Weird and Wacky Engineering
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Dave620
I knew I'd regret putting my old ac and dehumidifier in the trash. They most ...
Dave620
Thanks much. Robotics never occurred to me. I think my sons co-worker did ...
Engineer down! Someone needs our help!
Clive Maxfield
4/27/2012 3:50 PM EDT
I just received an email from someone who we will call Dave (because that's his name). Dave says:
Well, I was growing afraid that Dave was going to drop the ball and forget to tell me how wonderful I was, but he made a brilliant save right at the end (grin).
Now, I'm not an expert with pumps, but I know that the EE Times readership includes expertise in every subject known to humankind. So if you have any suggestions as to an appropriate pump, please post them here as comments or email them to me directly at max@CliveMaxfield.com and I'll pass your thoughts on to Dave.
PS Let's start with any pump that can do the job, irrespective of the price, and I'll take it from there. (If we find one for $20 or less, that would be a bonus, of course.)
If you found this article to be interest, visit Microcontroller / MCU Designline where – in addition to my blogs on all sorts of "stuff" (also check out my Max's Cool Beans blog) – you will find the latest and greatest design, technology, product, and news articles with regard to all aspects of designing and using microcontrollers.
Also, you can obtain a highlights update delivered directly to your inbox by signing up for my weekly newsletter – just Click Here to request this newsletter using the Manage Newsletters tab (if you aren't already a member you'll be asked to register, but it's free and painless so don't let that stop you [grin]).
Last but certainly not least, make sure you check out all of the discussions and other information resources at MicrocontrollerCentral.com, including blogs by yours truly.
Hi Max, I hope you don't find this is off topic, but you're interested in so many things I thought you might be able to help.
My 5th and 6th cervical vertebra are somewhat compressed. Actually almost all my cervical are not doing so good, but the docs say that 5 and 6 are the worst.
Physical therapy has helped, but to avoid the weekly trips to the physical therapist's office – plus the $20 per visit – I purchased a traction machine for home use. (Lucky this was covered by medical).
The down side is the home machine is manual. It has a small hand pump that cranks up a piston which is connected to a tram. For 20 minutes every other day, I lay on my back with my head fastened to a tram by Velcro and I "neck stretch" to 30psi for 1.5 minutes then rest for 0.5 minutes.
The good news is it works. If I miss a couple of sessions I certainly know about it.
The reason I told you all of this is so I could ask you the following...
Being an EE, I'd like to automate the manual operation. My biggest problem is I cannot find a small electric pump (for under $20). This only needs to pump up to 35-40 psi with a response time in seconds. I can do the programming and sensing but without the pump I'm stuck.
Any suggestions would be appreciated.
I thoroughly enjoy your articles. Keep up your great, enjoyable writings! Dave
Well, I was growing afraid that Dave was going to drop the ball and forget to tell me how wonderful I was, but he made a brilliant save right at the end (grin).
Now, I'm not an expert with pumps, but I know that the EE Times readership includes expertise in every subject known to humankind. So if you have any suggestions as to an appropriate pump, please post them here as comments or email them to me directly at max@CliveMaxfield.com and I'll pass your thoughts on to Dave.
PS Let's start with any pump that can do the job, irrespective of the price, and I'll take it from there. (If we find one for $20 or less, that would be a bonus, of course.)
If you found this article to be interest, visit Microcontroller / MCU Designline where – in addition to my blogs on all sorts of "stuff" (also check out my Max's Cool Beans blog) – you will find the latest and greatest design, technology, product, and news articles with regard to all aspects of designing and using microcontrollers.
Also, you can obtain a highlights update delivered directly to your inbox by signing up for my weekly newsletter – just Click Here to request this newsletter using the Manage Newsletters tab (if you aren't already a member you'll be asked to register, but it's free and painless so don't let that stop you [grin]).
Last but certainly not least, make sure you check out all of the discussions and other information resources at MicrocontrollerCentral.com, including blogs by yours truly.
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David Ashton
4/27/2012 7:47 PM EDT
It's not mentioned, but I presume you need an air pump? At Auto stores you should be able to buy a cheap 12v tyre inflator pump that might do the job. They're cheap and probably a bit nasty but they should do what Dave needs. They can normally go up to 100 PSI or so so (a) they should be adequate for the job) and (b) you may need a pressure switch to limit the pressure.
If I have it wrong, apologies.... if it's a water pump I have something in mind as well...
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Brian @ BDH
4/27/2012 9:18 PM EDT
As David Ashton mentioned above, I am not 100% clear on the detailed requirements. However, I too am assuming that Dave is looking for an air pump...
So, what about an air bed air pump? They're cheap and should supply the needed psi range.
Below are a couple of examples from Amazon.
$12.99 + $4.99 shipping
Smart Air Beds A/C Electrical Air Bed Pump (110-125v 60Hz, Black)
http://www.amazon.com/Smart-Air-Beds-Electrical-110-125v/dp/B003LIKRKQ/
$14.99 & eligible for FREE Super Saver Shipping on orders over $25.
Smart Air Beds Rechargable Pump for Air Beds and Other Inflatables (Black)
www.amazon.com/Smart-Air-Beds-Rechargable-Inflatables/dp/B004X63VBC/
Good luck! Brian
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David Ashton
4/29/2012 2:53 AM EDT
Bear in mind that an air bed probably only needs 1 or 2 PSI max as it has to support (say) 200 lb max over probably a few hundred square inches. Most air bed inflators are just fans and would not get up to 30 PSI? I'm not tooo sure of this and the links above don't have details.
The below is a tyre inflator which probably has a small compressor in and that would certainly get up to 30 PSI:
http://www.amazon.com/Slime-COMP02-12-Volt-Tire-Inflator/dp/B000ENQRD2/ref=sr_1_8?s=sporting-goods&ie=UTF8&qid=1335682312&sr=1-8
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Dave620
4/30/2012 10:27 AM EDT
Sorry guys but you're are both correct ... air pump is all I need. From Dave's last comment sounds like my Sleep Number bed pump wouldn't drive to 30 psi. I'll check out the local auto supply around town and see what they have. It would be really cool if I could find something that had a pressure gauge with BCD outputs (of course it's going to cost more) I could hack.
Thanks much.
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David Ashton
4/30/2012 7:12 PM EDT
"something that had a pressure gauge with BCD outputs..." - you don't want much, do you? ;-)
It should not be difficult to plumb in a commercial pressure sensor if you can't find one like this, or if you need a fixed pressure, just get a pressure switch (nice easily interface-able 1 bit input...
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Dave620
5/2/2012 9:43 AM EDT
I need to pump up to 30psi then hold for 1.5 minutes;then release the pressure for 0.5 min and start the cycle over. As the muscle in the neck relax the pressure goes down. Since I'll have a micro controller running this I'll set a upper psi and a lower psi and let the controller keep the pressure in that range. I'm finding pressure sensors are not cheap. I need to find a surplus store that has good deals !!
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clay_cowgill
5/1/2012 1:57 AM EDT
As another approach for consideration... Might an air tank work? They're basically just like the pressure tank on an air compressor-- just without the pump.
You 'fill' it from an air compressor (they're usually 5-10gallon sized) and then you have a nice, silent source of pressurized air.
A little 4V110 sized air valve (solenoid controlled ~$10 on eBay) and you've got an electrically controlled fill/exhaust air control.
The tank would just get around the noisy little compressor motor blasting away nearby (at the expense of having to fill it occasionally depending on the air volume required).
Harbor Freight sells the air tanks for ~$25-40.
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Max the Magnificent
5/1/2012 9:07 AM EDT
That's an interesting idea -- I know Dave is reading these comments -- we'll see what he says
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Dave620
5/2/2012 10:18 AM EDT
I almost purchase the Harbor Freight compressor. With a coupon it was around 8 bucks. Then I started to think about noise. My wife's nebulizer pump is not as big but I can hear it from the other end of the house. Maybe a tank would be a better way to go. I have a automotive compressor I could use to fill the smaller tank.
I'm not familiar with the
air values. I'd need three states: pump, hold and release. My online search resulted in sticker shock ! In the hundreds of dollar range. That was from Grainger.
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Max the Magnificent
5/2/2012 10:21 AM EDT
@"My wife's nebulizer pump is not as big but I can hear it from the other end of the house."
Well, now you can get your own back :-)
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Jonnie
5/1/2012 3:08 AM EDT
An alternative to an air-tank is to use an old tyre; I've known people using spare tires as pressure tanks for air gun spraying.
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Reagan.Thomas
5/1/2012 10:29 AM EDT
Oh, my!
I think you should also invest in a good quality pressure regulator and/or relief valve. I would hate to see Dave620 next log in as NearlyHeadlessDave!
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Dave620
5/2/2012 9:47 AM EDT
Not to worry. The tram I mentioned has two safety features. The first it the Velcro ... breaks loose around 35 psi. Second it the tram is on frame that is not fix it moves to release the pressure. I think I'll add a rip cord too so I can break the Velcro ... just in case the others fail.
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Max the Magnificent
5/2/2012 10:22 AM EDT
Better the "NearlyHeadlessDave" than simply "HeadlessDave"
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Phil.Gillaspy
5/1/2012 4:46 PM EDT
Blood pressure monitors provide the capbility to pump up to 160 psi in 15 seconds. I would suspect that they can generate 40 psi within seconds. They are typically turned on/off with membrane switches which could be stripped out and replaced by some external digital signal, thus automating the psi cycle.
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BicycleBill
5/1/2012 6:25 PM EDT
120 mm mercury (a nominal blood pressure reading) = just 2.3 psi. Not much pressure needed. 160 psi would cut the person's arm off!
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inthetwilightzone
5/2/2012 7:33 AM EDT
Love the comments here ! Blood pressure machine that cuts off your arm - what a product liability lawsuit that would be.
Hard to believe the traction unit mfg doesn't have an option for an electric pump. How do the 80 year old grandmothers who get this via medicare use it? If not, Dave needs to take his final design and sell it. I can see the television info-commercials now for the "Traction Pump Store".
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Dave620
5/2/2012 10:26 AM EDT
The hand pump on the unit started to fail about a month ago. A call to the mfg got me a new pump since it was still under warranty. I ask if they had a non-manual pump. Not luck .. only manual pump. I suspect it's a liability to put an automatic system in a home. Could also be the cost to get it approved by OSHA.
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Brakeshoe
5/2/2012 10:07 AM EDT
One issue with the inexpensive 12 volt tire pumps is that the volumetric flow is very low: It can take 10-15 minutes to fill a tire, which would alter the fill cycle time, and impact the therapy as prescribed. Although a tank is nice, a small tankless paint sprayer air pump like you'd get at Home Depot or Lowe's is a better choice.
The suggestion for the 4V110 solenoid valve is a good one.
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Dave620
5/2/2012 11:40 AM EDT
Does the 4V110 solenoid value have three states ?
That is can I have:
pump
hold
vent
This is an area I have very little experience as my questions probably indicate.
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Dave620
5/2/2012 10:32 AM EDT
Max this is like being back in the work force. All kind of ideas. I knew I'd miss my co-workers when I retired but didn't think it would be for technical reasons. When you work for a company for 35+ years you create all kind of friendships.
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Max the Magnificent
5/2/2012 11:39 AM EDT
I know what you mean -- one of the best things about working with other folks is the opportunity to bounce ideas back and forth...
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Jackever
5/2/2012 2:11 PM EDT
We have lots of still usable (but not resalabe) parts from service udates, etc, I do not think we have what Dave needs, but perhaps someone else uses pumps and valves in their products and have some leftovers from service returns or R&D
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ost
5/3/2012 4:04 AM EDT
I'd say this was a rather odd channel to solve "garage" problems like that. I bet there are giga's(*) of nntp groups (remember nntp?) with lots of people owning up to several spanners just waiting for a challenge like this.
(*) computer engineer equivalent of the cliché "ton's"
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Max the Magnificent
5/3/2012 10:04 AM EDT
I just received an email from a reader saying "I wondered if you may have considered using an automotive emergency compressor, which is a small 12 Vdc device for pumping up your tyres when you'd rather not have to :-)
You should be able to pick one of these up a your local automotive spares warehouse or outlet for way less than $50."
Not a bad idea...
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Max the Magnificent
5/3/2012 1:12 PM EDT
I just received another email that read as follows:
Regarding the gentleman who wishes to automate his traction machine (aka ‘rack’), here is one possible way to do this:
Use an Air pump such as the McMaster 4251K31 (http://www.mcmaster.com/#pneumatic-compressors/=hdhz3z). If the pressurization rate is too slow, add an ullage tank and a solenoid valve, cycle the solenoid valve briefly to pressurize downstream. He should add an orifice to regulate flow for slower and more accurate pressurization if using a higher pressure ullage tank and solenoid valve. And BY ALL MEANS ENSURE HE USES A RELIEF VALVE! Without proper physical safety measures in place, overpressurization may equate to injury.
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Max the Magnificent
5/3/2012 2:22 PM EDT
And yet another email from a reader who says:
Here is a web site that has new and used pneumatic items at reasonable prices.
Examples: a new 24 VDC 3 way solenoid valve for $4.99, a new 24 VDC valve with outlet vented when unenergized for $6.95.
Surplus Center Home Page
http://www.surpluscenter.com/home.asp
Solenoid Valves
http://www.surpluscenter.com/pages/Catalog285-095.pdf
Small Compressors
http://www.surpluscenter.com/pages/Catalog285-093.pdf
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Dave620
5/4/2012 10:26 AM EDT
WOW ! This is great. I'll have to check out these sites. I'm having some concerns with a pressure tank and a solenoid controlled value. It seems I need an analog control value so I don't apply 100psi to the down stream cylinder. Pulsing solenoid would somewhat achieve an analog control .
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demolitionxpert
5/3/2012 3:37 PM EDT
a reasonably inexpensive solution which I have used a number of times consists of an old refrigerator or air conditioner compressor, pressure tank, a regulator and pressure switch (the compressor is capable of up to 250psi so don't let it free-run into the tank). The whole works can be had for about $50 at surplus dealers. The only thing to add is the 3 way solenoid valve which could be made up from 2 humidifier water valves. They're good up to 150PSI and run from 24VAC. The compressor will be quiet, just the pressure switch will swish when it shuts off and relieves the pump.
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ChipBuilder
5/3/2012 7:22 PM EDT
The auto compressors are way too loud to use indoors. we used one in the First Robotics competition that were fairly quiet. you could go to the first robotics site and see all of the resources they have on valving, controls and the gardner-denver mini compressors they sell. a first team in your area would probably help set it up, we would do practice projects off season...
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Dave620
5/4/2012 10:29 AM EDT
Thanks much. Robotics never occurred to me. I think my sons co-worker did something with First Robotics. I'll well check this out. Thanks again for the lead.
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musiklab
5/4/2012 5:53 AM EDT
I have a really quiet workshop compressor using a household refrigerator type compressor, and a steel tank buffer. Chopping up a (still cooling) fridge, any old refrigerator compressor may still work well, they work for decades - but please note these compressors may need a little oil lubrication in the air stream if not running in a closed circuit. I don´t know if the pump flow is sufficient for direct use, but a buffer tank may solve that. re safety, you know what to do to save yout neck...
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Dave620
5/4/2012 10:31 AM EDT
I knew I'd regret putting my old ac and dehumidifier in the trash. They most likely had all the parts I needed. I'll be checking the garage sales.
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