# DIY Peristaltic - Again



## Robotguy (Jan 24, 2010)

mistergreen said:


> Have any of you tech heads thought about making one? ...
> 
> Any thoughts?


I didn't want to crash mistergreen's thread so I started a new one. 

I imagine I can put together an open source miniature molded plastic peristaltic pump and controller (MMPPP&C) for, well let's see:

Motor: $6
Bearings: 7*$1=$7
Custom molded housing: ~$2 worth of polyurethane
Misc hardware (tubing, screws, etc): $5

Total per channel: $20

6 channel Timer/Controller: ~$15

I am going to need something like this for my CNC Nano, and if I put a little extra work into it I can make it reproducible in small quantities. I really have no desire to mfg these, so I would probably make the custom parts available for purchase from Shapeways and BatchPCB, along with a BOM so anyone who wanted to could buy all of their own parts, or buy batches and resell them.

Does that sound like a decent price point for an autodoser setup? I there's interest, I could post a more detailed description tomorrow.


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## Gatekeeper (Feb 20, 2007)

Do you have a picture of one constructed?


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## mistergreen (Dec 9, 2006)

Nice to see you back robotguy.

Do you know what kind of torque that little motor can produce?
I found that the motor should be fairly strong to push onto the tubing.


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## Robotguy (Jan 24, 2010)

Gatekeeper said:


> Do you have a picture of one constructed?


It's still in my head, but you should see it. It's really cool! 



mistergreen said:


> Nice to see you back robotguy.
> 
> Do you know what kind of torque that little motor can produce?
> I found that the motor should be fairly strong to push onto the tubing.


Thanks! Good to be back. Can we call this the GreenDoser? It's your idea after all.

That particular motor (GM3) produces 50 oz*in at 5V. It's from Solarbotics, and they make quite a line of small plastic gearmotors. I am actually hoping I can get away with a GM6 which can put out 20 oz*in. The GWS continuous rotation servo produces 39 oz*in at 6V. Does that sound like about what you used, or did you have a high torque servo?

I am hoping that by using the motor with the small shaft, I can fit one of the 3mm bearings on the central shaft to keep everything running smooth. Plus I have a couple of those and a bunch of the bearings laying around already, so I can start prototyping.


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## mistergreen (Dec 9, 2006)

I got this

http://www.sparkfun.com/products/9347

it's 3.3kg/cm at 5V and 4.8kg at 6V.

I think anything lower would have a hard time with the friction ( to make a proper seal on the tubing). The GM3 is worth a try since it's fairly cheap.


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## mistergreen (Dec 9, 2006)

Robotguy said:


> Can we call this the GreenDoser? It's your idea after all.


heh, It's not for me to say.. I want it up and running on an actual tank first though.


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## Robotguy (Jan 24, 2010)

Gotcha! 4.8 Kg*cm is 66 oz*in so we are at least in the ballpark with the 50 oz*in.

A quick rummage through the lab turned up these supplies for prototyping:


The tubing is Top Fin silicone airline tubing:

OD: .25"
ID: ~.150"
A quick test shows it needs to be compressed to .075" to stop air when I blow through it.

The piece I had with the circular pocket is 1.742" ID, so the outside edges of the bearings should be on a (1.742-2*.075)=1.592" diameter. The bearings are .394" (10mm) diameter, so their centers will need to be on a (1.592-.394)=1.198" circle. Split the difference to get the diameter of the plate they will ride on (1.592+1.198)/2=1.395

Something like this:


Eventually I want to add a small channel around the ID of the body to hold the tubing so you don't need a front plate, and a dovetail on the outsides so that multiple heads will snap together into a single unit.



> I want it up and running on an actual tank first though.


Fair enough.

Here's my plan for "production." I am going to prototype what I can on my CNC, then when I am confident in the parts, I will get a set from Shapeways (and make the parts public so anyone can buy them). I will use those parts to make a silicone mold and then cast at least 3 sets for myself. Then I will probably cast a few more to send to people who want to help test. Finally if everything is working I will offer to send the molds to someone who would be willing to cast and sell parts. 

Well, it's time to put together a monthly menu and go grocery shopping, but I'll try to get some more done tonight...


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## mistergreen (Dec 9, 2006)

Definitely go with latex tubing. I tried silicone tubing and it was surprisingly rigid. My servo couldn't handle it.


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## majstor76 (Jun 11, 2010)

I was doing some dismantling of peristaltics so here are few pictures, maybe youll get some ideas. BTW , im also cnc operator, wouldnt it be cheaper to produce housing on cnc, rather than mold with plastic?

This is cheap peristaltic from ebay, about 40$. Difference from first one i have, this one has hose clamps, so when in action hose doesnt "travel" or doesnt suck in by the rotation of pump










Axis









Internal 










Difference between hoses. Cheap peristaltics come with left one. Right one is normal air hose. Maybe its easier for motor to run with left one?










This is peristaltic from inkjet printer. Notice the same hose and just one pressing part


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## Robotguy (Jan 24, 2010)

mistergreen said:


> Definitely go with latex tubing. I tried silicone tubing and it was surprisingly rigid. My servo couldn't handle it.


The best would be if I could find a way to make silicone air tubing work because most aquarists have a bit or at least know where to get it. If I can't get that working, I'll have to switch over to latex. It looks like Pololu actually makes their own version of this motor that can put out 100 oz*in at 6V, and can be driven up to 12V. I wonder what the torque is at 12V? It also says that there is a clutch that keeps it from stripping gears, so there will be a maximum amount of torque we can expect from this thing.



majstor76 said:


> I was doing some dismantling of peristaltics so here are few pictures, maybe youll get some ideas. BTW , im also cnc operator, wouldnt it be cheaper to produce housing on cnc, rather than mold with plastic?


Thanks for the pics. They should be useful. roud:

I believe for hobby quantities, casting polyurethane in a silicone mold is cheapest. I've done a bit of that with robot parts. For larger quantities, CNC is best. For really large quantities, injection molding would be the way to go.

I pushed off grocery shopping 'til tomorrow, so I updated the model a bit:

For a size comparison, each body is about 2" X 2".

I just got Solidworks, so I am having a lot of fun learning how to use it. Can you tell?

Should I work on reducing the cost as much as possible? For example, would it be worth it to use 2 sets of bearings instead of 3 to save $2? Should I make the molded parts use as little polyurethane as possible to shave off another $0.50 if I can, or is that not worth the effort?


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## majstor76 (Jun 11, 2010)

Robotguy said:


> I just got Solidworks, so I am having a lot of fun learning how to use it. Can you tell?


Types of programs like Solidworks i would not describe as fun to learn 



Robotguy said:


> Should I work on reducing the cost as much as possible? For example, would it be worth it to use 2 sets of bearings instead of 3 to save $2? Should I make the molded parts use as little polyurethane as possible to shave off another $0.50 if I can, or is that not worth the effort?


Hm, if theres no structural or any other compromise i dont see why not product would not be smaller and/or cheaper. 
Its question how would thing operate with just two bearings? Most cheap peristaltics have 3, and i have industrial one with 2.
Would motor and axle be under strain just on two bearings?


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## DarkCobra (Jun 22, 2004)

I'd focus on the bearings for cost reduction.

If the design can be modified to use common skate bearings, they can often be purchased for lower cost; especially in bulk if someone's going to be putting together complete kits for sale. If builders are going to have to get parts from different sources, skate bearings can be obtained locally, saving a shipping charge.

But are steel bearings necessary? The motor might drive simple nylon rollers with no problem.


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## mistergreen (Dec 9, 2006)

Robotguy said:


> Pololu actually makes their own version of this motor that can put out 100 oz*in at 6V, and can be driven up to 12V. I wonder what the torque is at 12V? It also says that there is a clutch that keeps it from stripping gears,


what does 90-Degree Output mean for this motor? That's a strong little motor.

And the more bearings you have, the more points of contact & friction.
2 works great.


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## Robotguy (Jan 24, 2010)

DarkCobra said:


> I'd focus on the bearings for cost reduction.
> 
> If the design can be modified to use common skate bearings, they can often be purchased for lower cost; especially in bulk if someone's going to be putting together complete kits for sale. If builders are going to have to get parts from different sources, skate bearings can be obtained locally, saving a shipping charge.
> 
> But are steel bearings necessary? The motor might drive simple nylon rollers with no problem.


These 3x10x4mm bearings were the cheapest ones I found at VXB ($0.99 each). My guess is that nylon rollers may be possible, but might put the motor under more stress and shorten it's life. No reason it couldn't be an option though.




mistergreen said:


> what does 90-Degree Output mean for this motor? That's a strong little motor.


I think they just mean the output shaft and the motor shaft are at 90 degrees.

So far:


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## Sharkfood (May 2, 2010)

That pump is just too cool.roud:


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## Robotguy (Jan 24, 2010)

Well the GM6 didn't have enough _oomph_ to drive the pump, but I found another in my box of motors that could do it, so I still have hope for the GM3. I also worked on the design a bit, reducing the bearing sets to 2, making the radius of the drive circle a bit smaller get more torque, and adding a set of small clips to keep the tubing from "walking" as recommended by majstor76. I still need to add the channel around the circumference that should hold the tubing in the right position. This is what it looks like so far:


and in multiples:


And the current model if anyone has the viewer:
http://robotguy.net/aquarium/pump2.easm

I uploaded the model to Shapeways. It looks like the body will cost about $16 in a useable material (White Strong and Flexible), or $27 for a material suitable for making a mold master (Transparent Detail). It is about .63 cubic inches volume, so would use .35 fluid ounces of polyurethane. In the smallest size from Tap Plastics the polyurethane is about $1 per ounce. Larger sizes bring the cost down to $0.35 and $0.22 per ounce.

I found the screws at Microfasteners.com. They have really good prices on small screws. M3X16 are $3.40 for 20, so $0.17 each, need 2. Nuts are $1.20 for 50, $0.02 each, need 2. These are the cheaper alloy and plated fasteners, figure double the cost for stainless.

I wanted to use the Pololu motor, but nobody has them in stock so I ordered a GM3. I am hoping I can get extra torque out of it by locking the clutch. It will be a few days before it gets here. Then I can check all of my dimensions, update the model and order the master from Shapeways for testing.


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## mistergreen (Dec 9, 2006)

Have you tried the latex tubing? That helps too.


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## Robotguy (Jan 24, 2010)

mistergreen said:


> Have you tried the latex tubing? That helps too.


I didn't have any on hand, but I'll see if I can find some. Does it just connect to standard airline tubing with a connector? I am guessing we'll need about 5" and I see it on Amazon for $16 for 10 feet, so 5 inches would be about $0.70. Thats not too bad. Airline connectors look like they can be had for $0.99 for a 6-pack. Maybe I'll work up an itemized BOM on Google Docs while I wait for the motor to arrive.


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## mistergreen (Dec 9, 2006)

Yeah, 3/16 ID but 1/8 ID connects tighter and seals better too I think. I googled around town and found a rubber company. It was next to a grocery store I go to once in awhile so it saved me the shipping cost. I can get it by the foot so no commitment for the 10feet that's usual.


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## majstor76 (Jun 11, 2010)

Thats a fine looking piece of machinery. Makes me wonder why some mass products suck when one man can design this...
Holes on plate of pump... Are they for fixing motor or fixing pump on the wall or such?


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## Robotguy (Jan 24, 2010)

majstor76 said:


> Holes on plate of pump... Are they for fixing motor or fixing pump on the wall or such?


Those holes are for mounting the motor to the pump body. I modeled up some mounts:


Other than that, not much progress today.


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## Robotguy (Jan 24, 2010)

I'm planning to start the controller PCB during lunch today. How many channels would be sufficient? Would 4 be enough (micros, macros, Excel + spare)? There are 4 hardware PWM channels on the processor, so motor speed control would be really easy. I could manage up to 8 if absolutely necessary, but the code would get a lot uglier.

I am planning on using some surface mount devices, but they will be really easy to solder (i.e. the resistors are 1206 size, almost as large as through hole parts). The processor at the moment is a ATtiny2313 in a DIP package (available for $2.16 from Mouser where I plan to source the rest of the parts).


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## Robotguy (Jan 24, 2010)

I know it's hard to get a sense of proportion from a solid model, so I added a soda can to show just how small these pumps are going to be:

I just drew the can myself so it's not exact, but easily close enough to get the idea.

I got a bit done on the controller PCB during lunch, moving forward with a 4 channel design, but I may rework a bunch of it:


I took the easy way out and just threw down whatever I had in my libraries already, but I will probably need to make some custom parts.

A few questions regarding preferences:

1) LEDs to show when each pump is being activated?
2) How many people would be interested in buying parts and soldering it themselves?
3) Stick with all through-hole parts? 
4) I was planning to make it necessary to plug the controller in to a PC to set up the timer. Is that acceptable, or will it be necessary to have a way to set it stand-alone?
5) If the controller needs to be plugged into a PC, should I add $5 worth of parts to each PCB, or require a $20 cable (that could be used to set up multiple boards)? Hmm, putting it like that makes it kinda obvious :icon_redf


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## JamesHockey (Nov 10, 2010)

Robotguy said:


> I know it's hard to get a sense of proportion from a solid model, so I added a soda can to show just how small these pumps are going to be:
> 
> I just drew the can myself so it's not exact, but easily close enough to get the idea.
> 
> ...


First off I'd love to be a tester, 

1)yes LEDs are good to see when the pumps are on
2) I could Solder the parts, but I'm lazy
3) soldering surface mount is a PITA
4) if plugging to a pc is cheaper go that route ifnot make it more user friendly and go stand alone
5) hard one, if you only want one controller, 5 bucks is cheaper, I'd say don't do a special cord


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## mistergreen (Dec 9, 2006)

Make it user friendly as much as possible, meaning that it should work straight out of the box, otherwise I can see only 2-3 people trying this. 

I've run into the userbility issue myself. I've thought about sequentially turning on each channel for 10 seconds. There would be potentiometers controlling each motor where the user can adjust the speed of each motor. Customizing the dosage with a knob is a lot easier than changing the chip's programming from a bystander's point of view.


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## Robotguy (Jan 24, 2010)

mistergreen said:


> Make it user friendly as much as possible, meaning that it should work straight out of the box, otherwise I can see only 2-3 people trying this.
> I've thought about sequentially turning on each channel for 10 seconds. There would be potentiometers controlling each motor where the user can adjust the speed of each motor. Customizing the dosage with a knob is a lot easier than changing the chip's programming from a bystander's point of view.


Yes. I see your point. Hmmm, I'm going to have to give this some thought. I was figuring on having this thing fully programmable, so each pump could be set up, for instance, to dose on Monday Wednesday Friday at 6 am for 3 minutes and 75% pump speed. That will be a little hard to set up with knobs. Maybe a small LCD and some buttons? It would add some cost, but it sounds like it's necessary.


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## mistergreen (Dec 9, 2006)

Yeah, an LCD is necessary. I added one onto my DIY par meter. Works pretty great. The cost is $14.

I'm a designer so I always take on the POV of a user, force of habit and training 

Hmmm. I'm going to have to think about getting an arduino, LCDs, and buttons for my pumps too. I bought the popolu servo driver for now but will have to move on to something more sophisticated down the road.


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## Robotguy (Jan 24, 2010)

So here's how it's looking so far:

PCB $5
Processor $2.16
LCD(8x2) $4.43
Connectors $0.88
LEDs $0.08 X 5 =$0.40
Switches $0.07 X 5 = $0.35
Resistors. $0.05 X 20 = $1.00
MOSFETs $0.79 X 4 = $3.16
Capacitors. $0.18 X 6 = $1.08

Total. $18.96

Just to be clear, I have no desire to sell anything. I just thought it would be cool to have a sort of reference design for the community. I plan to make the PCBs and plastic parts open source and available along with a parts list for anyone who wants to build one or sell kits themselves. Unfortunately, most of the cost reduction in this is based on DIY labor because I can't leverage economy of scale, so I don't think anyone is going to be able to make any money soldering PCBs. Maybe there could be a profit for someone in assembling kits if there is a demand for more than one or two. My main goal is just to make it possible for TPTers to get their hands on a 3 channel autodosing setup for less than $60. Maybe local clubs could set up a build day if there's interest.

I do plan to provide a few kits below cost to beta testers to verify the design. I will give preference to users who have been active in this thread. (How's that for bribery?)

Oh, yeah. I found Tygon tubing, specifically for medical/peristaltic applications for $0.31 per foot (10 foot min but that's only $3.10  ). It's 1/8" ID so it should be easy to connect to standard air line tubing, and it's 1/32" wall so it should reduce the torque requirement on the motor. It's not Tygoprene, but I found it on the same website posted by someone who was mentioning Tygoprene on a thread here. I'd look up the post and give credit where it's due, but I can't multitask on this machine until I update the OS. I'll add it in a later post when I'm on a PC.

Last but not least, I am also looking for suggestions on functionality. If you had a small computer running a couple or three pumps, what would you want to be able to get them to do? Maybe built in dosing rules EI, PMDD), just enter the tank size it will tell you concentrations and dosing schedule?


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## majstor76 (Jun 11, 2010)

Robotguy said:


> 1) LEDs to show when each pump is being activated?


No, there is no need. Since theres no housing trough which you cant see pump, theres no need to have a led to light up when motor is working. When its working you see it , in difference to lets say device plugd in digital timer where you (mostly) cant tell if its working or not so it must have leds.




Robotguy said:


> 2) How many people would be interested in buying parts and soldering it themselves?


Its hard to say, i am DIY-er (not into electronics but can solder easy staff), but i think most people would just like to buy it and plug it.




Robotguy said:


> 3) Stick with all through-hole parts?


Hm, i dont understand this Q




Robotguy said:


> 4) I was planning to make it necessary to plug the controller in to a PC to set up the timer. Is that acceptable, or will it be necessary to have a way to set it stand-alone?


Im for PC version. Its much easier to sit in front of pc and set up timers in some sort of schedule program than have 2-3 small buttons and 2x8 lcd. Possibility of error is much larger in stand-alone version.



Robotguy said:


> 5) If the controller needs to be plugged into a PC, should I add $5 worth of parts to each PCB, or require a $20 cable (that could be used to set up multiple boards)? Hmm, putting it like that makes it kinda obvious :icon_redf


What kind of cable costs 20$?


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## majstor76 (Jun 11, 2010)

Robotguy said:


> So here's how it's looking so far:
> 
> PCB $5
> Processor $2.16
> ...


So, what would be final price of pump with motor and housing and this one up?



Robotguy said:


> Last but not least, I am also looking for suggestions on functionality. If you had a small computer running a couple or three pumps, what would you want to be able to get them to do? Maybe built in dosing rules EI, PMDD), just enter the tank size it will tell you concentrations and dosing schedule?


Maybe something like this with some extra

https://spreadsheets.google.com/ccc?key=0AtnVK6bTULNhdEFudGhGWElJUGZQc0cxR0xCWno3anc&hl=en#gid=0

Its my pps pro calculator. Its on croatian but its simple

input fields are yellow

left upper yellow - volume of aquarium
right upper yellow - volume of fertilizer
lower left yellow - output of macro pump
lower right yellow - output of micro pump

Bellow yellow fields are ammount of chemicals you need to put into water to get right concetration of fertilizer for given upper data.
Some logging would be nice, to have data about when the pump have worked, how long and how much have pumped. With that info can be calculated amount of elements pumped into aquarium, amount of fert left in container (maybe some kind of low level alarm) and of course graphs can be made.
Now im entering in lower yellow fields data about outputs of pumps for micro and macro (since its fix values). But with your system i could enter into those fields whatever output i want . Pump would deliver output i want and program would calculate concetrations i need for that output (like it did now)


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## JamesHockey (Nov 10, 2010)

Robotguy said:


> Last but not least, I am also looking for suggestions on functionality. If you had a small computer running a couple or three pumps, what would you want to be able to get them to do? Maybe built in dosing rules EI, PMDD), just enter the tank size it will tell you concentrations and dosing schedule?


I think that would be cool



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## r3tic (Jan 4, 2011)

This sounds very cool! I would have no problem with a parts only kit type of deal, with surface mount components as long as they are larger components i'm good with that. I would prefer the pc interface, but then you should really do it in pc/mac/32bit/64bit flavors. I could see the being really handy for dosing my nano saltwater reef setup as well. I'll gladly help with beta testing if you need it.

_-- Sent from my Palm Pre using Forums_


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## mistergreen (Dec 9, 2006)

Robotguy said:


> If you had a small computer running a couple or three pumps, what would you want to be able to get them to do? Maybe built in dosing rules EI, PMDD), just enter the tank size it will tell you concentrations and dosing schedule?


I would leave it up to the user but having the MCP calculate and display the ppm given the solution, duration, speed, would pretty neat. You can find the peristaltic formula on wiki.


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## Robotguy (Jan 24, 2010)

Just a quick note before I head off to lunch with my wife (Wed is lunch date day!); I'll answer questions and address comments tonight.

It sounds like the appeal of this project would be a lot greater if I could eliminate the need to assemble the PCB. I have a buddy who sells his motor controller online and he has the PCB fabbed and stuffed in China "for less than I could buy the parts from Digikey." I may look into that. That way I (or someone else) can just sell complete PCBs and all of the DIY work will be light mechanical (screwing things together, etc). I may also look into Seed Studio. I believe they offer a service that hosts and sells open source designs.


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## Armonious (Aug 16, 2010)

Any ideas on how this will be mounted/ interface with the water in the tank.

I have some connections to medical suppliers/ manufacturers. I will see if I have anything that may interest you, and if I do, expect a PM.

I'm in line for this one once it comes to fruition.


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## JamesHockey (Nov 10, 2010)

Update please or I find u 


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## Robotguy (Jan 24, 2010)

james7139 said:


> Update please or I find u


Sorry, project ship date is coming up at work, so it's a busy time. I received the GM3 motor and wired it up to 6V to test the torque. Wow! this thing is strong. I think it'll have enough to do the job. I am going to double check the measurements tonight and, just maybe, try to CNC a prototype this weekend. I have to work this weekend so it's possible I may not get to it.

In the next couple weeks I want to have the PCB designed and laid out and the mechanical design somewhat finalized. Then, when I get my taxes back, I can throw some money at this project and buy the PCBs, prototype parts, silicone for the mold, urethane for molding parts and maybe some Tygon tubing.

My ultimate goal is still to make this thing capable of using silicone tubing from the LFS, but if the design can't handle the torque, I will try latex or Tygon.



Armonious said:


> Any ideas on how this will be mounted/ interface with the water in the tank.


Just run a tube from each of your fertilizer bottles, through one of these pumps and into your tank. Then set the controller to run the pumps the appropriate length/day/time.



mistergreen said:


> I would leave it up to the user but having the MCP calculate and display the ppm given the solution, duration, speed, would pretty neat. You can find the peristaltic formula on wiki.


Good idea. Several different modes:

You can use a predefined setup
You tell it what size tank (Gallons, liters), CO2 (DIY, pressurized,none), choose a method (EI, PMDD, etc.) and it tells you how strong to mix the ferts and establishes a dosing schedule.
Semi-custom setup
You tell it what size tank (Gallons, liters), CO2 (DIY, pressurized,none), which method (EI, PMDD, etc.) and tell it the concentration of your solutions and it establishes a dosing schedule.
Full-custom setup
You figure everything out yourself and then completely specify duration, time, speed, etc. for each for each pump.



majstor76 said:


> So, what would be final price of pump with motor and housing and this one up?
> 
> Maybe something like this with some extra
> 
> https://spreadsheets.google.com/ccc?key=0AtnVK6bTULNhdEFudGhGWElJUGZQc0cxR0xCWno3anc&hl=en#gid=0


I am shooting for $15 for each pump and $25 for the controller. So a 3 channel system would be $70.

That spreadsheet is really cool! Implementing something like that in firmware would be great.



majstor76 said:


> What kind of cable costs 20$?


http://www.sparkfun.com/products/9717


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## JamesHockey (Nov 10, 2010)

I love your ideas, now inwanna see it happen


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## Robotguy (Jan 24, 2010)

Here's the motor in action:
http://www.youtube.com/watch?v=V7bgw73l4kw

You can tell how far off center everything is by watching the motor wobble on every revolution and listening to the sound. One set of bearings pushes water better than the other two. But the main thing is that the motor has enough torque to drive silicone tubing. I may still try latex or Tygon though.


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## JamesHockey (Nov 10, 2010)

Diggin this thread out the dust


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## mistergreen (Dec 9, 2006)

Robotguy said:


> Here's the motor in action:
> http://www.youtube.com/watch?v=V7bgw73l4kw
> 
> You can tell how far off center everything is by watching the motor wobble on every revolution and listening to the sound. One set of bearings pushes water better than the other two. But the main thing is that the motor has enough torque to drive silicone tubing. I may still try latex or Tygon though.


oh nice. I didn't see this till now. That's how mine sound like too. Make sure the bearings seal is complete. Turn off the motor and see if any liquid falls back into the container, like a real-life situation.


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## Robotguy (Jan 24, 2010)

I ordered the pump body from Shapeways tonight, in Transparent Detail, so if all goes well I can make a silicone mold from it and cast a few more. I should be able to make the bearing rotor on the CNC so I won't have to order it, and it will give me a bit of wiggle room for adjusting the pinch on the tubing.

Hmm maybe I should order a bit of latex tubing also...


EDIT:

OK, just ordered ten feet each of three sizes of Tygon tubing from U.S. Plastics:

3/16" I.D. 1/4" O.D. and 1/32" wall @ $0.44/ft
1/8" I.D. 1/4" O.D. and 1/16" wall @ $0.57/ft
1/8" I.D. 3/16" O.D. and 1/32" wall @ $0.31/ft



> Crystal clear, flexible (Durometer Hardness, Shore A, 55) tubing of superior quality. Increases productivity in peristaltic pumps -- outlasts other clear tubing 2 to 1.


I'm hoping #3 works well as it's the cheapest, but in the amounts we'll need, it's not that big of a deal.


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## Robotguy (Jan 24, 2010)

The tubing arrived from U.S. Plastics this morning. The 1/4"OD x 1/8"ID is way too stiff to be of much use, I think. The 1/4"OD x 3/16"ID is nice and squishy, but after a bit of measuring I realized the channel that I put in the diameter of the pump body to hold the tubing in place is only 1/4" wide. When the 1/4"OD tubing gets squished it is .35" wide. It looks like the 3/16"OD x 1/8"ID is my best bet for now. It is just a hair over 1/4" wide when squished, and with a 1/8"ID, it should fit standard airline fittings, as mistergreen mentioned earlier.

I'm not expecting the pump body from Shapeways until next week (ordered on the 8th, 10 working days would be the 22nd). I have been playing around a bit though since I ordered it. First off; Man, is this thing small! I was drawing 1:1 scale parts and realized how teeny this thing is. I'll take a pic of the pump body in my hand when it shows up to give an idea. 

Second; I may be able to reduce the cost by using acetal (aka delrin) bushings as rollers (suggested by DarkCobra) instead of bearings like I have now. I found acetal bushing material at U.S. Plastics which is the same place I got the tubing. It is $1.12 per foot, but including cutting waste, I would only need about .85" per pump, so about $.08 per pump. That's a savings of $3.92 over the bearings. Plus I am looking at replacing the screws that were holding the bearings with molded parts so that would be another $0.35 in savings not to mention fewer parts to lose or assemble. This could bring the cost of the pump unit down to:

Motor: $5.95
Urethane: ~$0.50 ($25.50/quart, use ~12cc per, figure 20cc for wastage)
Screws: $0.30 (4 each #4-40x3/4 for example)
Nuts: $0.06 (2 x #4-40)
Tubing: $0.31 (1 foot, plenty)
Bushings: $0.08 (.85" @ $1.12 per foot)

Total: $7.12 (+labor, which is free, right?)

Hmmm, looking good. We'll see where I end up when I have something actually working and how much shipping costs factor in. I haven't worked on the controller PCB much yet, but that can probably wait until I get the mechanical parts functional.


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## VaultBoy (Nov 11, 2010)

This is great... i love your work robotguy, but you make me think destructive thoughts... i never thought about automated dosing until i read this... just 1 more project for my 29g


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## Robotguy (Jan 24, 2010)

Darn, I just realized that I hadn't uploaded the latest version of the pump body to Shapeways. My order status says it hasn't gone to production, so I uploaded the new model and sent an email to the service department asking if the new file could be used. If not, I may have to order another. The outer envelope is identical so unless they are doing some serious nesting of models during fab (which they may be), it shouldn't make a difference.


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## Robotguy (Jan 24, 2010)

Well, Shapeways couldn't change the file for me after ordering. I realized after I sent them the email that the new part was slightly larger and more expensive, so of course they couldn't swap files :redface:. They were, however, extremely helpful and offered to cancel the order and give me a credit for what I'd paid. I then placed a new order for the updated part using my credit (and added another $30 worth of robot parts that I wanted. Oooh, robot parts :drool

I just got the email from UPS today that they printed the shipping label and estimate the parts should be here on Monday (3/28). I am going to make the roller carriers this weekend and put together a mold box so I can cast copies as soon as it shows. I picked up some of Tap Plastic's new "Platinum Silicone" and am looking forward to trying it out. It looks a lot easier to use than their standard silicone, mostly because the platinum is a 1:1 mix, rather than the 10:1 for the standard. It's also supposed to be super flexible and tear resistant.

I had a thought yesterday (they are few and far between in my old age) and realized that it may not be good for the fert solution to sit in the (clear) tubing between dosings. If I had something I was dosing once a week, then the solution would be sitting in the tubing for an entire week. If the solution is light sensitive (and I have heard you should always store your ferts in the dark), could it go bad that fast? I have been considering trying to minimize the volume of solution in the tubing by using the smallest tubing feasible. This would also reduce the cost of the tubing and probably reduce overall price of the molded parts (smaller rollers, smaller pump body, etc.). Of course I would have to run the pump longer to deliver the same volume of solution, but a) it's not like I have to do it manually and b) I could probably increase the concentration of the solution for ferts I was mixing myself. The tiny Tygon tubing is cheaper than airline tubing (like down to $0.12/foot) so it would be easiest to just run a single length from the storage bottle to the pump and into the tank, probably with at least one check valve in between. This would mean fewer connections and fewer points of failure.


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## toofazt (Jun 18, 2005)

Great detailed explanation of your build! For light sensitive solutions (usually due to mold) I've heard you can add some Seachem Excel to your mix to help keep the mold at bay. It took about three weeks for mold to show up in my Micro mix. This time I've added some Excel to the Micro solution and will update if it stays clean longer... Although if you were to setup a Peristaltic pump you would probably mount it in a stand below the tank and wouldn't have the light problem.


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## Robotguy (Jan 24, 2010)

It's here. Now it's time to do something with it...









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Edit: Well ^$&$W!!! They did something to the forum that broke all of my links. I always host my own images and create thumbnails for people with slower connections, but now that's not working anymore. Ah, well. I'm certainly not going to take the time to fix all of those links. If you want to see the full size image, take the "tn_" out of the link address....


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## mistergreen (Dec 9, 2006)

whoa, that thing is tiny!


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## JamesHockey (Nov 10, 2010)

So when's mine getting sent out again?


Sent from my iPod touch using Tapatalk


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## Robotguy (Jan 24, 2010)

Let the cloning begin!









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The dovetail worked better than I had hoped. May have had something to do with the fact that the urethane hadn't set yet when I connected the two. I have another copy in the mold now. I'll let it cure overnight to see how it fits.


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## Arctangent (Feb 22, 2010)

You may have mentioned this, I haven't had a chance to read the whole thread yet (I intend to), but what method are you using for your molding process?


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## Robotguy (Jan 24, 2010)

Arctangent said:


> You may have mentioned this, I haven't had a chance to read the whole thread yet (I intend to), but what method are you using for your molding process?


Not pretty, but...








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I am using Platinum Silicone and Quik-Cast from Tap Plastics.

They have a demo video that shows the process:
http://www.youtube.com/watch?v=cj4kXAn83SA


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## Arctangent (Feb 22, 2010)

Yea that's awesome, should last for several casts too, eh? I'm finding a bunch of new resources following your posts. lol.


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## Robotguy (Jan 24, 2010)

Arctangent said:


> Yea that's awesome, should last for several casts too, eh?


The Platinum Silicone, though more expensive, is much more abrasion, tear and chemical resistant so it should easily produce over 100 parts. I'm thinking of giving the molds to my daughter when all of the design is done and letting her sell parts for people who can't or don't want to make the parts themselves. Alternatively, I can see a PT club buying a master from Shapeways and the silicone & urethane from tap and manufacturing a set for anyone who wants one:

Master - $27
Silicone - $34
Urethane - $25

Makes approximately 75 parts = $1.15 each.

An even better alternative would be to pass the mold from club to club. Then you could produce the parts for about $0.35 each. Plus group buys would make the other parts cheaper also, even in quantities as small as 10.



Arctangent said:


> I'm finding a bunch of new resources following your posts. lol.


Glad to hear it! I've been collecting links, resources, methods, etc. for, sheesh, almost 20 years now building hobby robots and other geeky stuff. I'm always glad to pass it on. The guy who turned me on to casting urethane was using it to reproduce D&D miniatures. He did some awesome stuff.

That reminds me. I am looking for a small, cheap vacuum pump to degas these parts. Anyone know where I might find one?


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## Wasserpest (Jun 12, 2003)

Awesome thread. Looking forward to seeing it in action. One critical piece here is the ability to compress the tubing completely to prevent backflow.

Not sure what you want to degas but have you looked at these: http://www.foodsaver.com/freshsaver/ ? They are sometimes on sale for under $10. Again, not sure if this is what you are looking for.


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## Arctangent (Feb 22, 2010)

Okay so I read the thread. Bravo for your ingenuity and progress.

For the nutes I think that only micros are really all that sensitive to light, could be mistaken here. You said you got the motor to push regular silicon tubing? Why not run black tubes? Is it possible to run the motors backwards? You could have the pumps clear the lines back into the container after every dose, probably wouldn't cause huge a contamination issue.

On functionality, some will prefer one way and some the other. I personally prefer a PC interface. I think with some simple instructions and clear indicators where data manipulations occur (at some high level of the programming I assume), most people could set their own schedule. I like the idea of multiple levels of automation, but they do need to be tweakable. I think you pretty much have this figured out.

I'm about a year and a half from gradation and need to start looking into career paths, robotics is something that I think I could get into and would hold my interests. I've always liked mechanical things, but for about the past year I've really enjoyed learning about the control side of things and smart devices. I want to scratch build one of these some day for a robotics project, maybe a senior design project?


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## Robotguy (Jan 24, 2010)

Small update.

I spent quite a while today fiddling with AutoCAD and G-code trying to make the roller carrier. I finally got a set made and tried out the pump, but I am not getting compression through the full cycle. It looks like the motor has plenty of torque and I plan to use the cheaper rollers rather than bearing, so I may go back to 3 rollers to get better coverage. Also I can see the body deforming as the rollers travel around the circumference, so I may need to stiffen up the body a bit.

Here's a (very) short video:
http://www.youtube.com/watch?v=HKwyHThKLgw

The motor is running at 5V and can handle up to 12V, so I don't think torque will be an issue. This Tygon tubing is much more flexible than standard aquarium air tubing.


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## mistergreen (Dec 9, 2006)

Where did you find the cheap rollers?


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## Robotguy (Jan 24, 2010)

mistergreen said:


> Where did you find the cheap rollers?


Somewhere in the middle of post #43 I mentioned that I found Delrin bushing stock at U.S. Plastics for $1.12 per foot.


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