5V TTL Signal ? and My limit switch solution.

[Joey]

I have the 4 Axis Driver Board and am trying to figure out how to use a pin signal via Mach3 to start/stop a Dispensing Valve Driver.
What I`ve done in Mach3 is set pin 16 as an output pin for Spindle on/off commands. I`d like to use M3 (spindle on) and M5 (spindle off) commands within my Gcode to run the valve.
Unfortunately I am only measuring 3.90 volts between pin 16 and ground which is not enough to kick start the valve.

If I physically touch the valve wire onto the VCC Connector on the board it gets the 5v signal and the valve works fine. So I`m happy that all my valve wiring is correct, I just need to somehow get the full 5v signal.
Any advice to overcome my problem would be greatly appreciated.

I`ve attached a pic of my circuit.
You`ll see I`ve used a 10k Ohm SIP Resistor soldered onto the Xylotex for my limit switches which works well. The Limit switches are also doubling for machine home switches working on X- Y- and Z+.
This concept has been taken from the fab@home setup.

[NC Cams]

Use an open collector transistor to drive the device.

Pull it up to 5v with a pull up - pull it down with either an open collector TTL inverting or non invetring buffer IC of appropriate logic or an appropriately sized transitor or fet in open collector mode.

Make sure the 5v and the open collector whatever all pull the signal down to the same "ground" potential.

[Joey]

Thanks for your reply NC Cams
I`ll try digest and research what you`ve told me.