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chemrox
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lab automation
I don't like to hang around watching my pots during long refluxes. I also don't like burning up reagents and gear. I have found two items very
useful. One is a temperature controller and the other a flow monitor for my water supply. If the temp goes above a preset point or the flow drops
below a percentage of the starting water flow, the reaction gets shut down. Here's what it looks like during an esterification reaction.
"When you let the dumbasses vote you end up with populism followed by autocracy and getting back is a bitch." Plato (sort of)
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Hexavalent
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That is an excellent idea, and would certainly save a lot of time and frustration for us.
However, how much does such a setup cost? I would assume it is rather expensive, something that is not in our favour generally as amateur chemists.
"Success is going from failure to failure without loss of enthusiasm." Winston Churchill
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triplepoint
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you may want to look at this Arduino thread: http://www.sciencemadness.org/talk/viewthread.php?tid=21153
or this lab automation thread: http://www.sciencemadness.org/talk/viewthread.php?tid=16440
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DJF90
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@Chemrox - I have that electrothermal controller too. Its neat shit.
While technically not quite "automation", one thing that has made my life (and lab) 100% more pleasant is one of these:
[Edited on 23-10-2012 by DJF90]
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phlogiston
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That's a cold water bath, right?
-----
"If a rocket goes up, who cares where it comes down, that's not my concern said Wernher von Braun" - Tom Lehrer |
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DJF90
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Its a little more useful than that. Its a refrigerated circulator, which means all I gotta do is hook up a condenser to the orange hose at the back,
turn it on, and set the temp. And it'll maintain that temp. All the way down to -10*C. I've also got a refrigerated cold trap, down to -55*C to
protect my highvac pump from the bulk of vapours that it may encounter. The gas ballast takes care of the rest.
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Hexavalent
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Very nice, DJF!
Where did you acquire such a unit, and at what price?
"Success is going from failure to failure without loss of enthusiasm." Winston Churchill
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DJF90
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I bought it on ebay for about £350. It arrived in good condition and powered up. I didnt have much time due to university, so it stayed in the box
for about 8 months. When I came to use it for a synthesis, I noticed the temperature was INCREASING when running a reflux. When I opened it up I
noticed the schrader valve on the compressor was missing and an old "tag" around the valve housing noting this. It was a bit long after the purchase
to contact the seller so I set about getting it refilled myself. This was recently completed and now it works fine.
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ScienceHideout
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I found this grill thermometer- it is pretty neat! It is essentially a thermometer probe attatched to a controller. It beeps when it gets to the temp
you set it to! Let's say you are distilling something from 70 degrees to 76 degrees- I can set it to 75 degrees, and I can sit back and relax. Then,
it beeps, and I know that it is almost time to change out my collection flask! How handy and inexpensive!
hey, if you are reading this, I can't U2U, but you are always welcome to send me an email!
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microtron
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There can be done many things on lab automation, depends how much you have free money and how good you're in IT and electrical engineering (sub-
automation--microcontrollers etc etc). but also there are(as opposite to positive a negative side) big dangers involved also, as with all software
part modulations, especially if you write your programs by yourself. Lab itself is a very dangerous place (depends of course the reactions you're
doing but still-in lab everything can happen and they usually come as a chain mechanism-works the same way as the automation laws).
If many microchip fabrics work light off rezime(fully automatic), then you can imagine what can be done on laboratory on routine procedures or
whatever processis..it all comes down to how effective it is. But in the future? no questions asked..all will be automated everything and
everywhere..but this is one big separate topic for general discussion.
I; will get into details later as I'm quite interested also and haven't put much thought on this before, but tonight haven't slept all night, no
sleep, but feeling very sleepy...nothing helps - it's almost morning here.
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CaliusOptimus
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Automation is kind of a simple task these days. There's an off the shelf part for just about every situation. Look at omega.com to get a quick
overview of the common stuff! Connect your I's and O's to a PC and start your own fully automated pilot plant...lol
That's a sweet chiller DJF... I wanted one so bad I set out to make one myself. Turns out it was a cheap investment, I was able to pull it off for
about 50 bucks! Got an old mini fridge for free, and submerged the evaporator into a plastic container full of antifreeze. Used a submersible pump and
plumbed it to some nice spigots on the outside of the fridge. Also got a thermostat on ebay for 10 bucks, that goes from 30c to -30c. The use able
range on the DIY chiller is from -10c on up! I made a thread on it a while ago... maybe I'll update it one of these days.
The real challenge is getting below -20c. You can't get away with common refrigerants like r-12 or 134a. I've wanted to build a -50c unit from
scratch, but it's looking like a $1K project. When you go below -20c, pumps won't pump, flexible tubing wont flex, fittings will leak or snap, etc.
[Edited on 27-10-2012 by CaliusOptimus]
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smaerd
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beautiful set up. Thanks for sharing I plan on automating with a PID in a few months.
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DJF90
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@Calius I think I remember seeing your DIY chiller. I think in reality the lower -10*C limit is very reasonable - you don't really need to circulate
coolant at a lower temperature through condensers and such; if you've got something that won't condense at that temperature then you're moving into
dry ice/LN2 territory. The plus side from this argument is that making a cooler at -50*C or so becomes more simple; the coolant remains stationary
(its a cold trap now!) and I guess you could use propane as a refrigerant. I suspect my cold trap needs a top up actually, as it only seems to reach
-38*C lately. When I open it up I suspect it'll tell me what gas is employed. Hopefully it runs on propane and not some obscure refrigerant, as this
makes things simpler for me to do myself. Although loading propane as a refrigerant doesnt seem like a nice/easy job. I also wonder how easy it would
be to adapt it to run at a lower temperature.
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chemrox
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@DJF90-- Now *that* was a really nice score worth showing us! Once in awhile ebay gives us some great deals. My vacuum line with a Welch Chemstar,
drap, dewar, electronic vacuum gauge with a sturdy cart, clamps and framework was under $600 shipping incl. I got a vacuum oven in working condition
for under $200. ( I do some soils chemistry on the business side and the oven works great for drying the samples.) I paid retail for the flow control
but got the temp controller for under $100. I found another flow monitor on ebay right after I ordered the one shown and I'll test it if anybody
wants to pay me what I paid. I think it was $125 but might have been cheaper. Anyway I'll test it and post a pic if there's interest. I'll also
look up the actual cost. With enough tubing and T adapters there's no need for more than one. Mark me down as very envious of DJF! That is really an
essential piece of gear for a solo chemist who doesn't want to stay up all hours and go running out for dry ice every other day. A word on vacuum
traps- size does matter! don't scrimp and go too small. I've got some small traps for those of you doing a lot of distillations in flasks of 10 - 50
ml. Ohh!! DJF- if you haven't already got one get an aspirator pump! I've mentioned these before. Since I don't have a recirculator I run the
condenser water from my evporator through the aspirator pump's tank. I ran into a glass aspirator (regular kind) that pulls under 10. The dual port
a.p. does as well or better. Thanks again DJF. You brightened up my evening! It's true that my modifications aren't really automation in the true
sense but they make my life a lot easier. A good friend and partner has offered to help me build a chiller/recirculator. I'd like to throw in one
last observation; aside from the greatest pleasure in having ones own lab is the pleasure of collaborating with intelligent and creative people who
have similar and often complimentary interests! Long live ScienceMadness.
[Edited on 30-10-2012 by chemrox]
"When you let the dumbasses vote you end up with populism followed by autocracy and getting back is a bitch." Plato (sort of)
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DJF90
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Hey Chemrox, thanks for the kind words. I dont need an aspirator as I have a KNF PTFE diaphragm pump, ultimate vacuum 8mbar (routinely gets 20 when
connected to apparatus), flow rate 10L/min. I've pumped all sorts of nasty vapours with that beast and it keeps kicking! As for the refrigerated cold
trap, the trap volume must be approximately 4-5L and hooked up to a 2 stage rotary vane pump with a 10.8CFM (300L/min) flow rate and ultimate vacuum
of about 1 micron (I must have a leak in my schlenk line or something because the mcleod gauge reads 0.5mbar. I've found a couple more pictures for
your admiration. Please enjoy
[Edited on 30-10-2012 by DJF90]
   
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chemrox
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One last reply to my dear friend Hexavalent. You are right and right and maybe right but maybe not quite so. I bought part of it retail and found an
older version of the flow control on ebay afterwards. I work in an industrial area and have my lab where I work. Many of us have labs in our homes.
What's $600 or so if it keeps you from burning your house down? As has been shown here and in related threads, there are some good DIY solutions. I
recommend those to anyone who can pul them together. AS DJF has shown patience is rewarded with very cool solutions too. If I hadn't been in a bind
to get something done before I could find cheaper gear I could have had the setup for right around $200. As it happened it was about $625. I think
either might be cheap peace of mind and cheap peace at home too... "Honey, I'll be back before 02:00 I just have to check on something I'm running at
work." Thanks for the insights and good questions Hex.
"When you let the dumbasses vote you end up with populism followed by autocracy and getting back is a bitch." Plato (sort of)
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DJF90
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Pictures are now uploaded. Sorry about the poor image quality in some cases.
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chemrox
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Thanks DJF-that is a nice pump!
I had another thought, question about equipment for amateur chemistry. How do you recommend controlling vacuum on the cheap? I tried using a needle
valve for three hours today. I wanted a 35 mm vac so i could imitate a published process. I could have hooked up my Cartesian diver manostat but I
wanted to do this in a way accessible to the hobbyist. It was very frustrating. I never had a stable vacuum. I was chasing it the whole time. I've
done better making a pin prick in thick walled hosing but the vacuum attained is arbitrary.
[Edited on 2-11-2012 by chemrox]
"When you let the dumbasses vote you end up with populism followed by autocracy and getting back is a bitch." Plato (sort of)
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DJF90
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I have several ideas. I can adjust vacuum to the nearest 5mbar just by opening another tap slightly on the schlenk line. Note that the smaller the
bore of the tap, the more controllable your leak will be. Another method is to use a capillary in the boiling flask and a hoffman clamp on some rubber
tubing attached to the other end. Loosen off the clamp to create the bleed. A third method related to your second idea is to use a subaseal and
needle. I've a few sizes of needle (19G, 21G, 23G and 25G) and I'm sure the smaller sizes (in particular the 25G) will suffice for a small leak.
Obviously this effect will depend on a) the highest attainable vacuum of the system prior to introducing the leak and b) the pumping rate of the
vacuum pump.
As a related aside, I've considered building a PWM controller for the KNF pump. I doubt such means would be any good for a rotary vane, but it should
suffice for control of a diaphragm. % on/off would dictate what pressure is maintained I guess. One fault with this idea is that if you have no leaks,
and you set the % on to say 20%, then when you reach the desired pressure it will continue pumping. Perhaps one of the more electrically minded
members of the forum (@Woelen?) can come up with a control system. I'd like to say a thermistor can be used as a sensor, but not in this pressure
regime I suspect (down to say 10mbar).
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CaliusOptimus
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This is what I use to control pressure. I got the vacuum regulator on ebay for about 15 bucks. It regulates accurately from about 10 torr to
atmosphere.
Quote: Originally posted by DJF90  | | As a related aside, I've considered building a PWM controller for the KNF pump. I doubt such means would be any good for a rotary vane, but it should
suffice for control of a diaphragm. % on/off would dictate what pressure is maintained I guess. One fault with this idea is that if you have no leaks,
and you set the % on to say 20%, then when you reach the desired pressure it will continue pumping. Perhaps one of the more electrically minded
members of the forum (@Woelen?) can come up with a control system. I'd like to say a thermistor can be used as a sensor, but not in this pressure
regime I suspect (down to say 10mbar). |
Is that a DC pump? If it's DC a PWM would work, but chances are it is AC brushless, in which case you would need a frequency inverter. If it's AC
brushed you can use a triac based control (ie light dimmer).
It would be a plausible but expensive project. A digital vacuum gauge would run from 100 bucks for something basic up to a grand or so for a high vac
gauge (piranni or baratron). Then you would need to connect that to a control to tell the PWM/Inverter what to do and when. I could justify this setup
for research or a pilot plant, but certainly not a home lab
Another thought: A mass flow controller would make for a good electrically controlled adjustable leak. We use these at work to regulate the
stoichiometry of nitrogen gas in a PVD process. They are also used with argon to set the pressure in a high vacuum chamber.
[Edited on 2-11-2012 by CaliusOptimus]
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DJF90
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I totally forgot to even think about the whole DC/AC issue. Thats that out the window then. I've grown accustomed to the digital vacuubrand systems,
very easy to work with but they cost a ridiculous amount. Too much for me to invest in for home use.
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Hexavalent
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Nice chemporn, guys!
What are you on about, chemrox?
"Success is going from failure to failure without loss of enthusiasm." Winston Churchill
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DJF90
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@ Hexavelent: see here http://pubs.acs.org/doi/abs/10.1021/i560158a016
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chemrox
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@hex
I was trying to hold a 35mm vac to check a published temp at that P. I screwed up by trying to use a controlled leak along with a Cartesian manostat.
Cartesian divers don't like leaks. You do one or the other; leak or manostat but not both. Next: Hg cleanup. I feel embarrassed for not thinking
this through.
"When you let the dumbasses vote you end up with populism followed by autocracy and getting back is a bitch." Plato (sort of)
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chemrox
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I found exactly the thing I needed. I also dug up some apparatus from storage. I got the Cartesian diver working for vacs < 1 torr
The di-N-butylpthalate bubbler for vacs 1<10 torr and the needle valve for 10<100 torr. They are all shown on pp 114-5 Vogel's 3rd. (I also
have the Vogel 5th edition if anyone wants one).
"When you let the dumbasses vote you end up with populism followed by autocracy and getting back is a bitch." Plato (sort of)
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