[kolias]

Looking inside my PC (DELL Optiplex GX280) all wiring is nicely organized and nothing is spare. From the PS there are only two groups of wires coming out. One contains about 20-24 wires and the other 4 and they both connect to the motherboard.

Alternatives are: there is a male DB9 outlet at the back of the PC (perhaps a serial port?). Also I could buy a USB cord and splice it assuming that the USB is 5VDC, or I can buy an AC adaptor with 5VDC out and splice one end to get the 5VDC

The AC adaptor sounds the best and easiest for me. My local store has a bin full of them around $2-5 each but don’t know if I could get exactly 5VDC. Is there an acceptable range like between 3 to 7VDC or it has to be exactly 5VDC?

[Al_The_Man]

The Dell must have the standard 4 pin that plugs into the H.D.? If so you can get a 2 way splitter from your local computer store, this gives you a spare +12 com-com +5v four wire power, red and blk are the com and +5v.
You can also source from the USB, if you use a Wall Wart make it 5v.
Get the regulated type, NOT unregulated.
Al.

[kolias]

Now I remember about the 2 way splitters, I searched my junk and have tons of them but none is the same 4 pin that plugs into the HD or DVD. But I found a USB cable I had from an old printer. I cut the end for the printer and I can see that it’s a shielded cable with Black, Red, White and Green wires inside.

Would this do the job?

If yes, how do I wire it between the G540 Input 4, the USB cable, the touch plate / alligator and the resistor?

[Al_The_Man]

As the +5v source is coming from your PC, and if you are going directly into the P.P. input pin 4, then all you need is the +5vdc source conductor (Red?) pin, the connection between the +5v to the 10k resistor and then to pin 4 is shown in the Cockrum print you posted.
Also a wire from the P.P. pin 4 goes to the insulated plate.
Al.

[kolias]

To be on the safe side, like the attached pic?

[Al_The_Man]

Yep, that's it.
Al.

[kolias]

Thank you Al

[kolias]

Sorry Al, if the store doesn't have 10K resistors, is there an acceptable range or it has to be 10K exactly?

[Al_The_Man]

Not that critical, 5k to 15k will do it.
Al.

[kolias]

Thanks Al, They had the 10K resistor but there is something I dont understand

The G540 Inputs 1 to 4 are for Limit switches etc. and I have connected all my Limits to Inputs 1 to 3 and kept Input 4 for the touch plate. Now each switch has the red / black wire and they work which to me it means the these inputs must have their own power supply (perhaps 5 or 10VDC and perhaps with an internal resistor?)

So why on my touch plate I have to provide 5VDC power and the resistor?

To me the touch plate is like a limit switch

[Al_The_Man]

I assume the G540 passes the inputs directly through to the P.P.?
But you could take a resistance reading from the input to the 5v and if it is in the 100k+ ohm range then you need a pull up, if it measures around 5k to 15-20k then you should be able to omit it.
Measure the resistance with the P.C. power off.
Al.

[john-100]

Hi Nicolas,

Good to see your making progress

its been a while since my last post but
the laptop I used to connect to the web needs the faulty main board replacing and its taken longer than expected to get this old PC to work correctly - compatability issues with the security software and some of the old software on this machine :drowning:

the four G540 inputs have optoisolators , the anodes connect to a +12V via a 2K2 resistor , the cathode is connected to the input terminal 1 , 2 ,3 or 4

when a G540 input is grounded to the common / 0V terminal 12
the opto isolators transistor grounds a printer port input pin 10 , 11 12 or 13 to the printerport ground pins 18 to 25

look at this thread -

http://www.cnczone.com/forums/open_s...e_easy-37.html

John

[kolias]

Yes the G540 passes the info to the PP because all limit switches are working with Mach.

As an example, with my multimeter set at 200 Ohms scale I measure between input 3 (where one of the limit switches is connected) and the ground on G540 and I get a reading of 1.3

Now I dont understand what you ask me to do but if I measure between the red wire from the USB (computer is off) to input 4 where the red from the touch plate is connected my meter shows 1 (no continuity). All is connected as per my last schematic and the touch plate and alligator clip are connected to allow continuity

Is this what you want?

[Al_The_Man]

Nickolas, essentially from what John is saying is that the diagram you got for your probe input is assuming an input direct into the P.P., but the G540 conditions it through the Opto before it gets to the P.P., so you don't need the resistor and 5v etc.
Al.

[kolias]

A bit confused here, so I just connect the red from the touch plate to input 4 and the black from the alligator clip to the G540 ground?

[john-100]

Hi Nicolas ,

this diagram may help



John

[Al_The_Man]

Yes, take a look at the G540 manual where is says (8) Inputs.
Oddly that the description for the type of input is not shown, at least in the PDF I have does not!
Al.

[kolias]

Thank you both and now back to work to get the touch plate to work

Glad to see you back John and sorry to hear about your laptop

[kolias]

Hi Al / John

I finally replaced the DB9 connectors with the 5A pin ones and on trial runs the machine works fine.

However I noticed that the VS Sherline motor runs smooth up to about 75% of the speed range but when I turn the VS control knob fully CW, the motor RPM seems is going up/dn. Not a lot but noticeable enough.

I wonder if you have any experience with this

[Al_The_Man]

I have never come across it but presumably the correct resistor is fitted, if so you could try slowly adjusting the IR trim pot, there is a procedure to do this in the manual.
Al.