DIY Peltier cooler for 25L tank

[rebel]

Hi everyone,

I am in the process of experimenting with a simple Peltier cooler for a tiny tank. Efficiency is not a concern for this build. My main concern is to have the cooler very small and hidden behind the tank. I plan to attach it to the external box of my hang on back filter. The aim is to drop the temperature from 26 to 22 for CRS. While it's possible to just hook up some fans, I won't enjoy having to top up constantly.

I have been experimenting with a simple setup thusly.
[pic]


The problem is that when the unit switches off, the heat transfers backwards through the heatsink into the filter. To reduce this, I need for the fan to stay on for 3 minutes or so after the unit switches off.

Can I use a relay like this to do that job?
https://www.ebay.com.au/itm/12V-Tim...666?_trksid=p2349526.m4383.l4275.c10#viTabs_0

 

[zozo]

I think for a time delay it will work, why not.. 🙂 Another option could be to use a thermostat to switch the fan. Than it runs as long as required and not a fixed time delay.

For example this one
https://www.ebay.com.au/itm/DC12V-W...90:m:m_5EA6L9R4Q6WNL9duTPNAA&var=562721879466

Factory default its set as cooling switch, but it can be set for heating as well. They also have a treshhold setting and a calibration setting to calibrate with the thermometer..

I have several of these in use for quite some years now, pretty durable and nifty little thermostats. Nice stuff fr the money. Can give nothing but a positive review..

 

[soggybongo]

if you are home most days you could install a small dosing pump on a timer to top up, just measure your top up each day required and adjust the dosing pump to give that ammount of water either split over the day or all at once. my only concern would be evaporation during the colder nights/ days and fluctuations in water needed. this is where sumps and auto top off come into play or you have a large aquarium and dont mind seeing the top off equipment.

 

[rebel]

if you are home most days you could install a small dosing pump on a timer to top up, just measure your top up each day required and adjust the dosing pump to give that ammount of water either split over the day or all at once. my only concern would be evaporation during the colder nights/ days and fluctuations in water needed. this is where sumps and auto top off come into play or you have a large aquarium and dont mind seeing the top off equipment.

That would be a luxury in my office where this tank is located. I don't want any equipment to show at all if possible. 🙂

thanks for your suggestion.

 

[rebel]

@zozo , yes I am already using such a thermister setup for the Peltier module to switch on and off. Perhaps I can use another just for the fan! Thanks for the idea.