# The Ideal Drop-Checker



## essabee (Oct 11, 2006)

I would like to add the following improvements to the DIY drop-checker:-
1) Air tube behind the indicator chamber.
2) Wall between the indicator chamber and air tube to be made with white opaque acrylic.
3) Two more chambers, one on either side.
4) First chamber containing transparent colour chart in the front and a white LED light with reflectors directing the light sideways through the indicator and forward through the ph colour chart.
5) Second chamber containing a green colour filter on the indicator side and photo resistor inside to be affected by the light through the indicator.
6) The outer walls - back, sides, top, bottom - to be made of opaque acrylic.
7) The common ground and the other two wires sealed and going to a beeper system arranged for alarm/or a digital system(in which case you would need magenta, cyan, yellow filters before their respective photoresistors)


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## dennis (Mar 1, 2004)

Now add a relay to control a solenoid for the CO2 and you have the drop-checker controller!


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## hoppycalif (Apr 7, 2005)

dennis said:


> Now add a relay to control a solenoid for the CO2 and you have the drop-checker controller!


You would also want a time delay circuit involved, to prevent the system hunting, due to the relatively slow drop checker response. I trust you are working on this design right this minute? Don't forget the "bells and whistles" to make it sell better!!:mrgreen:


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## Squawkbert (Jan 3, 2007)

essabee said:


> I would like to add the following improvements to the DIY drop-checker:-
> 1) Air tube behind the indicator chamber.
> 2) Wall between the indicator chamber and air tube to be made with white opaque acrylic.
> 3) Two more chambers, one on either side.
> ...


If you can fit all that in <55g, you may have something!


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## essabee (Oct 11, 2006)

Squawkbert said:


> If you can fit all that in <55g, you may have something!


The drop-checker size can be just 2"X2"X.5" so can be the beeper, but my trouble starts with getting the transparent colours for the chart and the light filter, just don't know how to acquire the very small quantity I would need, any ideas?


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## d3millikin (Jan 22, 2007)

r there any fish that i can put with a betta in a planted 10gl very well lighted tank?


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## essabee (Oct 11, 2006)

I should acknowledge that the thought of this thread was caused by a comment by a senior member to the effect that- it is difficult to judge the colour of the indicator in a drop-checker. The member's solution to the problem did not allow use for different levels of CO2 contents of aquarium water and hence this thread.

As I am going to start using CO2, I am thinking of the gadgets I might need to understand what is going on in my aquarium.

While using my test kit for aquarium water, I have the same difficulty in 'reading' the colours, unless I hold the test-tube and the chart in strong light.


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## hoppycalif (Apr 7, 2005)

The drop checker makes it easier to read the color correctly, by using 4 dKH distilled water in it, with more than normal pH indicator solution. If you look at the pH color chart for the test kits, a 6.6 pH will be green, and not yellow green or blue green. That will give you 30 ppm of CO2. Yellow green would be 6.4 pH and blue green would be 6.8 pH. So, you should be able to judge that the color is more green than blue green or more green than yellow green, which would be 6.5 to 6.7 pH, which correspond to 24 to 38 ppm of CO2. That would be roughly the range of errors you would have. That is why I think it is more appropriate to say we have 25 to 40 ppm of CO2 instead of saying it is 30 ppm. In my experience any amount in that range is satisfactory for both the plants and fish.

I doubt that a LED plus filter plus photocell would be able to do any better on accuracy.


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## essabee (Oct 11, 2006)

hoppycalif said:


> The drop checker makes it easier to read the color correctly, by using 4 dKH distilled water in it, with more than normal pH indicator solution. If you look at the pH color chart for the test kits, a 6.6 pH will be green, and not yellow green or blue green. That will give you 30 ppm of CO2. Yellow green would be 6.4 pH and blue green would be 6.8 pH. So, you should be able to judge that the color is more green than blue green or more green than yellow green, which would be 6.5 to 6.7 pH, which correspond to 24 to 38 ppm of CO2. That would be roughly the range of errors you would have. That is why I think it is more appropriate to say we have 25 to 40 ppm of CO2 instead of saying it is 30 ppm. In my experience any amount in that range is satisfactory for both the plants and fish.
> 
> I doubt that a LED plus filter plus photocell would be able to do any better on accuracy.


I would love to have a drop-checker which could give me reading in ppm CO2 at the point of time (I do know that a drop-checker's reading is delayed) for I intend to use DIY CO2 and I would not reach the 25ppm level of an EI follower.

The LED lighted drop-checker with the opaque back ground is to stop the interference from the ambient light and give a more accurate comparison with the colour chart for reading the ppm of CO2.

The beeper circuit sensor photo-resistor is unnecessary for me personally, but will alert a pressurised CO2 user when the CO2 level has crossed the high he has set, and tell him that his CO2 injector needs to be reset.


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## hoppycalif (Apr 7, 2005)

The best way I know of to get what you want is to use a pH probe, with a tiny amount of known KH distilled water inside a gas permeable membrane, with that stuck into the aquarium. Tom Barr suggested doing this, and has one of the probe makers looking into selling such a probe. It can pretty easily be done as a DIY project, but I have chosen to work only on the colored water drop checker for now. One quick idea I had was to use the protective cap on my probe as a container for the reference KH water, drilling a large hole at the end and covering it with a piece of membrane. This would work, but working out the details would take some time.


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