Phantom limit switch warning

[Wolfrr]

Hi all,

been a while since i posted but having loads of fun with my machine and learning bobcad etc. I have been experiencing a problem though and wondered if any one could shed some light on it. I keep getting a limit switch hit warning coming up in the middle of my program, I have learnt to deal with it by setting run from here in mach3 and have pretty much tried everything I can think of to eliminate the problem ( set the moter currents lower, reduced the speed of the machine significantly, even changed the 1/8 pulse to 1/4 pulse.) But still having no luck. I don't think its emi as all wires except moter wires are shielded can anyone add some suggestions as to what the reason for this would be.

Thanks Andy

[rockcliff]

Hi Andy

with your switches set to Normally Closed, it could be a single switch not making perfect contact, for an instant, enough to trip the overtravel, it's very common, with the low voltage the parallel port has,

Did you try to increase the de-bounce time in Mach? which will delay any input signals, giving a non-contacting switch a little more time to recover, from a non-contact occurance

Also FYI: the motion part of the circuit is totally isolated from all the inputs and outputs, changing current, or microsteps will not have any affect on those inputs.

[Wolfrr]

Thanks Nick. I will give it a go today ,Ill probably need to check the manual to work out how though. What is strange though is that when i get the limmit switch warning none of the limit swith leds are lit on the settings page of mach 3 so I cant tell which one is causing the problem.
One more thing, can you tell me what the maximum safe voltage is that I can set the moters to on the driver board. my 425oz moters are rated at 5v currently I have set it at 2.6v but the manufacturer of the moters recomend that i set this higher to decrease lost steps and to increase speed. I am getting 600mm per min which is ok but would like to squeeze more out if at all possible.

Thanks Andy

[rockcliff]

Hi Andy

Click / Config / General Config / top right corner you will see de-bounce, try a 5 in each colum, I suspect one or more of your switches loose contact, for just a very small amount of time, then close again, but this is enough to trip an overtravel condition, setting the debounce for some delay should help, not the best solution, but might work, finding the bad switch would be best.

As for your speed, Can you provide your exact specs of the motors you have, eg. a Data sheet

Nick

[Wolfrr]

hi Nick , will be giving a go tomorrow, I have attached a pdf of the specs for my motors which are wired in series.

I was mucking about with the number of steps ( 1/8 1/4 ) settings on the driver board and mistakenly got it wrong on mach 3 motor tuning and my motors were running around really fast losing a few steps here and there but still travelling quite well, which makes me wonder whether or not I can get more speed from the machine.

Cheers Andy

[Wolfrr]

Hi Nick,

I set the de bounce today and cut a couple of signs for people with no stopping in between so thanks for you advice it seems to have worked and I will be changing and altering limit switches soon . I also set the step rate to 1/2 and this seems to have given me a little more speed ( 700mm/min ) which is great but wondered if you had time to check the data sheet on my motors yet to see if the settings I use are ok or if you could give me advice on what settings I should be using.

Thanks Andy

[rockcliff]

Hi
the wiring of your motors for series is good, which would have current rating of 2.1A this should relate to a voltage current setting on your board at around 3v

It's imposible to determine the exact speed you can do, every machine and setup are different, trials have to be made, if 1/2 steps works better then that's what you should use, the main point is Repeatability, and much more important, find a safe speed that repeats, and leave it.

[ASC]

I had a similar issue with phantom limit switches going off, even with 500 + us debounce time, and I finally deduced that the large size of my machine meant the limit switch wiring was picking up noise. I used an optoisolator circuit to trigger the limit switch reading to the board while keeping all signals inside my control box. No more phantom signals, woo! I ended up doing the same for my home and e-stop signal wires as well. Now I have debounce set to 10 and have yet to have an issue.