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Old Jan 16, 2006, 01:39 PM
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Vacuum switch, where/how ?

Hi,

I've gotten my hands on a very nice vacuum pump with a 3-phase motor. It's a *bit* overkill but I got it for free, so...

It's one of those heavy duty rotary vane pumps, which is nice. Problem 1) is that it doesn't come with a vacuum tank and 2) that it doesn't have a presure regulated on/off switch. A solution to 1) is dead-simple, but problem 2) is a bit more intricate.

I've scanned the web for a few hours but cannot find anything suitable and obvious that would work at a moderate price. The closest I've gotten so far is a 1-phase (240V) switch directly actuated by the vacuum pressure at a semi-high US$70 (roughly). It is a bit on the high side though since it is not enough as a complete solution.

Does anyone have experience with solving this problem ? All input is appreciated.

Thanks,
Anders
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Old Jan 16, 2006, 04:37 PM
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United States, AZ, Surprise
Joined Jul 2002
397 Posts
Anders,
CST sells vaccuum switches, they are not rated for that pump. Solution is to use the switch to drive a relay or solid state switch tha can handle the current used by the pump. That way the switch would only handle the current of the relay.
John
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Old Jan 16, 2006, 05:21 PM
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USA, GA, Stone Mountain
Joined Oct 2000
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The CST switch will work like jcyr1 said with the relay and will cost about $35-40.

Also to take care of the vacuum tank issue, I used an empty Helium tank on my setup and drilled a hole thru the case and screwed in a fitting with RTV around it to make sure it was sealed. It works great and cheap. Some people use a section of 4-6" PVC pipe with endcaps on it and make a vacuum tank out of it.

Ernie Schlumberger
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Old Jan 17, 2006, 04:41 AM
chetosmachine's Avatar
Madrid, Spain
Joined Sep 2004
1,102 Posts
Hi,
i'm working on my pump and have a pair of questions:
-i bought a vacuum switch which i want to operate through a relay. Does anyone have a scheme of the connection?
-i have an empty gas can. It's from a torch, and is around 15" tall * 4" diameter. Does it have the right size or is it small?
thank you,
Chets
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Old Jan 20, 2006, 11:42 PM
RussMc
Olympia WA
Joined Nov 2004
73 Posts
I looked all over when I was trying to find a vacuum switch. Check out the vacuum switches sold by Digi-Key. The one I use (part # 384-1009-ND) is rated at 25A and can be set from 6" Hg to 24" Hg (81" to 330" H2O). You shouldn't have to use a relay with the switch and the Best thing about it - it cost $16.24 + $5.00 S&H.

Look at the bottom of the page for the World Magnetics Pressure (& vacuum) switches.
http://dkc3.digikey.com/PDF/T061/1703.pdf

Digi-Key home page is http://www.digikey.com/

When you choose a vacuum tank, remember that you will want the most capacity that you can reasonably get away with. The reason is you are only working from 0.0 to 1.0 atmosphere (or 0.0 to 14.7 psi), unlike the normal range of compressors which operate over several times atmospheric pressure (100 psi is almost 7 atmospheres). I set up my system with a 6' length of 4" PVC pipe, which works OK but if you get a leaker vacuum bag, the cycle time on the vacuum pump is still noticeably short.

Good Luck

Russ
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Old Jan 27, 2006, 04:21 PM
qv_
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Sweden
Joined Nov 2005
59 Posts
I have not build my yet. But I like to use the vacuum part from a car engine.
The vacuum bell that adjust the timing of the spark.

Just add a spring and a switch.

/jan
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Old Jan 31, 2006, 12:13 AM
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Melbourne, Australia
Joined Dec 2004
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G'day, have you guys sussed out the diagram on the ACP website. I was able to follow this for connection of the relay switch and associated wiring.
http://www.acp-composites.com/vacuum-switch.html

Also they have Vac switches for $39US. Works pretty well in my set up.
http://www.acp-composites.com

Jason
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Old Jan 31, 2006, 09:45 AM
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Cittadella(PD)(Italy)(Europe)(World)
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Home made vac switch

I solve the problem in that way!
And only 2 $ !!!!!!
Ago
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Old Jan 31, 2006, 11:42 AM
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Quote:
Originally Posted by AgoMago
I solve the problem in that way!
And only 2 $ !!!!!!
Ago
Very ingenious...Rube Goldberg would've been proud

Steve
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Old Feb 03, 2006, 12:52 AM
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United States, CO, Denver
Joined Sep 2005
258 Posts
lid Flex ?

The vacuum causes the lid to flex enough to trigger the microswitch ?

MikeN


Quote:
Originally Posted by AgoMago
I solve the problem in that way!
And only 2 $ !!!!!!
Ago
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Old Feb 04, 2006, 04:35 AM
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That is too efficient to be Rube Goldberg. Rube was forced to study engineering and chose to be an artist.

It must switch off when the vacuum is highest, so the switch would lose contact. That would require the jar to be glued to the base, for the flexing of the lid to control the contact. Evacuating the jar causes the lid to want to cave in, i.e., flex down switch off. The spring provides tension to delay the flexing down and encourage the flexing up? The tension is adjustable, if you look closely. ??????? Choose the wrong spring and it wont work?

Looking at the arrangement of the tubing, is critical to understanding this rig.
I imagine a venturi effect putting pressure on the jar, causing the jar to lose contact with the switch, but when? When the vacuum is building or after?
Maybe Tarzanenglish can explain.

Unlike Rube, I studied Art first and can only admire engineering.
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Old Feb 04, 2006, 09:32 PM
Registered User
Portland Intl, Oregon, United States
Joined Jul 2003
1,155 Posts
I posted this quite a while ago but here is where I found a place to get vac switches
not sure if they have any 3 phase or not but you might check them out.

this is a repost of my response to another question about vac set ups....

I found a place to get the same vac switch sold at one of the composites stores for less than half price.
air-logic.com
look in their subminature vac switch section, the one I like is
V-5100 28 FM B85 25a
it is variable from 3-28 inches of vac and can be bought at 15 amps or 25 amps
(thats the 25a number at the end).
Air logic only sells wholesale, but if you call them they will tell you where the nearest
dealer is.

good luck

TIM
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Old Feb 05, 2006, 12:56 AM
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Quote:
Originally Posted by AgoMago
I solve the problem in that way!
And only 2 $ !!!!!!
Ago
Ago,
Is the glass jar firmly attached to the wooden base? I can see that you sealed the connection to the lid, so eVacuating the jar must be the goal.
Is it the flexing of the lid that controls contact?
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