#robotics Logs

Apr 16 2020

02:57 AM Jak_o_Shadows: cause they were losing sync?
03:03 AM Jak_o_Shadows: so by going slower, they kept sync better?
04:41 AM Jak_o_Shadows: Hmm. Did I have any 4017s
04:41 AM * Jak_o_Shadows vaguely remembers buying them.
04:45 AM Jak_o_Shadows: Haha rue: "ptr = 0; // forgetting to do this could lead to hours and hours of debugging."
04:54 AM Jak_o_Shadows: Hmm. I could use the DMA to write to i2c
04:55 AM Jak_o_Shadows: Probably cost me more RAM
04:55 AM Jak_o_Shadows: probably not worth the effort
08:28 AM rue_bed: oops
08:28 AM rue_bed: did I post the stm32 version for up to 44 servos or the avr version for 8 servos
08:35 AM rue_bed: https://github.com/ruenahcmohr/m328hobbydriver
08:36 AM rue_bed: thats the avr version
08:36 AM rue_bed: no 4017
08:36 AM rue_bed: the stm32 one I needed lots of channels, so I muxed with a 4017
08:38 AM rue_bed: oh to 88, I must have thought of another trick
09:37 AM rue_mohr: (A single key press can generate up to 6 scancodes.)
09:37 AM rue_mohr: ^^ there is the beggining of where PC keybaords went wrong
09:56 AM polprog: i was thinking of a keyboard that had no midifier keys except for esc and control
09:56 AM polprog: just the character keys, escape, and control
10:02 AM deshipu: and only one key
10:03 AM rue_mohr: if they were ALL reporting just pres and release, then there would be no issue, every key, its own press and release code, no multiple coedes
10:03 AM deshipu: there were typing machines with keyboards that had lower and upper case letters on separate keys
10:04 AM deshipu: I think linotype was like that as well
12:11 PM Donitzo: guess I'll ask here too
12:11 PM Donitzo: https://www.dropbox.com/s/361ck6motq40q59/arm_p01.png?raw=1
12:11 PM Donitzo: what kind of connection can I do between the two highlighted parts which would be stable and take up a small amount of room
12:12 PM Donitzo: as opposed to have two tapered roller bearings
12:12 PM Donitzo: having*
12:36 PM Donitzo: are there flanges which keep a shaft stable along the axis while allowing rotation around the axis?
01:20 PM Tom_L: Donitzo, what keeps the pinion against the ring gear?
01:20 PM Donitzo: nothing in that image
01:20 PM Donitzo: that's part of what I'm trying to make
01:21 PM Tom_L: what is it for?
01:21 PM Tom_L: and does it need full rotation?
01:22 PM Donitzo: robot arm, and no but preferably
01:23 PM Tom_L: not enough detail there to tell but that doesn't look like a great design
01:23 PM Donitzo: imagine the bottom plate connects to the top part, so it forms a long arm
01:23 PM Donitzo: well, it's supposed to be a tiny robot arm after all
01:23 PM Donitzo: no need for industrial design concepts
01:23 PM Tom_L: no matter the size
01:24 PM Tom_L: for full rotation it will be difficult to keep the ring gear engaged
01:24 PM Donitzo: I don't see why it would be so inherently. Would depend on the method which keeps the two parts together
01:24 PM Tom_L: you could put a bearing on the outter ring to keep the ring against the pinion but that would limit to less than full rotation
01:24 PM Tom_L: yes, you didn't show us that
01:25 PM Donitzo: so far the best ideas have been to make a round plate above and below the ring, and put grooves on the top/bottom of the ring and on the top and bottom plate
01:26 PM Donitzo: which you put some kind of ball in
01:26 PM Donitzo: screw the top plate into the bottom plate until the desired tension is on the ring
01:27 PM Donitzo: and use spring washers I guess
01:27 PM Tom_L: just a plate would do
01:27 PM Donitzo: would you not need two plates, to keep the ring stable in the center
01:27 PM Donitzo: ie, so it can not move up or down
01:28 PM Tom_L: but you still have the problem of the gear not staying engaged
01:28 PM Donitzo: in the above scenario, there would be little play in the ring
01:28 PM Donitzo: so it should stay engages
01:28 PM Tom_L: an idler bearing on the outside of the ring would hold it
01:28 PM Donitzo: engaged*
01:28 PM Tom_L: the drawing doesn't indicate that
01:29 PM Donitzo: no, that's still in progress
01:29 PM Tom_L: also, google harmonic drive
01:29 PM Tom_L: might save you some pain
01:29 PM Donitzo: ah yes
01:30 PM Donitzo: and of course planetary gears
01:30 PM Donitzo: would also be acceptable
01:30 PM Donitzo: though it does get a bit complex at this size
01:30 PM Donitzo: (if I want to 3d print the gears)
01:30 PM Donitzo: for reference, the motor is 8 mm wide
01:30 PM Donitzo: no no
01:30 PM Donitzo: I mean, 2 cm long
01:30 PM Donitzo: it's NEMA 8