measuring the resistance of water

[kleen]

hi guys! i hope u could help me. i would like to build an automatic water changing aquarium. as the title says, it changes water by itself after detecting the resistance of the water in the aquarium. i believe that the resistance of dirty water in the aquarium is lower than clean water. but my problem is it went crazy whenever i put it on the aquarium. maybe because of the submersible pumps are interfering.

does anyone have a better idea electronically knowing if the water in the aquarium needs to be changed?? and also can u provide the schematic diagram?? it is going to be connected to a microcontroller. pls help me. thanks a bunch in advance!

 

[panic mode]

Clean water should have higher resistance but I'm not sure if this is good
indicator if it's time to change the water. If it needs to be changed
why not change it periodically?

 

[Someone Electro]

Build an clock that trigers the pump

 

[kybert]

What an interesting project!

Like the others said, just change the water every 3 months or so.

A cupple of Q's:

How are you going to ensure the new (fresh) water is at the right temp. so you dont kill the fish every time you change it?


How are you going to measure the amount of water taken out of the tank? and the amount put back in?

 

[zevon8]

Neat idea. Maybe you could measure the PH of the water, along with resistance, and get an idea of when the water is due for change.

For pumping, you could use peristaltic pumps ( tubing pumps like you see on medical equipment .) The freshwater intake line could be immersed in the tank to get it at the right temperature. Since these types of pumps operate effectively at low speed, the water would have time to get to the right temp. You could have two operate simultaneously, displacing and replacing the water. This would ease measuring how much water you need to move.

 

[stevez]

The resistance or conductivity of water depends on a number of things. Even very clean water can be fairly conductive because of dissolved minerals. The conductivity of water varies depending on source of supply. Here in Rochester, NY we have two sources of water with differing conductivities. The supplier provides data for both sources and warns that the mix is not controlled therefore the conductivity could be expected to vary widely thru the course of a day or week. This doesn't mean it's a bad indicator - just that some experimentation might be in order.

 

[kleen]

thanks guys! i'll just build a switching circuit with a clock on it which would trigger the pumps. thanks!

 

[Klaus]

Kleen, I think you are barking up the wrong tree, so to speak, in trying to determine dirty aquarium water by resistance measurement.

All the aquarium test kits I ever came across measured the PH of the water, fish are far more sensitive to that. This assumes you are talking about a fresh water aquarium, for salt water I have no personal experience at all.

Now, you should have an aerator pump and also a carbon filter to filter & clean the water. Maybe you could design something that detects when the filter starts clogging up and needs changing. The water can stay in there for very long times if your filter(s) work well. You should not change all the water at a time anyway, it *really* upsets the fish.
What I did was siphon a portion (maybe 1/4) off at regular intervals, say once a month, and replace it with water that had settled in a container for a few days.
Just keep in mind that fish are sensitive to stray electrical currents when you poke powered devices into the aquarium :shock:
Klaus

 

[kleen]

thanks klaus! but my problem is how to create a PH circuit?? ive been searching at google and all it gave me is a commercial PH test.. do u have a circuit in mind that u would like to share?? i would gladly appreciate it.

 

[zevon8]

now, this is almost freaky.... a website about a saltwater reef aquarium, with just what you are looking for.

https://www.cyberreefguru.com/

there are lots of circuits, including a PH meter.

 

[kleen]

ok guys thanks a bunch!! if u have any other ideas about knowing if the water is still suitable for the fishes or not, pls post it here... thank u guys!

 

[grrr_arrghh]

how about some kind of infrared thing. Have the LED on one side of the tank, and an infrared transistor thinfy on the other, and when the light gets blocked, its timeto change the water. By then the fish will probably be dead, but as a last resort...

 

[kleen]

hmm, come to think of it... that could also be good.. but can u give me more info on infrared? i dont know much about it and how to use it... i would glady appreciate it.

 

[grrr_arrghh]

lol, it was a joke...because presumably you want to change the water before there is any visible difference...?

but for the educational value...

basically, you have an infra red led, connected as you would with a normal LED. then on the other side you have an IR Photo transistor, which works like a normal transistor, but instead of being controlled by the voltage at the 'base' leg, it is controlled by the amount of IR light it receives.

Maplin do a transmitter/receiver pair **broken link removed** but they would have to be mounted quite close together

 

[stevez]

Google on this - 'water quality measurement aquarium' - the first hit revealed some interesting things about ammonia and nitrogen. I suspect that further reading will reveal much of what is important in the maintenance of a proper environment for fish. It looks like it's a pretty complex but interesting subject.

I would think that pH or conductivity would change somewhat as the water changes from acceptable to unacceptable but it's also possible that two substances could be going toward "bad" yet offset changes in the simple measures. A quick read of a paragraph on pH shows that sensors might be tricky to build at home.

If I were faced with the challenge AND had the time I'd make a pair of electrodes from different materials and measure the voltage generated between them when immersed in the aquarium. I'd collect data and see if the changes in water quality, as measured by traditional means and changes in voltage correlated at all - possibly well. I don't think I'd leave the electrodes immersed for long without knowing the impact of some dissolved metal on the fish. A periodic sampling device would have to be employed.

I have some experience with water quality in industrial situations and found this to be an interesting subject.

 

[grrr_arrghh]

why not just have a timer to replace the water on a regular basis? Replacing it too often can't hurt, can it? And waters usually free...

 

[kleen]

ive also taught about that but i think it would also be good if i could also know the quality of water. what do u think?? any circuit in mind?? thanks in advance!

 

[hotwaterwizard]

Here is a Circuit to start with. You would have to build a circuit that turns on the pump when the Ph is too high.

 

[hotwaterwizard]

You are going to LOVE this!

https://www.thekrib.com/Plants/CO2/hurley-co2.html

**broken link removed**

 

[hotwaterwizard]

Check these out as well.
**broken link removed**

**broken link removed**