+-10v

Hi All,

I am using a Allen Bradley Micro830 analogue output 0-10V to control a directional proportional hydraulic control valve which has +-10V input.

My initial thought is to use two 10V analogue outputs (software interlocked) with one reverse polarity to control this? will I stick in a couple of diodes to protect the controller?

OR use a relay on a digital output to switch polarity then software can control direction?

or is there a better (industry standard) way of interfacing these?

Thanks

Craig

Hi Craig,

Do you have the details on the valve? You should just be able to give it a value and it should move to that position... 5v being the middle then 7.5 being 3/4 open and 2.5 being 1/4 open, if its a 'fail safe' then it may have a spring return

The valve is directional so +10V sends the shuttle in the valve one direction and -10V sends it in the opposite direction (to return the hydraulic cylinder)

this is a similiar valve;
http://www.parker.com/portal/site/P...LVE,+OBE+SERVO+PERFORMANCE+1+STAGE++D05&Wtky=

Then I would do it all in the software of the CPU, I have seen a lot that had relay's controlling and if its a mechanical relay its going to fail after X cycles if you use a solid state then you will get more life but still another chance for it to fail

It doesn't look like there's an analog output card available for the Micro800 series that does -10 to 10 VDC. The old addage once again rings true: you get what you pay for. If you're going A-B and want +/-10v output, then you are looking at a CompactLogix L16 or L18 series at the very least. This will give you access to the 1734-OE2V Point I/O Analog Output Module that can be configured for +/-10v

No Micrologix output card I could find is capable of +/-10v, not even from Spectrum. You'd either have to use a SLC (which is obsolete) or an L16/L18

Does using the 0-10V analogue output but with reversal of the polarity handled by a double pole change over relay connected to a digital output sound ok?

FactoryTalktotheHand said:

......CompactLogix L16 or L18 series .......

Click to expand...

just looked at the cost, fortunately I was sitting down

Any known issues with reliability with the Micro800 series (i'm using the 830)?

craigdiver said:

just looked at the cost, fortunately I was sitting down

Click to expand...

Just wait until you see the cost of the software....

craigdiver said:

Any known issues with reliability with the Micro800 series (i'm using the 830)?

Click to expand...

The 830 is a good CPU for the cost, I just dont care for the software

craigdiver said:

just looked at the cost, fortunately I was sitting down

Click to expand...

If you want native +/-10v support in an A-B controller, that's what you have to pay. If you don't want to pay it, you'll either have to hack-n-slash something up by reversing the polarity with a relay as suggested above, or switch to another brand that offers it at a lower price point. I totally understand where you're coming from. That's the maddening thing about A-B. They'll offer these ultra-low-cost PLCs and talk about them like they're the bees knees, but what they don't tell you are all the "gotchas" you'll run into if you actually try to use one. For example, sure the Micrologix 1100 is available with embedded analog inputs...but it's voltage only...and only 10 bit resolution. So if you have an application where high analog resolution is critical for something with tight tolerances, that embedded input is going to sink you if you planned on relying on it.

All I have to say is be VERY careful when specifying low-end PLCs for a job and make DOUBLY sure they will do what you need them to do. The lower the cost, the less basic functionality you can assume they'll have.

FactoryTalktotheHand said:

All I have to say is be VERY careful when specifying low-end PLCs for a job and make DOUBLY sure they will do what you need them to do. The lower the cost, the less basic functionality you can assume they'll have.

Click to expand...

Thank you for the advice.

craigdiver said:

...I am using a Allen Bradley Micro830 analogue output 0-10V to control a directional proportional hydraulic control valve which has +-10V input.

My initial thought is to use two 10V analogue outputs (software interlocked) with one reverse polarity to control this?...

...OR use a relay on a digital output to switch polarity then software can control direction?...

...Does using the 0-10V analogue output but with reversal of the polarity handled by a double pole change over relay connected to a digital output sound ok?...

...just looked at the cost, fortunately I was sitting down...

...Any known issues with reliability with the Micro800 series (i'm using the 830)?...

Click to expand...

You don't like the cost of the CompactLogix, fair enough, but look at the lengths you are going to in order to circumvent the lack of support the hardware has for your application. If this really is a low budget job, then low budget control is what you will end up with. That's ok if that is what you are happy with.

Does it need smooth control? Apart from wear and tear, for smooth modulation, using digital outputs to switch relays would not be ideal. Using two unipolar outputs to simulate a bipolar signal is also far from ideal. The hardware really just does not suit the application here. As the Micro800 have so few, it is also such a waste of an expansion module slot, which may be required now, or in the future.

But if needs must?

For the Micro800, it is possible using two OF2 modules to achieve a simulated bipolar range. Rockwell does provide sample code using two OF2 modules to switching a -10V to +10V output range. However, they state it is not to be used as actual application code, but instead only used as a guide as to how the program and controller operates. Whether they mean that the code, as is, should not be used, but if edited to suit your application it can be, I'm not sure? So whether you can, or should, adapt this method and code, edited or otherwise, into your application, is up to you...

473523 - Micro800 OF2 module negative output
Access Level: Everyone

Even though it's unlikely you will run with it, I would second the use of a 5370 CompactLogix controller, or similar, for proper analog modulation of this valve. Again, it comes down to how fine you need to control it?

With regard to the reliability of the Micro800, specifically for analog...

The resolution of the I/O is 12-bit unipolar using UINT (unsigned - no negative numbers), so they have a 0 to 65535 data range for voltage (0v to 10V), or current (0mA to 20mA). This is comparable with the SLC and MicroLogix controllers analog I/O, except that they are natively bipolar.

EDIT: & what FactoryTalktotheHand said...native features cost more...

Regards,
George

Thank you Geospark, I think the cost of the other controllers and software would kill the project so am going to go with the 0-10V analogue output with a relay reversing the polarity and therefore the valves direction of travel. I will use a high quality relay for durability. The valve control will most likely end up being 100%, 50% and maybe 25% and not much precision required. And the only use of the relay would be when a change of cylinder direction was required, the speed would be controlled by the analogue output therefore as it would only be changing over a zero potential, I would hope it would not introduce any noise into the circuit.

Thank you all so much for your continuing input.

How about Siemens ? I think the 1200 may work, their hardware and software is cheaper http://support.automation.siemens.com/WW/view/en/42038794/td?Datakey=46394437