Cheap peristaltic / doser pumps investigation

I've been dosing with a couple cheapy 12V pumps for a few months using a simple sketch and an Arduino Nano-so far so good. But the pump with a stepper motor looks like a much better unit. Could the stepper be controlled by the same sketch, in the same way, as the cheap 12V pump?

I'm not worried about right on the money precision. I keep my eye on things and adjust the run time. Besides, I don't understand most of the electronics you guys toss around. I'd be happy with my current arrangement, but with higher quality pumps.
 
salty joe said:
I've been dosing with a couple cheapy 12V pumps for a few months using a simple sketch and an Arduino Nano-so far so good. But the pump with a stepper motor looks like a much better unit. Could the stepper be controlled by the same sketch, in the same way, as the cheap 12V pump?



I'm not worried about right on the money precision. I keep my eye on things and adjust the run time. Besides, I don't understand most of the electronics you guys toss around. I'd be happy with my current arrangement, but with higher quality pumps.
Click to expand...



You need two H bridges (or a two channel one) to control the stepper motor. There are a variety of sketches to do the stepping, but the basic theory is pretty simple.

Adafruit's new motor shield can also micro step (PWM the motor coils) which is a lot quieter and smoother (though it's not perfect).
 
Stepper Motor Specs

Stepper Motor Specs

Quick question for the OP:

Your mentioning specs for the stepper motor you got of eBay. I haven't managed to find any real specs anywhere. Even the vendor has no idea. I'm using the the DRV8825. Works OK but, I'm not getting much torque. Can you tell me what you set your VREF to on your driver?

I'm thinking these pumps/motors present a great opportunity for very accurate and reliable dosers. I'm having 2 problems - getting specs (as I've already mentioned), and finding decent tubing that the motors have enough torque to push their way through.

BTW: the beige tubing used by the Jebao DP-4 works perfectly. I just can't find a supply anywhere.

Sorry, this is getting a little long - in any case, if you have the motor's specs I'd appreciate it.

Thanks
 
I don't have the actual specs on the motor, but through experimentation it's a bipolar 200 steps per revolution 3V motor. Expect about 700mA-1A per coil IIRC (varies if you're PWMing the coils or holding, etc)

I don't remember the normal NEMA size but I'll be able to check the measurements in a week or two (busy with some other things at the moment).

As for tubing I have the same problem. They don't have enough torque for thick wall norprene tubing - the more flexible silicone stuff does work well but won't be as durable if you're running the motor for long periods of time or continuously. I grabbed an assortment of sizes from Amazon - you can also get direct replacement tubing from various eBay sellers for pocket change. (I use thick wall norprene in my Masterflex Calcium reactor setup and that tubing is very durable)

My main motivation is to dose fine particle foods at night and various traces (I suck at water changes ;)), so duty cycle is very low for me. I don't see a problem with using them for two part, but use caution if you want to do a matched continuous water change setup.
 
Thanks for the info. I built a doser with 4 pumps. Runs on an Arduino Mega 2560. I used the sketch from Disc1 (here on RC). I just modified it to handle steppers. I have to say, I get extreme accuracy over the 4 motors. If I set all 4 to deliver 125 ml, I get 125 ml - on every pump. I'm very impressed from that point of view.

Again, biggest problem for me is lack of torque. It means you are extremely limited as to what tubing you can use. I bought some Tygon 1/6" x 3/16" with a ShoreA of 50 from APT instruments. I figured a tubing that flexible should be OK. No go. Needs just a little more torque. I'm seriously think about upgrading the motors to get about 80 oz. That oughta do it.

BTW: You mentioned you found the tubing on ebay - would you mind pointing me to a listing. I haven't managed to find one.

Thanks
 
Looks very much like the DOS units, good find :).

The motor looks to be roughly the same NEMA size - unsure of the torque rating.

As for the tubing, I'll dig up a link - can't seem to find it at the moment but its been there in the past. It was the cheap silicone stuff.

I'm cleaning up the board some, almost out of I/O pins since I went down the route of making every stepper controller signal individually available. I added a 2x4 header for each channel as well so you can add your own microcontroller signalling. Also tossed in an RTC to simplify messing with the main firmware and power management - the nRF52 is more than low power enough to survive just on a coin cell doing RTC functions when there isn't available power, but it does complicate testing and firmware design, so for first shot I'm going the lazy route. I'll toss up some pictures later.
 
Sneak peak at a more fleshed out board. Still some tweaks needed.

doser1.png


4.5x2.5 in
 
I don't have the knowledge to design a PCB but, here is a pic of a breadboard based "connection board" for my 4 stepper motor doser, The pin numbers refer the Arduino Mega 2560 pins and are defined in the sketch - a modified version of Disc1s software. I bought a Solderable PC BreadBoard which allowed me to copy the temp set up exactly. Worked real well.

DoserBoardWeb.jpg
 
Nice drawing - are you using Fritzing? What control scheme are you using for the stepper in the Sketch - half steps, full steps or PWM?
 
theatrus said:
Nice drawing - are you using Fritzing? What control scheme are you using for the stepper in the Sketch - half steps, full steps or PWM?
Click to expand...

Yes, Fritzing. 1/16 step - setting gives me all kinds of control and makes it very accurate. I played around a little to see how far I could go with the accuracy. I managed to get it to 1/4 ml but, then the problem is how to ensure that your measurements are accurate. I just left the pumps calibrated for 1 ml a minute. If I input 7 ml I get 7 ml. I've tested the calibration from 1 ml to 150 ml. Exact, every time. More than good enough for what we (maybe I) need

Only thing that bothers me is the tubing. The junk that came with the pumps wasn't even the right size! A .1 mm (or so) to small. It allowed air to be sucked into the tubing. Started using the tubing from a Jebao DP-4 I bought but didn't use. Works perfectly but I'm sure it's cheap stuff and won't last long. I've got lots of the beige Norprene 3/16 OD X 1/16 ID but the motors won't cut it. I think I'll be buying hi-torque motors - about 84 oz/inch - that should handle anything.
 
That board is so cool (sorry I'm a senior citizen)! Very impressive. Can't wait to see how the doser turns out...
 
Assembled board:

assembled_sm.jpg


The power rails are doing the right thing (5V in, 3.0V out of the switch, loaded down to 4A). The Bluetooth radio comes up. Now to do some basic motor driving :)
 
A few fixups later (need to work on solderability / masks / paste layer for the motor drivers), we have motion:

https://youtu.be/nob_Q3xRC5g

This is 32 microsteps at somewhere near max speed for the motor when microstepping. It can of course go much much much slower (for that continuous tiny alk drip!)
 
Nice, that's Something i'd be interested in! i've been looking up these pump for a while but didn't have time to come up with a solution to control them
 
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