Easy question about 5V output

[Grobich]

Hi,

I'm hooking up my first CNC machine with Mach 3 and I was wondering if it was possible to get a constant 5V output from one of the parallel port pins.  I would use this 5V as supply voltage for my limit switches (max supply current (8 ma). My limit switches are similar to those on page 37 of this manual :

http://www.dovermotion.com/downloads/knowledgecenter/DPS_MCH.pdf

G

[Hood]

I would either take a wire from one of the molex connections for a hard drive or if you dont want to go into the computer get a USB cable and chop one end off to bare the wires, red is 5v black 0v (or they should be) then you can just plug into any spare USB to get your power.

Hood

[Tweakie.CNC]

Hi G,

It is really not a good idea to use the parallel port as you suggest. Either take the 5 Volts from the PC as Hood suggests or use a voltage regulator to get 5 Volts from your stepper driver supply.


Tweakie.

[rrc1962]

Or just use small 5V power supply.  I think I paid $14 for the last one.

[DaOne]

USB is the best for this as it will most likely regulated to 500ma output. It will also have low ripple and the same ground return as the PP. This will help with noise as well as preventing problems if you pull too much current due to a short. The PP can be used if the input is pulled high. Most ports are this way. Use ground as the loop return and wire it so when a switch is pressed the contact is broken. This allows for multiple switches on the same input as well as an error if you have a broken wire. I would recommend using shielded wire to your switch as 5 volts requires a low noise floor. Another tip... Set your "Debounce" level to around 10 to start with under "General Config". This will help with noise by sampling out false signals as well as a bouncy switch issue.