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non stepper motor based dosing pumps
#1
current stage I am at:
I have connected the kamoer dosing peristaltic pumps to the DC ports.  and tested that indeed I can control them via the reefpi.  they even can be switched on with less than 1 duration (0.5)  just like a "click".  I am about to start calibrating. Need to measure the required time per each pump for the required liquid volume.  

I have stumbled on one of the posts in the forum, that Rob is saying that using a non stepper motors like I do , will result in a non stable and not accurate dosing.
Is this really the experience that people have ? 

will my setup do what I need?  
I am talking about the usual add-ons that people use for reef. I have a 500l system so its not very sensitive like a nano. so a little more or less of the additive should not matter much. unless I am totally wrong here.  I am new to reefing...

thanks 
David
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  • Rob F
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#2
any thoughts / advice on this please ?
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#3
Well what the heck is going on here, I replied the same day, I know I did, guess I didn't press post, crazy... I'll try again. :)

Stepper motors are more accurate due to how they work. Instead of using time to determine how long it runs stepper motors use steps. Lets say the stepper motor has 200 steps per revolution and you wanted one revolution, you simply tell the stepper to turn 200 steps. With a regular DC motor you can't do that, you can only hope you get one perfect revolution. As the motor ages or if power supply gets weak maybe you only turn 98% of a revolution or 102%. Stepper motors are the main reason 3D printers function and can reproduce the exact same results, if a 3D printer had normal DC motors it would never work.

So yeah only for absolute precision is the stepper motor needed. If you wanted to dose 5 drops every time you would want stepper but for most aquarium dosing a standard dosing pump is fine. If you want to keep regular motor semi accurate it's probably good to recalibrate it every 3-6 months or verify it's still close.
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#4
You can also increase accuracy by dropping the voltage on the dosing pump.
I have one of my 12v dosing pumps running on 5v which has increased the accuracy dramatically

Running a steppermotor on a dosing pump doesn’t account for worn out hoses, mix errors in you additive solution, clogging of hoses, forgetting to refill the containers.
Al sorts of human error, my point being is that using expensive steppermotors and interfaces doesn’t have to be much better than the normal DC pumps
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#5
Good points, running it slower sounds like a good idea. I agree on all those other issues, one thing I've noted in the past is if the pump isn't used every few hours a little fluid will fall back in the hose so if you want 10ml you need to dose 12ml to make up for the missing.
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#6
With check valves fitted in the dosinglines and making sure your containers are sitting lower than the endpoint of the dosing hoses eliminates that issue
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  • Rob F
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#7
Good to know, thanks!
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Current time: 12-09-2021, 12:59 AM