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Author Topic: Trying to make a simple series of timed events...  (Read 618 times)

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Offline gobo760Topic starter

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Trying to make a simple series of timed events...
« on: July 18, 2011, 04:23:48 AM »
Hi, I'm completely new to the world of micro-controllers.  I've always been old school up until now and, when I needed to automate something, I would just build it out of a mess of 12 volt relays and timer kits.  I have a project right now where I have to automate a machine that's pneumatically driven (it's a machine that fills boxes of wine) and I need to control 9 different pressurized air valves per station and there's 10 stations, so I'm looking at around 90 electrically controlled air valves.  Each batch of 9 valves basically does stuff based on timed events.  The operator hits the "Start" button, at which point that stations control panel LED changes from green to red, and an electric actuator opens a fill valve and the bag starts to fill.  The bag is sitting on a scale so once the scale gets to 30lbs, a circuit on the scale is closed and the fill actuator turns off.  After 5 seconds, the next valve opens, which pressurizes a pneumatic piston that pushes the wine box pour spout closed (the bags get filled through the pour spout head) and then while the piston is holding the pour spout closed, another valve opens, blasting the inside of the spout with pressurized water to wash out the residue.  It then closes 4 seconds later and another valve opens which blasts 300PSI pressurized air in to the valve to dry it.  At that point, the pneumatic piston valve closes and an air relief valve opens to retract the piston and then closes.  At that point, the control panel LED for that station goes from red back to green to tell the operator to pull the release handle to drop the bag in to the box, attach the new bag to the fill head, hit "START" and move on to the next station (the operator just keeps walking in a constant loop around the stations which are arranged in a circle).

Essentially, this machine only needs a sensor input for three commands (the command to "START", "EMERGENCY STOP" and the circuit that closes when the scale hits the right weight.  Everything else is just a series of timed events.  I'm admittedly a total noob, but what would be the simplest, and still most cost-efficient way to build a controller for this laundry list of timed events for so many stations?  As I said, I'm new to micro controllers so I'd really value anyone's suggestions.

Thanks in advance! :)
Chris

Offline corrado33

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Re: Trying to make a simple series of timed events...
« Reply #1 on: July 18, 2011, 02:38:59 PM »
This could definitely be done with a microcontroller, but I'm sure there are easier ways as well.  How accurate must the timing be?  Can it be... +-0.1 seconds?  Does it have to be exactly 4.000 seconds? 

How are the valves opened and closed?  What are the specs for the mechanism?  How much power does it take to open them (V @ amps?)

Offline gobo760Topic starter

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Re: Trying to make a simple series of timed events...
« Reply #2 on: July 19, 2011, 12:43:36 AM »
This could definitely be done with a microcontroller, but I'm sure there are easier ways as well.  How accurate must the timing be?  Can it be... +-0.1 seconds?  Does it have to be exactly 4.000 seconds? 

How are the valves opened and closed?  What are the specs for the mechanism?  How much power does it take to open them (V @ amps?)

Hi Corrado,

Thanks so much for replying!  The timing can be down to the second, it doesn't have to be exact.  The valves are opened and closed by an electric solenoid on each valve that activates when the solenoid is supplied with 120VAC.  The valves are essentially the same as sprinkler irrigation valves, except they open and close a lot faster and are more compact.  I can order any make or model of relay based on the advice you give me.  I usually order my relays from Newark and they have 120VAC relays that open/close with almost any range of DC or AC current.  That's basically the only specs.  I need to order a bunch of relays (based on the output current available by the microcontrollers) and there needs to be 3 inputs to the microcontroller for sensing when buttons are pressed.

Let me know if you need any other information from me.
Thanks again!
Chris

Offline Soeren

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Re: Trying to make a simple series of timed events...
« Reply #3 on: July 23, 2011, 01:57:47 PM »
Hi,

Hi, I'm completely new to the world of micro-controllers.  I've always been old school up until now and, when I needed to automate something, I would just build it out of a mess of 12 volt relays and timer kits.  I have a project right now where I have to automate a machine that's pneumatically driven (it's a machine that fills boxes of wine) and I need to control 9 different pressurized air valves per station and there's 10 stations, so I'm looking at around 90 electrically controlled air valves.  Each batch of 9 valves basically does stuff based on timed events.  The operator hits the "Start" button, at which point that stations control panel LED changes from green to red, and an electric actuator opens a fill valve and the bag starts to fill.  The bag is sitting on a scale so once the scale gets to 30lbs, a circuit on the scale is closed and the fill actuator turns off.  After 5 seconds, the next valve opens, which pressurizes a pneumatic piston that pushes the wine box pour spout closed (the bags get filled through the pour spout head) and then while the piston is holding the pour spout closed, another valve opens, blasting the inside of the spout with pressurized water to wash out the residue.  It then closes 4 seconds later and another valve opens which blasts 300PSI pressurized air in to the valve to dry it.  At that point, the pneumatic piston valve closes and an air relief valve opens to retract the piston and then closes.  At that point, the control panel LED for that station goes from red back to green to tell the operator to pull the release handle to drop the bag in to the box, attach the new bag to the fill head, hit "START" and move on to the next station (the operator just keeps walking in a constant loop around the stations which are arranged in a circle).
Whoa there, if you want others to be able/want to help, don't brick us by such a block of easy to misinterpret info. Try again in a more digestible form like:
1) Start button pressed
2) fill valve opens
3) wait for weight to signal an adequate fill
4) close fill valve
5) wait 5 seconds (why?)
6) open valve B
7) wait nn seconds
8) open valve C
9) close valve B
Etc.
And describe just what is needed from a controlling units perspective, not things that may be implemented already/in other ways, or whatever happens but is unrelated to the controller.

Things like "the bags get filled through the pour spout head" isn't relevant for this, but each delay and such is
Whatever you add to further the explanation should be separate from the "timing sheet".

This not to bash you, just to make it easy to get a simple and precise understanding of what it needs to do.


Essentially, this machine only needs a sensor input for three commands (the command to "START", "EMERGENCY STOP" and the circuit that closes when the scale hits the right weight.  Everything else is just a series of timed events.
It would be best to have the emergency stop separate from all other stuff, in a sort of higher priority position, to make sure that a glitch doesn't activate valves while cutting out the functionality of the emergency stop.

Besides the timed events, you'd need outputs to control the valves as well.


I'm admittedly a total noob, but what would be the simplest, and still most cost-efficient way to build a controller for this laundry list of timed events for so many stations?  As I said, I'm new to micro controllers so I'd really value anyone's suggestions.
Well, we're still waiting for the mentioned "laundry list",  ;D

There's basically two (sensible) ways to shave that goat: A series of monostable circuits put together to take the inputs into consideration and a microcontroller.

Monostables will require a larger bord, but the upside is that each stage will wait for the previous and each time can be adjusted while it's running.

A microcontroller will make for a small circuit, a module can be reprogrammed for other tasks/times or a completely different functionality (meaning that you can have boards in stock and just program them for the job at hand), they'er cheap, but the downside is that you need to learn how to program and you need the equipment for doing this.

Only you can decide what'll work for you, but if you're planning on making industrial automation projects, microcontrollers really is the way to go.


Just to recap... You need 9 outputs, 2 inputs (plus the emergency switch, which should not be part of the microcontroller)?
And you have what voltage available?

Select the relays/valves that's best suited to the process and give us their drive data (or a link to their datasheets), then the electronics can be made for those (rather than the other way around).
Regards,
Søren

A rather fast and fairly heavy robot with quite large wheels needs what? A lot of power?
Please remember...
Engineering is based on numbers - not adjectives

 


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