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Thread: perfect temperature control

  1. #1
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    Lightbulb perfect temperature control

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    Hi everyone, i am new on aquariums but i have been messing for a long with electronics, i have seen some attempts to control temperature with noisy fans and a small fridge
    (the second one doesnt seem so practical to be honest)... i have a great idea to share with u, a small ADJUSTABLE diy solution that will keep your aquarium in the temperature you want it. you will need 1x peltier, 1x waterblock, 1x heatsink, 1x adjustable thermostat switch, 2x 12v relay 1x power transformer(115 to 12 or 240 to 12, wattage depending on the peltier you will choose), a diode bridge and the tubes to connect it to your system. this will act as a chiller when the temperature goes even a litle higher than u you set it and instantly as a heater when the temperature is lower than needed. if anyone wants to give it a try let me know!! (the system has been tested on a computer with extreme cooling requirements, as a heater on power on and as a cooler on 30 degrees, operated flawlessly for about 6 months and it could have been till today if i hadnt sold it.)

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    Some pictures/drawings of your "old" setup would be great!
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    Quote Originally Posted by 3r4ndo View Post
    Hi everyone, i am new on aquariums but i have been messing for a long with electronics, i have seen some attempts to control temperature with noisy fans and a small fridge
    (the second one doesnt seem so practical to be honest)... i have a great idea to share with u, a small ADJUSTABLE diy solution that will keep your aquarium in the temperature you want it. you will need 1x peltier, 1x waterblock, 1x heatsink, 1x adjustable thermostat switch, 2x 12v relay 1x power transformer(115 to 12 or 240 to 12, wattage depending on the peltier you will choose), a diode bridge and the tubes to connect it to your system. this will act as a chiller when the temperature goes even a litle higher than u you set it and instantly as a heater when the temperature is lower than needed. if anyone wants to give it a try let me know!! (the system has been tested on a computer with extreme cooling requirements, as a heater on power on and as a cooler on 30 degrees, operated flawlessly for about 6 months and it could have been till today if i hadnt sold it.)
    Good setup you have there but if it only works at 30 degrees it is a bit too warm for most plants.

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    Quote Originally Posted by cheetf View Post
    Good setup you have there but if it only works at 30 degrees it is a bit too warm for most plants.
    hi there, it is adjustable, you can set it at the temperature you need and keep it exactly there you can get from 15 to 55 (depending on the range of the thermostat)
    i will post a drawing and i will try to find pictures of the parts today.

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    here is a drawing that i made now i am looking for the parts!!
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    you seem to reverse/switch the voltage polarity to perltier. Why is that? why not just switch on or off the peltier?
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    here i have a picture of the half system, includes a heatsink, a peltier and a waterblock mounted together, you can also see the tubes plugged on the waterblock. materials used: s775 heatsink, s775 waterblock, a small peltier, i cant tell about the wattage but doesnt realy matter because anyone has to use a different depending on their tank.
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    Quote Originally Posted by Shadow View Post
    you seem to reverse/switch the voltage polarity to perltier. Why is that? why not just switch on or off the peltier?
    actualy i was thinking of a little more complex system that would keep the peltier dead while in the right temperature and operate it when the water in the tank needs heating or cooling. by reversing the polarity you force it to reverse its operation, so instead of cooling it acts as a heater. this will make it sure for you that the temperature has less than 1 degree difference than you set it whether its hot or could outside.

    you can definetly make a double thermostat system and set the lower and higher temperature on your aquarium and let the peltier rest between the two limits.
    Last edited by 3r4ndo; 13th Feb 2009 at 05:43.

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    Cool final schematic

    here i come with the final schematic, i will give a description about anything included and how the system works. lets start with the basics, we have two 5 pin relays that will change the polarity when needed (one 8 pin can also be used, ask for schematic if u want) and 2 thermostat switches. in the picture i have named them as max and min.

    now i will make a simulation:

    max is set to 26 degrees
    min is set to 24 degrees

    tank water temperature 23 degrees: both thermostats are engaged and the relays are triggered, polarity is reversed and peltier is heating the water.

    tank water temperature 25 degrees: max thermostat is engaged but min thermostat is not, polarity is reversed but heating circuit is dead, peltier is off.

    tank water temperature 27 degrees: both thermostats are disengaged, polarity is normal and peltier is cooling the water.
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    My two cents:

    The idea to cool a fish tank using peltier elements and a water circuit is not a new one. There are even companies that already manufacture that sort of equipment (this one's in German, but you should get the basic idea from the pictures).

    The problem is that a peltier element only transfers heat, not eliminates it, and so needs conventional air (read: fan) cooling on its other side, too. Peltier elements are quite expensive to get, and need a lot of power to operate. They draw upwards of 125 to 150W(!) for a 100 liter (25 gallons) tank. In addition to that, they operate best if the temperature difference is kept within a "sweet spot", and consume much more power outside of that range, so in order to keep them efficient they need much more controlling than a simple temperature sensor that turns it off and on. And even if working at their maximum efficiency, such a peltier system is running at just about half the efficiency of a common compressor/refrigerant chiller.

    Given that you need fans to cool the peltier system, too, you just pretty much save on evaporating water, and pay that with a complicated liquid and electrical system and a lot of power consumption. It's an alternative to a simple clamp-on PC fan alright. But, in my humble opinion, not a very reasonable and certainly not a "perfect" one.

    (Also, I've discussed with a lot of fish keepers and fish breeders on the topic of keeping water temperature absolutely steady, and the consensus is that fish do seem to need a certain variation of temperature over the day/night cycle. One breeder even told me that his fish do inevitably develop sickness if he keeps the temperature absolutely stable, he blames it on their immune system.)

    Again, just my two cents.
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    Quote Originally Posted by ankank View Post
    My two cents:

    The idea to cool a fish tank using peltier elements and a water circuit is not a new one. There are even companies that already manufacture that sort of equipment (this one's in German, but you should get the basic idea from the pictures).

    The problem is that a peltier element only transfers heat, not eliminates it, and so needs conventional air (read: fan) cooling on its other side, too. Peltier elements are quite expensive to get, and need a lot of power to operate. They draw upwards of 125 to 150W(!) for a 100 liter (25 gallons) tank. In addition to that, they operate best if the temperature difference is kept within a "sweet spot", and consume much more power outside of that range, so in order to keep them efficient they need much more controlling than a simple temperature sensor that turns it off and on. And even if working at their maximum efficiency, such a peltier system is running at just about half the efficiency of a common compressor/refrigerant chiller.

    Given that you need fans to cool the peltier system, too, you just pretty much save on evaporating water, and pay that with a complicated liquid and electrical system and a lot of power consumption. It's an alternative to a simple clamp-on PC fan alright. But, in my humble opinion, not a very reasonable and certainly not a "perfect" one.

    (Also, I've discussed with a lot of fish keepers and fish breeders on the topic of keeping water temperature absolutely steady, and the consensus is that fish do seem to need a certain variation of temperature over the day/night cycle. One breeder even told me that his fish do inevitably develop sickness if he keeps the temperature absolutely stable, he blames it on their immune system.)

    Again, just my two cents.
    i would like to tell you that 2 pcs of 136.8w peltier cost at most 13 euro, if you payed more for them you got owned... actually for a 100 liter (25 gallons) you need no more than an 80 watt peltier to handle it if you add a cooler on the heatsink, of course the peltier system is not as efficient as compressor (an 80 watt comressor can bring the temperature of a 100 liter (25 gallons) tank down by 5 degrees in less than one hour) but it is much more complicated than a peltier and it also transfer heat, doesnt eliminate it, therefore it has the same dissadvantages plus one, its huge and definetly too much for a small tank!! this system will keep the tank in a range that you select and it will let it cool at night without operating the peltier, a temperature cycle will be achieved as if it was on its own but wil always keep it between the selected area!!! just think of it operting on a 15 gallon tank and try to find me a better option, or maybe a less complicated system that will be close to the performance of that one.
    not to mention that we are talking about diy here, of course such a system is alrady on the market but i didnt searched for it, just came up with the idea and wanted to share it....

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    Talking finaly done!!

    my temperature controller is finaly completed but i found an error, i had to rename the to thermostats in order to make the system more usable. the max temperature is actualy "heat up to"(witch should be below "cool down to") nad the min "cool down to".

    i could keep the temperature within 0.4 degrees in my 6 gallon wave x-cube with a 80.6w peltier and a 800rpm silent fan!! now i am working on a digital system with non mechanical piecies for control in order to reduce size of controller and increase reliability.

    Also i tested the effectivness with a typical 120w heater running in the tank and it could just keep up, to be honest i wasn't expecting that much but it even lowered the temperature to the selected and then shut off for about a minute.

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    hi everyone, i made a review and found out that i have made a few mistakes. the connection on the thermostats should be on if above for both and you have to rename to "heat until" for max and "cool down to" for min.

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