View Full Version : +5V TTL Signal

12-08-2007, 12:26 PM
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.

John S
12-08-2007, 01:29 PM
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.

12-08-2007, 02:46 PM
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.