G540 output pins not behaving

Running XP, Mach3, gecko G540.

So far, I've been successful at assembling my 4x4 CNC machine and getting it to run while connected to my Dremel tool which is manually switched on by me before running the gcode through Mach3:

CNC: dremel and plastic. - YouTube

I'm trying to trigger the Dremel (or whatever other tool I plan on running) with the output on the G540, but I'm having a heck of a time. Here is what I've confirmed:

1. Mach3 is set up correctly: I am seeing 3.3v at the parallel port at pin #17 on the computer when I toggle the spindle control in Mach3.
2. The parallel cable is good: I see just under 3.3v at the other end of the parallel cable on pin #17.
3. My understanding of the how the output pin grounds out when activated is good, and I have wired up my test relay correctly: V48+ on one end of the coil, and output pin #5 on the other.
4. The relay itself is good: I've connected one end of the coil to V48+ and the other to V48-, and the relay kicks over just fine.


Anybody familiar enough with the g540 to give me a rundown on why my relay isn't kicking over as expected? What else can I test to trace down the problem? Do I need more than 3.3v at pin #17? When I get home, I can try running a 5v power supply to it to see if it activates output pin #5, but in the meanwhile, is there anything else I might be overlooking?

Thanks in advance!

Have you verified that ground is present at the output terminal of the g540.
Are you using a 48v relay?

If ground is there, then it should work. If you are using a 12v relay it has probably smoked the transistor inside the g540. It happened to me once. I don't know why I thought i could run a 12v relay on 48v. I never stopped to think about it I guess.

I assume you use the same power supply for the g540 and the relay. If not you need to connect the grounds together.

alan_3301 - I am using the same power supply for the G540 and the relay.

When you ask if I've verified that ground is present at the output terminal of the G540, I'm a little confused. I'm under the impression that the output terminal switched TO ground when it's activated by pin #17 on the parallel port. When it's not activated, it's *not* connected to ground, right? Otherwise, you'd end up with a continuous V48 through the relay (V48+ on one side, output pin on the other).

As for 12v relay... I did start that way, but nothing happened. I've been testing without a relay (just using my volt meter) to see voltage pass between V48+ and the output terminal.

Further testing:

I'm getting 12.25k ohms between terminal 12 and the output terminal... and when I toggle the spindle switch in Mach3, it goes from 12.25k ohms to 12.97k ohms. Sounds like a problem w/ the G540...

Correction. I'm getting resistance between output terminal and POSITIVE, but nothing between output terminal and ground. Sigh. Still trying to piece it all together...

Further testing:

Running ohm-meter between GROUND and terminal 5 gives no reading, toggle on or off on Mach3. However, when I turn off the power supply *and unplug it,* after about 30 seconds, I end up with resistance that starts around 30 m-ohms, and it slowly decreases.

Sorry, yeah I meant checking for ground when the output is activated.
I'd probably just stay on voltage measurement instead of worrying about resistance.
The g540 has 2 outputs, are you sure you are activating the correct one.
Try all your tests on the other output to see if it works or not. This would tell you if your problem is in the g540, or the computer.

If your step and direction is working I would assume 3.3v is fine for triggering the output relays also, but it shouldn't hurt to give that pin 5v to see if that makes a difference.
Do you have a p-port breakout board to easily do that? It seems like a large change to short things out or do damage trying to sneak 5v into a single pin while everything is attached/assembled.

To clarify about what I said about 12v relays. It shouldn't do immediate damage, I actually used the 12v relay for weeks before it finally melted the relay coil, shorting it out. That is when it smoked the g540.

Yeah - step/direction are working, and I read up on the g540, and it takes 3.3v to 5v, so that shouldn't be the problem. I'll throw 5v at it and see what happens. I don't have a breakout handy for the p-port, but my office is right next to a Radio Shack, so that shouldn't be too difficult to throw together.

The only reason I was checking resistance is because the support folks at Gecko said to check between my output and ground. Because the output is supposed to dump to ground when triggered, resistance should drop to almost nothing when the signal from p-port #17 is activated. And... that isn't happening. In fact, the only time resistance drops is when I've unplugged the G540 and let my ohm-reader slowly drain the machine, and after 30 seconds or so, I see high resistance slowly drain down.

Unless somebody has another solution, I'm going to send the G540 back and see if they can fix/replace it for me. It's still under a 1-year warranty, and their service folks are very helpful. A++.

But... I'd rather have it working than have to send it back. I want to play with it! :P

Activate Output2 in Mach 3 (pin 1 on D25) then toggle the active low setting (still in Mach3) and see if pin 6 on G540 goes to ground.
That will confirm if only output 1 has a problem...?

Ok. I decided to manually apply 3.3v with an outside powersource to the gecko and... it kicked over the relay as it should. So that's exciting - I don't have to send my gecko board back, as it clearly is working properly.

So I went back to my parallel cable see what was going on, and apparently I was incorrect in my original post. I stated there that I was seeing 3.3v at pin #17... and in fact, that is not the case. I'm seeing 3.3v at EVERY PIN (from 1-16), but .004v at pin #17. And toggling the spindle control in Mach3 doesn't appear to change anything.

My brain hurts. I can't figure this out.

Ok. Uninstalled, reinstalled. Relay in the Gecko still kicks over when manually applying 3.3v to pin#17. Parallel port is throwing 3.3v at pin #17 when I toggle the spindle control in mach3. But the relay does not kick over when the parallel plug is plugged into the gecko.

Ok. I'm going to close this thread and start a new thread, because the problem is not the Gecko, and the thread title is no longer relevant.