[SOLVED] want to automate CO2 analyser system

[jay_3189]

I have 6 Valves (Solenoid Valve of Parker Company operate at 24(DCV) and 0.5A) that I open and close manually on fix time by miniature toggle switch and repeating this cycle in each 6 Hours from first Valve.
Now I want to do this Automatic for fix duration of time that will automatically open and close the valve and after completion of 1 cycle again it have to start from first onwards automatically. and I also want to interface my circuit with computer so I can also able to change the timing for valve open duration if I want to.
so, please can anyone suggest me idea for making circuit for this.

 

[kripacharya]

You will need a clock generator which is capable of the durations you want - 1 hour. Its not clear exactly what your open-close sequence is, and some design issues will depend on precise definition. Also not clear what accuracy of time you need.
With a uC this is easy to do.

From your description I understand that you want the 1st valve open for 1 hour, then 1st closed and 2nd opened for 1 hour, .... etc.. then 6th closed and 1st opened loop ?

So essentially you need a 1-hour clock generator. There are many ways to do this. You could use a uC chip, or a divide-by-n counter chain triggered by AC mains zero crossings, or a simpler divider whose clock is maybe a 555 based timer. Of course if you want to eventually interface it to a computer, then the most flexible method is to use a microcontroller.

Next you feed this clock to a Johnson counter iC. If the bit length is more than 6, then you have to put in a reset circuit to make it loop at the count of 7. Each output pin of your johnson counter can be used - via a BJT + Relay, or even a Mosfet, to directly operate your 24v solenoids.

Once again, if you are using a microcontroller, then there is no need for a separate johnson counter. It can be done by the uC itself.

So - bottom line - use a uC to do ALL of the above functions, with only the solenoid drivers and the computer interface as external components.

And thats it !!