<nmz787>
I thought the SEM for $200 was a good deal
<nmz787>
(the one I just got)
<nmz787>
I too thought turbos were more than $150/250
<_Sync_>
yeah, I'm also still looking for a sem
<_Sync_>
but I don't really have the space
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<nmz787>
is there a 'best' motor controller over on fusor.net? I see one that uses some NAND gates, and then a few pages later someone posted an improvement using a full H-bridge chip... but while they have inputs for the hall sensor, I can't quite tell how they slowly ramp up the motor speed then hold it there once the max RPM is reached.
<_Sync_>
I never looked into that because I have controllers for all my pumps
<whitequark>
nmz787: does your pump have a hall sensor?
<whitequark>
or does it rely on back-EMF?
<nmz787>
whitequark: haven't bought one yet... currently I have a diffusion pump, but after looking on ebay it /does/ seem possible to get something with a comparable pump rate
<_Sync_>
it's not hard
<_Sync_>
and turbos are so much easier to deal with
<nmz787>
the diffusion pump says 400l/s but I read someone else replaced a diffusion pump with a lower pump rate turbo and they actually pumped down /faster/
<nmz787>
i know a friend made a centrifuge once using a BLDC and back-EMF so I am going to ask him for tips
<nmz787>
but the multiphase seem like a bit more of a challenge
<_Sync_>
I just ran the leybold from a simple fixed frequency driver
<_Sync_>
but yeah turbos usually pump faster
<nmz787>
SpeedEvil: are you going to try and replicate some MOSFET (just based on your interest in those die MOSFETs)?
<nmz787>
_Sync_: are you the one who got the varian starcell IGP?
<_Sync_>
yeah
<nmz787>
did you say it stopped working?
<whitequark>
nmz787: my advice is to use a dedicated BLDC driver
<whitequark>
there's a whole lot of them these days and they're very easy to use
<_Sync_>
no, there just was an itsy bitsy spider in there
<nmz787>
whitequark: looked through your lab notes last night... some cool stuff you've been doing!
<_Sync_>
they want quite a lot of current starting up
<nmz787>
whitequark: you give me hope for interfacing HV circuits with microcontrollers/etc
<nmz787>
whitequark: I'm not sure what you were thinking about the decoupling caps being so far away in the first place though... :) that's the first rule in all the datasheets 'C1,C2,C3 should be as close to the IC as possible' :D
<nmz787>
etc
<_Sync_>
well, there is no problem in interfacing them
<_Sync_>
you just gotta be aware where what is
<_Sync_>
but yeah bad choice of the inductor
<_Sync_>
but I'll test the ion pump with one of my power supplies I have floating around
<_Sync_>
oh whitequark
<_Sync_>
can you please go fuck yourself?
<_Sync_>
your twitter account reminded me of the solar physics lecture last semester
<_Sync_>
where we had to calculate the amount of generated charge carriers in a solar cell by hand.
<_Sync_>
doing so is no fun at all.
<whitequark>
nmz787: I did place them 'as close as possible'!
<whitequark>
except I did not have a very good idea of what is possible
<whitequark>
(seriously)
<whitequark>
like I went over it in a few days and went "lol. wtf did I do here"
<whitequark>
nmz787: generally keep tuned, I want to make a whole bunch of these, with a standardized STM32-based controller, all bound in a single ethernet network and controlled via UDPv6
<whitequark>
_Sync_: "doped with europium" actually refers to strontium aluminate
<whitequark>
glow ceramic
<_Sync_>
I meant your tweets about how fets and bjts
<whitequark>
oh
<whitequark>
oh yeah I can't imagine doing like 80% of undergrad physics by hand
<whitequark>
why bother with symmetric approximations if you have FEM?
<whitequark>
like it's not even pedagogic, the only thing it teaches you is "physics is boring"
<_Sync_>
because you need to understand what synopsys does before you mess with it
<whitequark>
I'm aware of this argument but not convinced by it
<whitequark>
like.. by all means, do tell me to write this integral
<whitequark>
then let me compute it numerically or something
<whitequark>
fuck analytical solutions that just make you waste paper
<_Sync_>
okay, I'll give you a session of synopsys and a few parameters and your task is to optimize it for a certain efficiency (solar cells)
<_Sync_>
you can just #yolo and have it simulate *all* differences within reason
<_Sync_>
but then you are waiting for it to converge in the next century
<whitequark>
let me rephrase: you absolutely should understand the underlying effect. but I am not convinced that doing dozens of plug-and-chug type problems does anything to help understanding
<whitequark>
or rather, I know it doesn't for me
<_Sync_>
well, it is the same for me
<_Sync_>
but I can understand the teachers
<whitequark>
oh, I *can* understand the teachers. I see where they're coming: a place where the most advanced computational tool is a slide rule
<_Sync_>
because it is easier to have people chew on a hard example to work through than to explain it to death
<_Sync_>
haha no
<whitequark>
well
<whitequark>
that is more malicious :p
<_Sync_>
not really
<_Sync_>
it helped me to do it on my own
<_Sync_>
to see what parameter does what
<_Sync_>
and that is all simple maths
<_Sync_>
should be in your toolkit
<whitequark>
full disclosure: I dropped out after failing diffequations eight times
<nmz787>
whitequark: sounds like you did your due diligence with trying to pass at least!
<whitequark>
I sort of like the concept behind, but in the time I wasted trying to learn doing them by hand, I could probably write a computer algebra system or two
<nmz787>
the last calc class i took last fall to get my degree, I used sagemath cloud and it made the class a lot nicer IMP
<nmz787>
IMO
<_Sync_>
although if you are on the level of the wave functions it starts to get over my head
<nmz787>
and I started looking into the different solver software out there... coding helps me organize complex tasks with mundane portions of work for sure
<whitequark>
exactly
<_Sync_>
and you then need to understand the grand canocial ensemble to actually understand pauli
<_Sync_>
I was like F that then
<whitequark>
oh ha I was just reading about that yesterday
<_Sync_>
but what do I know about solid state physics
<_Sync_>
I'm just an EE
<_Sync_>
and thank god I'm done with all that semiconductor bsnz
* whitequark
looks at _Sync_ then at channel name
<nmz787>
heh heh
<_Sync_>
well, from an education standpoint
<_Sync_>
I might take some more of it if I finally decide to study further
<SpeedEvil>
In about 15 seconds, she would be sweating heavily from the IR
<whitequark>
how about purifying low-grade Si by recrystallization
<SpeedEvil>
whitequark: It's all quite achievable.
<_Sync_>
sure, if you can buy low purity Si
<_Sync_>
which again is not easy
<_Sync_>
but the thing is
<SpeedEvil>
whitequark: But almost certainly insane
<SpeedEvil>
_Sync_: broken solar cells?
<_Sync_>
you do *not* want to deal with the chlorine chemistry
<whitequark>
SpeedEvil: I never laid a claim to sanity!
<_Sync_>
SpeedEvil: impossible
<_Sync_>
gotta fish all the dopants out and the lead
* SpeedEvil
imagines unbreakable solar cells.
<whitequark>
_Sync_: that's simple. Step 1: take a bucket of sand
<whitequark>
;D
<_Sync_>
...
<whitequark>
on a serious note, ebay has plenty of low-purity Si
<whitequark>
anyway, I wanna try a few things with it when I get a massspec working. SIMS should be enough to confirm the purity of samples
<whitequark>
if it's intractable within my lifetime, so it will be
<_Sync_>
just buy a quadrupole
<_Sync_>
those are the things that are sexy to DIY but just really not possible
<_Sync_>
because you want them to just work
<whitequark>
a QMA is something I'm definitely making from scratch and publishing as OSHW
<whitequark>
well, QMA, detector, and control electronics
<SpeedEvil>
TOF is interesting too
<whitequark>
TOF is a real pain
<whitequark>
TOF seems conceptually simple but the engineering is nasty
<_Sync_>
so is a QMA
<whitequark>
QMA involves shit like rf+dc fields but the engineering is quite tractable if not simple
<_Sync_>
if you want any sensible resolution
<whitequark>
_Sync_: what would you say be my worst problem with a QMA
<_Sync_>
and requires really annoying fixturing
<_Sync_>
because the alignment of the quadrupoles is critical
<whitequark>
yes, it needs precision machining
<whitequark>
I've considered using a commercial head but I think designing one could prove useful
<whitequark>
maybe just a commercial rod assembly, if I turn out incapable of making a good enough one
<_Sync_>
I mean I reversed most of my spectra mass
<_Sync_>
the thing is not even the rods
<_Sync_>
you can buy them
<_Sync_>
because you don't really need profiled ones
<_Sync_>
but alignment is tricky
<whitequark>
sure, hence "assembly"
<_Sync_>
and you need a good MS to get that teaked
<_Sync_>
+w
* whitequark
grumbles
<whitequark>
*hopefully*, by the end of next week, i will have the chamber that i designed
<whitequark>
*finally*
<whitequark>
it took fucking weeks to convince some of the machine shop to take my money
<SpeedEvil>
:)
<SpeedEvil>
How large a chamber? Bakeable?
<whitequark>
two NW160 flanges at the ends and 200mm long
<whitequark>
should give you an idea of size
<whitequark>
should be bakeable.
<whitequark>
it's fully SS+viton
<whitequark>
so... 150 or so
<whitequark>
the pump is connected via a long bellows so that should take care of it
<whitequark>
it's mainly to prove that I can do a viable chamber before moving on to something more complex, but it should serve me well as it is
<_Sync_>
should be pretty easy, just gotta bore out two flanges and weld the pipe in
<whitequark>
mmm actually nope
<whitequark>
that's not at all how I went at it
<whitequark>
I had the flanges turned--not even from rod stock since that's too large diameter, the machinist got it cut from 2cm SS sheet
<whitequark>
and the pipe was roll-formed, or it WILL be roll-formed on monday assuming the transfer clears, with holes for two additional KF40 and KF25 laser cut before forming
<whitequark>
all in all it the entire custom chamber will cost me $400 or slightly more
<whitequark>
well, no
<_Sync_>
I'd buy the flanges and just bore the extra holes
<_Sync_>
there is no need to roll form the pipe
<whitequark>
the chamber, the viewport, and a NW160 to 2*KF16+2*KF25+KF40 adapter
<_Sync_>
which only adds a leak point
<whitequark>
eh, it's going to be welded anyway
<whitequark>
flanges are too expensive to buy rather than machine
<whitequark>
and they also have nearly their own cost in shipping
<_Sync_>
DN160 flange is around 44€
<whitequark>
anyway, what's the point, if I'm machining these anyway?
<whitequark>
I don't have my own lathe or anything
<_Sync_>
the point is that it is cheaper to buy them rather than to machine them
<_Sync_>
because the stainless costs about 2/3 of that
<_Sync_>
and is annoying because you waste a lot
<whitequark>
machining a single KF25 is $10 with labor and material included
<whitequark>
it's not cheaper
<whitequark>
*KF25 nipple
<_Sync_>
and all the usual steel suppliers will charge for a 180mm plate
<whitequark>
and i don't pay for what's bored out anywya
<_Sync_>
kf25 flange with pipe 304 stainless, 11€
<_Sync_>
can't pay someone to do it for cheaper
<whitequark>
316L here but yes
<whitequark>
it's about same
<_Sync_>
316L has no benefit
<whitequark>
oh? I've seen conflicting opinions on this
<whitequark>
from what I gather the main difference is carbide precipitation in welds, which doesn't really matter for vacuum
<whitequark>
or for the small thicknesses i would have
<_Sync_>
well, the thing is 304 contains sulfur
<whitequark>
but i went for 316L to be safe
<_Sync_>
but for everything besides UHV 304 is preferred because it machienes way easier
<whitequark>
ah i see
<_Sync_>
then your machine shop is very nice to you, because if I'd be making the flanges for you you'd be paying for the slug that comes out
<_Sync_>
too small to be really useful
<_Sync_>
but too much material to waste
<whitequark>
dunno maybe they recycle it
<whitequark>
it seems like they should?
<_Sync_>
well, you can calculate about 5mm per side wasted, so you get a disc maybe 140mm in diameter 12mm thick
<_Sync_>
depending on the shop that might be okay to recycle