Wasserpests cheap Liquid-doser

[Wasserpest]

While my powerhead autodosing works pretty good, there are a few small drawbacks. One is that the solutions start to degrade somewhat over time. Second, every 2 weeks or so <gasp> I have to clean and refill them.

For $70 or so you can get the Liquidoser, which (probably) works great, but if I can help it I don't want to spend that much, plus it needs to be refilled too, plus it needs to be somehow integrated into the canopy.

Inspired by this ingenious invention by Dr. Ruben, I went through my bins and boxes and found

an unused mechanical timer,
an oral syringe,
a T (actually an X, but I put a cap on one leg)
a check valve (need two though)
a metal angle
something to hold the syringe in place
screws and pieces of airline

Total value of parts $7 estimated.



Then I cut a piece of wood (one of those paint stirrers that they give away in HD), drilled two holes, and attached it to the timer. A little off-center, I screwed a screw which will be the driving force of this thing. The position of the screw determines the movement of the plunger and therefore the dosed amount. In my collection of unused parts, I found a plastic holder for heaters which I used to seat the syringe, instead of an U-profile which I did not have.



In the Dutch version, the syringe tilts to not interfere with the circular motion of the timer. I simplified this somewhat, using a wire that connects the screw on the timer to the plunger.



I can't believe it, but it seems to work! I have it set to dose 2 ml with each cycle. I was out of check valves, so I used one of my DIY bubble counters until I get another CV.

So now it is sitting there and thinking... I will let it run for a few weeks to make sure it works. Then, one just needs to stick the "in" air line into a bottle of Flourish (or whatever you put into your tank) and maybe give it a little shakey every month or so.

(Keep in mind this is still in beta, I will most likely change/improve this design. I might give the Dutch tilting version a try, to reduce the stress on the timer.)

[Anti-Pjerrot]

Thats brilliant. But im affraid that the extra work on the motor in the timer will destroy it. So I would think the tilting version would come out far better.

[Wasserpest]

Yeah, this remains to be seen. These little motors are surprisingly strong. I managed to almost shear off the little nipples that turn the light on and off by unintentionally blocking their movement.

I attached the syringe for the wire to be pushing straight towards the plunger, when pulling it back out there is a little angle, that's okay because it is easier to pull than push.

[darkfury18]

Looks awesome... something I'll have to try once I figure out a dosing schedule. And yeh.. those timers are pretty tough!

[actioncia]

That is awesome. Wasserpest you never cease to amaze me.

[toofazt]

That's great. Thanks for posting

When you screwed the wood to the timer did you just use screws that barely screw into the timer? How long were the screws?

[RoseHawke]

I really don't understand how this works, and my Dutch is rather dusty , could you explain it please? I did do your pump doser for macros, and after a bit of tinkering it's working like a champ, but this looks like it would be just the thing for the micros.

[toofazt]

As the timer slowly rotates throughout the day it sucks the syringe up and then plunges it back down releasing the liquid. Then it does it again the next day.

[RoseHawke]

Hmmmm. Then I suppose since the syringe would probably be a fair distance (inches to feet) from any bottle of additive/ferts/etc., it would need to be primed first? Run it through several cycles until you actually get the solution coming out the tube?

[fshfanatic]

Originally Posted by RoseHawke

Hmmmm. Then I suppose since the syringe would probably be a fair distance (inches to feet) from any bottle of additive/ferts/etc., it would need to be primed first? Run it through several cycles until you actually get the solution coming out the tube?

Yes or the first few times would be limited to filling the tube.

[g8wayg8r]

I love it. Purely mechanical and no stinkin' electronics - just plain 'ok juice from the wall. I suspect you start by priming both legs of the tube. If you do that, you shouldn't have to concern yourself with dilutions and it should be very reliable. Kudo to the Dutch and acting on it.

[Wasserpest]

Sorry for not keeping this up at the moment. Spending some vacation time in Europe, while some of the early prototypes are pumping their first couple of weeks to see how different solutions work out. I went back to the tilting action, but a little simpler, with a hose tie that locks the syringe and moves a little back and forth.

Regarding the priming, yes you would probably manually move the clock a few rotations until the solution starts trickling out of the hose. I am planning to use the "mini airlines" to reduce the amount of liquid stuck in the hose. Also, you would probably want to keep this close to the tank, and minimize the length of the hoses.

When I come back from vacations, I will update the thread and show some of the designs that worked better. Along with some clear instructions on how to Do It Yourself.

[Jubs]

How did this end up working out for you? I am very interested in setting something like this up and would like to know if this is worth the time to setup.

[Wasserpest]

Hey Jubs, thanks for asking, I have this working on almost all my tanks at the moment, still refining some of the details.

The challenge is to find check valves that can handle the extremely slow flow, while not allowing a siphon to drain the fertilizer bottle too quickly, or fill it full of water.

I use this in connection with the water pump method. The Liquid-doser injects the micros into the airline that goes from the macro container to the tank, and then once a days the macros get pumped into the tank, taking the micros along on their journey.

Right now I fill the bottles with enough Flourish to last for four months. Then, after 4 months, I check and see how much is left. If there is too much remaining in the bottles, I need to increase the dosed amount.

I need to take a picture of a more recent version. It's a bit simplified, where the plunger is directly connected to the timer wheel, and the syringe itself tilts.