pwm control of a hydraulic valve

RD

Hello,

I'm trying to use a stamp to control a proportional·hydraulic valve on a boom lift.

This valve, if I understand it correctly, uses a pwm 'pulse' to excite a coil, or keep it exited, while delivering a range of current.

So anyway, since I can make a stamp blink an LED, I thought I would delve into this valve control project.

The new controls are around a thousand quatloons, and Captain Kirk's too old and busy to bet.

So, I have to make do!

If anyone has any tips before I begin, much obliged.·

But either way, once I figure this out, you're all going to know it too.

Grassy ***.
·

Amaral

since you valve may work with single pulse width modulation and Basic Stamp PWM command works in different way (propely for driving voltage levels ) would be better to use PULSOUT command.

I would try a single loop program with Pulsout and a pause on it, then varying the pulsout, then varying the pause to check how your valve will respond. Normally Proportional valves works with PWM straight , and they are fast response valves.

hope to help !

Amaral


Just one thing , I´m Brazilian and I don´t know what´s a boom lift ! (never heard this is it something for lifting babys ?)

agfa

Hey Grassy ***!

I like the name.· It's kind of grassy and kind of assy.· But anyway.

Your asking about a valve on a boom lift.· The boom lifts I'm familiar with don't use pwm to control the valves the valves are off or on and are direction dependent.· Could you be more specific about the lift and the valves involved?

Not sure about the babys, but I do have 500 quatloons I could donate to the project.

Good luck, all the best, let us know what you do to resolve.

Philip Gamblin

The Stamp PWM command is good for small dc motors and stuff, but probably not the valve in question. I tried something similar and we used a PAK 5 http://www.awce.com/pak5.htm. (~$25) We needed our Stamp to do a bunch of other stuff besides drving the valve. Since the Stamp can only do one thing at a time, and it has to devote a bunch of time for controlling the valve, we used a PAK 5. With the PAK5, you use a serial interface to wite to the PAK 5 and it maintains the PWM freq and duty cycle til YOU write another value to it. BUT you still need an output interface (driver circuit) to the valve.

We did our work prior to the availability of HB25 http://www.parallax.com/detail.asp?product_id=29144 motor controller. The problem we had was not so much in the code, but in the interfacing the Stamp/Pak control outputs to the solenoid for the valve. The HB25 solves a lot of problems that you haven't even encountered yet. Yeah they're not cheap at $79.95/pair but consider the following. You drive the HB25 directly from the Stamp outputs, 6-16 VDC output voltage, 25 A output current continuous, 35 A surge, it only uses a single Stamp pin and and requires only a single pulse to drive it. Additionally, if you don't smoke it you can use it on other projects instead of having to create another one off circuit to dive something else.

Had the HB25 been available, I'd have spent more time working on the code and less time replacing burned out mosfets. Sounds like a great project.
Good Luck.

RD

agfa

There are generally two versions of boom lifts.· Those with on/off type controls, and those with proportional controls.· You are familiar with the first only, apparently...

The proportional control type machines use a PWM system to control the hydraulic valves which supply a proportional hydraulic force to the controls.· In essence, the proportional control valves are variable speed controls that are generally much more smoother.· And much less terrifying when you are many feet up in the air.

If I understand the PWM, pulse width modulation, type of controls that control the proportional hydraulic valves, they are basically current supplying devices that supply a range of current to the valve coils to move the valve a certain distance, so that a certain amount of hydraulic pressure can be applied to the particular cylinder.· And the pulse modulation is supplied to the valve coil so that the valve coil will be more responsive.· More responsive than the 'simple' on/off type valve systems.

Grassy ***, which is crude for the spanish Grascias`

So anyway, I hope to use a stamp and perhaps some sort of transistor or amplifier circuit to produce the PWM signal that will drive the valves appropriately.

agfa

RD,

You are correct, Grassy *** is crude.· You are also correct, I'm not familiar with pwm controled valves.

Why are you wanting to use another system to control the valve (valves)?· Is there a problem with the exixting system?· Are you converting to pwm.· There is a mention of hb25's. sounds like a reasonable substitute, have you explored that as an option?· I understand that funds·can be·a factor, is that why you are wanting to change the control to a stamp?

Just curious.· Good luck.