
<Noxz>
I watched a few linux-fest related talks and one speaker asked the audience at the beggining: what cool things have you done with a rpi beyond a blinky LED? no one asnwered... towards the end she basically asked the same thing, and a guy responded: a blink led
<Noxz>
a blinky led
<Noxz>
they are just fairly underpowered for what they are
<Noxz>
the interface that is used is actually a usb->serial onboard, so lots of things could interface with it.. I tried to tap directlyonto the serial line and didn't really get much of an output, I may revisit that later
<john_cephalopoda>
I am using my RasPi as a web server. It serves my website.
<Noxz>
because then it will be fairly easy to interface with
<Noxz>
yeah, but for what purpose?
<Noxz>
like, why not use a 24core server, in a rack with a hundred others?
<Noxz>
hosted in a datacenter with uptime
<Noxz>
like, the idea you are running stuff that runs on normal hardware is ridiculous
<john_cephalopoda>
I want to have control over my server.
<Noxz>
the only advantage is you can hide it in an altoid can under your bed
<Noxz>
I think you are missing the point
<Noxz>
it is under powered for any large amounts of work
<Noxz>
and, does your web server do ANYTHING with the GPIO?
<john_cephalopoda>
The latest one is pretty strong. Quad-core ARM.
<john_cephalopoda>
I am not doing anything with the GPIO, but I have used other boards and did stuff with their GPIO.
<Noxz>
I get it, my irc box is a lil ARM device..
<Noxz>
but the idea of WHY is still echoing
<Noxz>
like, why not have a more powerful U1 racked server somewhere?
<john_cephalopoda>
It saves energy and is cheap.
<john_cephalopoda>
Cheaper than a racked server.
<Noxz>
it saves energy because it's not computing much
<Noxz>
but what about controlling the piezo stages with such a thing? you still need to interface with it somehow
<Noxz>
make a web frontend wher eyou upload from one computer a gcode file or similar to that one?
<Noxz>
I think it adds an unecessary step
<john_cephalopoda>
?
<Noxz>
I dont see the point of using such a thing
<Noxz>
it doesnt serve a purpose
<john_cephalopoda>
The piezo stages and sensors can be easily controlled by the Arduino.
<Noxz>
I just somewhat stated no, due to the usb->serial driver, which can surely be emulated, but meh
<john_cephalopoda>
Reading out sensors that use U(S)ART with a computer is really shitty.
<Noxz>
also sensor control isnt difficult with a computer, you just need an interface
<john_cephalopoda>
That's the issue. Where do you get that interface from?
<Noxz>
it could be an arduino.. or whichever kind of thing that has GPIO
<john_cephalopoda>
Exactly.
<Noxz>
but the point of not needing to program a uC and having sensor interface boards available is an idea
<Noxz>
like, this is an industrial thing
<Noxz>
solutions exist
<Noxz>
I love to DIY, but will it be held together with hot glue at the end of the day?
<Noxz>
not that it wont work
<Noxz>
but reading sensors from a computer I think is a non-issue
<Noxz>
it's been solved a million times over
<Noxz>
if you want to build a system around those sensors, instead of using a computer, then sure, but I think a rpi running ubuntu/whatnot is the wrong way to go about it
<john_cephalopoda>
It has been solved by putting some small computer between the sensor and the computer.
<Noxz>
to call it a computer is sometimes misleading though
<Noxz>
rpi is one, sure, but you dont need that
<Noxz>
you just need an interface
<john_cephalopoda>
Always depends on what you want to do with it.
<Noxz>
so why spec out a full computer with a full OS?
<john_cephalopoda>
A RasPi would allow you to run a nice UI, which allows you to set parameters on-the-fly without having to connect a computer to your setup.
<Noxz>
arduino et al is for prototyping
<john_cephalopoda>
You could also buy some industrial solution or make your own board for 500€.
<Noxz>
production CNC controls have LCDs and whatnot, is that not nice enough?
<john_cephalopoda>
Production CNC controls are probably ARM boards, so pretty much the same as a RasPi.
<Noxz>
I would pay $500 instead of wasting days of my life trying to make such a thing myself
<Noxz>
well, at least I would when I was still working, but since I am back in school, I may change my aspect slightly
<Noxz>
saving money is nice, sure, but saving time I think is better
<Noxz>
in tech I was getting near 500/day, so you can kind of see the idea of: just pay the man
<john_cephalopoda>
Reading out sensors and controlling hardware with an Arduino board is _trivial_. It will take you a few hours. And it will cost you less than 20$.
<Noxz>
I'm pretty sure I would spend more than a few hours tweaking stuff ot get it all right
<Noxz>
and then building a UI for it all?
<Noxz>
I am sure solutions exist
<Noxz>
ie open source controls and whatnot
<john_cephalopoda>
UI is not really required. You can just send commands from your computer.
<Noxz>
ie: upload a gcode file
<Noxz>
or send them, rather
<Noxz>
I'm more or less imagining a white/black bitmap - nothign more is really needed
<john_cephalopoda>
I'm sure that there are pre-made CNC solutions for Linux+Arduino already.
<Noxz>
bitbang some pixels
<Noxz>
but there are CNC boards as well
<qu1j0t3>
john_cephalopoda: there definitely are
<Noxz>
which is my whole point
<Noxz>
that are application specific
<john_cephalopoda>
Those CNC boards are most likely not made for the job that you want to use them for.
<Noxz>
they are for stepper motor driver.. what I have is a piezo driver board though
<john_cephalopoda>
And getting those boards to work for lithography is probably harder than just taking an Arduino and tweaking it a little.
<Noxz>
I've interfaced arduino-esque boards with CNC controllers before
<Noxz>
but all they did was send gcode in ascii
<Noxz>
I spent over two days trying to get it all working, whereas it worked fine from the computer from the get-go
<Noxz>
a bit of that was learning the ARM board I had
<Noxz>
which I am no longer using
<Noxz>
anyways.....
<Noxz>
rapid prototyping is a real thing, and I get that
<Noxz>
but I dont get why people would use something like a rpi which runs a complete linux OS, simply for gpio pins
<john_cephalopoda>
When I said RPi, I just listed it as a thing that is used a lot. Of course it is overpowered. You could maybe do nice stuff with it if you really wanted (e.g. using it as a wireless device that you can just send your stuff to etc.).
<john_cephalopoda>
All in all, an Arduino should do.
<john_cephalopoda>
I'm just using the RPi for my server because it was super-cheap and is energy-saving and fast enough.
<john_cephalopoda>
An advantage of using cheap parts is, that more people might be able to replicate the set-up (if you write down instructions) and might contribute improvements.
<Noxz>
nice chattin, I have to do some work on the house
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