Q: Automatic fertilizer injector

Hello, I am setting up new automatic watering system and I want to not only automatically water my plants, but also feed them. The problem is that organic fertilizers dont last very long diluted. So I want to do DIY fertilizer injector. I already have 2 L container of water which fill itself from 20L container every other day using timer, valve and gravity. After its filled, there is other valve which is opened (via timer) and the water goes to the pots. When the smaller container is filled, its the right time to inject some food for the plants.


My idea for this injector is simple.
I want to get big needles, each with different volume, so I can inject for example 2 ml of this and 5 ml of that. The bigger the needle the more it inject. I will of course calculate exact values. Now I need some device that will move for just a few centimeters/milimeters pushing the syringes and injecting fertilizers. It has to start working when there is electric current, has to be slow and has to be strong enough to push three or four filled syringes. I want to do this with timer, the device should move for constant speed , lets say 1 milimetr per second. So I set the timer to go on for example for 5 sec (=5 milimeters) (it would be great if it wouldnt be affected by needles, ie it would move at the same speed with or without syringes). Sure it could be done with electric motor and gear wheels, but I d rather do it differently. Does anyone have idea which device would do the job ? Thanks

Look at a pool supply company, they have many different types of pumps for injecting chemicals at different intervals.

Yeah I looked that up and nothing, except expensive systems for hundreds of bucks came up. Thanks for advice though. I need to do it by myself, only thing that is missing is that device which moves under electric current, very slowly and only by fractions of inch.

i wish you luck. i like your spirit. i just prefer to see my plants twice a day on most days and i think they prefer it too. plus rep because it's tinkerers like you that create the things that make growers jobs easier.

dannyboy602 said:

i wish you luck. i like your spirit. i just prefer to see my plants twice a day on most days and i think they prefer it too. plus rep because it's tinkerers like you that create the things that make growers jobs easier.

Click to expand...

thats very kind, thank you. By the way I think I found exactly what I need: http://en.wikipedia.org/wiki/Linear_motor

they make a type of pump that is designed specifically for this type of thing. It will move the same amount of liquid every time very accurately when applied current for the same duration. Of course I can't remember what it's called at this point...maybe someone else will chime in.

I seem to remember them not being very expensive either. Just a matter of accurately controlling them with a relay or something.

EDIT: I think they are called positive displacement pumps. not 100% sure but the more I read the more I'm thinking thats the type of pump that would work best.

I think what you're after is called a "Peristaltic Pump"
check them out here - http://www.aptinstruments.com/Merchant2/merchant.mvc?Screen=CTGY&Store_Code=AI&Category_Code=P2
could do what you need.

Just found them on ebay too, quite cheap too.
http://www.ebay.com/itm/Dosing-pump-Peristaltic-dosing-pump-for-aquarium-lab-/160843417627?pt=LH_DefaultDomain_0&hash=item257303c81b

also found this one which is 3 dosing pumps which can be set to dose whatever and whenever you want.
http://www.ebay.com/itm/MC-03-M-Dosing-pump-Peristaltic-pump-for-aquarium-lab-/400309248381?pt=LH_DefaultDomain_0&hash=item5d344a617d

im interested to see how you go with this, keep up the good work!

Yes you need peristaltic pumps as mentioned above. Auto dosers are often used by aquarists. You can buy some made for aquariums and set them on timers if it floats your boat. However the next step is doing something like what this guy has http://peterphrastus.com/drupal/ he runs a 3 part fert system with ph control while only using one peristaltic pump. Pretty neat set up he includes a guide and software too. However if you want to keep it simple look up some aquarium auto dosers on real short timers. Aquarists and growers have a lot more in common than you'd think when you look at planted tanks EDIT: oh by the way home hydro soft calculates doses for you. It's also a free program, just get the hardware, piece it together, and let your computer care for your plants. I'm planning on setting one up when I get the space.

They make fertilizer injector systems that uses water pressure to deliver 1:100, 1:50 etc. dilution ratios. If you mix your nutes you will get a chemical reaction and bad things. If you put your part A in one injector and part B in a second however this may work. I notice that I don't get precipitates when I mix ph down and part B in a 2 part system so I suspect this method could ph also. The guy that sells them says they are very reliable but a pain in the ass for people that use them for yards etc. and bury them. I'll know if this works in three months. Until then, anyone else used an injector system? I'm lazy. I want to mix nutes once when vegging and once when budding. I would also like my buds to trim themselves if left near sharp objects.