Hi guys,
This is my first post so bare with me. So I'm working on a project that requires a small amount of compressed air to be released on the touch of a button when needed. I originally went down the mechanical route, as this is my background, but soon realised I could utilize a micro 3v air pump and solenoid valve to release the air. The problem I have is that I need the micro pump to turn on for x amount of time to get pressure in the system, then turn off. I need it to be like a tiny compressor and keep topping up the air pressure every time the solenoid releases some. I'm guessing that some form of pressure sensor needs to be incorporated into the system or I can just time how long it takes to get to the pressure needed then set the pump to turn on for that amount of time, but not sure how to get it all to work together. So just to clearly outline the system I need :
1. 1.5-6V 130mA dc micro air pump turns on until 5-10 psi (call it 5 for now) is achieved.
2. once 5 psi is achieved the pump turns off.
3. push button is pressed and the solenoid valve opens for a set amount of time (I would like to be able to alter the time here as well if possible).
4. after a set amount of time the solenoid valve closes
5. back to stage 1.

There will be a minimum of 15 seconds between button presses (pressure drop). Its just like a compressor but using components like those used in a blood pressure monitor (micro pump, solenoid valve etc.)

So any ideas on how I can go about this guys? Please remember that I'm a lathe/milling machine type of guy not a resistor capacitor guy so as basic as possible please folks.

 

Hello,

Is there a one way valve between the pump and measuring point of the pressure?
When the pump shuts off and there is no one way valve, the pressure might leak away through the pump.
At what rate will the pressure be released by the valve?

Bertus

 

Hello,

Is there a one way valve between the pump and measuring point of the pressure?
When the pump shuts off and there is no one way valve, the pressure might leak away through the pump.
At what rate will the pressure be released by the valve?

Bertus

hi there, thanks for your reply, yes there will be a one way valve after the pump and i believe the solenoid valve releases somewhere around 5l/m,

 

Hello,

What is the volume of the 5 psi holder?
When there is 5liter/min and you want 15 seconds flow until no pressure, the holder must have a minimum volume of 5 liter / 4 = 1.25 liter.

Bertus

 

hi there, thanks for your reply, yes there will be a one way valve after the pump and i believe the solenoid valve releases somewhere around 5l/m,

just read the specs and it says it takes 3 seconds to go from 300mmhg to 15mmhg from a 100cc tank

 

Hello,

What is the volume of the 5 psi holder?
When there is 5liter/min and you want 15 seconds flow until no pressure, the holder must have a minimum volume of 5 liter / 4 = 1.25 liter.

Bertus

the volume will be around 10-20ml and the release time should be fractions of a second

 

Hello,

What is the volume of the 5 psi holder?
When there is 5liter/min and you want 15 seconds flow until no pressure, the holder must have a minimum volume of 5 liter / 4 = 1.25 liter.

Bertus

I need to release around 1-2ml at a time

 

Hello,

300 millihg = 5.801 033 361 4 pound/square inch
15 millihg = 0.290 051 668 07 pound/square inch
Using this site: http://www.onlineconversion.com/pressure.htm

Bertus

 

Hello,

300 millihg = 5.801 033 361 4 pound/square inch
15 millihg = 0.290 051 668 07 pound/square inch
Using this site: http://www.onlineconversion.com/pressure.htm

Bertus

ok so that solenoid should be fine right?

 

Hello,

300 millihg = 5.801 033 361 4 pound/square inch
15 millihg = 0.290 051 668 07 pound/square inch
Using this site: http://www.onlineconversion.com/pressure.htm

Bertus

its getting the pump to turn on after the pressure has dropped below a certain point and getting the solenoid valve to open for a set amount of time I'm, having trouble with

 

Hello,

When the valve has a flow of 5 liter / min and you want to release 2 ml , the time is only 24 mSec.
How fast can the valve switch?
Do you have the specifications?

Bertus

 

Hello,

When the valve has a flow of 5 liter / min and you want to release 2 ml , the time is only 24 mSec.
How fast can the valve switch?
Do you have the specifications?

Bertus

i cant seem to find that info at the moment do you know if they make mini solenoid valves that act that fast?

 

Hello,

Perhaps then a restriction to lower the flow may help.
That way you can stretch the opening time.

Bertus

 

Hello,

Perhaps then a restriction to lower the flow may help.
That way you can stretch the opening time.

Bertus

my thinking was that a normally closed solenoid valve when energized would open then as soon as you cut the power the valve closes again? so energize for 25 milliseconds then turn off to close (25 to allow time for valve to close)

 

Hello,

Depends on the construction of the valve.
There are also two way valves that will switch between two ports.

Show a datasheet of the intenden valve you want to use.

Bertus

 

Hello,

Depends on the construction of the valve.
There are also two way valves that will switch between two ports.

Show a datasheet of the intenden valve you want to use.

Bertus

iu cant find a data sheet but here's what i'm thinking of

 

Hello,

Depends on the construction of the valve.
There are also two way valves that will switch between two ports.

Show a datasheet of the intenden valve you want to use.

Bertus

it says when the power is on the valve is open and when the power is off the valve closes

 

Hello,

That does not help much: http://www.fspump.cn/cbdcf/46.html
The text is all chinese.

Bertus

 

Hello,

That does not help much: http://www.fspump.cn/cbdcf/46.html
The text is all chinese.

Bertus

so let just say I have a solenoid valve with those specs that closes when off and open when on and is fast enough etc. hiw do I get the pump to turn on when the pressure dips below a point and turns off when at pressure?

 

just found this

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