On Tuesday 22 May 2018 23:10:24 jeremy youngs wrote: > On Tue, May 22, 2018, 20:53 Gene Heskett <[email protected]> wrote: > > Ouch, unless its a timing belt, otherwise there will be slippage, > > making the scale more of a SWAG than accurate. > > Yes, 1 inch wide xl 037 > > > That, and the fact that I wasn't aware the encoders > > > output was differential, meant I had to use some under a buck a > > copy, rs485 gismo's setup as receivers only to convert the > > differential to TTL for the 5i25 inputs. But to get to the 5i25, I > > had to rip out the opto's in the BoB's input for the A/B inputs. > > My encoders are completely unknown to me, and I cannot find much > > > information on them. > > I have 2 Bob's that are just vias directly to db 25. I may have to > make a 50 pin adapter for them .
You won't need a BoB, the 7i42TA is both a BoB and 7i90 protector. 24 pins at a time. Just make sure that all things being controlled are active low. The 7i90 can sink lots more currant than it can source. > I don't know yet if I will have to buffer the signal, how did you know > you needed to ? If you are refering to the encoder, the spindle servo went wide open at about 250 revs on the gui's tach, while the tach went to zero. The opto's simply weren't fast enough to get the A/B signals into the 5i25 inputs. So the PID thought the spindle was stalled and fed the motor the whole 127 volts the supply is capable of. Its a 90 volt motor. In my case, the BoB's are Sainsmart BoB's, no opto's in any output. But this isn't germane to your setup, I just want you to be aware it might be needed if the encoder is spun too fast for the opto's. The rs485 gizmo's are under a buck each on ebay. Get a 10 pack, they are handy as can be for fixing bad signals, giving you a clean rail to rail output. They'll need a ground from the 7i42TA's and some 5 volts, and a solder blob IIRC to convert them from bidirectional to just a receiver of the diff signals from the encoder. Tested here on the bench, works well at more than my cheap function generator can manage, which is 2 megabaud. > > > is there any reason I should choose a higher count? > > > > Way more than that is well tolerated now. If you are 1/1, then I > > wouldn't consider an encoder under 1000 lines, your PID tuning will > > be much much easier. > > > > > > > > 1/2" 13 tpi, is a tall order. How much torque is available? > > 620 oz inches , 3.2 kw at this time. Thats not enough. A 10x geardown might be enough. > I have my eye on a bldc at 37.5 n/m at 5kw if I can scratch up the > funds. Rigid tapping isn't an immediate issue but would be nice. Fixing that later is spending the money twice. And once you've seen it work, you'll wonder why you ever considered it to just be "nice". Even if the power to drive it all the way in one pass isn't there, my case with this G0704, and you have to write peck loops, you won't be willing to go back to turning T handles and breaking taps. You'll have to init some vars, but the peck loop looks like this: o300 WHILE [#<_ztmp> gt #<_tapbot>] g33.1 z[#<_ztmp> + #<_tapdec>] k#<_tpmm> #<_ztmp> = [#<_ztmp> + #<_tapdec>] o300 ENDWHILE That taps one of the 4 grub screw holes in this tap hat I'm making a bunch of. 76 L.O.C. drills all 4 holes, change from a shank sized drill to a tap, and rerun after setting the if triggers to tap, and it then taps them 12mm deep. Put the tap into the "hat", install the grub screws to grip the square butt of the tap, tightening to about 1/8th turn from broke/stripped, done. > > Gripping the tap in a collet, R8 or a TTS ER-20 without the positive > > coupling, tightly enough to prevent slippage. > > I have a bt30 spindle in the works. Now I'm jealous. :) But I'll have to settle for a metal gear kit and some better bearings in the head of this G0704 at some point. The thing has plastic gears! > I hope soon to have this thing reassembled, it's been a couple months > since it made chips. Thank you for your advice. NP Jeremy. -- Cheers, Gene Heskett -- "There are four boxes to be used in defense of liberty: soap, ballot, jury, and ammo. Please use in that order." -Ed Howdershelt (Author) Genes Web page <http://geneslinuxbox.net:6309/gene> ------------------------------------------------------------------------------ Check out the vibrant tech community on one of the world's most engaging tech sites, Slashdot.org! http://sdm.link/slashdot _______________________________________________ Emc-users mailing list [email protected] https://lists.sourceforge.net/lists/listinfo/emc-users
