Proportional valve and analog output

[dlmidget]

VALVE MODEL # 4WRPEH 6 C3 B04P-20/G24K0/A1M VALVE MODEL #

http://www.boschrexroth.com/country..._servo_valves/a_downloads/re29035_2009-02.pdf
I am atttempting to control teh speed of a hydraulic motor by replaceing a valve (DG4V-3S-20-M-FW-B5-60)
with the proportional valve indicated above.

However, my valve doesn't ever seem to shift.I am suppling +24vdc to pin A and common to pin B.

Also have a +- 10 v signal on Pins D and E from a 1771 ofe analog output card. I have all my voltages at the valve connector but never receive any change from the valve.

The valve has onboard electronics so I have not installed any amplifier.

Am I missing something obvious?

Does Pin C require a reference to ground?

I'd appreciate any feedback.

 

[bernie_carlton]

It appears that the pair C-F is for monitoring only.

 

[dlmidget]

Thanks Bernie, that i how I interpreted the data sheet also. However, I was beginning to have my doubts. I know that some models use pin C as an enable and therefore thought there may be something to it. I had to put everything back to prepare for startup. I am hoping to rig up a test of some sort so I will know what I have next weekend.

How usefull is the lvdt feedback. If I put out +10 volts and get +10v from the feedback does that mean the spool move? I did not wire these pins to my connector and now wishing I did.

The original valve was ported side valve
left right
A
P T
B

proportional valve left right
B
T P
A

I swapped the pressure and Tank lines on the manifold but to no avail.
With original plumbing had pressure on all lines. With P and T swapped only pressure on P and T. Regardless of signal output.

 

[Peter Nachtwey]

This is a little off topic but very important.

Did you really want a non-linear valve? It will make speed control difficult unless you are doing it open loop.

 

[dlmidget]

Maybe I should start at the beginning. Currently we have a set of chains controlled by a hyd motor.
The only speed control is a manual flow control. I have altered the program but need to be able to adjust the speed to follow a set of chains ahead \ fill gaps. I was hoping to find a simple way to acheive this QUICKLY!
In order to validate that I could dop it this way I used a valve that was on site. (My first choice was not in stock)
Actually need a valve that is blocks all ports when fails.
I iniatially was looking a flow control I could screw in the manifold and control electronically.
As we have been using one set speed, there is room for error. However, with accuracy comes potential to do more.

 

[Peter Nachtwey]

OK, that explains lots. You want a closed center valve that is linear once in the active section. That would block the float when the control signal is close to 0. You just have to remember that closed center valves are not linear until the control signal is outside the dead band.

A closed center valve will close the A and B ports to the motor when centered. These valves are TERRIBLE when used for position control but work OK for velocity control as long as you only need to go in one direction which sounds like your case. If you look at the pdf file you posted you can see that this valve does have a fourth power fail position but you should have the C1 option. The C4 may work but I am not familiar with Bosch's C4 symbol. Perhaps Norm can help here as his company sells Bosch valves.

The valve you are using is very non-linear. The reason I point this out is that my customers run into this problem all the time and it winds my integrator up tight and I go ballistic when I see the Bosch distributor or Bosch sell non-linear valves to unsuspecting customers that should have linear valves.

This is one of my biggest pet peeves. You should return the valve unless you really do need a non-linear valve or specified this valve.

As far as your original problem goes this should be a no brainer. It works or it doesn't. You can verify the spool position from the feed back signal. If the LVDT voltage doesn't roughly match your control signal there is something wrong with the valve.

 

[dlmidget]

The valve I have cam e with a secondary block. Therfore it had the small cable connecting the valve to the secondary solenoid position transducer. Usually without the secondary block there is a small cap to cover the terminals. I do not have this cap currently and just put a blank plug on it. Im wondering if there is some connection that must be made, as in a jumper, in order for the vale to work.

I have the valve set up on my bench with 24v dc across pins A and B and a 4v signal across D and E.

Feed back signal is -12.45v. Regardless of signal. The valve is not pulling any current from the supply.