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  • Click Series Analog Output

    Has anyone tried to hook up an analog pneumatic valve (Clippard brand) to a click series plc analog output? The output impedance for the click series analog output has to be a minimum of 4k ohm. My pneumatic valve only has a resistance of approximately 50 ohms. I tried installing a 4k ohm resistor in series with the valve but it limits the output voltage coming out of the plc output to approximately 1.3 volts or less. I am using a 0-10 VDC analog output with a 0-10 VDC analog clippard valve. I put a meter on the output terminals without hooking up the valve and I do get the 0-10 VDC when the program calls for it. Anyone have any ideas? I checked with support for both the PLC and valve manufacters but no one had any answers. Appreciate any input! Thanks!


  • #2
    50 Ohms sounds like a current loop device, while >4K sounds like you are using a voltage output. If you are using the built-in outputs on an analog enabled CLICK CPU, then I'd try the current output. If you bought a voltage output add on module, I suspect you are going to have to swap it for a current model.
    Now, if, for example you are using a module and need some of the outputs to actually be voltage and only have the one valve then there are conditioners/converters available e.g. fc-33

    Another thing; do you happen to have the model number of the valve handy? I happen to have a Clippard catalog laying here at my desk. Looking at the EVP series (just for example) I see that while they specify the according to coil "voltage", the valve alone does not have a common industrial interface, a 0-10V model needs about 0-185mA not a 0-20 ro 4-20mA loop. Clippard does sell the EVPD driver to give a standard interface, if you do have an EVP I think you'd be best off buying the driver, a CLICK won't be able to drive the valve directly.

    EDIT: yow! just out of curiosity, I looked up the price of the EVPD $250 !!! and that is in addition to the valve itself, I don't know what you are controlling, but I would consider taking a look at Automation Directs offerings (this is their forum after all)
    Last edited by Tinker; 01-16-2019, 04:34 PM. Reason: addition

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    • #3
      I am using the analog output on the Click PLC model C0-DRE-2-E which is a 0-10 VDC output. I could swap it with a current model PLC model instead but the clippard valve is spec for 0-10 VDC. I am using a clippard model EV-PM-10-25 valve which is the EVP series. It doesn't state that this is a current loop device that I can see. In fact, I talked to Clippard support and they didn't have any advice for me. And, your right the EVPD driver is too expensive. I will look at the offerings the Automation Direct offers. I still think this should work!

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      • #4
        The analog voltage output modules require at least 1000ohm minimums for voltage outs, same for BRX built in analog out too. As far as I can see, nothing Automation Direct carries has anywhere close to the low impedance used by your air cylinder for voltage outputs. Like Tinker mentioned, only the current outputs list ohm ratings down there like your air cylinder.

        What is the part number you have on the air cylinder? Are you sure you have the right specs on it?
        Last edited by MikeN; 01-17-2019, 01:11 PM.

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        • #5
          Well, I learned something new, the older (non Ethernet) analog CLICKs had both voltage and current output options in the same unit, I guess they decided there were better uses for the available terminals.

          I'm surprised Clippard didn't recommend their driver, I wonder if they just assumed you were using one and they didn't want to bother with why your CLICK wasn't talking to it. (what the heck is a CLICK anyway?, if talking to vendors it might be useful to have a few AB model numbers handy the throw out from time to time so they take you seriously)

          The Clippard EVP series s not intended to be driven directly by a conventional analog control signal. I can think of a couple of cheap options, since the total power involved (10V @ 185mA is less than 2W) low efficiency is not going to be a huge problem. One can make a linear current source with a transistor or MOSFET and a resistor or two that could probably be driven by your CLICK output. Or, possibly (but maybe not) simpler to understand, would be to buy a C0-08TD2 (about $36) and setup a resistor ladder to drive the valve.

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          • #6
            MikeN, the air cylinders are made by us. Straight forward pneumatic cylinders, nothing special. Require 80 psi., flow is not a big concern. We want them to open slowly. We currently use Humphrey 310 2VDC (4.5 watts, .17 CV) valves for our system but they are not proportional valves. That's why I reached out to clippard since they make the EVP series proportional valves. The cliipard sales/technical guy said they would work with an analog PLC. The valve coil has approximately 50 ohms of resistance. Well, they do not work. Like Tinker stated in his post, I think I will need a driver or make my own driver to get this to work. I am checking on other PLC manufacturers as well. I have used AB in the past but they alwasy seemed to be higher priced. Compared to what I need for the automation direct PLC, it might be a wash. Thanks for your input!!!!!

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            • #7
              Tinker, I will look into the suggestions you made. Based on what I am seeing, I don't think the Automation Direct voltage or current analog output PLC will work without a driver for the valves. I do have a sample ASCO proportional valve which has a driver built into it but it was over $250 for one of these. I will keep looking to see what I can find and look into what you suggested. Thanks!

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              • #8
                One other idea, I see in the Clippard catalog they say (regarding the EVP line) "The valve may be controlled using DC current, open or closed-loop control, and even PWM (Pulse Width Modulation)..."
                Considering the $250 for Clippard's driver, and about $180 for your CLICK, I personally would consider using a BRX and PWM, an 18 point Ethernet BRX is less than $200 more then the CLICK (and therefore less than CLICK + Driver) plus you'd then get to use Do-More Designer, yes, there may be a bit (or a lot) of a learning curve to change over but in the end it is much more powerful with stages and other cool stuff.
                Actually, depending on the requirements of your system one might even manage low frequency PWM with a CLICK, but there are no built in provisions for that and it might be too slow for many applications.

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                • #9
                  Originally posted by Ventilation Guy View Post
                  I am using the analog output on the Click PLC model C0-DRE-2-E which is a 0-10 VDC output. I could swap it with a current model PLC model instead but the clippard valve is spec for 0-10 VDC. I am using a clippard model EV-PM-10-25 valve which is the EVP series. It doesn't state that this is a current loop device that I can see. In fact, I talked to Clippard support and they didn't have any advice for me. And, your right the EVPD driver is too expensive. I will look at the offerings the Automation Direct offers. I still think this should work!
                  Well, depending on your definition of 'work'. Like you, I have no idea why adding a 4K resistor in series doesn't cause the output to work correctly (at the PLC terminals). BUT....even if it did, you're still only going to drop 1.25% of the voltage through your 50ohm valve, so it's still not going to do what you need it to (deliver 0-10V at the VALVE terminals).

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                  • #10
                    Originally posted by ControlsGuy View Post

                    Well, depending on your definition of 'work'. Like you, I have no idea why adding a 4K resistor in series doesn't cause the output to work correctly (at the PLC terminals). BUT....even if it did, you're still only going to drop 1.25% of the voltage through your 50ohm valve, so it's still not going to do what you need it to (deliver 0-10V at the VALVE terminals).
                    I'm not sure why Clippard even describes those valve as "10V" since they are just a dumb coil of wire, current is the only thing that matters (sure, you need voltage to push current, but still, it is the current that matters) To make things even more fun (unless one just spends the $250 for Clippard's driver) the valve doesn't even start flowing until about 60mA, so no common PLC analog output is going to drive it, then full flow is at about 185mA

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                    • #11
                      Originally posted by Ventilation Guy View Post
                      MikeN, the air cylinders are made by us. Straight forward pneumatic cylinders, nothing special. Require 80 psi., flow is not a big concern. We want them to open slowly. We currently use Humphrey 310 2VDC (4.5 watts, .17 CV) valves for our system but they are not proportional valves. That's why I reached out to clippard since they make the EVP series proportional valves. The cliipard sales/technical guy said they would work with an analog PLC. The valve coil has approximately 50 ohms of resistance. Well, they do not work. Like Tinker stated in his post, I think I will need a driver or make my own driver to get this to work. I am checking on other PLC manufacturers as well. I have used AB in the past but they alwasy seemed to be higher priced. Compared to what I need for the automation direct PLC, it might be a wash. Thanks for your input!!!!!
                      My questions to the original poster is: Do you need the speed to change during a move? Also I hope you do not need to position the air cylinder mid stroke. If you need positioning this is a whole different ball game (expensive). If you just need to cushion the speed at the end(s) of the stroke there may be other options. I'm also concerned about the comment
                      Originally posted by Ventilation Guy View Post
                      flow is not a big concern
                      This is what analog control is all about!
                      Last edited by Anvilsoup; 01-19-2019, 08:56 AM.
                      Futti Utu

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                      • #12
                        Originally posted by Anvilsoup View Post

                        My questions to the original poster is: Do you need the speed to change during a move? Also I hope you do not need to position the air cylinder mid stroke. If you need positioning this is a whole different ball game (expensive). If you just need to cushion the speed at the end(s) of the stroke there may be other options. I'm also concerned about the comment This is what analog control is all about!
                        To clarify this, you are right. That is why I want analog control. But, the intent is to control a pneumatic cylinder that opens/closes a ridge vent or a side curtain on a livestock barn. We have a 2 way cylinder with differential air pressure on each end to effectively control the position to a certain point. The flow and speed it takes to move the ridge vent and/or curtain is typically not a big concern of our customers. They can control it to some extent by adjusting the pressure regulators to accomodate their application or barn. Our control releases air pressure to overcome the differential pressure in the air cylinder to start moving the ridge or curtain. We currently have a pneumatic controller that works for this design but several of our customers are requesting an "electric over air" version". This is what I attempting to develop! So, you are correct in your comment. I appreciate any advice/suggestions! Any help is appreciated!

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                        • #13
                          Using pneumatics to control a position is not usual. Reasons: pneumatics donít carry heavy loads; pneumatics will fail when mechanically overloaded ( fittings break, lines get loose); pneumatics is not good at maintaining a certain position under load (Air tends to hiss and the cylinder will move)

                          i have only only seen it once on an elevating table which needed to maintain height on emergency stop. I have also seen two situations where pneumatics was not a good engineering solution.

                          to control a certain position, the hydraulics is the right way. Is reliable, accurate and easy to tweak (the hammering that is prone to occur). All at an added cost of acquisition.

                          The analogue control using voltage has a couple shortcomings: is sensitive to interference; requires good grounding; depends on length of lines. If all works well, then the analogue control is fast and accurate. Using current eliminates the shortcomings, but I guess you canít choose.

                          To conclude so far: seems to me youíre using pneumatics instead of hydraulics and voltage instead of current to control the motion. Yet, letís assume it worked before or there is warranty to this solution.

                          to adjust to a different load resistance, you need an amplifier able to carry 200mA off a 20mA or less for input. Sry, I have to get back soon

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                          • #14
                            Originally posted by Ventilation Guy View Post

                            To clarify this, you are right. That is why I want analog control. But, the intent is to control a pneumatic cylinder that opens/closes a ridge vent or a side curtain on a livestock barn. We have a 2 way cylinder with differential air pressure on each end to effectively control the position to a certain point. The flow and speed it takes to move the ridge vent and/or curtain is typically not a big concern of our customers. They can control it to some extent by adjusting the pressure regulators to accomodate their application or barn. Our control releases air pressure to overcome the differential pressure in the air cylinder to start moving the ridge or curtain. We currently have a pneumatic controller that works for this design but several of our customers are requesting an "electric over air" version". This is what I attempting to develop! So, you are correct in your comment. I appreciate any advice/suggestions! Any help is appreciated!
                            OK, so how about this: Have your cylinder act against a spring, either a spring-return cylinder or a return spring built into the mechanism. Since the spring force is proportional to deflection, then air pressure will be also. Then, to drive the cylinder, use an I/P (essentially a regulator where the setting is a 4-20ma signal). ADC has those. Now, the air volume from the I/P will be small, so you would probably need to couple it with a volume booster (also a regulator, but with the setting in the form of a low flow air pressure signal). You can get those from ControlAir and others. Your 4-20 sets a pressure coming from the I/P, which sets the high-flow-capable pressure from the volume booster, which balances against the spring to make the deflection proportional to the 4-20 signal. You can use position feedback, or pressure feedback as a proxy for position, or just run open loop if it's not that critical and you trust everything to work OK.

                            Then, if you want to make sure the axis doesn't move if the air fails, you can get fittings that have a valve built in, that will seal on loss of air pressure.

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