driver for hydraulic valve

Hi, all.
Right now I’m doing a project in which I need to control 8 bi-directional hydraulic valves from Parker.
But the controller + software suggested from Parker would cost us more than $3000. So I’m look for a cheaper solution to solve the problem.

Those solenoid valves can take current input. Maximum current of 500mA is needed to control them.
So any suggestion for the current driver?
It would be good if the current driver can use PWM input or digital input like I2C or SPI so that I can control the driver with Arduino.
Also if the driver has the built-in feedback control for the current output, that would be awesome.

Btw, the driver doesn’t have to have 8 output channels. As long as the total price is not way too high, it would be acceptable.

Thank you in advance.

The link to the valve. www.parker.com/literature/Hydraulic%20Valve%20Division/hydraulicvalve/Catalogs-Bulletins/Pulsar%20[misc%20bulletins]/Bul%20HY14-2101-B2%20VPL%20Prp%20Vlv.pdf

You don't mention the voltage and such used by the valves (AC or DC). The below page has some simple relay setups you might use depending on the action desired. Bottom is an h-bridge that might be used if the valves are fairly low voltage DC powered.

http://web.comporium.net/~shb/switch.htm

http://www.ebay.com/itm/Dual-H-Bridge-DC-Stepper-Motor-Drive-Controller-Board-Module-Arduino-L298N-236-/360666665494?pt=LH_DefaultDomain_2&hash=item53f9689216

Sorry for the missing information and thank you for your reply. The input voltage is 12V DC. As the time issue for me right now, I would prefer to get some products other than building it myself. I read the webpage in the second link. It seems to me that it's a driver for step motor. Can I get relatively constant current using such kind of driver? I don't know too much about dual H bridge DC stepper motor drive controller.

I don't think you want to drive the valves with PWM. How long do you normally want the valves to stay on or off? You would only want to send a signal and hold it until you want it to turn off. 12 volts and 500ma is not to heave. You may want to use SSR (solid state relay) for that. It is pretty easy to hook up. You want to use arduino to control when the valves turn on and off? Based on what?

Thank you for your reply. I think I do miss lots of key information in my previous posts. Sorry about that. Those valves are all proportional valves. Two of them control two hydraulic motors and the rest controls 6 cylinders.

The work of the driver is to output constant current so that I can control the rpm of the motors or the positions of the cylinders. The Arduino is used to generate the inputs for the drivers so that I could have proportional current outputs.

The model of the valves is Bul Hy14-2101-B2 VPL Prp Valve from Parker. The coil resistance is 28 ohms at 12VDC and 65 ohms at 24 VDC. The current draw is 430mA at 12VDC and 370mA at 24VDC.

Let me know if any more information is needed. Thank you for your help.

Sounds like what you want is a current controller (up to 24 volts). Sorry, I have no experience with that. Maybe someone else here has.
Also, it may be good to provide the URL to the specs on those valves.

Thank you anyway. I added the link to the valve now.

So, you want something pre-built but don't want to spend any (real) money on it.... How are we supposed to help?!

The valve's claim to be controlled using a "33 Hz" PWM signal. So I'd simply try generating a PWM signal, run it through a transistor to get the 12V and try it....

Well, I just don't want to spend way too much money like $1000 on the controller. I could still spend like $200 ~$500 on the drivers.

The 430mA current draw will sometimes cause problems like heating. As I have to drive the motors and the cylinders constantly, so I prefer a product other than building it myself so that I could get higher reliability. It would be best if the driver can have a built-in feedback output feature so that I can have more accurate outputs.

Maybe I can try PWM inputs for the valves using transistors. I think I can control the valves for a short time, but still I have some concern over its reliability during long term work.

suggested from Parker would cost us more than $3000

. Yea, over that is worth looking at.

Ok, we are now think it is not requiring a constant current source, but PWM. You need a reliable driver. Back to a SSR for DC.

Yeah, I think what you said is reasonable. Based on the manual, the PWM input should work.

In fact I attached the two terminals of a 12VDC battery directly to one of the inputs of the valve once, and the cylinder moved to its maximum distance immediately. I think the valve can be controlled both by PWM and current input.

The only concern over using SSR is that it may not have any feedback function. Of course I don't know too much about SSR, maybe some driver with SSR can have feedback function. I will consider using SSR for preliminary test. That's a good suggestion. Any recommendation for the SSR?

Thank you.

I don't understand what you mean by

feedback functions

What feedback do you expect? position?

I am thinking if your PWM is 30%, then the valve will be positioned at 30%. If your PWM is 60% then the valve will be positioned at 60%. It should act like a servo. A servo has feedback internally, it does not send any feedback to the device controlling it.

What wiring is on that valve? Does it have a ground, +12 volt, and a control wire?

I reconsider the concept of feedback function in valve control. It mainly comes from the feedback function for a current driver. Probably a constant current output is hard to maintain, that's the reason they added feedback function for the current driver. I thought the SSR should have one to maintain its output.

I think you are right. If I'm using the PWM input, the feedback would not be necessary. I should be able to get a relatively stable PWM output using SSR.

The whole valve is built by connecting several smaller pieces of valves in series. Each piece of the smaller valve has two input wires. The two input wires can control the movement of one actuator (cylinder or motor). As the manual doesn't list the detail of the wiring, I guess one wire should be the control wire which receives the control signal and the other one should be connected to the ground.

If there are only two wires, then one is probably ground, and the other for the + side of the coil (no control wire). So you will be driving the coil from the SSR (that's why it requires 1/2 amp I guess). Most SSR are rated well above that (10X). Be sure to get an SSR designed for DC output. They make both DC output and AC output, and they work differently (not interchangeable).

That makes sense. I will try to use SSRs to build my controller. Thank you so much for your help.

This is only 12V/430ma. All you need is a mosfet (two per valve); no reason for the expense of an SSR that I can see(?). I also have no idea why they'd specify a 33Hz PWM signal -- unless they're trying to demonstrate how low of a PWM can be used.

http://www.phtruck.com/download/hvd/catalogs/IndividualDCVCatalogs/ClosedCenter/PulsarValve_Catalogs.pdf

The doc shows that the valve starts to open at a PWM ratio above 40% (analogWrite() values over ~102) and linearly moves to full flow at full on.

I believe the OP is not wanting to learn how to solder mosfets, and resistors, he wants something pretty much pre built that has connectors that can easily connect to his valves. If he was looking to learn by experimenting with his hobby, I may have suggested mosfets. But he is trying to save part of $3000, so a few expensive SSR s, ($6 - $16) is a great savings, and is mostly pre-built, and reliable. Just my opinion.

I also have no idea why they'd specify a 33Hz PWM signal

I agree. That could be the slowest rate, I would not think it would be reliable much less than that. I suspect the 500hz range of arduino would be fine. If it is not, I think there is a way to change it, but I don't know it offhand.

Thank you all the replies.

I went through the manual again. The valve is kind of a digital device. "Being a truly digital device means the valve is either open or closed". So I think the PWM input directly controls the movement of the spool of the valve which makes orifice be either open or closed. Because of the PWM type movement of the spool, a certain amount of flow rate can be controlled. So 33Hz is reasonable considering the physical meaning behind the whole thing.

The tricky part for me right now is that I have 8 bi-directional valves. It means I will need 16 relays if I want to build the controller with relays. The Arduino Mega 2560 only has 15 PWM outputs on board.

I'm thinking maybe I have to use AMIS-39101, http://www.onsemi.com/pub_link/Collateral/AMIS-39101-D.PDF, which allows me to have 8 outputs at the same time. It would take me some time to solder everything up, but right now I think this would be a solution.

You say bidirectional. If it uses PWM, and you had the duty cycle at say,, 80%,, then you went down to 40%, wouldn't that make the valve reverse direction? If that is the case, that is how it is bidirectional. I don't know, just guessing. Do you have one that you can do tests with?