Post by thread:[EE:] Temp test tank

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. _________________________________________________________________ Plan your next US getaway to one of the super destinations here. http://special.msn.com/local/hotdestinations.armx -- http://www.piclist.com hint: To leave the PICList spam_OUTpiclist-unsubscribe-requestTakeThisOuTmitvma.mit.edu>

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. _________________________________________________________________ Plan your next US getaway to one of the super destinations here. http://special.msn.com/local/hotdestinations.armx -- http://www.piclist.com hint: To leave the PICList .....piclist-unsubscribe-requestKILLspam@spam@mitvma.mit.edu

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 {Quote hidden}> 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. > > _________________________________________________________________ > Plan your next US getaway to one of the super destinations here. > http://special.msn.com/local/hotdestinations.armx > > -- > http://www.piclist.com hint: To leave the PICList > piclist-unsubscribe-requestKILLspammitvma.mit.edu -- http://www.piclist.com hint: To leave the PICList .....piclist-unsubscribe-requestKILLspam.....mitvma.mit.edu>

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 {Quote hidden}> 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. > > _________________________________________________________________ > Plan your next US getaway to one of the super destinations here. > http://special.msn.com/local/hotdestinations.armx > > -- > http://www.piclist.com hint: To leave the PICList > EraseMEpiclist-unsubscribe-requestspam_OUTTakeThisOuTmitvma.mit.edu -- http://www.piclist.com hint: To leave the PICList piclist-unsubscribe-requestspam_OUTmitvma.mit.edu

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@johnferrellKILLspamearthlink.net http://DixieNC.US NSRCA 479 AMA 4190 W8CCW "My Competition is Not My Enemy" {Original Message removed}

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 KILLspamjohnferrellKILLspamearthlink.net http://DixieNC.US NSRCA 479 AMA 4190 W8CCW "My Competition is Not My Enemy" {Original Message removed}

>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. _________________________________________________________________ Let the advanced features & services of MSN Internet Software maximize your online time. http://click.atdmt.com/AVE/go/onm00200363ave/direct/01/ -- http://www.piclist.com hint: PICList Posts must start with ONE topic: [PIC]:,[SX]:,[AVR]: ->uP ONLY! [EE]:,[OT]: ->Other [BUY]:,[AD]: ->Ads

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 -- http://www.piclist.com hint: PICList Posts must start with ONE topic: [PIC]:,[SX]:,[AVR]: ->uP ONLY! [EE]:,[OT]: ->Other [BUY]:,[AD]: ->Ads

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 _________________________________________________________________ Optimize your Internet experience to the max with the new MSN Premium Internet Software. http://click.atdmt.com/AVE/go/onm00200359ave/direct/01/ -- http://www.piclist.com hint: PICList Posts must start with ONE topic: [PIC]:,[SX]:,[AVR]: ->uP ONLY! [EE]:,[OT]: ->Other [BUY]:,[AD]: ->Ads

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. > -- http://www.piclist.com hint: PICList Posts must start with ONE topic: [PIC]:,[SX]:,[AVR]: ->uP ONLY! [EE]:,[OT]: ->Other [BUY]:,[AD]: ->Ads

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 -- http://www.piclist.com hint: PICList Posts must start with ONE topic: [PIC]:,[SX]:,[AVR]: ->uP ONLY! [EE]:,[OT]: ->Other [BUY]:,[AD]: ->Ads

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 -- http://www.piclist.com hint: PICList Posts must start with ONE topic: [PIC]:,[SX]:,[AVR]: ->uP ONLY! [EE]:,[OT]: ->Other [BUY]:,[AD]: ->Ads

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}>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}

> 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 -- http://www.piclist.com hint: The list server can filter out subtopics (like ads or off topics) for you. See http://www.piclist.com/#topics