Random arc signal lost

The only difference is adding the option for arc ok, everything else stays the same. What is so complex about that?

phillc54 wrote:

The only difference is adding the option for arc ok, everything else stays the same. What is so complex about that?

I feel like Rod might be being intentionally obtuse, or he didn't actually read it, since you defaulted the new Arc OK debounce (on a separate control thread) to 0, which I think effectively just enables users with an easier means to solve any problem that arises.

I did wonder why you added a debounce of 0 and recommend leaving it at 0 though, that seems a bit counter intuitive. If it's because of the recent protest of one user who's never seen switch bounce on mechanical contacts ever, I'm not sure that's the best idea. I think defaulting it to a value that actually debounces it, even if it's really small (say 3) would give the new users it affects (who generally don't understand all of this stuff) the highest probability for success "out of the box". I maintain that even 5ms wouldn't change their pierce quality by any appreciable amount.

My other $0.02 is that there is a mention of one servo thread cycle and how that translates to Z motion, but it doesnt give an example for the timing as a whole. Maybe consider adding to the effect of:

each increment changes the debounce timing by one servo thread cycle. For example, using a servo period of 1000000 (measured in nano seconds) and a debounce value of 6 would translate to a 6000000ns debounce, or 6ms. This equates to a 0.001mm (0.00004") increase in the probed height result when applied to probing inputs.

I think that ohmic sensing via THCAD is a special use case, and any user wishing to do that could follow the multiple examples here which instruct them to comment out the debounce on the ohmic probe input.

Lastly I like that you explain how to add more debounces without the need to reference the linuxcnc debounce manual, which can be a bit cumbersome to read for new users.

The reason I left the default at zero for Arc OK it that this issue doesn't seem to occur very often. Although I do agree that a few mS of extra pierce time is not going to cause much of an issue, we are only using air plasma after all. It may be a different kettle of fish if it was high definition plasma but that is not what PlasmaC is aimed at. Maybe I will make it 2 or three, I'll see if there are any more responses.

If the debounce was 6 then it would actually be 0.006mm ( 0.00024")

The reasoning behind the additional info in the docs about debounce was because it is one of the few components that cannot be loaded multiple times. I didn't really think I would get shot down for that, plus it has been in the docs for a long time.

phillc54 wrote:

The reason I left the default at zero for Arc OK it that this issue doesn't seem to occur very often. Although I do agree that a few mS of extra pierce time is not going to cause much of an issue, we are only using air plasma after all. It may be a different kettle of fish if it was high definition plasma but that is not what PlasmaC is aimed at. Maybe I will make it 2 or three, I'll see if there are any more responses.

You get a value of 2-3 vote from myself (and I'm sure Cody as well). Seemed like Tommy was for it as well.

If the debounce was 6 then it would actually be 0.006mm ( 0.00024")

Oh, right was before my first cup

The reasoning behind the additional info in the docs about debounce was because it is one of the few components that cannot be loaded multiple times. I didn't really think I would get shot down for that, plus it has been in the docs for a long time.

I'm for it being there, it's definitely a better explanation than what is in the standard debounce manual. I feel like everyone who builds a table should understand what switch bounce is, and what those numbers represent/how to modify them.

Finished up my Saturday "have to's" so I'm going to go play, which involves the table, some welding, and maybe taking the Hypertherm apart to see what's up with the relay there... just for fun

As promised, I took the Hypertherm apart to see if there is any sort of hardware debounce.

Dry Contact Relay:




Circuit (traces marked in red to make it easier to see due to the board coating):




The traces on the left hand side go directly to a connection for a set of wires that go to the CPC port. There is no hardware debounce (RC style or otherwise).

At any rate, just wanted to confirm that the it wasn't "dry contact relay" with some hardware bounce filtering they failed to mention.

Also it took far longer than I care to admit with a mirror and a flashlight to get the part number from the relay. The specs for the relay (TE T77S1D10-24) did mention a min. recommended contact load of 100mA at 5VDC. Further investigation showed that manufactures recommend that spec for contact wetting to break through oxide layers and "clean the contacts" to keep the resistance as low as possible. Several sites said that when contacts fail due to this condition, they usually just plain don't work. At any rate, I think Rod and I are describing two different problems, and their solutions.

I’d think the same 100mA would apply, the reading I did suggested they pick a standard amperage value. So for 24V I’d need a 240ohm resistor... somewhere... to make the same 100mA draw. I do know my board is rated at 800mA max (7i76). I planned to measure the current amperage draw tomorrow out of curiosity.

I’m sure oxide does form, just not sure how much of an issue it is. If Jim Colt has advised these same relays have been used for years and years, again, you’d think the manual would bring it up so they didn’t see as many field issues.