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Servo Injection Pump

A project log for Reagent Robot

Automate the Reagent (take a sample, put a drop of stuff in, shake, look at the color) testing of water for Aquaponics, Ponds, Aquariums.

James NewtonJames Newton 11/23/2015 at 00:571 Comment

Finally figured out a way to mount the servo to the syringe... I used solid core wire wrapped around the syringe and the servo. :yike: "Get'r done"

And I built a link from the servo horn to the plunger out of a paperclip. The link is actually pretty good, but the plunger bends badly up and down. I may need to move to a more expensive glass syringe just to avoid the bending. e.g.
http://www.zoro.com/air-tite-glass-syringe-metal-luer-lock-5-ml-7140-33/i/G4824181/

I'd post pictures but... I have some pride left. ,o)

And then I went to wire the servo up and realized I don't have any source of 6 volt power. :facepalm:

I'm wondering if the servo will fry if I connect it to the 12 volt supply I'm using for the stepper motor and solenoid. No specs on the Adafruit site for max voltage.
https://www.adafruit.com/products/1450

I could also use the LM317 regulator option on my BOB PCB to produce 6Vs with a 240 and a 910 ohm resistor set in R6/R7 then cut the trace between C5 and VCC on the Arduino connector to isolate the supply, and pick off the resulting 6 volts at R5 (top pad) but 1. I'd love to avoid populating all that (and C4-6... C4 is huge) and 2. I'm not sure how much current that servo draws. Dropping 6 volts (from 12 to 6) the LM317 should be good up to an amp or so ( I think ) so is that enough? Enquiring minds...

So I've posted a request for more data on the servo at:
https://forums.adafruit.com/viewtopic.php?f=19&t=84433

Hopefully will get some guidance soon... I'm supposed to show this thing working at STEAM Fest on the 5th:
http://www.sansmf.org/

Discussions

James Newton wrote 11/29/2015 at 20:04 point

Looks like there is a very nice injection pump design available right here:

https://hackaday.io/project/1838-open-syringe-pump

The servo / syringe I'm using is pure crap, but it seems to work ok. I'm not 100% certain the accuracy is good yet, but I think it's pretty close. If I need to improve it, I'll try a smaller syringe and multiple actuations. 

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