DIY solenoid alternative - The Planted Tank Forum
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post #1 of 26 (permalink) Old 01-31-2014, 10:34 PM Thread Starter
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DIY solenoid alternative

First of all I want to say that Iím new to this forum. I became a member of the planted tank to share my following idea with you.

Needle valves or solenoid valves in combination with a time switch are often used to automatically turn of CO2 at night. I came up with an alternative idea to do the same.

The basic of my idea is that an air pump is used to shut of the CO2 at night. The air pump is connected to the air tube that runs from the CO2 pressure regulation valve to the CO2 diffuser. A one-way valve has to be connected to the air pump output in order to make sure no C02 can leak form the system. I used my awesome photoshop skills to make a picture of it.



How it works: The air pump is switched on with a time switch at night. The pressure generated by the air pump is greater than the pressure of the CO2 system, so only air will run through the CO2 diffuser at night. The air cannot go pass the CO2 pressure regulation valve because the pressure in the CO2 tank is too high.

This link demonstrates what will happen at night:

An extra advantage of this system is that there will be extra oxygenation at night.

I donít know whether or not this setup is more economical than buying a solenoid valve. However I think there might be quite a lot of people who have an old air pump lying around.

I wonder what you think about itÖ
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post #2 of 26 (permalink) Old 01-31-2014, 10:44 PM
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I don't see what prevents the co2 from mixing with the air and going to the water anyway

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post #3 of 26 (permalink) Old 01-31-2014, 11:17 PM Thread Starter
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Quote:
Originally Posted by Salmon McCloud View Post
I don't see what prevents the co2 from mixing with the air and going to the water anyway

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The air and CO2 will not mix because the CO2 pressure (red) is very low due to the CO2 pressure regulation valve. This is the reason only one drop per second of CO2 is going in the aquarium at day time. The air pressure (green) is much larger, ďmore drops per secondĒ.



In physics Flow (drops per second) is pressure divided by resistance (the CO2 diffuser). So in this case more drops is more pressure.
Flow will only be from higher pressures to lower pressures thus no CO2 will flow to the CO2 diffuser.
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post #4 of 26 (permalink) Old 01-31-2014, 11:35 PM
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this system is flawed. c02 pressure will keep building up and so will mix in with air. if you have a bubble counter you'll see c02 coming from the regulator still
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post #5 of 26 (permalink) Old 01-31-2014, 11:51 PM
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If you use a pressure regulator to drop the CO2 bottle pressure down to 20 psi or so, the air pressure would have to be above 20 psi to stop the CO2 flow. No air pump I know of that is used on an aquarium would produce that much pressure. But, you would certainly be diluting the CO2, and reducing the flow of CO2 because there would be so little pressure drop across the needle valve that very little CO2 could get through. I'm not sure yet if this can actually stop the CO2 flow, but I suspect it can.

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post #6 of 26 (permalink) Old 02-01-2014, 03:16 AM
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This is like one of those logic puzzles.

Surely when the air goes around the corner (as shown in diagram above) some of the Co2 will blend in with it (mix if you like) even if the pressure on the co2 side is only a wee bit higher than the pressure on the air side. Put another way, I think the air will sorta pull the co2 along with it. Don't know how much co2 will get pulled in -- that would have to be tested. It seems like a brilliant idea 'cos it is "kiss". But my bet is that most of the co2 will still go in the tank. That's not physics though -- that's just an old fart's instinct (:-)
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post #7 of 26 (permalink) Old 02-01-2014, 03:53 AM
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Originally Posted by jeremy va View Post
This is like one of those logic puzzles.

Surely when the air goes around the corner (as shown in diagram above) some of the Co2 will blend in with it (mix if you like) even if the pressure on the co2 side is only a wee bit higher than the pressure on the air side. Put another way, I think the air will sorta pull the co2 along with it. Don't know how much co2 will get pulled in -- that would have to be tested. It seems like a brilliant idea 'cos it is "kiss". But my bet is that most of the co2 will still go in the tank. That's not physics though -- that's just an old fart's instinct (:-)
Remember, there is a needle valve between the CO2 regulator and the place where the air is pumped in. The flow rate through a needle valve is proportional to the pressure drop across the valve. For a typical CO2 setup, the pressure entering the needle valve will be 20 psi, but the pressure on the output side of the needle valve will be perhaps 0.1 psi or less. At that pressure drop the flow will be 4 bubbles per second. So, if I pump air downstream of the needle valve at a pressure of 5 psi, I have reduced the pressure drop across the needle valve, so I have reduced the flow rate of CO2. Obviously it takes a lot of air pressure to stop the flow, about 20 psi for that example. But, if you could get that much air pressure without blasting all the water out of the tank, you would stop the flow of CO2.

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post #8 of 26 (permalink) Old 02-01-2014, 04:08 AM
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Yes, the design is severely flawed and there is no way that it would work. Install a solenoid inline and that would accomplish the task.

Also, there's no way to work as pictured. The check valve is positioned in a way that prevents any air from the pump to enter the main line.
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post #9 of 26 (permalink) Old 02-01-2014, 05:41 AM
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I'm surprise no one mentions this already.


*Ahem


Why don't you just ...... run the air pump in the tank on a timer?


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post #10 of 26 (permalink) Old 02-01-2014, 08:32 AM
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You would need some sort of valve in order to make this work. If you have a valve that has a piston in it and the piston head is a larger diameter on one side. Then if calculated right the air from the pump can create a greater force than the air from the CO2. This could push back sealing the CO2 and stopping it. When the pump is turned off the CO2 pressure would push the piston back out and allow CO2 into the tank.

The problem is I don't know of such a valve that would be cheap. But there could be one or you could make your own I suppose. But it would need to not only be rated for the pressure but probably over pressure in case the CO2 regulator fails and have a pressure relief. I don't know maybe you could use a ball pump in some way to achieve this.
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post #11 of 26 (permalink) Old 02-01-2014, 01:02 PM
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So, replace the air pump with an old paint compressor and put a really tight lid on the tank. The water will roil around a bit but it won't be "blasted out of the tank". Problem solved. (:-)
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post #12 of 26 (permalink) Old 02-01-2014, 01:09 PM
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Interesting idea. I agree with [Hoppy]'s analysis, though.

If you're a fan of Rube Goldberg, you could use the air pump to inflate a balloon, which pushes on a lever, which generates enough mechanical advantage to pinch off the CO2 line.
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post #13 of 26 (permalink) Old 02-01-2014, 03:15 PM
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Nothing beats a magnet valve aka solenoid in simplicity or function.

I think this picture is more accurate.

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Last edited by mistergreen; 02-01-2014 at 03:26 PM. Reason: +
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post #14 of 26 (permalink) Old 02-01-2014, 04:03 PM
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Quote:
Originally Posted by DarkCobra View Post
Interesting idea. I agree with [Hoppy]'s analysis, though.

If you're a fan of Rube Goldberg, you could use the air pump to inflate a balloon, which pushes on a lever, which generates enough mechanical advantage to pinch off the CO2 line.
By Jove!!! You nailed it. Simply surround the CO2 line with a larger diameter tube, sealed at each end. Pump air into that surrounding line and it squeezes the CO2 line closed. Or, make the air crimp the CO2 line. Or, and this is the real best, foolproof solution, buy a new solenoid valve.

(Or, use air pressure to lift up a brick, which has the CO2 line below it. Shut off the air, and the brick crimps the CO2 line.)

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post #15 of 26 (permalink) Old 02-01-2014, 04:17 PM
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sledgehammer / nut?

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