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'[EE:] Temp test tank'
2004\02\15@005702 by Mike Hord

picon face
I find myself in need of a cheap method to make an 80 liter aquarium
run through a temperature range between ~0 and 50 degrees C.

Accuracy and safety are not huge concerns, because if the thing
overheats or fails, nothing bad will happen (of course, fire safety
and electric shock hazards are points).  In fact, it need not even
be a closed loop control mechanism, because it should spread the
change out over 72 hours at least, which could be done by a very
slow increase in voltage.

Short question is:  what is the cheapest way to do this?  The
current idea is to stick it in a refrigerator close to 0 degrees
and then slowly ramp up the heat in the tank.  Does anyone know
of a cheap heater that can be easily controlled, say by a PIC with
an RTC module?

Mike H.

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2004\02\15@005702 by Mike Hord

picon face
I find myself in need of a cheap method to make an 80 liter aquarium
run through a temperature range between ~0 and 50 degrees C.

Accuracy and safety are not huge concerns, because if the thing
overheats or fails, nothing bad will happen (of course, fire safety
and electric shock hazards are points).  In fact, it need not even
be a closed loop control mechanism, because it should spread the
change out over 72 hours at least, which could be done by a very
slow increase in voltage.

Short question is:  what is the cheapest way to do this?  The
current idea is to stick it in a refrigerator close to 0 degrees
and then slowly ramp up the heat in the tank.  Does anyone know
of a cheap heater that can be easily controlled, say by a PIC with
an RTC module?

Mike H.

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2004\02\15@015217 by Denny Esterline

picon face
Hmmm.. You're working with an aquarium, and you haven't thought of an
aquarium heater? :-)

Actualy an aquarium heater probably wouldn't work, I don't think thier
thermostats will go high enough. But how about the typical cheap imersion
beverage heater? Usualy like $5-$10 for about 500 watts.

If that isn't enough add a couple more, or go strait for a standard
electric water heater element. Seems like the last one I bought was 4500
watts at 220V for about $18. Smaller is available or you could run it on
110V to cut the wattage. Add a transistor and a relay and bob's your uncle.

Watch out for the very small high-wattage elements. They get hot enough to
boil the water localy, can have all kinds of unpleasant side effects. They
sell physicaly larger elements (usualy marketed with the term "Long Life")
With more area they run cooler.

If you need to you can bend them to shape. Don't go wild, but you should be
able to form them by hand, just don't work the same area back and forth
alot, and try to keep the bend radius more than a couple inches.

On the cold side, a fridge would probably work, but there are other options
without getting too complicated. A couple bags of ice will get you pretty
close to freezing, add a little table salt to the ice to get it MUCH colder
(like -65 F). Or you could run a pipe through a freezer and your tank and
pump coolant through it (saltwater or automotive antifreeze)

Will any of that help?
-Denny


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2004\02\15@015217 by Denny Esterline

picon face
Hmmm.. You're working with an aquarium, and you haven't thought of an
aquarium heater? :-)

Actualy an aquarium heater probably wouldn't work, I don't think thier
thermostats will go high enough. But how about the typical cheap imersion
beverage heater? Usualy like $5-$10 for about 500 watts.

If that isn't enough add a couple more, or go strait for a standard
electric water heater element. Seems like the last one I bought was 4500
watts at 220V for about $18. Smaller is available or you could run it on
110V to cut the wattage. Add a transistor and a relay and bob's your uncle.

Watch out for the very small high-wattage elements. They get hot enough to
boil the water localy, can have all kinds of unpleasant side effects. They
sell physicaly larger elements (usualy marketed with the term "Long Life")
With more area they run cooler.

If you need to you can bend them to shape. Don't go wild, but you should be
able to form them by hand, just don't work the same area back and forth
alot, and try to keep the bend radius more than a couple inches.

On the cold side, a fridge would probably work, but there are other options
without getting too complicated. A couple bags of ice will get you pretty
close to freezing, add a little table salt to the ice to get it MUCH colder
(like -65 F). Or you could run a pipe through a freezer and your tank and
pump coolant through it (saltwater or automotive antifreeze)

Will any of that help?
-Denny


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2004\02\15@102458 by John Ferrell

face picon face
I would approach it this way:
Calculate how many watts it should take to raise the water to that
temperature.
Estimate heat losses and include them in the power required. (it may be more
practical to use an ice chest cooler kind of container to minimize
undesirable heat transfer).

Prepare the start temperature by mixing crushed ice and water. Be certain to
remove ALL of the ice before you begin the experiment. It will be easier
than accounting for the heat required to account for melting an unknown
volume of ice.

Use multiple 40 watt soldering irons WITH an isolation transformer for a
heat source. Figure out how many from calculations above. You can couple the
soldering irons to the water by clamping heat them to heat sinks. If you can
find an appropriate immersable heater, so much the better.

It will be best if you can devise a thermometer to stay in the water and be
read remotely.

The terminal temperature of the apparatus will occur when the heat losses
equal the power input.

This is roughly how the shipping containers for spent Yankee Nuclear reactor
fuel elements were designed in 1959.

Other thoughts:
If the input power is not a consideration, you could also do this with a 30
gallon steel barrel with your 20 gallons of water over an electric hot
plate. Having said that, ain't no way 40 watt irons are going to do the job.
Consider jacketing the drum with fiber glass insulation.

If you really do need to use the aquarium, make sure the cement will take
the heat.
John Ferrell
6241 Phillippi Rd
Julian NC 27283
Phone: (336)685-9606
@spam@johnferrellKILLspamspamearthlink.net
http://DixieNC.US
NSRCA 479 AMA 4190  W8CCW
"My Competition is Not My Enemy"

{Original Message removed}

2004\02\15@102458 by John Ferrell

face picon face
I would approach it this way:
Calculate how many watts it should take to raise the water to that
temperature.
Estimate heat losses and include them in the power required. (it may be more
practical to use an ice chest cooler kind of container to minimize
undesirable heat transfer).

Prepare the start temperature by mixing crushed ice and water. Be certain to
remove ALL of the ice before you begin the experiment. It will be easier
than accounting for the heat required to account for melting an unknown
volume of ice.

Use multiple 40 watt soldering irons WITH an isolation transformer for a
heat source. Figure out how many from calculations above. You can couple the
soldering irons to the water by clamping heat them to heat sinks. If you can
find an appropriate immersable heater, so much the better.

It will be best if you can devise a thermometer to stay in the water and be
read remotely.

The terminal temperature of the apparatus will occur when the heat losses
equal the power input.

This is roughly how the shipping containers for spent Yankee Nuclear reactor
fuel elements were designed in 1959.

Other thoughts:
If the input power is not a consideration, you could also do this with a 30
gallon steel barrel with your 20 gallons of water over an electric hot
plate. Having said that, ain't no way 40 watt irons are going to do the job.
Consider jacketing the drum with fiber glass insulation.

If you really do need to use the aquarium, make sure the cement will take
the heat.
John Ferrell
6241 Phillippi Rd
Julian NC 27283
Phone: (336)685-9606
KILLspamjohnferrellKILLspamspamearthlink.net
http://DixieNC.US
NSRCA 479 AMA 4190  W8CCW
"My Competition is Not My Enemy"

{Original Message removed}

2004\02\16@145805 by Mike Hord

picon face
>If that isn't enough add a couple more, or go strait for a standard
>electric water heater element. Seems like the last one I bought was 4500
>watts at 220V for about $18. Smaller is available or you could run it on
>110V to cut the wattage. Add a transistor and a relay and bob's your uncle.

Something from a water heater, eh?  I hadn't considered that.

>On the cold side, a fridge would probably work, but there are other options
>without getting too complicated. A couple bags of ice will get you pretty
>close to freezing, add a little table salt to the ice to get it MUCH colder
>(like -65 F). Or you could run a pipe through a freezer and your tank and
>pump coolant through it (saltwater or automotive antifreeze)

This is actually a pretty good idea; since it's important that the water in
the
tank be fairly homogeneous in temperature and in oxygenation, the
standard method is to buy a pump that has a heater built into it, thus
simultaneously mixing, oxygenating, and heating the water.  The problem
is, those are quite pricey.

>Will any of that help?
>-Denny

I hadn't considered running a hose or tube through the freezer; that may
be helpful.  It still doesn't solve my problem of an easy method for varying
the heater.

Ideally I need a 500-1000w aquarium heater that uses a serially input 16
bit number to determine its power output.  Of course, all you can find
in fish stores are turn-the-knob heaters.  I haven't stripped one of those
yet; if the pot which adjusts the temp doesn't have to handle much
current, maybe I can use a digital pot.

Maybe.

Mike H.

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2004\02\16@145805 by Mike Hord

picon face
>If that isn't enough add a couple more, or go strait for a standard
>electric water heater element. Seems like the last one I bought was 4500
>watts at 220V for about $18. Smaller is available or you could run it on
>110V to cut the wattage. Add a transistor and a relay and bob's your uncle.

Something from a water heater, eh?  I hadn't considered that.

>On the cold side, a fridge would probably work, but there are other options
>without getting too complicated. A couple bags of ice will get you pretty
>close to freezing, add a little table salt to the ice to get it MUCH colder
>(like -65 F). Or you could run a pipe through a freezer and your tank and
>pump coolant through it (saltwater or automotive antifreeze)

This is actually a pretty good idea; since it's important that the water in
the
tank be fairly homogeneous in temperature and in oxygenation, the
standard method is to buy a pump that has a heater built into it, thus
simultaneously mixing, oxygenating, and heating the water.  The problem
is, those are quite pricey.

>Will any of that help?
>-Denny

I hadn't considered running a hose or tube through the freezer; that may
be helpful.  It still doesn't solve my problem of an easy method for varying
the heater.

Ideally I need a 500-1000w aquarium heater that uses a serially input 16
bit number to determine its power output.  Of course, all you can find
in fish stores are turn-the-knob heaters.  I haven't stripped one of those
yet; if the pot which adjusts the temp doesn't have to handle much
current, maybe I can use a digital pot.

Maybe.

Mike H.

_________________________________________________________________
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2004\02\16@152128 by Peter L. Peres

picon face
My guess is it would take about 2.5 hours for a 2000W heater to bring the
tank from 0 to 50C. For slower, use a smaller heater, and stir. You can
achieve 0C by putting ice in the aquarium until it stops melting. If you
want slightly less than 0C add some salt first. Would this be slow enough
? If the tank walls are insulated with polystyrene it could take two days
to go from 0 to ambient.

Peter

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2004\02\16@152128 by Peter L. Peres

picon face
My guess is it would take about 2.5 hours for a 2000W heater to bring the
tank from 0 to 50C. For slower, use a smaller heater, and stir. You can
achieve 0C by putting ice in the aquarium until it stops melting. If you
want slightly less than 0C add some salt first. Would this be slow enough
? If the tank walls are insulated with polystyrene it could take two days
to go from 0 to ambient.

Peter

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2004\02\16@185329 by Mike Hord

picon face
The oxygenation sensor this is intended to test takes 5-10 minutes to
settle; we want to test it over 72 hours or so.

Accuracy in temp is unimportant, really, just so long as it doesn't get TOO
hot.  All we need is a heater that is capable of heating the aquarium to
50C which can be controlled by some programmable means.

Mike H.

>My guess is it would take about 2.5 hours for a 2000W heater to bring the
>tank from 0 to 50C. For slower, use a smaller heater, and stir. You can
>achieve 0C by putting ice in the aquarium until it stops melting. If you
>want slightly less than 0C add some salt first. Would this be slow enough
>? If the tank walls are insulated with polystyrene it could take two days
>to go from 0 to ambient.
>
>Peter

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2004\02\16@185329 by Mike Hord

picon face
The oxygenation sensor this is intended to test takes 5-10 minutes to
settle; we want to test it over 72 hours or so.

Accuracy in temp is unimportant, really, just so long as it doesn't get TOO
hot.  All we need is a heater that is capable of heating the aquarium to
50C which can be controlled by some programmable means.

Mike H.

>My guess is it would take about 2.5 hours for a 2000W heater to bring the
>tank from 0 to 50C. For slower, use a smaller heater, and stir. You can
>achieve 0C by putting ice in the aquarium until it stops melting. If you
>want slightly less than 0C add some salt first. Would this be slow enough
>? If the tank walls are insulated with polystyrene it could take two days
>to go from 0 to ambient.
>
>Peter

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2004\02\16@214823 by Denny Esterline

picon face
I don't think an aquarium heater will get to 50C. Keep in mind these are
built for keeping tropical fish alive. Most of those wouldn't be too happy
at 50C. For liability reasons I'd expect them to have overtemp cutoff
switches, but I'm only guessing.

Basically, you're looking at a resistive electric heater, whether you use
soldering irons, beverage heaters, waterheater elements, heat lamps, power
resistors, industrial Cal-Rod, or something else, the control options are
basically the same: Relay (solid state or mechanical), Triac (AC), or power
transistors (DC).

Driving any of these from a PIC is reasonably well understood with plenty
of examples.

Keep in mind that with 20+ gallons of water, it's not going to change
temperature very fast. Dependent on insulation, ambient temp and heater
wattage, I doubt the heater would cycle more than every few minutes. So a
slow control algorithm and mechanical relays isn't a bad option.

I don't have all the information about your test, but I'd probably look
into a (small) standard residential hot-water heat circulation pump, build
a heater with a few pipe fittings and a water heater element, and run it
through the tank. If you pumped the same water that's in the tank it would
also provide agitation.

Some water heater elements have a threaded mount, IIRC it matches 1-1/2
inch iron pipe thread... Add a Tee, a nipple longer than the element, and a
couple adaptors and you have a heater.

-Denny


> The oxygenation sensor this is intended to test takes 5-10 minutes to
> settle; we want to test it over 72 hours or so.
>
> Accuracy in temp is unimportant, really, just so long as it doesn't get
TOO
> hot.  All we need is a heater that is capable of heating the aquarium to
> 50C which can be controlled by some programmable means.
>
> Mike H.
>

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2004\02\16@214823 by Denny Esterline

picon face
I don't think an aquarium heater will get to 50C. Keep in mind these are
built for keeping tropical fish alive. Most of those wouldn't be too happy
at 50C. For liability reasons I'd expect them to have overtemp cutoff
switches, but I'm only guessing.

Basically, you're looking at a resistive electric heater, whether you use
soldering irons, beverage heaters, waterheater elements, heat lamps, power
resistors, industrial Cal-Rod, or something else, the control options are
basically the same: Relay (solid state or mechanical), Triac (AC), or power
transistors (DC).

Driving any of these from a PIC is reasonably well understood with plenty
of examples.

Keep in mind that with 20+ gallons of water, it's not going to change
temperature very fast. Dependent on insulation, ambient temp and heater
wattage, I doubt the heater would cycle more than every few minutes. So a
slow control algorithm and mechanical relays isn't a bad option.

I don't have all the information about your test, but I'd probably look
into a (small) standard residential hot-water heat circulation pump, build
a heater with a few pipe fittings and a water heater element, and run it
through the tank. If you pumped the same water that's in the tank it would
also provide agitation.

Some water heater elements have a threaded mount, IIRC it matches 1-1/2
inch iron pipe thread... Add a Tee, a nipple longer than the element, and a
couple adaptors and you have a heater.

-Denny


> The oxygenation sensor this is intended to test takes 5-10 minutes to
> settle; we want to test it over 72 hours or so.
>
> Accuracy in temp is unimportant, really, just so long as it doesn't get
TOO
> hot.  All we need is a heater that is capable of heating the aquarium to
> 50C which can be controlled by some programmable means.
>
> Mike H.
>

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2004\02\16@220733 by Jim Korman

flavicon
face
Denny Esterline wrote:

> I don't think an aquarium heater will get to 50C. Keep in mind these are
> built for keeping tropical fish alive. Most of those wouldn't be too happy
> at 50C. For liability reasons I'd expect them to have overtemp cutoff
> switches, but I'm only guessing.
>
> Basically, you're looking at a resistive electric heater, whether you use
> soldering irons, beverage heaters, waterheater elements, heat lamps, power
> resistors, industrial Cal-Rod, or something else, the control options are
> basically the same: Relay (solid state or mechanical), Triac (AC), or power
> transistors (DC).
>
<snip>


A 100 watt heater in a 20 gal tank could get close. I had one wide open
on a new tank (No fish!) and it ran the tank up to 110F. With some
foam insulation around the tank 122F should be doable. Don't think
that there would be any control that high though!

Jim

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2004\02\16@220733 by Jim Korman

flavicon
face
Denny Esterline wrote:

> I don't think an aquarium heater will get to 50C. Keep in mind these are
> built for keeping tropical fish alive. Most of those wouldn't be too happy
> at 50C. For liability reasons I'd expect them to have overtemp cutoff
> switches, but I'm only guessing.
>
> Basically, you're looking at a resistive electric heater, whether you use
> soldering irons, beverage heaters, waterheater elements, heat lamps, power
> resistors, industrial Cal-Rod, or something else, the control options are
> basically the same: Relay (solid state or mechanical), Triac (AC), or power
> transistors (DC).
>
<snip>


A 100 watt heater in a 20 gal tank could get close. I had one wide open
on a new tank (No fish!) and it ran the tank up to 110F. With some
foam insulation around the tank 122F should be doable. Don't think
that there would be any control that high though!

Jim

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2004\02\16@221807 by SavanaPics

picon face
I have an aquarium that I built into the wall in my living room that is 8
feet long and close to 200 gallons. I  had to put a heater in it due to the fact
that I keep my house at 68 in the winter.  I use a 300  watt heater that has a
scale on it from 65 to 85 degrees F  basical that is up to close to 30
degrees C...  imagine if you used it without the built in thermostat it will get
hotter than you want. You will just have to control it via a sealed  LM35Z and
some software.. I forgot who made it but if you need me to, contact me offline
and I will find out for you

Eddie Turner, kc4awz

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2004\02\16@221807 by SavanaPics

picon face
I have an aquarium that I built into the wall in my living room that is 8
feet long and close to 200 gallons. I  had to put a heater in it due to the fact
that I keep my house at 68 in the winter.  I use a 300  watt heater that has a
scale on it from 65 to 85 degrees F  basical that is up to close to 30
degrees C...  imagine if you used it without the built in thermostat it will get
hotter than you want. You will just have to control it via a sealed  LM35Z and
some software.. I forgot who made it but if you need me to, contact me offline
and I will find out for you

Eddie Turner, kc4awz

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2004\02\16@222015 by Jonathan Johnson

flavicon
face
I just checked the heater in my sons aquarium and it only goes to 34 degrees
C.

What about those jug elements used for camping? I think they are 12v though
so you are going to have a fairly hefty current draw, but, considering that
you will be ramping the temp up slowly....possibly not?

Cheers,

JJ

{Original Message removed}

2004\02\16@222015 by Jonathan Johnson

flavicon
face
I just checked the heater in my sons aquarium and it only goes to 34 degrees
C.

What about those jug elements used for camping? I think they are 12v though
so you are going to have a fairly hefty current draw, but, considering that
you will be ramping the temp up slowly....possibly not?

Cheers,

JJ

{Original Message removed}

2004\02\16@222430 by Jonathan Johnson

flavicon
face
Rena make the most reliable aquarium heaters I have ever used. Its been a
few years since I have done a great deal of anything with aquariums though,
things may have changed. Your right Eddie I don't think it would take much
to hack one of them to make it go higher, just take into consideration any
components that are inside the glass tube will be heated to a higher temp
then the water outside as well.

Regs,

JJ

{Original Message removed}

2004\02\16@222430 by Jonathan Johnson

flavicon
face
Rena make the most reliable aquarium heaters I have ever used. Its been a
few years since I have done a great deal of anything with aquariums though,
things may have changed. Your right Eddie I don't think it would take much
to hack one of them to make it go higher, just take into consideration any
components that are inside the glass tube will be heated to a higher temp
then the water outside as well.

Regs,

JJ

{Original Message removed}

2004\02\17@124656 by Mike Hord

picon face
Ahhh!  Thanks guys, you've put me on a good track with the camping
heaters and the water heater idea.

It's also good to know that a 100 watt heater can get a tank up above
100F.  That's a good estimate to start from.

Mike H.

{Quote hidden}

>{Original Message removed}

2004\02\17@124656 by Mike Hord

picon face
Ahhh!  Thanks guys, you've put me on a good track with the camping
heaters and the water heater idea.

It's also good to know that a 100 watt heater can get a tank up above
100F.  That's a good estimate to start from.

Mike H.

{Quote hidden}

>{Original Message removed}

2004\02\17@172435 by Peter L. Peres

picon face
> The oxygenation sensor this is intended to test takes 5-10 minutes to
> settle; we want to test it over 72 hours or so.

I did not understand if this was for one test or if you are building a
long time test jig for testing/calibration.

I suggested dumping ice into the water to cool it but this may change
salinity and such and upset your oxygenation measurement. For one off I'd
get a horizontal type food freezer and put a tub in it with the water,
then use an immersion heater of the large kind (2000W) with a stirrer and
a modular power control element (I don't know what you call them - it's a
dimmer in a case with nema rail mount with 4-20mA control). I am not sure
you need a heater control. With that mass of water just turn on a small
heater in the tank. All other things being equal 2000W will heat it in
2.5hours, 200W in 25 hours etc. If the freezer is rated say 3/4hp it
should remove heat to the tune of 300W or so so you need to make up the
difference of less than 50W. You could use a simple dimmer to set the rate
coarsely and let it be.

Peter

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