jmkasunich: I think you are right - eagle causes people to make crappy schematics.. Sure couldn't be me..
[01:23:16] <skunkworks> http://www.electronicsam.com/images/KandT/servostart/newschem.png
TL082 as a comparator?
op-amps make crappy comparators
hi skunkworks, jmkasunich
how was the trip?
is "cam" the right term for the thing that protrudes from the table in order to activate a switch at a certain point in travel?
ok, I wasn't sure and the wikipedia article on cams is all about their use to turn rotary into linear motion
or at least, that is one perfectly acceptable name for it (I'm sure there are others)
I really can't think of any other name at the moment.
I've jerry-rigged (that term's racist, right?) a limit switch on my machine, and wondered what anyone thought: http://emergent.unpy.net/files/sandbox/limit-switch-plan.jpg
skunkworks: if you replaced the AND gate with a NAND, you could use the remaining unused sections as inverters and reduce the total chip count
er, "gantry bridge" probably isn't the right term either .. the cam is on one of the "legs" of the gantry
jmkasunich: nah he needs to put a CPLD in there instead
so - lm392 would be better..
lm211 would be my choice (faster)
I was trying to decide if I was going to try to do 2 servo amps on 1 board...
the combination of round cam and angled switch leaf will lead to not-very-precise switching
with that - I have only 2 extra or gates.
the rest is used.
the "let the cam move past the switch" school makes sense for machines where the switch might get smashed
but for your machine, I bet you'd get better accuracy if you put the switch at end-of-travel and head right at it
jmkasunich: why not 2 diodes instead of a or?
I could easily mont it that way..
in fact I did that initially but I know it's the "wrong" way :-P
skunkworks: speaking of diode or... you could use the spare gates to combine the overcurrent trip signal and the enable signal
keep in mind that real comparators (as opposed to opamps) rarely have internal pullups
do you have a source of 4000 series chips (they're getting rare)
is everything operating on the unregulated(?) 15V supply? or is there a regulated supply I don't spot?
yeah, I noticed that too - 4000 series is the only thing that will run on high voltage
personally I'd make 5V for the logic side
there is a 15 volt 3 leg regulator.. But I don't remember why I picked that.. (it was all cmos)
the gate drive supply needs to be enough to fully turn on the fets
but 12V should be plenty for that
maybe I thought the low side of the of the driver ic only used...
I dunno what the upper limit of 4000 series is, but I bet 15V is close to the edge
I think it is 15v
I have to do a 'lot' of cleanup of the schematic
I didn't have problems getting cmos last time.. maybe I need to do some research.
jepler: love what you did with zenbot
cmos does have some advantages - large logic swings and slow propagation delays improve noise immunity, and relatively low output slew rates reduce crosstalk, etc
skunkworks: with the new table I can actually cut circuit boards now .. still working out the kinks, though, and I'm quickly tiring of the dremel
so next I'll blow a couple hundred dollars on a spindle/motor combination that chris found on ebay
did he like it?
I don't think he's actually used it yet
if he'll let me I'll borrow his before I buy one
heh - I know it got a few good reviews on cnczone
hmm, the video at http://www.youtube.com/watch?v=nzSjIV9tr3E
is not as impressive as the speaker thinks it is
looks like 3/4 of a thou
not bad really, but not super
I measure about 12 thou on my dremel using a similar test
so it's literally an order of magnitude bettre
hmm, in the longer vid he says he couldn't measure any runout even with a 0.0001 indicator
which was posted first?
I wonder if the runout in the first vid was actually machine flex?
I think the runout one, the long one is still playing
yeah, runout vid was oct, longer one was dec
also for comparison, sherline claims "Runout at spindle nose: .0003" or less, Runout at 3" out from spindle nose: .0005" or less"
(I'm measuring at about 1")
* jmkasunich compares $169 to who knows how many hours if I make my own
don't forget the cost of the motor if you don't have a suitable one
I was planning to use a dremel in round 1 with my homemade spindle
dremel runout is fine if all it's driving is a belt pulley
yeah I suppose
my spindle idea is based on this: http://jmkasunich.com/pics/fast-spindle-2028.jpg
11krpm? I'd take over 30 if I could get it .. (1krpm = 1 inch/min is apparently the formula cradek uses to compute feed for pcb milling -- http://timeguy.com/cradek/cnc/pcb)
(what is that in sfm?)
speed depends strictly on motor and pulley - I'd probably use a bigger pulley on the motor end for more speed
SFM depends on cutter diameter
heh, with a 0.005 cutter, even 20K rpm is only 26 sfpm
use .01 inch
52 - still crawling
yeah something in that neighborhood
until I solve backlash issues a spindle would just be a waste of $$
wtf? is there DRM for pdf files?
how big's your backlash? I'm using BACKLASH = 0.0055 (X) and 0.0045 (Y) and backlash now seems to be only a minor issue
yes, the PDF standard includes DRM features
[02:18:25] <jmkasunich> http://www.thk.com/documents/us_pdf/products/generalB/LMGuide/en_B_085.pdf
can't seem to save it locally
I think my lash is about twice that
I agree; evince greys out the "save" option (ubuntu 6.06)
wget would probably save it
jmkasunich: to fix that: launch gconf-editor, navigate to the item /apps/evince/override_restrictions and turn it on
gconftool --type bit --set /apps/evince/override_restrictions 1
time to tend to the real world .. talk to you later
wish my spindle was as simple as R8 to make stuff for
what kind of stuff do you have in mind?
R8 is a drawbar thread, a diameter, a bunch of who-cares, and then a short taper that can be cut with a compound
I was just looking at your photo of the spindle and how easy that part is compared to what I'd have to go through
for a spindle, I'd be tempted to clamp around the nose of the quill and forget the spindle
guess I could hold it in a 1" ER collet or something
the mill has the habit of willy-nilly pulling the quill all the way up...
triangular piece of 1/2" plate, three holes, one for quill, one for spindle, one for motor
that would be bad
if using emc, I could add and honor another limit switch
but putting an accessory spindle assembly in the main spindle and then accidentally turning the main one on would also be bad
it has a neutral - I use it when I mount an indicator etc
(no brake though, then)
fwiw, I agree, smash into the switch head-on. if it's at the end of travel so it's protected, that's best
I don't think I'd use the word "smash"
cradek_ is now known as cradek
jmkasunich: reading back on the discussion last night - it finally dawned on me what you ment about diodes and or-ing the overcurrent trip signal and the enable signal.. Duh.. that would get rid of the 2 diodes and 'I think' use up all the logic gates on all the chips.. puting 2 drives on 1 board. Neat.
EMC: 03bigjohnt 07TRUNK * 10emc2/docs/src/examples/gcode.lyx: Added more example discriptions
EMC: 03bigjohnt 07TRUNK * 10emc2/nc_files/lathe-g76.ngc: Added example with more descriptive name