Building an autoclave?

[Paul Anderson]

I was wondering if anyone on the group had thoughts about what would
be involved in building an autoclave. Mind, I can machine parts, weld
and do electronics. So I can make some pretty complex bits. Any
thoughts are greatly appreciated.

--
Paul Anderson
VE3HOP
wacky...@gmail.com
http://www.andersonloco.com
QRP ARCI #13228, GQRP #12447

[Nathan McCorkle]

Seems pretty dumb to machine any of it... get a pressure cooker/canner, a pressure guage that's digital or just a celsius temp sensor, a hot plate, a relay, a transistor, a couple diodes, and an arduino, PIC, or STM85 microcontroller ($7) and a 5V wall power supply. Done.

http://www.st.com/mcu/contentid-130-113-STM8S_DISCOVERY.html

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[Len Sassaman]

Buy a pressure cooker for $15.

[Mackenzie Cowell]

I don't think it's dumb.

I'm interested in exploring espresso machines to see if they could be modded into cheap autoclaves.

http://groups.google.com/group/diybio/browse_thread/thread/7f67c81b9a61bcf3

Mac

+1.231.313.9062 / m...@diybio.org / @100ideas

[Marshall Louis Reaves]

On Jan 31, 11:11 pm, Mackenzie Cowell <m...@diybio.org> wrote:
> I don't think it's dumb.
>
> I'm interested in exploring espresso machines to see if they could be modded
> into cheap autoclaves.

I think the pressure cooker--you can get both electric and stove-top
models--is precisely to specs: 122 C and 15 psi. Plus, their low cost
should satisfy any thrift DIY'er.

Typical laboratory autoclaves use the 122 C and 15psi as the standard
procedure for sterilizing most things. There are "solid" and "liquid"
cycles. The latter of which vents more slowly to prevent boil-over
from liquids, while the "solid" cycles vent fast. Some fancier
machines have "wrapped solid" settings which do some drying at the end
to keep those pipette tips or whatever from having condensation on the
lid.

Dentists, piercing/tattoo shops, and other industries all use
autoclaves of various sizes, which all operate on these same
principles. One could also get small autoclaves from folded shops. The
ones at piercing/tattoo shops are microwave sized, which would be
pretty nice for some higher-traffic DIY-labs.

[Jay Woods]

On Sunday 31 January 2010 05:56:31 pm Paul Anderson wrote:
> I was wondering if anyone on the group had thoughts about what would
> be involved in building an autoclave. Mind, I can machine parts,
> weld and do electronics. So I can make some pretty complex bits.
> Any thoughts are greatly appreciated.
>

I write the controller software for a living at Primus Sterilizer
(http://www.primus-sterilizer.com/). What is it that you want it to do?
If you use a pressure cooker/canner, it would be handy to have a
resistance thermocouple hooked to a gauge and a timer triggered by a
particular temperature but not a necessary thing. After all the pressure
gauge spitting steam indicates the temperature and a clock tells the
time.

Beyond that it is only a question of what you want to automate. Primus
automates the door opening/closing and sealing/unsealing. They also (for
jacket and chamber) automate steam addition/removal, air
removal/addition, water removal/addition, and automated testing of the
chamber under vacuum and pressure for leakage. There are additional
gauges for time, pressure and temperature as well as limit/presence
sensors for doors, steam, water, air. All this is driven by the need
(from the FDA) to be able to record that the sterilization conditions
were met during a cycle of loading, sterilization, and unloading a
sterilizer and to notify the operator (and to automate the amelioration
of the extent) of a process upset during the cycle.

[Nathan McCorkle]

On Sun, Jan 31, 2010 at 11:11 PM, Mackenzie Cowell <m...@diybio.org> wrote:

I don't think it's dumb.

I think its dumb to attempt to machine something that could blow up in big heavy chunks in your kitchen, when you can buy the exact same thing at walmart for $20-25... more for increasing size. I got a canner at goodwill 6 or 7 years ago that goes to 20 PSI and can fit 7 quart mason jars inside... cost=~$35

I'm interested in exploring espresso machines to see if they could be modded into cheap autoclaves.

that's not machining something though, its made to withstand those temperatures, if it blows up you can sue.

[Nathan McCorkle]

Do you write your own PID??? that would be the hardest part that I can think of.

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[Jay Woods]

On Monday 01 February 2010 04:09:08 am Nathan McCorkle wrote:
> Do you write your own PID??? that would be the hardest part that I
> can think of.
>

I improved on the PID that was inherited with the project when I came on
board.

[Paul Anderson]

On Mon, Feb 1, 2010 at 1:10 AM, Marshall Louis Reaves
<marshal...@gmail.com> wrote:
>
>
>
>
> Typical laboratory autoclaves use the 122 C and 15psi as the standard
> procedure for sterilizing most things. There are "solid" and "liquid"
> cycles.
>

Really? I thought it would be higher pressure than that. That's easy
enough, I've got my share of pressure cookers here. Even have a spare
omron temp controller hanging around.

>
> Dentists, piercing/tattoo shops, and other industries all use
> autoclaves of various sizes, which all operate on these same
> principles.
>

I've had my eye on ebay for a while looking for autoclaves. It seems
they never get much below $200. Granted, for most that's not much -
but my economic situation is not quite so favourable at the moment.

[Paul Anderson]

On Mon, Feb 1, 2010 at 5:06 AM, Nathan McCorkle <nmz...@gmail.com> wrote:
>
>
>
> I think its dumb to attempt to machine something that could blow up in big
> heavy chunks in your kitchen, when you can buy the exact same thing at
> walmart for $20-25... more for increasing size.
>

There's one quick detail I left out - I'm a ticketed pressure vessel
welder whose tickets have expired. TSSA all position pipe. I can do
a weld that can withstand upwards of 1,000 PSI using a 6010 root pass.

[Paul Anderson]

On Mon, Feb 1, 2010 at 1:53 AM, Jay Woods <wood...@cox.net> wrote:
>

> I write the controller software for a living at Primus Sterilizer
> (http://www.primus-sterilizer.com/). What is it that you want it to do?
> If you use a pressure cooker/canner, it would be handy to have a
> resistance thermocouple hooked to a gauge and a timer triggered by a
> particular temperature but not a necessary thing.
>

I'm looking to put together a basic means of sterilization on a
budget. By budget, I mean less than a hundred dollars:) Preferably
made from junk I have kicking around. Not as hard as it may seem, my
junk pile is prodigious. I have a couple PLCs, even some industrial
DP cells floating about. Plenty of thermocouple wire. I have a
healthy stock of AVR microcontrollers, and a few PICs(though the AVR
is really my taste these days).

[Paul Anderson]

On Mon, Feb 1, 2010 at 8:05 AM, Jay Woods <wood...@cox.net> wrote:
>
> I improved on the PID that was inherited with the project when I came on
> board.
>

I wouldn't think implementing the PID algorithm would be that
complicated - it's pretty well documented. Tweaking the reset and
derivative terms is the hard part. Though, in this application I'd
think boring old proportional control would be sufficient. It seems
you have to worry more about the process deviating *below* a certain
threshold than above it. i.e. 17psi is more tolerable than 14psi,
even though the error at 14psi from a 15psi setpoint is smaller.

[Cathal Garvey]

You know, if you've got this much experience with PID, AVR Microcontrollers etc, you'd probably be one of the best equipped people around here to hack together an Open-Source Peltier Thermal-Cycler? Now that would be a real high-impact project for DIYbio, because although we can get by using pressure cookers for sterilisation, there are many applications of thermal cyclers that we can only crudely emulate with the tools available at present.

Peltier + High-Current Motor Driver/5v switching Relay + Standardised heater block + Arduino + PID Control = Ideal Thermal Cycler

--
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[Meredith L. Patterson]

On Mon, Feb 1, 2010 at 7:25 AM, Cathal Garvey <cathal...@gmail.com> wrote:
> Peltier + High-Current Motor Driver/5v switching Relay + Standardised heater
> block + Arduino + PID Control = Ideal Thermal Cycler

So, a few months ago I did some back-of-the-envelope math based on the
characteristics of aluminum, various ATX power supplies, and some
peltiers I was able to find on the web (many of which used voltages
over 5V, though that's not really here or there). I wasn't able to
come up with a configuration yielding greater than 1C/sec ramping
speed. Commercial ones offer more like 3C/sec. Did you find a way to
approach this?

I want to check out the thin-film/substrate heating elements at
http://www.thermostone.com/ at some point -- they look useful.

Cheers,
--mlp

[Paul Anderson]

On Mon, Feb 1, 2010 at 11:04 AM, Meredith L. Patterson
<clon...@gmail.com> wrote:
>
>
> So, a few months ago I did some back-of-the-envelope math based on the
> characteristics of aluminum, various ATX power supplies, and some
> peltiers I was able to find on the web (many of which used voltages
> over 5V, though that's not really here or there).
>

How do things like with a block made of copper instead of aluminum?

>I wasn't able to
> come up with a configuration yielding greater than 1C/sec ramping
> speed. Commercial ones offer more like 3C/sec. Did you find a way to
> approach this?
>
>

Now, that 3C/sec - is that heating *and* cooling?

[Paul Anderson]

On Mon, Feb 1, 2010 at 10:25 AM, Cathal Garvey <cathal...@gmail.com> wrote:
> You know, if you've got this much experience with PID, AVR Microcontrollers
> etc, you'd probably be one of the best equipped people around here to hack
> together an Open-Source Peltier Thermal-Cycler?
>

I can take a look. Does anyone have a webpage up with the current
status of such efforts?

[wood...@cox.net]

---- Paul Anderson <wacky...@gmail.com> wrote:
> On Mon, Feb 1, 2010 at 11:04 AM, Meredith L. Patterson
> <clon...@gmail.com> wrote:
> >
> >
> > So, a few months ago I did some back-of-the-envelope math based on the
> > characteristics of aluminum, various ATX power supplies, and some
> > peltiers I was able to find on the web (many of which used voltages
> > over 5V, though that's not really here or there).
> >
> How do things like with a block made of copper instead of aluminum?

Aluminum has more heat capacity per kg than copper (but not per cubic centimeter) and a third of the price per kg.

>
> >I wasn't able to
> > come up with a configuration yielding greater than 1C/sec ramping
> > speed. Commercial ones offer more like 3C/sec. Did you find a way to
> > approach this?
> >
> >
> Now, that 3C/sec - is that heating *and* cooling?
>
>
> --
> Paul Anderson
> VE3HOP
> wacky...@gmail.com
> http://www.andersonloco.com
> QRP ARCI #13228, GQRP #12447
>

[Cathal Garvey]

I'd love to see your notes, if you still have them and it's not too much trouble?

Personally I'd be happy with 1C/s, that's actually what I set my high-end thermal cyclers to in the lab I work in for PCR anyway! I find a lower cooling rate from 95 to 60 helps my primers to anneal to difficult templates more easily. If you want to ramp *up* faster, you can always use Nichrome to heat, and Peltiers to cool.

Did you look into using more than one peltier at a time? They stack well, I think.

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[Cathal Garvey]

Before I really came to grips with how much current Peltiers need, and how little the Motor chip I was using could take, I tried to set up a hack-job thermal cycler and put up some details here:
http://letters.cunningprojects.com/?p=58

It seems that motor chip isn't really up to task, I burned one out trying and burned my finger while I was at it. I think you'd need a relay, but when I went relay shopping I was too much of a noob to find one that switches at Arduino-level 3V and can deliver enough amps to drive a Peltier.

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[Meredith L. Patterson]

On Mon, Feb 1, 2010 at 8:46 AM, Cathal Garvey <cathal...@gmail.com> wrote:
> I'd love to see your notes, if you still have them and it's not too much
> trouble?

They are on the back of a literal envelope, on my table in Leuven.
I'll probably just end up reworking them, though. Next week I'm going
to my parents' place in Houston, and my dad and I are going to do some
aluminum machining and see what we can do as far as driving a peltier
directly from an ATX power supply. I'll report back.

--mlp

[Paul Anderson]

On Mon, Feb 1, 2010 at 11:49 AM, Cathal Garvey <cathal...@gmail.com> wrote:
>
>
> It seems that motor chip isn't really up to task, I burned one out trying
> and burned my finger while I was at it. I think you'd need a relay, but when
> I went relay shopping I was too much of a noob to find one that switches at
> Arduino-level 3V and can deliver enough amps to drive a Peltier.
>
>

The thing to do is have the arduino drive a transistor that can switch
a higher voltage supply. If the transistor is driving a relay,
remember to have a diode mounted backwards across the transistor to
absorb the transient created by the coil's magnetic field collapsing.

In a situation like this I like the ULN2803a. As I recall, it has the
protection diodes built in.

[Paul Anderson]

On Mon, Feb 1, 2010 at 11:21 AM, <wood...@cox.net> wrote:
>
>
> Aluminum has more heat capacity per kg than copper (but not per cubic centimeter) and a third of the price per kg.
>>
>>

Now, unless I'm very much mistaken, wouldn't that be a bad thing in an
application such as this? Greater heat capacity makes it harder to
change the block's temperature. If you want it to ramp faster, you'd
want it to store less heat, not more. Of course, I may be
misunderstanding things.

[Derek]

You might try the L293's bigger brother the 298. Solarbotics makes a
nice L298 kit, http://www.solarbotics.com/products/k_cmd/. With a
decent heatsink we're driving some good sized motors with it in a
mechanotronics class I'm taking right now...

--Derek

On Feb 1, 8:49 am, Cathal Garvey <cathalgar...@gmail.com> wrote:
> Before I really came to grips with how much current Peltiers need, and how
> little the Motor chip I was using could take, I tried to set up a hack-job
> thermal cycler and put up some details here:http://letters.cunningprojects.com/?p=58
>
> It seems that motor chip isn't really up to task, I burned one out trying
> and burned my finger while I was at it. I think you'd need a relay, but when
> I went relay shopping I was too much of a noob to find one that switches at
> Arduino-level 3V and can deliver enough amps to drive a Peltier.
>

> On 1 February 2010 16:14, Paul Anderson <wackyvor...@gmail.com> wrote:
>
>
>
> > On Mon, Feb 1, 2010 at 10:25 AM, Cathal Garvey <cathalgar...@gmail.com>

> > wrote:
> > > You know, if you've got this much experience with PID, AVR
> > Microcontrollers
> > > etc, you'd probably be one of the best equipped people around here to
> > hack
> > > together an Open-Source Peltier Thermal-Cycler?
>
> > I can take a look.  Does anyone have a webpage up with the current
> > status of such efforts?
>
> > --
> > Paul Anderson
> > VE3HOP

> > wackyvor...@gmail.com

> >http://www.andersonloco.com
> > QRP ARCI #13228, GQRP #12447
>
> > --
> > You received this message because you are subscribed to the Google Groups
> > "DIYbio" group.
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> > To unsubscribe from this group, send email to

> > diybio+un...@googlegroups.com<diybio%2Bunsu...@googlegroups.com>

[Edward Elhauge]

* Paul Anderson <wacky...@gmail.com> wrote on [2010-02-01 06:20]:
> On Mon, Feb 1, 2010 at 8:05 AM, Jay Woods <wood...@cox.net> wrote:
> >
> > I improved on the PID that was inherited with the project when I came on
> > board.
> >
> I wouldn't think implementing the PID algorithm would be that
> complicated - it's pretty well documented. Tweaking the reset and
> derivative terms is the hard part. Though, in this application I'd
> think boring old proportional control would be sufficient. It seems
> you have to worry more about the process deviating *below* a certain
> threshold than above it. i.e. 17psi is more tolerable than 14psi,
> even though the error at 14psi from a 15psi setpoint is smaller.

PID is not that bad. I did them for several years for motion, pressure
and temperature.

> --
> Paul Anderson
> VE3HOP
> wacky...@gmail.com
> http://www.andersonloco.com
> QRP ARCI #13228, GQRP #12447

---end quoted text---

Start out with a P (proportional term). Then you'll always have an
offset. If you set the P term too high, you get overshoot and
oscillation. Add in a I (integrate term) to close the gap. Once you tune
that, if you want higher performance you add a D (derivative term) as a
sort of friction term to oppose the motion. When you do that you can
then increase the P term and possibly the I term (to close the gap
faster).

Things to consider. 1) A stable sample rate. Jitter is bad. But it's all
proportional to the dynamic of your system. 2) A sample rate high enough
to keep up with the dynamics of your system. For a big heavy system like
a pressure cooker, with a lot of heat capacity, once a second is
probably fast enough. If you were to control motion you might need 100
Hz or more.

Look up "Critically Damped Systems" in a Physics textbook or online.

Cheers,

Ed Elhauge

--
Edward Elhauge <e...@uncanny.net>
http://www.linkedin.com/in/edwardelhauge
"The right dose differentiates a poison and a remedy." -- Paracelsus (1493 - 1541)

[Nathan McCorkle]

This is a direct copy-paste from a google doc for a thermocycler setup I've had planned. It's just using a power FET and an H-bridge, but covering each side of the cooling block with a peltier should help the heating/cooling rate:

Peltier Related

--Digi-Key List Of Peltier Devices - at least 1 For Base Heating, and 1 for Lid Heating
---http://search.digikey.com/scripts/DkSearch/dksus.dll?Selection

--H-Bridge Schematic
---http://chemelab.ucsd.edu/uFtempcntl/intro.html

--50v * 27A ( 120w max) FET transistor 4 * $0.86
---http://search.digikey.com/scripts/DkSearch/dksus.dll?Detail&name=FQP27P06-ND

--Transient Suppressor (for voltage spikes, in case peltier acts like inductive load between pulses)
---http://www.mouser.com/Search/Refine.aspx?N=10903742+4294648015+4294440381+4294646183+4293998103+4294648248+4294643517&Keyword=transient+suppressor&FS=True

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[Nathan McCorkle]

On Mon, Feb 1, 2010 at 9:06 AM, Paul Anderson <wacky...@gmail.com> wrote:

On Mon, Feb 1, 2010 at 1:53 AM, Jay Woods <wood...@cox.net> wrote:
>

> I write the controller software for a living at Primus Sterilizer
> (http://www.primus-sterilizer.com/). What is it that you want it to do?
> If you use a pressure cooker/canner, it would be handy to have a
> resistance thermocouple hooked to a gauge and a timer triggered by a
> particular temperature but not a necessary thing.
>

I'm looking to put together a basic means of sterilization on a
budget.  By budget, I mean less than a hundred dollars:)  Preferably
made from junk I have kicking around.  Not as hard as it may seem, my
junk pile is prodigious.  I have a couple PLCs, even some industrial
DP cells floating about.  Plenty of thermocouple wire.  I have a
healthy stock of AVR microcontrollers, and a few PICs(though the AVR
is really my taste these days).

<$100 = go to walmart, get pressure cooker and hot plate. Use your LM35 or thermocouples with your PIC and transistor and power FET/relay (upload schematic), do PID control (upload code to internet for me and others), plug in... is your time worth welding and etc etc, wouldn't it be easier and cheaper time wise to do what I just said (also it would be easily reproducible)

 

--
Paul Anderson
VE3HOP
wacky...@gmail.com
http://www.andersonloco.com
QRP ARCI #13228, GQRP #12447

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[Nathan McCorkle]

Going higher means increased boiloff... and its less reproducible... say you make media today and its 98mL when it comes out, and tomorrow you make the same recipe and its 95mL... it may be tolerable, but depending on what you're doing with it and on what scale, it may not be.

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[Nathan McCorkle]

On Mon, Feb 1, 2010 at 10:25 AM, Cathal Garvey <cathal...@gmail.com> wrote:

You know, if you've got this much experience with PID, AVR Microcontrollers etc, you'd probably be one of the best equipped people around here to hack together an Open-Source Peltier Thermal-Cycler? Now that would be a real high-impact project for DIYbio, because although we can get by using pressure cookers for sterilisation, there are many applications of thermal cyclers that we can only crudely emulate with the tools available at present.

Sure we can "get by" with a pressure cooker, but if you don't have a good stove, it can be a real pain in the ass to have to monitor the stove for the hour or so that it takes to cook everything. Automation means set it and forget it, and get other lab work done to prepare for whats coming out sterilized.

 

Peltier + High-Current Motor Driver/5v switching Relay + Standardised heater block + Arduino + PID Control = Ideal Thermal Cycler

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[Brian Degger]

Hi All

For pressure cookers on steroids, tattoo shops list this one
http://www.thetattooshop.co.uk/shop/products/tattoo-sterilzer-autoclave.htm
(£299) they also have a autoclave: Hydra 100 Autoclave 9 Litre
£599.99. These are expensive compared to a pressure cooker and an
electric hotplate + controller.

On the thermal cycler,

Been thinking that an open source pcr machine is the way to go. No
other machines seem to be as expensive. At a recent education trade
show, saw an education grade spectrophotometers for sub £500(vernier
spectrovis plus) and a fairly cheap thermocycler(edvotech) for £1000.

Derek, I'm using L298, and they too get really hot, but at least they
can drive 2amps/channel. Getting the sample to change at 1c/sec is my
target(0.5 is about what I am hitting, though have more combinations
of amperage/peltiers to try). It dosen't have to be superfast, just
looking for a machine that gets from a-b. If you look at the 3C/second
pcr machines(or their patents!), they have a stack of peltiers on top
of each other, or use hot air or hot liquid pumped from a resevoir.

Paul, if you look at the original peltier thermo(us patent 4,865,685),
as far as I understand they had a block of aluminium that could be
disengaged from the samples with a motor allowing the samples to cool
(Think Tito dissasembled a pcr machine to show this). In that case it
is good to have a larger thermal mass.
Cheers
B

On Feb 1, 5:57 pm, Derek <dere...@gmail.com> wrote:
> You might try the L293's bigger brother the 298. Solarbotics makes a

> nice L298 kit,http://www.solarbotics.com/products/k_cmd/. With a

[Jacob]

Not sure if anyones gotten far enough in their builds to answer this
but what type of power are yalls builds drawing? I ask because the
Hospital I went to with EWB last month had an autoclave that used 13A
240V and while that isn't too much in the States, the power isnt
constant and we may end up installing a battery backup. Worse case
scenario, power outs on the day they have to do 2+ operations and they
have to decide between sterile equipment or Oxygen.

[Aaron Hicks]

 
I don't get why oxygen has an electrical demand. Are they using an oxygen concentrator? Tanks are under pressure, and even LOX is boiled off with heat sinks. Perhaps you are referring to a respirator for surgery.

Anyway- unless my math is off, 13 amps at 240 volts = about 3 kilowatts, well within the range of a Honda gasoline generator- probably the lightest, safest, most reliable power source you could use. Another option: Listers. Last option: an external boiler that can be powered with electricity or fossil fuels such as kerosene.

-AJ

[Cathal Garvey]

I'm pretty sure 13A at 240 is just within the boundaries of a regular Irish wallsocket.. perhaps I should get one of these!

On Feb 9, 2010 3:54 AM, "Aaron Hicks" <aaron...@gmail.com> wrote:

On Mon, Feb 8, 2010 at 5:06 PM, Jacob <king...@gmail.com> wrote: > > Not sure if anyones gotten fa...

 
I don't get why oxygen has an electrical demand. Are they using an oxygen concentrator? Tanks are under pressure, and even LOX is boiled off with heat sinks. Perhaps you are referring to a respirator for surgery.

Anyway- unless my math is off, 13 amps at 240 volts = about 3 kilowatts, well within the range of a Honda gasoline generator- probably the lightest, safest, most reliable power source you could use. Another option: Listers. Last option: an external boiler that can be powered with electricity or fossil fuels such as kerosene.

-AJ

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