# DIY Auto Dosing Solution



## neilanh (Feb 19, 2007)

I'm horrible when it comes to remembering to dose my tanks. I used to do EI, and I was lucky to get 1 day each of macros and micros in the tank, I just never remembered to do it. The guys over at my local club, GWAPA, had built some autodosers, so I stole this idea from them. You can read their information here.

Anyways, I was asked to post this after some discussion in the PPS forum, so here goes.

I obviously needed a way to dose automatically, since I was so bad about it. There are several different products you can buy, but all of them, in my opinion, are way overpriced. This one, for example, is several hundred dollars for a twin system. While I've never used them, they may be much more accurate and controllable, but it just wasn't worth the money to me.

So, I set out to make some, thanks to the info from GWAPA.

At first, I modified what they had done and attempted to use some aqualifter pumps. Those have a maximum head height of 30", and that didn't work out for me for where I wanted to house the ferts in the stand of my 125.

So, I picked up a pair of mini-jet 606 pumps and used them as the heavy lifters of the system.

Knowing I would be using a lot of liquid, I wanted containers that could hold a good amount of fluid. I had a hard time finding exactly what I wanted, so when I finally found it I bought it, but I know that if I'd had kept searching I could've found something for much cheaper. The idea was something tall and somewhat skinny, to help keep the levels in the container above the PH, and make it more visible to how much is remaining. These are what I ended up getting, 3.2L containers. A bit pricey for what they are, but they worked.

The last piece to the puzzle was the timer. Hamilton makes a dual outlet digital timer that can be set in increments of 1 minute. They also make a single outlet as well. Since I'm giving PPS Pro a try, I opted for 1 dual outlet, but if you're doing EI you'll need two in order to set your doses for different days. The dual outlet cannot control the individual outlets, they're either both on or both off, unfortunately. Here's the one I got.

Next was to figure out how to convert the 1/2" outlet on the 606s into standard airline tubing size (3/16"). This was a trick, but here's what I came up with. I used a piece of 1/2" tubing I had laying around and a medication dosing syringe (that the pharmicist at Target gave me for free) to convert to 3/16" standard airline.

Here's a standalone shot of the pump and the "converter".










Put it all together, and next was to run some tests. I filled the containers up with water, placed the pump, and ran the tubing to where I wanted it to go. Set the timer for 1 minute, and captured the water in a measuring cup to determine how much fluid would be pushed per cycle. In my configuration, after several tests at different water levels in the container, I averaged 100ml per cycle.

I drilled some 1/4" holes in the lids of the containers to push the tubing through. I wasn't worried about the power cords, but if the tubing was to get pinched or bent, I wouldn't keep the same flow rate, so I wanted to make sure this didn't happen.

Having this information, I took the PPS Pro solution and "watered it down" (pun intended) to meet what my autodosers pushed vs. their recommended dosage. I have a spreadsheet I used to calculate this in the PPS forum if you're interested.

Finally, I mixed up the ferts and set it all up. Here it is:










Here you can see the setup inside the container.










And the oulet above the tank - taking special care to make sure they cannot get in the tank and create a backflush onto my floor. I opted to not use check valves, so it's critical to ensure they can't get in the tank and create a backwash when the pumps aren't working:










All in all, a much cheaper way to go. My total cost breakdown ended up at:
2x Mini-jet 606 pumps from F&S: 33.98
2x 3.2L containers from BB&B: 27.98
1 Hamilton dual outlet digital timer: 19.99
Misc tubing and syringes: Free since I had them laying around

Total cost for 2 autodosers: 81.95 (plus some shipping fees I guess).

A little pricey yet, maybe. Compare it to a $300 retail system, worth it.


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## orlando (Feb 14, 2007)

Great write up!


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## hoppycalif (Apr 7, 2005)

Very good explanation of a simple, but very effective idea. And, if you dose EI on a daily basis, dosing both solutions at the same time, instead of every other day basis, this works just as well for EI. 

Did you pick the cheapest pump you could find that would lift the dose up to the top of the tank?

Another good reason not to use check valves is the pressure loss across them, which would use up some of the head pressure from the pumps. And that was good thinking to make sure the tank water can't rise up to the outlet tubes.

It looks like you get about 3 weeks of doses out of each container, before the fluid level is too low for the pump to pick up more.


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