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Need 50 psi micro compressor

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Guyfrom7up

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I'm going to be building a 2 - 3 foot tall human like robot, I found a 7.2v, 36 maH li-ion battery. I need a small air compressor that can easily produce 50 psi (easily as in it won't break itself by continuesly pumping out 50 psi). I would like it to be powered off of 6 volts, but 12 volts is fine too. This compressor will be pumping into a holding chamber, which in turn will power some air muscles.


Thanks in advance!


EDIT: I've been looking around and I want something that's rated for maybe like 100 psi, just to be safe and if I want to use it in other robots. The closest I got was a hand size pump that could do up to 300 psi
 
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You're never going to get a long term usable amount of compressed air from a 7.2V 36maH battery. Have you thought about using something like CO2 canisters, perhaps high pressure air such as in paint ball guns, with a regulator? Converting the chemical energy in a battery into electricity into kinetic energy into compressed air is a damn sloppy way to power a robot, and a single Co2 cartridge would probably last longer and be many times smaller.
 
Just looked up a little bit more information. CO2 canisters produce 850psi of pressure, regardless of their size at room temperature, even with the limited capacity of a 12 gram cartridge that's a lot of pressure to work with. Simply regulate it and use the battery to actuate the air valves. Compressed air (nitrogen) tanks store at 3000psi, but they don't make the tanks very small.
 
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Guyfrom7up said:
I'm going to be building a 2 - 3 foot tall human like robot, I found a 7.2v, 36 maH li-ion battery. I need a small air compressor that can easily produce 50 psi (easily as in it won't break itself by continuesly pumping out 50 psi). I would like it to be powered off of 6 volts, but 12 volts is fine too. This compressor will be pumping into a holding chamber, which in turn will power some air muscles.


Thanks in advance!
Running an air compressor from a battery!?! I can hardly contain myself. I practically jump out of my chair when the one for my air tools goes off unexpectedly. It runs from the mains and gets to 110-120 psi. When I think of the work involved, I sure am glad I don't have to pump it up by hand.
 
The closest thing I can suggest for 6V is a battery operated air mattress pump
**broken link removed**
but what that can do in volume rate is nothing compared to the PSI you need.

If you're trying to get an idea of how much power it takes to produce 50 PSI, well, a bicycle tire pump can produce that much. 50 PSI is what I think most bicycle tires are rated for, but anyone who's pumped up a bike tire knows that by the time you get to the end (that is, you're matching the pressure coming out of the tire valve), it gets really hard - a small person can put their entire weight on the pump and not get it up to 50 PSI!

I hate to be the fly in your ointment, but I can't see a small humanoid robot being practical, given the mass of the air compressor, air muscles, holding tank, power supply, and supporting structure. That is, unless you're content with the final product having some sort of tether so that the power and air supply are not being physically supported by the robot. If you don't want a tether, I think it's back to the drawing board.
 
The more I think about this project, the more I think that it might be possible on a smaller scale. I think you'd have to be willing to design your own air muscles, out of something like balloons. Given the work involved, you'd have to have a compelling reason (or curiousity) to not use a more conventional approach to motivating your robot.

Papabravo said:
I can hardly contain myself.
Get a stronger container than whatever Papabravo's rated at.
 
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Nigel Goodwin said:
The CO2 cartridge sounds like a nice easy solution, small and fairly light as well.
So when he's built his robot, we'll all get out our paint guns and shoot it at point-blank. How far do you suppose it'll move before we have to reload?
 
I'm sorry, I meant to say the battery is 3600 mah battery. I thought if I used a battery instead of a pump it could last longer, for example, if the pump takes 1 amps of power, I'll have 3.6 hours of battery life, and the battery is really light, just 7 oz. also I don't really want to deal with extremeley high pressures such as 850 psi, cause this robot might be around a lot of people and if something explodes, well that's not going to be very good. I don't see what's wrong with pumping it, even if the pump weighs 20 pounds as long as you can compensate it with air muscle it should be fine.

I don't fully understand how air muscles work, does the rubber tube inside inflate, making it shorter, and the weavings on the outside contains it so it doesn't explode?

I found this website of to make you own air muscles: https://www.imagesco.com/articles/airmuscle/AirMuscleDescription03.html
Anyone know if the results are any good?

Ps: I'm willing to add an extra battery to get 14.8 volts.
 
Guyfrom7up said:
I don't see what's wrong with pumping it, even if the pump weighs 20 pounds as long as you can compensate it with air muscle it should be fine.

It's not just the weight of the pump, it's the weight and size of the battery as well - obviously it depends on the amount of air you're going to require, but I presume you've seen the car tyre pumps you get? - they suck loads of power, are VERY noisey, and take a long time to inflate a tyre.
 
hmmmm, yeah I see what you mean... I'm new to phumatics, what's the unit of how much air it can push? I don't know how much air flow I need... I don't think I need a ton because these air muscle don't use to much, but Maybe 2 big air muscles and 5 little ones might be operating at the same time...
 
I've got one of those little electric tire inflators in my truck. Says 250 psi, but it takes about 15 minutes to bring a flat tire up enough to drive on. For under $10, it's saved my butt many times over the past 10 years or so (seldom buy new tires...).

Haven't seen this stuff in a while, but use to be pretty common. It's call surgical tubing. Some kind of synthetic rubber tubing, very strong stuff, holds pressure well. As kids, we made all kinds of fun stuff out of it. For school, the water-weenie... tie a knot in one end of about a foot length, slip the othe end over the threaded part of the point half of a ballpoint pen. Just shove it into a drinking fountian, lot of water, good range. This it what makes me think it would make good air muscle material

Anyway, for under $20 (maybe more) you could get a compressor and the tubing. Valves will cost you, but shouldn't be too bad. Try some experimental stuff, see what you can do on the cheap. There is a type of nylon rope that is hollow down the middle, might be useful. Also have seen some plastic stuff in cars for protecting wiring, braided and semi-flexiable.
 
The OP needs to do a calculation of the power required for the robot's needs. Compressed air pressure and volume needs can be converted to power (i.e., watts) required by relatively simple formulas. The following article gives a conversion ratio of 4 SCFM per horsepower: https://www.pneumaticsonline.com/Articles/NorgrenArticle062000.htm

From that, the OP can determine whether a battery powered compressor is even realistic. John

Edit: Looking at it another way, 7.2 V at 3.6 A is only 26 watts for 1 hour. The robot would probably work for only a few minutes, based on some of the common electric motors that are used.
 
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If you can determine the airflow rate then you should be able to estimate the amount of battery you'll need - you've indicated the pressure. The conversion won't be very efficient so assume 50% as a place to start.
 
surgical tubing is an extermemly good idea! I think I'll definetly use that as the bladder for the air muscle. I've been looking up solenoid valves, but I havn't really been able to find any really cheap ones, like under 5 dollars a piece, however I did find this site that had the valves for 0.10 euros (I'm in the US so about 14 cents), there's 2 problems with it though:

1. I couldn't find any specs, I don't know how much psi and voltage it takes.
2. I'm pretty sure that you would probably have to order in bulk and they don't ship to the US.

**broken link removed**

SMC Pneumatic Valve SY100-33-1

Price: £0.10 (Excluding VAT at 17.5%)

SY100-33-1

(it's the one for 0.10 euros, about half way down.)
 
I found a data sheet **broken link removed**. It looks like SY100-33-1 isn't an entire assembly, it's just a screw. (m1.7 x 13).

Also, £0.10 is 0.10 pounds, not Euro.
 
How small does it have to be ?

Paintball air tanks could be a good option.

We use 0.8 liter to 1.5 liter tanks, which can store air at 3000-5000psi.

The 0.8 liter 3000 psi (metal) tanks are usually about £40 with regulator, which would regulate it down to 850psi. From this, you can then use a low pressure regulator to regulate it further.

I have a 1.1 liter 5000psi tank which is made from fiber-wrapped aluminium which is really light, and stores A LOT of air.

Paintball sites will usually fill your tank for a very small charge, if not for free.

Remember that high pressure air (3000psi+) is very dangerous so be careful with it.
 
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