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Topic: how can I have suction in 2 cups from same vacuum? (Read 1 time) previous topic - next topic

twirap

Mar 07, 2012, 02:31 pm Last Edit: Mar 07, 2012, 07:44 pm by twirap Reason: 1
I need to build a light weight suction system with battery powered vacuum.

basically what i am trying to do is attach motors to an arm and at the end of each arm are suction cups that are connected to a vacuum. There are 2 arms and 1 suction cup at the end of each arm. I want to minimize weight and the vacuum would be battery powered. When one arm/suction cup is being vacuumed the other suction cup/arm should not be vacuumed, any idea how I can accomplish this or what vacuum/design you recommend? I am doing this for my own enjoyment, I like building robots using arduino. I have built 2 so far using potentiometers and servos but they havent been anything complicated involving pressure or anything else.


Essentially I am trying to make one arm stick while the other isnt stuck. Can I somehow use electricity to induce polarization charge into the surface so that the arm would be oppositely polarized to the surface and it would stick? this I am assuming would weigh too much. I would like to keep the cost below 50$ for suction cup and vacuum. I am trying to make a robot that walks on walls.  

Delta_G

Sounds like a job for a simple valve.  When one is stuck, shut of the valve to the other one. 

twirap

#2
Mar 07, 2012, 05:25 pm Last Edit: Mar 07, 2012, 05:42 pm by twirap Reason: 1
can you please provide some pictures of what the setup might look like with a valve? I have never used one but I assume ill need to add a small motor to turn on/off the valve depending on when a suction cup is attached. To detect when a suction cup is attached to the surface i use a distance sensor with a range of 2 cm max so it does fairly well at .5 cm.

Ok, After looking from what you said I found the perfect valve for the job:

http://upload.wikimedia.org/wikipedia/commons/f/f7/Valve_cross-section.PNG
I think these valves are called ball valves right? I need to get 3 way ones I suppose.

Now the question is what kind of suctions cups/vacuum do I need?

AWOL

Quote
I need to build a light suction system

Light is unaffected by a vacuum, in fact, it travels faster in one.
"Pete, it's a fool looks for logic in the chambers of the human heart." Ulysses Everett McGill.
Do not send technical questions via personal messaging - they will be ignored.

PeterH


I am trying to make a robot that walks on walls. 


I guess you're planning to have some sort of walking motion where the cups grip alternately. In that case there will be times where you need both cups to have vacuum. I expect this will not seal imperfectly and will require your pump to run continuously to maintain suction, so in that case you would need to have a separate valve for each suction cup so that you can turn them on and off independently.

I suppose you have already figure out by now that the bigger the cups the better they're likely to work due to the area/circumference relationship, but I suspect your first challenge is going to be to set a weight budget and determine what cups and pump you need to support that weight and then find a suitable power source that fits within your weight budget.
I only provide help via the forum - please do not contact me for private consultancy.

Chagrin

RC airplanes with pneumatic wheel retracts use a small spool valve, actuated by a servo, to control the flow of the air. You could recreate the same but as Peter mentioned you'd need to make adjustments so that when the spool switches between feet that there's a period of time when both feet have suction.

A pretty simple problem if you have a small metal lathe and can build a custom spool.

liudr

Look for electrically controlled valves. They are like relays. You energize them to pull a stick to open and close the valve. No need for motors to turn mechanical valves. Just thinking, if you could point the vacuum exhaust downward, it may help with the climb ;)

If you really want to suck light, you need some serious mass like a black hole.

twirap

No, I do not want to suck light....that would be useless to me unless ofcourse I could alter dimensions  ]:) ]:)


I have come up with a design for a suction cup, I am not sure whether these exist already or if I have to make them myself. If they already exist what are they called? If they dont exist what kind of material should I use to make these little windows inside the suction cups? This will enable me to keep the suction in one cup strong even though the pump isnt sucking anymore in that valve.





Chagrin

You're describing a check valve. It'll probably be difficult to find one that's small and light enough for your purposes though; the best guess I'd have would be using a check valve for aquarium tubing, but then those aren't really designed for vacuum pressure. YMMV.

As an aside here's a little pneumatic valve I came across that might fit your needs.

twirap

#9
Mar 12, 2012, 01:06 am Last Edit: Mar 12, 2012, 01:24 am by twirap Reason: 1
that valve uses 12 v which addes to the weight quiet a bit because of batteries. I will try and modify a suction cup and pipe to make this valve myself. I am sorry I have 1 last question. I dont know too much about power and circuits, if I had a 12 v DC motor that was externally powered how could I hook it up to the arduino to control when to turn it off or on? I obviously cant use the arduino for power like the small 3 v dc motors so how do you control loads with arduino that require a lot of voltage? I know how to do it with servos because all I need for servos is hook the digital pin into arduino digital pin but for DC motors and similar loads that only have 2 wires and such high voltage requirement how do you control them with arduino?


PS: I just finished making an easy check valve with a new design so that is solved.

justone

Sounds like a fun project. In looking at doing away with an actual vacuum pump maybe use a mechanically activated cup like the ones used for holding gps units to car windows. Also came across this: https://www.echidnasontheloose.com.au/product.php?productid=17798

Have fun.

BlackLab1

#11
Mar 12, 2012, 04:31 am Last Edit: Mar 12, 2012, 04:34 am by BlackLab1 Reason: 1
FYI---
Twirap - The valve you show up above is called a globe valve. >>

Ball valves have a hole through the ball part of valve like this one >>


BTW- They have ΒΌ inch threaded brass check valves, like this one. >>

{ I know this one is what they call a slip, but they make them also in threaded. This was just a quick picture of what I could come up with as an example.}

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