G540 - blown inputs?

[madtownrob]

HELP! I am out of solutions right now other than to send it back!

Background:

I currently have the machine setup with the following limits/homes

Pin 1 on G540 X+/-home, Y+/-Home, Z+ Home
Pin 2 on G540 A home
Pin 3 on G540 Probe

Machine is a Joes 4x4 with the Y/A slaved in mach3

I have always been able to use the refall home function to auto-square the gantry.

One of my G250's is an offspec one and I have had to run it in 1/2 pulse sherline mode from day one

Problem:

I was running a part file and hit the physical e-stop NC button when I detected a problem.

I wanted to re-home the machine to make sure I could go back to the job coordinates (g54) of the part I was running....

RESET Mach3, and went to jog closer to the home switches (takes a long time at 10% home speed when you are far away so I normally jog to within an inch or two) - noticed it was jogging very SLOW - looked in diagnostics and I was over-riding an activated limit on all axis. Tried to see if I had a stuck switch - nope - thought that's why it was jogging slow.

Trouble shooting:

Mach3 diagnostics - limits/homes lit as activated
NC switches in series - tested continuity with a meter from the first to the last - ok.

changed to a backup PC with the same configuration - No go
changed to the secondary parallel port on the back up - No go
changed to the backup parallel cable on the original machine and the backup PC (both ports) - no go

replaced the leads from pins1&2 to the limit switch termination point - no go

Disconnected the lead from Pin 1 to my switches - shorted it to ground (when I say gound I mean Pin 12 on the G540) - mach3 did not show any lights changing state in the diagnostic tab RAW PORT INPUT BIT ( 4 lights in a row lit up more or less centered in the row of lights)

Did the same for Pin 2 - no change in state, as above

Did the same for Pin 3 (probe) - light changed it's state

Connected a lead to Pin 4 - shorted to ground - light changed it's state


So having said all this - any ideas? Did I blow an opto on the G540 BOB?
I feel naked with the ability to refall home and limits right now. I guess I could eliminate the probe and move to Pins 3 and 4 - but this has me perplexed! Any help is appreciated!

[MarkA.]

I have the same type of thing happening. My X axis limit/home doesn't work. I am using a PMDX 132 BOB. The LED for the input switches fine but on the diagnostics page the status is stuck on. I purchased a new PMDX 132 BOB because I thought I had blown an opto but I get the same results with the new one. I tried a new parallel port cable, no luck. I have yet to try a different computer but I am hoping I didn't blow anything on the PC side.

did you find any solution?

[Tom Siler]

That's really wierd. I have been using an input pin for a zero position touch sensor since I built my machine last spring and mine quit working as well this past weekend.

It worked on Friday, I shut the machine down for the night, and it didn't work when I powered up Saturday.

I tested leads and continuity all the way back to the G540. Do the inputs on these things occasionally go bad?

I'm going to order another one just to have a spare... but I'm curious if I need to send the current one back.

[Action-KAT]

Hi Guys I know this is an old post but did anyone get the route of the problem to these blown inputs.

I looks like I have the same problem working one day
only to find it had stopped working the next day
nothing has changed on the setup just stopped
switches work fine but nothing from the G540

any ideas what to look for or test to see if anything has blown,
and the 6 million dollar question what did I do wrong

I would be grateful for any pointers to sort the problem

cheers

[Action-KAT]

Just an update

Have measured the voltage from the parallel port pins 1-13 got 4_volts
power supply is measuring +48VDC

when connected the parallel port to the G540 with Estop in place
flipped charge pump off & got green light
then measured pins 1 - 4 on the G540 measured 10volts

any idea if these readings are correct & any ideas why the input 1 to limit switches are not working any more

any pointers what else I need to check

cheers

[john_100]

Hi Action KAT

10 V at the G540's inputs is what I'd expect ,
as the input terminals are connected to +12v via a 2200 ohm resistor and the LED inside the optoisolator

with the G540 connected to the computer ,
have you checked the voltage between the printerport ground and the printerport pins 11 , 12 , 13 & 15

John

[Action-KAT]

Hi John thanks for the readings,

I have checked the printer cable coming out of a PCI buffer card which has a 5v power supply to it,
as I don't have an on-board parallel card so used a PCI card

the readings from the parallel cable before plugging into the G540 are 4v on the pins from 1 through to 13.

KAT

[john_100]

Hi KAT ,

I assume you have checked the printer cable is OK

unless the cable has molded plugs ,

can you check the voltage on pins 11, 12 ,13 & 15 with the G540 connected to the printer port


if you can't do this ,

you could connect pins 11, 12 , 13 & 15 to ground pins 18 to 25
and see if you can see the logic 0 on Mach 3's display

just to see if the problem is in G540 or the printer port


John

[Action-KAT]

Hi John

Sorry moulded cable mate what a bummer

not sure what you mean

"if you can't do this ,
you could connect pins 11, 12 , 13 & 15 to ground pins 18 to 25
and see if you can see the logic 0 on Mach 3's display"

are you saying power up the gecko with the printer cable attached but not plugged into the pc end ?
then connect a wire to pin 1 & a ground pin say 25 on the parallel cable,
if so what am I looking for or check what

cheers

[john_100]

Hi KAT ,

the grounding of the printer port pins 11 ,12 , 13 & 15 was to test the printer port without the G540 being connected


the transistors inside the G540's input opto isolators can only connect a printer port pins 11 , 12 , 13 or 15 to ground

mach 3 will see this as a logic 0 , (closed switch to ground)

when the transistor is switched off , the printer port pins are open circuit
and are at a logic 1

John

[Action-KAT]

Hi John appreciated the help.

To recap what to try next.

while running Mach3 without the G540 connected
insert say the red lead from my multimeter into pin 10 of the parallel cable connected to the pc only & the black into pin 25 ground,

this should not only give me a volt reading (which I get 4v)
but this should light something on the diagnostics page of mach3

Is this correct before I try it don't want to make things worse by miss understanding you

cheers Kat

[john_100]

Hi Kat ,

the original IBM printerport was built with TTL logic IC's

an input pin left open circuit was at logic 1
and a pin connected to ground ( pins 18 to 25) or at least no more than 0.8v
is logic 0

a closed limit switch or a good signal from the charge pump / fault detector circuit , results in the transistor inside an optoisolator connecting an input pin
(10 , 11 , 12 , 13 , 15 ) to ground

with a working port you should be able to see the logic level change in
Mach 3's display

you can use a 220 ohm resistor and a Red LED as a simple indicator to test the printer port outputs

John