Hello guys, I try to use external relay with my PMDX-122 board to control a relay, the problem that I can't resolve it and need some help, it's like that,  when no power(5v) to board I see a little light on my external relay that I want to add it to be the second relay, when I turn on the power to the board automatically the relay energized without the pin 16 activate! So, how I can resolve this issue? I want the external relay energized just if I active the pin 16?
Thanks you in advance...

To test the relay board disconnect the wire on pin 16 and touch it to GND. If the relay turns on when the wire is on GND the input is active low, If the relay turns on when the wire is touched to +5V it's active high. Removing the blue jumper should reverse the polarity of the relay board inputs.

It's active low, if I change it to active high then the problem is when I start the mach3 the relay energized 1 second and then off, this is not ok and do not help me to use this second relay..

When you say "It's active low" do you mean the MACH setting?
Have you tried removing the jumper?

Yes Mach3 setting, if I remove the jumper, the relay do not work, just the main red ligh work, but the relay itself do not work

If when you say " just the main red ligh work" you mean the LED on the relay board? Is that LED lighting without the relay contacts changing?

Try the test I mentioned earlier both with the jumper on and jumper off. One way should active the relay with the pin 16 wire touched to GND and the other with the wire touched to +5V.

I understand you brother, and I tried what you said, but If I remove the jumper, the relay it's self do not work..
The best way is to make pin16 active high, and then the external relay work very good with Mach3, the one problem is that when I enter or start Mach3 the external relay work 0.5-1.0 second and return to it's situation, but this is not ok for me and dangerous and not useful if the relay energized before start the starting the work on the machine..

I would try the other relay on the board. It should be possible to reverse the input polarity so the Mach3 output can be set to work safely. A different relay board may be needed.