G28 Home function doesn't work TCNC 4.01

[rustyolddo]

The G28 home function won't work. I've got my N/O home switches wired to 10,12,13 & Gnd. Set the ports to active low, "Home is Limit", Home SW 1-3 enabled. When I enter the G28 command, it sounds like the controller trys to move the motors, they kinda grunt but nothing happens. Also, when I'm running a program, it randomly stops due to a "limit error" yet no limit switch is activated. Using the port monitor, I can see the switches change states when manually activated.

In the jog mode, I can jog the axis by using the discrete mode but the continous mode doesn't work, it just kinda grunts. I think the two issues are related.

Any ideas?

[Bubba]

rustyolddo
I am sitting on my house machine and "THINK" my test file on the computer is set up the same as my unit in the shop, and I have my home switchs set active LO, BUT my switches are set NC!
What I would suggest is that you disable all but ONE axis and then play with the setting on that axis to get things to work. Then disable that one and do the next one etc. until all three are working. Then go back and enable all of them. It is hard to say which is going to be correct as each setup is different (breakout boards etc).
Also, I found out the hard way, IF you use combination home/limit, you disable the limt switch funtion in the config file. It will automatically handle limits if you set the function Home=Limit.
Hope this helps.

[rustyolddo]

rustyolddo
I am sitting on my house machine and "THINK" my test file on the computer is set up the same as my unit in the shop, and I have my home switchs set active LO, BUT my switches are set NC!.

Since mine are N/O, I'll try setting to active HI

Also, I found out the hard way, IF you use combination home/limit, you disable the limt switch funtion in the config file. It will automatically handle limits if you set the function Home=Limit.
Hope this helps.

Can't find any referece to a limit switch function in the .ini file, only homeislimit= Am I missing something or do I need to add something?
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[ger21]

Try homeislimit = yes, if it's set to no.

[rustyolddo]

(MDI using G28)

I set homeislimit=NO, that allowed the manual jog to function.

I set homeSW1 up, tried active high & active low. Made sure no other ports were enabled & using line 10

No luck. It just rocks a little and zeros the axis setting on the screen but the switch is not contacting anything. I tried enabling both the Limit & Home Sw on the same port, no homing action. But if I manually activate the switch, I'll get the "Limit sw activated " dialog on the screen. Tried playing with the home speed, reducing it, made no difference. Can't think of anything else to try. I'll post my .ini if that will help.

[Bubba]

rustyolddo
you have me at a loss now. you might want to post this information over on the yuhoo group for TCNC and let the pros have a go at it! They have been most helpful to me in times like this!

[rustyolddo]

Would the printer post setting STD vs EPP make a differenece? Gonna try that next.

[rustyolddo]

Problems: Intermittent program halt due to limit switch, no limit
switch activated. Home command G28 did not function, axis would rock
and reset to 0.00 but never jog into Home.

Software Port Monitor showed switches changing state whenever
manually activated indicating no problem.

Changed "Home is Limit", changed Active High/Low, Compared as
supplied .INI file with modified .INI file. Reloaded software. Set
sofware debounce time higher. Changed Computer Port type, Std, EPP,
ECP, deactivated all power management in CMOS setup, deactivated all
non essential features in BIO setup.

I'm using an old Pentium laptop to drive a HobbyCNC 4 axis board.
Alot of folks told me the laptop was no good because the port voltage
was too low. Indeed it was, the port voltage is around 3.3 volts or
so. So I tried a desktop system and I still had all the same
problems. Folks told me I needed a port breakout board to solve the
problem.

I'm using normally open switches for my home switches, folks told me
only normally closed switches would work. The switches I purchased
came from Digikey, they are watertight D2SW series and have a high
positional accuracy. Haven't measured it to see, but spec is around
0.4mm.

Finally had the old dim bulb go on. H-CNC board is chopper drive, &
stepper motors are obviously pulse drive. Noisy, trashy stuff. I
included my limit switch wires in the same cable with the motors. I
put my scope on the limit swith leads at the controller board and I
found 3 Vpp of noise on the switch lines. <Big Smack to the Forehead>
I put a .01 cap from the lines to ground and viola, noise was gone
and the home switchs worked as designed. I suspect shieled cable for
the home switches would be in order but I'd still use a cap across
any & all of the I/O lines to reduce the chance of a spike tripping
things. Hope this helps someone else.

--C

[anoel]

sounds like your rapid speed is set too high and your motors just simply poop out and can't keep up. slow your maximum speed down pretty low and then increase it gradually to find out what you maximum rapids are.

[rustyolddo]

sounds like your rapid speed is set too high and your motors just simply poop out and can't keep up. slow your maximum speed down pretty low and then increase it gradually to find out what you maximum rapids are.

I had solved that problem, but you are correct. Big issue was the Home switches.

[abasir]

...H-CNC board is chopper drive, &
stepper motors are obviously pulse drive. Noisy, trashy stuff. I
included my limit switch wires in the same cable with the motors. I
put my scope on the limit swith leads at the controller board and I
found 3 Vpp of noise on the switch lines...

Great news that your CNC is working now. As for the cause, I guess everyone assumed that you've adhere to CNC101... never bundle limit switches wires with the motor wires...