644xG Air Assist Wind Pin always energized

[Christopher White]

We have an 80W Chinese Red Laser running on a Ruida 6442G. I have made the following mods so far:
- All three axes motorized
- Cloudray Auto focus mod
- Door protection switch installed (didn't come with it, I added one)

I have been installing Russ' Ultimate Air Assist mod on this machine. I've spent the past week on it. Everything is wired and connected. I still need to mount the solenoids to the machine but that comes last. Unfortunately the wind pin has decided to be my main problem for this adventure. What I am seeing is that the air assist pneumatic relay is always energized when laser is running regardless of whether I have set Air Assist on or off for my cut. I have tried this in both RDWorks and Lightburn with the same results.

30 years ago, in a former life, I was an electronics technician in the Navy, I just didn't stick with it afterwards and lost most of it. I am able to do basic troubleshooting and can understand most of the symbols. Most importantly I know which direction things should be pointing . I have checked that the installation matches the wiring diagram and I as far as I can tell it is correct. I have watched Russ' videos and have read all of the previous posts about this that I could find. I have noted the recommendations in those posts before posting myself.

Here is what I know:
- Air Assist is enabled in Machine Settings/Vendor Settings
- The air pump turns on and off correctly with the switch when the laser is not running
- When the laser is running the switch can be in either position and the air pump turns on to allow the pneumatic value or its bypass to maintain air pressure at the nozzle
- There are no stuck relays. Both the pump power relay and the pneumatic solenoid work correctly when energized and not.

Given all of this info, any suggestions as to what I am missing or can try would be extremely helpful.

One other thing. I am not sure how the wind pin is supposed to work. If I want to see if the Wind pin is working correctly, do I measure across Wind and Ground or Wind and +24V or something else?

If I am measuring correctly what should I see with the following:

Code: Select all

                  Air Assist Cut Option
______________________________________
|                  |   On   |  Off   |
--------------------------------------
|Panel Switch On   | +? VDC | +? VDC |               
|Panel Switch Off  | +? VDC | +? VDC |
______________________________________

Thanks in advance,

Chris White
Creatorpult 3D Manufacturing

[Gene Uselman]

The wind terminal supplies a ground- so from 24V+ to wind should trigger your solinoid.

[Mike Tuppen]

Beware of how much current you sink into the wind pin. It is a very small MOSFET driver pulling the line down. I managed to destroy the mosfet with my relay. reasonably easy to replace the blown device with a more capable one. But it was annoying!

[Gene Uselman]

Thanks Mike- any guess how much current is too much? And a short tutorial on how [and with what] to replace or wire around the blown mosfet would be very interesting. Gene

[Christopher White]

Thanks for the help. I am not certain the wind pin mosfet being blown is my issue but I guess it depends on how that affects the system. Does the pin fail short, open or floating (my guess would be open but I'm no expert as I mentioned)? Right now the wind pin is always negative(shorted?), and the solenoid is always energized, so the air assist is always on whenever the laser is running (in other words the only thing controlling the air assist at the moment is the status pin). I am considering the possibility that the controller has been defective all along and that we just didn't know until we tried hooking up the air assist.

Thanks,

Chris

[Gene Uselman]

Trouble shooting these infernal [ ] machines can be trying. Generally 6442 contollers are pretty stable in my experience but anything is possible. I do know that the 6445 had bad firmware for a while that did not enable the wind terminal and that controller has been out for... a couple years? In the meantime, I have two addl switches on my control panel, one turns the high air assist on [if it's off] and one turns it off [if it is on] that I found very useful when my controller was giving me a rash.

[Mike Tuppen]

Sorry, I thought I had photos of the modification/repair I made to the controller board. I cannot find them now, and it was only a few weeks after I got the machine that I killed the driver - some time ago! and I used a surface mount logic level MOSFET device that i had lying around.

Something else was that you need to provide:
Back emf protection for the solenoid coil to prevent the high voltage generated when the drive is switched off damaging the driver (still true with new device I fitted) This is a diode rating 1Amp or more with voltage rating greater than the supply the cathode + end usually marked with a bar on the diode goes to the positive supply to the coil the other end goes to the drive/coil.

When the driver device is damaged it can go short circuit or open circuit depending on the power of the damaging fault and on the way the cookie crumbles.

[David Lock]

Thanks for the help. I am not certain the wind pin mosfet being blown is my issue but I guess it depends on how that affects the system. Does the pin fail short, open or floating (my guess would be open but I'm no expert as I mentioned)? Right now the wind pin is always negative(shorted?), and the solenoid is always energized, so the air assist is always on whenever the laser is running (in other words the only thing controlling the air assist at the moment is the status pin). I am considering the possibility that the controller has been defective all along and that we just didn't know until we tried hooking up the air assist.

Thanks,

Chris

Hi Chris

Did you come to a conclusion on this issue?

I had the same issue with the Cloudray supplied Ultimate Air Assist and can tell you they supply, even now, the wrong flow control valve for the bypass with it resulting in full air assist regardless of the solenoid being switched. This may give the impression the solenoid is always energised.

The flow control supplied valve has a built in check valve to for controlled flow in one direction and full flow in the opposite direction.
The adjusting head on the supplied valve has a 'B' marked on it (meters out) whereas it should be marked 'A' (meters in). The result is that the adjustable amount of low volume air that bypasses when the solenoid is off is always full flow.

I had been in touch with Cloudray about this but they said they couldn't get the other valve and continue to supply the wrong one. I even sent them the Airtac data sheets for the valve but they were not really interested to correct it.

I replaced mine with https://www.ebay.co.uk/itm/111255306658 ... 0267020030 which controls flow in both directions.

[Jeffrey Aley]

One other thing. I am not sure how the wind pin is supposed to work. If I want to see if the Wind pin is working correctly, do I measure across Wind and Ground or Wind and +24V or something else?

The Wind pin is an "open-collector" output (Google it). Therefore, when Wind is turned on, the pin is connected to ground; when it is off, it is floating (high impedance). If you want to measure it with a voltmeter, you'll need to use a pull-up resistor -- voltmeters can't tell the difference between GND and high impedance (an open circuit). You could use an ohmmeter, but I prefer to use a voltmeter and a pull-up to Vcc (+12V in this case). How big a pull-up resistor? Doesn't really matter; a few K ohms is fine.

[Jeffrey Aley]

This is a diode rating 1Amp or more with voltage rating greater than the supply the cathode + end usually marked with a bar on the diode goes to the positive supply to the coil the other end goes to the drive/coil.

Umm, there's some confusion here.

The anode is the + (positive) connection on any diode.
The cathode is the - (negative) connection on any diode.
The cathode is the end indicated with a stripe on the diode.
Positive current flows from the anode to the cathode.

Now here's the tricky bit: when using a diode as a "snubber" to suppress kickback from a coil (as in this case), the diode is to be connected BACKWARDS. In other words, the anode to the GND or negative portion of the circuit, and the cathode to the +12V or supply portion of the circuit. In normal operation, you want the diode to be "reverse biased" so that it does not conduct current (and does not simply bypass the solenoid coil). When power is removed (i.e. you try to shut off the solenoid), the coil will try to produce a huge voltage to try to keep the current flowing*. The reverse biased diode will prevent this by giving the current a place to flow.

So the way Mike told you to connect the diode is absolutely correct, but the terminology was confusing.


* This is how the spark coil in an old automobile works - they don't have (or want) snubber diodes.