+5V TTL Signal

Hi Guys
I`m trying to use the Spindle commands M3 (ON) and M5 (OFF) in Mach3 to generate the TTL Signals to
open/close my micro-dispensing valve. Mach3 is set to use Port 1 Pin 16 and this connects to the s c r e w terminal
of my Xylotex 4 Axis Board.

Now my problem. Without the valve connected in any way I can issue a spindle ON command and measure 3.90 volts
between pin16 and GND on the s c r e w terminal, as soon as I connect this to my valve driver the voltage drops to 1.7v
I`m getting no signs of life on the valve.
How come I`m not measuring 5v with nothing else connected ?
and why is the voltage dropping to 1.7v

Would it be possible to use a 2nd port in Mach3 and maybe send the spindle signal out on the RS232 (COM1 Port)
then at least it would be independant of the Xylotex Board.

Probably because your valve driver is needing too much current ?
What about taking pin 16 and putting it thru a small relay and then using a separate 5v volt supply to trigger the valve driver.
You only have 3.9 volts to start with so you probably only have a 3.5 volt mother board and not a 5 volt MB.

John S.

Hi John
Thanks for your reply.
That sounds like a good plan. So if I`m reading it right, Pin 16 gets the signal from Mach3 - tells the relay to release the 5v. When pin 16 drops the signal the 5v returns to zero ?

Please bear in mind I`m a complete dunce with electronics, I`ll need to be shown how to build the relay circuit.
any help would be very appreciated.

I want a dedicated PC for this project and have cobbled together an oldish system
AMD Athlon XP 1800+
1.53 GHz
640 RAM

On the Xylotex there is 5v available on the small connector where I have stuck the Limit Switches Common wires. It`s marked VCC is there anyway I could tap into that ? ?

EDIT :: 3 mins later
I have just turned on the system and physically touched the TTL signal wire for the valve onto the VCC 5v on the xylotex
and yep the valve looks like it`s working.