Possible to control 4 proportional valves with one analog signal output

[newbieeng]

hi everyone, I am preparing a labview project intended to control 4 proportional valves (Bürkert 8605 with 2873) sequentially via NI USB X 6343.  For now, 4 amperage AO are enough to control 4 valves, however, in the future, it would be necessary ampera AOs for other tasks in the scope of the project. In that case, is it possible to control 4 valves sequentially with just one ampera AO via an additional circuit, signal etc?

[Henrik_Volkers]

Well, the poor mans AO is a DIO with a PWM and a RC lowpass. 😉

If you need the AO and still have the 4 counter free, you can use them to output a PWM that integrates to a DC voltage that control the output PWM of the valve....  

(or use the PWM directly to control your valve, just add a driver??)

[newbieeng]

Hello Henrik, thank you for your response. I could not understand what you mean clearly since I am new in that kind of job. Did you mean that I could use counter ports to get ampera AO with PWM and a DC supplier? By the way the DAQ that I will use is not USB 6343, it is USB  6353. I wrote it wrongly. Thanks in advance.

[Henrik_Volkers]

There are thousands of applications, where an analog output value is created by a digital output that is modulated .....

In your first post you wrote you want to control 4 valves. the controller of the valves accepts an analog voltage input, and outputs a PWM (!!) for the solenoids of the valve.  If you are out of AOs , but have plenty of DO and 4 counters it will need only a driver transistor, a free running diode and a powersupply to control your valves without the 2872 😉 

What kind of engineer are you?  Practical background in EE?

It migth be cheaper (faster, easyier for you to implement, etc)  to buy some more AOs 😉

[newbieeng]

The valves have ampera analog inputs, they accept ampera analog inputs and NI USB 6353 has 4 channels of AOs for ampera. It is enough 4 AOs at the first stage of my project, however, in the future, I would need more AOs (ampera) for different tasks. That's why I asked about this.

I am a mechanical engineer so I am not too keen on electric/electronic stuff.

What did you mean with buying AOs? The DAQ (NI USB 6353) is not like a compact daq chassis, I cannot add AO moduls on it. Or can I?!

[Henrik_Volkers]

I don't know how you calculate man-hours, and how long it migth take you to get a not so strait ready prepared solution running. thats why I suggest a USB modular system for a professional solution.( scaleable with the project 😄 )

But you can buy two USB 600? with 4 analog outputs in total for 300?? bugs, and good enough for a proof of concept

What's a days saved worth in your world?

Back to the hacks 😉

google PWM to analog and make yourself familar with it.

Grab a resistor and a capacitor (about 10k resistor and try 1µF )  and hook it up to a digital output of your card together with a DMM (or better a scope)

Read the examples and tutorials how to create PWM with LabVIEW and DAQmx

Your analog in of the controller has a input impedance of 10k or 20k  instead of 1M or higher with a scope or DMM. Maybe you need to implement another OP as a driver and amplifier.

AND it's a good idea to ask the company if the input can also accept PWM (some industrial parts do)

Another way would be to use 4 sample and hold circuits like the LF398 , one analog output and 4 digital outputs for the sample-trigger, or a mux with storage caps and buffer OPs or bitbanging the digital ports to a I2C and hook up DACs ....  things you can think of if you have the time and knowledge, but no money.

[BradW]

If I understand correctly, the Burkert 2873 controller you mentioned, can utilize a voltage or current (20 mA) input which drives it's output to the proportional valve solenoid.  Your USB 6353 only sources voltage analog outputs, up to 10V and can only source up to 5 mA.  Therefore, you will be using analog voltage outputs from the 6353 to drive the 2873.  If you want the same control action for more than one valve simultaneously, the 2873 only draws 0.5 mA input, so you could parallel several 2873 modules on one output channel of a USB 6353.  Beware of ground loops, though!

[newbieeng]

Thank you BradW. You understand correctly. I want to control 4 Burkert 2873 with USB 6353. Yes, it may be controlled multi-valves from one channel of NI USB 6353 but it cant be simultaneously. For instance, I want to open one valf while the others stay at closed position, so it cant be possible from one channel without any board or etc. (at least I do not know how to do it if it is possible). With one channel, I may control all of the valves but only in the same manner.

[johnsold]

Egemen,

I think you should plan on obtaining enough DAQ devices to provide one AO channel for each valve. As Henrik mentioned, there are other ways that might work. An external anlog sample and hold circuit per channel could also be used. However, all of these tend to require some electronics skills which it appears that you do not have.  While you could probably learn those skills, the time it would take would cost more than buying additional DAQ devices which can do the job directly.

My recommendation is to determine the maximum number of valves that may be required in the future and then contact your NI sales rperesentative. It is the sales rep's job to help customers determine which equipment is required to do the job.  They may ask key questions which could affect the choices but that might no get asked here on the Forum.  For example you may need an external powered USB hub or isolation.

Lynn