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Today's Topics:
1. Controlling valves (Andrew)
2. Re: Controlling valves (Alaric Snell-Pym)
3. Re: Controlling valves (David Smith)
4. Re: Controlling valves (david)
5. Re: Controlling valves (Andrew)
----------------------------------------------------------------------
Message: 1
Date: Thu, 26 Sep 2013 14:40:56 +0100
From: Andrew <andrewsoltau@gmail.com>
To: Bristol and Bath Linux User Group <bristol@mailman.lug.org.uk>
Subject: [bristol] Controlling valves
Message-ID: <52443968.5080402@1dtv.com>
Content-Type: text/plain; charset="iso-8859-1"; Format="flowed"
Hi All
I have been asked to do a project which involves using the pc to turn on
and off some valves with reasonably accurate timing. I would be grateful
if someone could point me in the right direction. I have done some
googling but the subject seems to be massive and lots about robotics and
nothing terribly simple. Terribly simple is what I am after!
Firstly, what sort of software does one use for this? And where do I get
the control valves - I assume I don't go to maplin, or is that the
simplest way? Pressures are quite low, 10 psi or so, and the pipes will
be quite small bore, like windscreen washer stuff. Might need to use a
passed volume sensor / flow meter / however one does that.
This would all get prototyped on a standard pc with Debian. The final
objective is a using a raspberry pi with simple go buttons to set off
different sequences of operations.
Cheers
Andrew
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Message: 2
Date: Thu, 26 Sep 2013 15:06:49 +0100
From: Alaric Snell-Pym <alaric@snell-pym.org.uk>
To: bristol@mailman.lug.org.uk
Subject: Re: [bristol] Controlling valves
Message-ID: <52443F79.7030006@snell-pym.org.uk>
Content-Type: text/plain; charset="iso-8859-1"
On 26/09/13 14:40, Andrew wrote:
> Hi All
>
> I have been asked to do a project which involves using the pc to turn on
> and off some valves with reasonably accurate timing. I would be grateful
> if someone could point me in the right direction. I have done some
> googling but the subject seems to be massive and lots about robotics and
> nothing terribly simple. Terribly simple is what I am after!
>
> Firstly, what sort of software does one use for this? And where do I get
> the control valves - I assume I don't go to maplin, or is that the
> simplest way? Pressures are quite low, 10 psi or so, and the pipes will
> be quite small bore, like windscreen washer stuff. Might need to use a
> passed volume sensor / flow meter / however one does that.
>
> This would all get prototyped on a standard pc with Debian. The final
> objective is a using a raspberry pi with simple go buttons to set off
> different sequences of operations.
Well, the solution could well be different for a PC than for a Pi, as
the Pi has some GPIO lines you could use to drive the solenoids and the
PC doesn't...
Can you get the Pi and start off by building solenoid valve drivers for
it, and then once it's working, attach it to a network and have the
prototype software on the PC talk to the Pi purely to use it to drive
the outputs? Then port the software over later!
As for the physical side:
The thing you want to google for is a "solenoid valve", I gather, and
which one you want is all about the flow rates and pressures and what
the fluid is and all that. And the driving voltage.
See if you can get 12v (or 5v? I dunno if they go down that far) ones -
many solenoid valves run on 240v mains, and it's best to avoid that if
you can.
Then how you drive them from the Pi depends on their current
requirements. Perhaps the Pi can drive a transistor which drives a relay
which drives the valve. Perhaps you can skip the relay if the current
requirement is low enough to be within the current capacity of the
transistor. Get somebody who's done this kind of thing b efore to check
your circuit before wiring it to the Pi, as IIRC the Pi doesn't have
much protection on its GPIO header :-)
How many valves do you need? If you need more than there are available
outputs on the Pi, it gets more complex.
As for the software - well, you get to write that, I believe :-) Once
you've got the low-level interfacing to valves (and sensors) done, you
should be able to access that from your favourite programming language
with little difficulty and write a little app that sits in a loop
polling the sensors, deciding if the valves need to change, and changing
them if required. And probably logging stuff somewhere. Everyone loves
sensor logs.
If all the above sounds really daunting, come to Bristol Hackspace in
Bedminster from 7pm this evening, bringing as much information about
your requirements as you can, and somebody will be able to offer
step-by-step advice :-)
ABS
--
Alaric Snell-Pym
http://www.snell-pym.org.uk/alaric/
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Message: 3
Date: Thu, 26 Sep 2013 15:17:07 +0100
From: David Smith <Dave.Smith@st.com>
To: <bristol@mailman.lug.org.uk>
Subject: Re: [bristol] Controlling valves
Message-ID: <524441E3.7080708@st.com>
Content-Type: text/plain; charset="ISO-8859-1"
On 09/26/13 14:40, Andrew wrote:
> Hi All
>
> I have been asked to do a project which involves using the pc to turn on
> and off some valves with reasonably accurate timing. I would be grateful
> if someone could point me in the right direction. I have done some
> googling but the subject seems to be massive and lots about robotics and
> nothing terribly simple. Terribly simple is what I am after!
>
> Firstly, what sort of software does one use for this? And where do I get
> the control valves - I assume I don't go to maplin, or is that the
> simplest way? Pressures are quite low, 10 psi or so, and the pipes will
> be quite small bore, like windscreen washer stuff. Might need to use a
> passed volume sensor / flow meter / however one does that.
I doubt you'd find that sort of stuff at Maplin. I'd start by doing
some searching (try "miniature solenoid valve" as a starting point) and
maybe look at RS.
> This would all get prototyped on a standard pc with Debian. The final
> objective is a using a raspberry pi with simple go buttons to set off
> different sequences of operations.
Personally I'd be tempted to go for Arduino rather than a RPi. I'd say
that the Pi is probably a little "heavyweight" for this application.
The Arduino has its own custom software environment for doing exactly
this sort of thing.
As for how to do the control, it depends on what valves you get, what
voltage/currents are needed to drive them, and what sort of switching
frequency and longevity you need - for example, if you need a
significant current and/or voltage, you might want to use relays, but if
they're switching frequently and need to last for a long time (rather
than this just being a demo project or something used occasionally) then
you may need to go solid-state. Either way, it's unlikely you'd be able
to drive the valve directly from the Arduino/RPi because the valve would
require more power than the device can supply.
------------------------------
Message: 4
Date: Thu, 26 Sep 2013 15:21:08 +0100
From: david <david@avoncliff.com>
To: bristol@mailman.lug.org.uk
Subject: Re: [bristol] Controlling valves
Message-ID: <524442D4.7070203@avoncliff.com>
Content-Type: text/plain; charset=ISO-8859-1; format=flowed
It depends on the scale, I am doing a lot of this commercially using
Labview.
That is a expensive National Instruments product.
But some years ago they did give away a Linux version, which can still
be downloaded from a German site. It is good and powerful, but has quite
a learning curve.
Labjack do some interface boxes with labview drivers for < ?100
However I would recommend starting on the Raspberry, looking at the home
robotics shops, and use Python or any language you are happy with.
David
On 26/09/13 14:40, Andrew wrote:
> Hi All
>
> I have been asked to do a project which involves using the pc to turn on
> and off some valves with reasonably accurate timing. I would be grateful
> if someone could point me in the right direction. I have done some
> googling but the subject seems to be massive and lots about robotics and
> nothing terribly simple. Terribly simple is what I am after!
>
> Firstly, what sort of software does one use for this? And where do I get
> the control valves - I assume I don't go to maplin, or is that the
> simplest way? Pressures are quite low, 10 psi or so, and the pipes will
> be quite small bore, like windscreen washer stuff. Might need to use a
> passed volume sensor / flow meter / however one does that.
>
> This would all get prototyped on a standard pc with Debian. The final
> objective is a using a raspberry pi with simple go buttons to set off
> different sequences of operations.
>
> Cheers
>
> Andrew
>
>
>
> _______________________________________________
> Bristol mailing list
> Bristol@mailman.lug.org.uk
> https://mailman.lug.org.uk/mailman/listinfo/bristol
>
------------------------------
Message: 5
Date: Thu, 26 Sep 2013 15:26:52 +0100
From: Andrew <andrewsoltau@gmail.com>
To: Bristol and Bath Linux User Group <bristol@mailman.lug.org.uk>
Subject: Re: [bristol] Controlling valves
Message-ID: <5244442C.5090405@1dtv.com>
Content-Type: text/plain; charset="iso-8859-1"; Format="flowed"
On 26/09/13 15:06, Alaric Snell-Pym wrote:
> On 26/09/13 14:40, Andrew wrote:
>> Hi All
>>
>> I have been asked to do a project which involves using the pc to turn on
>> and off some valves with reasonably accurate timing. I would be grateful
>> if someone could point me in the right direction. I have done some
>> googling but the subject seems to be massive and lots about robotics and
>> nothing terribly simple. Terribly simple is what I am after!
>>
>> Firstly, what sort of software does one use for this? And where do I get
>> the control valves - I assume I don't go to maplin, or is that the
>> simplest way? Pressures are quite low, 10 psi or so, and the pipes will
>> be quite small bore, like windscreen washer stuff. Might need to use a
>> passed volume sensor / flow meter / however one does that.
>>
>> This would all get prototyped on a standard pc with Debian. The final
>> objective is a using a raspberry pi with simple go buttons to set off
>> different sequences of operations.
> Well, the solution could well be different for a PC than for a Pi, as
> the Pi has some GPIO lines you could use to drive the solenoids and the
> PC doesn't...
>
> Can you get the Pi and start off by building solenoid valve drivers for
> it, and then once it's working, attach it to a network and have the
> prototype software on the PC talk to the Pi purely to use it to drive
> the outputs? Then port the software over later!
Can do. Good plan.
>
> As for the physical side:
>
> The thing you want to google for is a "solenoid valve", I gather, and
> which one you want is all about the flow rates and pressures and what
> the fluid is and all that. And the driving voltage.
>
> See if you can get 12v (or 5v? I dunno if they go down that far) ones -
> many solenoid valves run on 240v mains, and it's best to avoid that if
> you can.
>
> Then how you drive them from the Pi depends on their current
> requirements. Perhaps the Pi can drive a transistor which drives a relay
> which drives the valve. Perhaps you can skip the relay if the current
> requirement is low enough to be within the current capacity of the
> transistor. Get somebody who's done this kind of thing b efore to check
> your circuit before wiring it to the Pi, as IIRC the Pi doesn't have
> much protection on its GPIO header :-)
Yes. I was thinking the pc would have the volts to run the solenoids,
but of course the pi won't.
>
> How many valves do you need? If you need more than there are available
> outputs on the Pi, it gets more complex.
Probably only 5, definitely less than 10.
>
> As for the software - well, you get to write that, I believe :-) Once
> you've got the low-level interfacing to valves (and sensors) done, you
> should be able to access that from your favourite programming language
> with little difficulty and write a little app that sits in a loop
> polling the sensors, deciding if the valves need to change, and changing
> them if required.
Happy to write some sofware, C or Java. I just had the idea there must
be some templates around. Given that people are doing this all the time
all over the world. I assume. In particular, I imagine that solenoid
valve drivers, for instance, must have been done again and again.
> And probably logging stuff somewhere. Everyone loves
> sensor logs.
Oh yes!
>
> If all the above sounds really daunting, come to Bristol Hackspace in
> Bedminster from 7pm this evening, bringing as much information about
> your requirements as you can, and somebody will be able to offer
> step-by-step advice :-)
>
> ABS
>
Thank you very much for all that. I'm in Bath and I don't think I get
over to Bristol tonight. But a Hackspace meeting is obviously a good
place to get info at some point.
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