Automatic Control of PRESSURE & TIME of gas flow from H tank cylinders

geekscosmos_at_yahoo.com
Date: 01/10/05 

Date: 10 Jan 2005 03:28:50 -0800

I have a gas cylinder - H Tank (that can hold oxygen, helium, etc... at
50 psi pressure) that is used for clinical simulation. It has its own
valve that can be switched on / off manually.

1) My requirement is to automate this valve by having a controller to
control the flow of gas in terms of both PRESUURE and TIME based on the
user inputs.

2) Provide a set of knobs / digital input switches each for TIME period
of gas flow - 2 seconds, 5 seconds, and 10 seconds.
(If I choose 10 seconds TIME, the valve opens for 10 seconds, sends the
gas and automatically shuts after 10 seconds)

3) Provide another set of knobs / digital input switches for the LAG
period of gas flow - 10 seconds, 15 seconds, 25 seconds.
(If I choose 15 seconds input, then the valve has to be in the closed
mode for 15 seconds after which it automatically opens
for TIME input that I have chosen in step 2)

4) Provide another set of knobs / digital input switches for the
PRESSURE of gas flow - 25 psi, 35 psi, 50 seconds.
(If I chose 25 psi, then the pressure of the gas coming out of the
cylinder should be 25 psi)

5) My final extension is to control the same knobs / inputs remotely
from my computer through a user interface

(Example, If I chose TIME = 5seconds, LAG = 10 seconds, PRESSURE = 25
psi, the gas flows out of the cylinder at a pressure of 25 psi for a 5
seconds period after a periodic 10 seconds break meaning 5sec ON, 10
sec OFF, 5 sec ON, 10 sec OFF, etc...)

Is there a readymade product that can handle this and what are the
specifications*** that I should look for when I buy such a product ?

How do I approach if I would like to assemble my own system to handle
my requirement and what would be the design ?

In order to handle from the computer remotely, I can connect using a
serial / USB port, is there a free downloadable software
that can convert the serial / usb signals to handle such requirements
based on the circuit ?

I assume that I can have a timer and a pressure sensor to do this that
again converts to mechanical energy in order to stop /
open the valve and regulate the pressure. At the same time, I can also
have some readymade PCBs that understand the serial /

usb signals that I send from my computer to do the job, but I need a
very clear cut design with specifications and implementation procedure
in order to execute this. What are the basic technical specifications
that I have to look for in this new system ? I am basically looking for
an economic solution that can be implemented in my lab for experiments.

Any pointers to this would be of greatest help.
Thanks in advance!!!
SARITA

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