Cheap DIY liquid doser - Page 2 - The Planted Tank Forum
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post #16 of 35 (permalink) Old 05-13-2007, 07:23 PM
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So I finally understand this. Like Naja I had to read it about 6 times but I finally tried it and, brilliant! I just tried a little demo with a water bottle and a 20" coil of regular airline tubing in the bottom. I think the coil tends to trap air in itself due the the fact that it is coiled. I am going to try a small container of the correct volume. A quick calculation shows that 1/2" PVC pipe is ~11.85ml per inch. I'll report back if it works.

Wow!

Dennis Dietz
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post #17 of 35 (permalink) Old 05-13-2007, 07:50 PM
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Actually, I made a mistake on the math. There are ~4.47ml in 1" of 1/2" PVC.

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post #18 of 35 (permalink) Old 05-14-2007, 04:34 AM
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Update... Two things actually. First, I am having a little trouble getting this to work correctly. I have tried both the tube coil and the PVC volume regulator method I mentioned above. Both setups give me a good initial first dose but then I get an intermittent spray or a drop or two every 5-10 seconds. This adds about 5ml or so extra per minute that the pump runs. I have tried several things but none seem to fix, or even change, the problem. I started with a sewing needle hole in the lid and in a 90degree tubing elbow. I slowly expanded the hole in the lid to the size of a paperclip (heated). The bottle I am using is a very thick, 2000ml lab-type Nalgene bottle and the pump is an old, el cheapo "Profile" that was part of a 10 gallon set I pick up long ago.

Also, this happens with the lid on or off and regardless of breather hole size. Both the tubing coil and the PVC chamber do exactly the same thing. It would seem that a venturi forms and a little fluid is continually sucked in to the dosing tube or chamber.

I suppose it would be fine to simple measure the amount dosed for the entire period that the pump runs or get a time that works in minutes. Having one that works in minutes though is a bit counter productive to a cheap setup since a timer is about $30, half the price of an APT peristaltic pump.

Any thoughts on how I can fix this issue?

Dennis Dietz
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post #19 of 35 (permalink) Old 05-14-2007, 06:16 PM
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I played around with this design too and changed it somewhat and still couldn't get it figured out reliably.

Initially, I added a very small slit to the tubing. Very small is somewhat subjective, and in the beginning it was so small that the solution didn't enter the tubing, and later, when it did, air would bubble out of it, turning the flourish into a foamy mess (I want to dose concentrated stuff).

So, I thought, let's play... with some checkvalves. They should work great, allowing the solution to slowly fill the tubing one way, and when the air comes on, block it so all of it will go through the outflow.

Something unexpected happened, which you saw as well... every 5 seconds or so, a little drop of solution made it through the check valve and added to the dosing volume. That wasn't the problem... the problem was that when the air turned off, some drops would still be stuck in the tubing, now preventing the refill action. I had planned on using that sitting in the stand, going up to the tank a couple of feet. If you have it sitting at tank level, with shorter tubing, it might work better.

To prevent the droplets going through the checkvalve during operation, I tried a couple of things. I reduced the outflow at the end of the tubing, which didn't work well - too small, and the tubing would not refill, too large, droplets would still make their way through the checkvalve.

I added a third checkvalve to increase the backpressure so no liquid would make it through the other valve while the pump was operating. Didn't work well either. Maybe adding the checkvalves complicated things too much, and I need to work on the slit thing. Didn't quite understand the need for it to be covered up and "almost" airtight.

Around that time I received some peristaltic pumps, connected them and put the airpump away for later.
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post #20 of 35 (permalink) Old 05-14-2007, 07:19 PM
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My issue is that all the timers I have laying around work on 30 minute intervals. The only way for this to be really cheap is to be able to use cheap timers. If I have to go out and buy minute interval timers your talking about $30 each either after shipping or after tax. So,two timers is the price of one peristaltic pump and it can be sized to work for a 1/2 hour period.

I found that having the lid on added some pressure and actually made things work better, though not perfect. I am going to play around with some of these ideas a bit more. We will be off on our wedding/honeymoon in two weeks, for two weeks, and I really need to have something figured out before hand. I don't really have the liberty to spend the money on two peristaltic pumps or two really good timers but the last time I had someone feed the fish and dose the tank, it did not go so well.

I've tried your syringe/timer doser but my timers are only strong enough for a 10cc syringe (which means about 6ml can be dosed) Not enough for me, especially for micros. Larger diameter syringes are to stiff for the timers I have. If, though, I could find a nice heavy duty timer capable of moving a larger syringe, I could add larger wheel and build it to run two syringes at the same time, solving all of my problems.

I certainly need to think on this more....

Thanks for your reply. Your posts have been very helpful and insightful for me.

Dennis Dietz
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post #21 of 35 (permalink) Old 05-14-2007, 08:45 PM
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Look for deals on digital timers, Target and WM have them for less than $10, sometimes quite a bit less. I picked up a few that were discontinued models in WM for less than $5, once in a while RiteAid (of all places) has some for free or almost free after rebate.

10cc not enough for you? Wow. My 100gal is (under?)dosed with 4cc daily.

Congrats and have fun on your honeymoon!
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post #22 of 35 (permalink) Old 05-14-2007, 10:28 PM
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I dose Flourish and Fe gluconate at 1ml per gallon per week. Yup, its a lot but the growth is good and I have no fish or inverts issues. So, since it has to happen daily, 60ml total for 7 days is 8.6ml daily for micros. Macros I could mix to get the dose right but I was hoping for a fool proof, easy to use and accurate- oh and really cheap- method of autodosing.

My current test setup in the laundry room seems to give about 47ml per 1/2hour cycle. This may change a little if it is moved to the tank if hose length or head heights change. This also uses 18" of airline tubing in the bottom of my container for the initial dose, which is about 7ml if the tubing is full. I've tried all manner of hole sizes and check valve configurations, all yield similar situations, an eventual venturi that spits. I may try modifying the timer I have so that the actuator is narrower, thereby letting the power be on for a shorter period of time. I am sure I could get it down to only 5-10 minutes of run time this way.

The next option is something like magicmagnani's air doser but I don't like the variation in dose size over time, nor have I been able to control it to dose less than several hundred ml in 1 minute.

Bahhh!

Thanks for the tip on cheap timers. I remember seeing some digital ones at Walmart but did not look closely at the time. Now I just need an excuse to go back there.

Dennis Dietz
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post #23 of 35 (permalink) Old 05-15-2007, 12:27 AM
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You could also go with Wasserpests water pump dosing which doses consistently, and you can play with the concentration of the solution to dose the right ppm's. All you need is a little water pump, they can be had for $10-15, or maybe you have a spare one sitting in your stand anyway.

Let us know if you figure out a way to get this cheap liquidoser to work... it has a lot of potential. One of these days I will start poking holes into airtubing again.
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post #24 of 35 (permalink) Old 05-15-2007, 04:03 AM
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I think this would work perfectly fine if a minute timer can be found cheaply. Because large coils of tubing do not seem to work well it seems adequate to dose only in the 5-10ml range for short periods. I may be able to adjust that by playing around with large "chambers" in the solution bottle. Also, a cheap timer capable of minute intervals would make magicmagani's doser a good solution for toping off a little also. I'll hit Walmart or Target tomorrow and see if there is anything under $10. I would need two doser setups so it seems that going the "cheap" route is only worth it to me if I can do the whole thing for under $30 bucks and with some degree of reliability. Otherwise, if I cannot find suitable timers and need the $25 intermatics, I might as well spend a little more and get the accuracy of peristaltic pumps that will dose the right amount in 30 minutes and use cheapy timers.

Thanks for the help so far.

Dennis Dietz
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post #25 of 35 (permalink) Old 05-16-2007, 03:22 AM
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Walmart has Brinks brand digital timers for $8.73. They only have one on-off setting but they work in minute intervals so its perfect. The price is right also. I've done a lot of playing with the concept for the original topic to this thread, as well as magic's AirDoser and Wasserpest's powerhead method.

I'll start a new thread of my own for further updates.

Dennis Dietz
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post #26 of 35 (permalink) Old 05-20-2007, 05:41 PM
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Looks like great idea.

All in all after the time spent shopping and fabricating, why not just get one of these?
http://www.marinedepot.com/aquarium_...er.asp?CartId=
Iím not being critical; I want to set up something like this and am looking at the pros and cons of each option.

thnx
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post #27 of 35 (permalink) Old 05-20-2007, 08:57 PM
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The one negative I saw with the Eheim liquid doser is the amounts it can handle. You can do a max of 1ml, 8 times a day (providing I am reading the literature right). In my case, that is not enough to handle my trace supplementation. You should be able to mix all your macros at a concentration that would work with but it would not be enough for me for traces.

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post #28 of 35 (permalink) Old 05-20-2007, 09:16 PM
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Quote:
The one negative I saw with the Eheim liquid doser is the amounts it can handle.
I could see a few more negatives... first and foremost, the cost. While one of them doesn't hurt too much, in my case I would need quite a number to supply traces (and maybe PO4) to all tanks. With some easy shopping, I can get a dual output airpump for around $10.

Keep in mind this is a hobby... time spent tinkering with things is something that I don't consider lost, and don't want to do without. Of course, if you apply your hourly wage to the time playing with tubing, you might be better off just to order the Liquidoser.

Another dealbreaker (for me) is that it has to sit on the tank rim, unless you have a sump. I like to cover my tanks as completely as possible, and use a slim canopy that just so fits some T5 bulbs with reflectors. Don't wanna have anything stick out.
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post #29 of 35 (permalink) Old 03-25-2010, 06:35 PM
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It works great! Here are my photos...




All it took was a little patience, 2 liters of spilled cool-aid, a broken t, and 65" of my tubing... Iv got a digi timer so Im gonna try it

75 gallon "Piranha Kingdom"- wet/dry, FX5, CO2, pH controller, T5HO 4x54, ferts, SunSun Pimp Club Lucky #11, Fluval Pimp Club #17
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post #30 of 35 (permalink) Old 03-25-2010, 08:26 PM
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I built one too. I didn't understand the issues by just reading..

I haven't been able to avoid a venturi effect on the 'fill hole' at the bottom of the coil. This becomes a problem when you're using a timer that has a minimum of a 1 - 15 minute cycle. Unfortunately I think the venturi is more 'random' that reproducible, and I'm not sure if it can be calibrated with the venturi issue.. I tried adding valves/etc on the fill hole to adjust the venturi, and to keep it away from the coil, but it didn't help..

Instead, I dug out a bunch of the $1 automatic plant watering machines "Green Genius" that I bought at big lots on clearance. They're battery powered, but they have a dial to specify frequency of dosing (i'm using 2 days) and quantity in ml...

Prior to that I did some testing on water pumps, and dug out and calibrated a bunch of 4$ Cascade filters they had on clearance at Petsmart. Used epoxy putty to attach 1/8" hose to the outlet. Consistently within about 5% accuracy over the course of a minute..
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