Pump recommendations for micromedic project?
rwgast_logicdesign
Posts: 1,464
Ok so I signed up in the micro medic contest when it started, I just got some funds today to start getting the things I need for it and another project. For those of you who do not know I am trying to build an automated camel pack the can sense hydration levels and give the person wearing it the correct dose(s) of water. Now I was hoping some one may have some good input on the pumping system for the pack. Here is the other thing I don't have a ton to spend so I am trying to keep the pump =<$30.
I have a little experience with pumps as I use to be an avid over clocker and built custom water cooling systems. Usually in these set up's you want the water to flow fast with a lot of pressure, so I always used external DC pumps that could push about 10 head ft at 20 (iirc) gallons per min, these type of pumps are much more than I need and much to big. They also require priming, and I am hoping to find a pump that can run dry to make things easier.
Now my first thought is to use a peristaltic pump like this one @ adafruit. My biggest issue with this pump is basically price plus shipping, as I don't order anything from adafruit and it would be a one of kind of thing. I would not mind the price so much if I knew it were perfect but I do not think it is. First off I would like a smaller voltage pump maybe around 6v. Also Ideally I would like to put the pump inside the blatter of the camel pack, I know this could be done with a small filterless aquarium pump, but those will burn up if ran dry. I ran a search for peristaltic pump on google shopping and those were all way to much $100+, I also looked on ebay and saw a few like the adafruit pump for $15 out of china.
See i am thinking the peristaltic pump would be great if it would provide enough head pressure with a 6v PWM channel, and water proofing. The problem is I have never seen one of these pumps before, let a lone used one! So im not sure just how much pressure they have, and looking at the way it works, even if I were to water proof it I don't know if it would work submerged I figure worst case the peristaltic is my best option and I will have to run it in series with the drinking tube of the pack, but I am hoping there may be some other options I don't know about out there I will be stopping at an aquarium supplier after Radio Shack to see some of there options.
I have a little experience with pumps as I use to be an avid over clocker and built custom water cooling systems. Usually in these set up's you want the water to flow fast with a lot of pressure, so I always used external DC pumps that could push about 10 head ft at 20 (iirc) gallons per min, these type of pumps are much more than I need and much to big. They also require priming, and I am hoping to find a pump that can run dry to make things easier.
Now my first thought is to use a peristaltic pump like this one @ adafruit. My biggest issue with this pump is basically price plus shipping, as I don't order anything from adafruit and it would be a one of kind of thing. I would not mind the price so much if I knew it were perfect but I do not think it is. First off I would like a smaller voltage pump maybe around 6v. Also Ideally I would like to put the pump inside the blatter of the camel pack, I know this could be done with a small filterless aquarium pump, but those will burn up if ran dry. I ran a search for peristaltic pump on google shopping and those were all way to much $100+, I also looked on ebay and saw a few like the adafruit pump for $15 out of china.
See i am thinking the peristaltic pump would be great if it would provide enough head pressure with a 6v PWM channel, and water proofing. The problem is I have never seen one of these pumps before, let a lone used one! So im not sure just how much pressure they have, and looking at the way it works, even if I were to water proof it I don't know if it would work submerged I figure worst case the peristaltic is my best option and I will have to run it in series with the drinking tube of the pack, but I am hoping there may be some other options I don't know about out there I will be stopping at an aquarium supplier after Radio Shack to see some of there options.
Comments
If you are dosing a conscious person orally, then why not use the person's body action (their hands or sucking action) as a "pump" and then have your control system only measure out/control how much water dose the person gets? Or is this for somebody who is unconscious/paralyzed?
Edit: You may want to have the moderators move this over to the Micro Medic Forum as it is a requirement to participate in that Forum.
Ok, the source of the water is the Camel Pack.
Where is the water going?
The mouth?
An infusion, sp?, through a needle?
What pressure and volume flow is require when delivering the water?
Duane J
Maybe he's aiming for a tactical enema?
http://www.deathvalleymag.com/2010/03/01/medical-how-a-tactical-enema-could-save-your-life/
Does the existence of a tactical enema imply there is such a thing as a strategic enema??
Yes, butt the North Korean military leaders are way a head of us in that arena.
Duane J
Basicallu if the system dictates the user need to drink 5 ounces of water I need a way to track that. The idea is to use the pump to slowly pump water through the hose, this way the volume the user consumes can be calculated via the pumps flow rate. Im not saying they have to take one huge 5 ounce gulp with 20ft of head preasure behind it. The water will flow slowly and allow for breaks.
Ditching the pump is fine, and very beneficial at this point! But I need a way to figure out how much water has been consumed, maybe however a gas guage works with its float.... cheaper is better.
I would use a small motor that can measure resistance attached; some sort of flotation device to give resistance.
kinda like the inside of your toilet haha
Where does it say this?!?!
Advantages:
1. The fluids don't make contact with any of the mechanical components of the pump except for the tubing.
2. The pump can be attached to tubing without breaking any of the tubing connections.
3. The pumping rate is highly controllable by varying the rotation from zero on up.
4. Generally, they can be considered "Constant Displacement".
5. The flow is close to constant, i.e. doesn't pulse.
Duane J
I agree that peristaltic pumps are great for measurement. So perhaps you can use a type of peristaltic pump which is powered by human movement of some sort (hands, twisty thing, squeezy bulb, whatever, etc.) but have an encoder type of gizmo record the number of revolutions the pump rotor makes. Then use a pinch valve solenoid to keep open for only as long as the pump is in motion and the number of rotations has not exceeded an allowable limit for the calculated dose. You get the best of both worlds - human power, electronic tracking of dosage.
http://www.futurlec.com/Flow_Sensor.shtml
I did not even know these existed, there are a bunch more on e-bay a bit cheaper I guess they are for coffee makers..... The point of the ones on ebay is that I can get one already barbed for the size of tubing I am using. I wonder if I just stick this in line with the hose if it could be used to measure how much water is being sucked out, with out being to restrictive.
Those are nice flow meters.
I think they are vane or turbine types. Something like that.
Anyway, they are not positive displacement types.
All of them are not rated for flows that include the 0 flow range.
Duane J
http://www.kohls.com/product/prd-1025909/columbia-sportswear-company-ravenous-hydration-alarm-chronograph-digital-sport-watch-ct006302.jsp
@Duane, I am not sure what you are trying to tell me. I browsed the data sheet real quick too. Are you saying that these can not be powered up dry, like a pump that requires priming? I was thinking this type of sensor could be attached to the hose when the user sucks the water it would spin the turbine and which would allow me to start counting pulses to help measure flow rate. When the user is not sucking the sensor would would just send a low signal. My basic understanding is this thing works just like a motor encoder.
Perhaps that at very low flow rates, the stiction of the bearing will prevent the vane from turning and thus the measurement system will not register any flow at all, thereby giving false results. Your patient could cheat by sucking very gently, in other words. This is a big problem with automated beer dispensing machines.
The problem is this type of flow sensor is not accurate outside its calibrated range.
Think of these as a kind of water wheel. If you run water by it tangentially the wheel spins.
When the flow is below the minimum friction and maybe other effects start to affect the accuracy.
So, if the patient drinks the water at a very slow rate the wheel essentially slips and lets un-counted water past. This is called a non-positive displacement flow sensor. Don't get me wrong, they can be quit accurate within the calibrated flow rated.
There are positive displacement sensors. Often they involve pistons or diaphragms and valves. These are accurate over a wide range of flows. Even flows down to 0 flow.
The peristaltic pump is positive flow, although it is a pump. No liquid can be move in error.
I believe there are peristaltic flow sensors. But I don't have a reference.
Wikipedia:
Positive displacement meter
Duane J
When I first got it, I tested it on 5 volts. It worked fine. A 500 ms activation consistently produced .125 ml of water.
A 500 ms activation at 7.5 volts produced .25 ml of water. I tested it again today to set it up for a demo, I couldn't get it to activate at 5 volts. I have never had any problem with 7.5. I have not looked at current draw yet. I think I always have it 1 amp.
So far I really like the pump. It is very hard to find inexpensive peristaltic pumps. I think it is work the purpose. Hopefully my crude data will be of use. If you have something specific you would like me to test, let me know.
Stillsuit
A stillsuit is a fictional body suit in Frank Herbert's Dune universe, first introduced in the 1965 novel Dune[7] and appearing in every subsequent novel in the series. Stillsuits are worn by the native Fremen of the desert planet Arrakis to maintain their body moisture in the harsh environment.[7] The Science of Dune (2008) analyzes Herbert's stillsuit and its feasibility in the real world as described.[1][2][3]
Description
As described in Dune, a stillsuit is a "body-enclosing garment" of Fremen design which performs the "functions of heat dissipation and filtering bodily wastes," as well as retaining and reclaiming moisture.[22] As the planetologist Liet-Kynes is assisting Duke Leto Atreides with the fitting of his stillsuit, he explains it in this manner:
It's basically a micro-sandwich — a high-efficiency filter and heat-exchange system. The skin-contact layer's porous. Perspiration passes through it, having cooled the body ... near-normal evaporation process. The next two layers . . . include heat exchange filaments and salt precipitators. Salt's reclaimed. Motions of the body, especially breathing and some osmotic action provide the pumping force. Reclaimed water circulates to catchpockets from which you draw it through this tube in the clip at your neck... Urine and feces are processed in the thigh pads. In the open desert, you wear this filter across your face, this tube in the nostrils with these plugs to ensure a tight fit. Breathe in through the mouth filter, out through the nose tube. With a Fremen suit in good working order, you won't lose more than a thimbleful of moisture a day..."[7]
Analysis
In his essay "Stillsuit" in The Science of Dune, John C. Smith suggests that "Stillsuits designed using strict literal interpretations from the Dune books probably would not work and most likely would cook the wearer like a Crock-Pot ... However, engineering solutions can be envisioned for all the suit's shortcomings."
That's basically how your lymph circulatory system works.
Which is yet another reason why being a couch potato is so devastating.
@Erco
FUNNY, you mention that DUNE is one of my favorite movies of all time, to bad my girlfriend can't sit through all 6 hours. I had actually drew some inspiration for this project from those suites, and thought about trying to filter urine after the rest of the project is complete, although I do think that may raise moral or sanitation issues.
@NWCCTV
I have posted in the MicroMedic forum before. I felt this may be more relevant here though. The reason being is more people view this forum who can give input, and while this may be for MicroMedic the question is more of a what kind of sensors/products are out there that may help me measure water, than a question specific to the actual MicroMedic contest. Mostly posting here was to get a wider viewing audience who have experience with all kinds of parts.
Another way to go might be a small air pump and just use positive pressure in the bag and a flow meter at the tube inlet or outlet.
FF