#robotics Logs

Mar 06 2020

05:42 AM DnzAtWrk: is it possible to drive a larger gear by a smaller gear inside it with a non 1 to 1 ratio
05:48 AM DnzAtWrk: both gears being equally high
05:48 AM DnzAtWrk: wait a second. dumb question
05:48 AM DnzAtWrk: can just offset the smaller gear
05:48 AM DnzAtWrk: ( (O ) )
05:48 AM DnzAtWrk: derp
05:48 AM DnzAtWrk: so maybe this would the best method method for driving the arm while saving space
05:54 AM DnzAtWrk: what do you call a gear with inside-facing teeth which is supposed to be used with a pinion gear
05:55 AM DnzAtWrk: says "annular gear" here, but I can't find anything like that on amazon
08:33 AM rue_bed: ok
12:47 PM norkle: hi!
12:58 PM enthdegree: Hello all
12:58 PM enthdegree: Anyone know how to approach this?
12:58 PM enthdegree: https://news.ycombinator.com/item?id=22505550
07:41 PM rue_bed: enthdegree,
07:57 PM enthdegree: Yes
08:02 PM rue_bed: hmm I dont think I get it
11:06 PM Jak_o_Shadows: oh good, rue, you did use a HIP4081 chip. They let you use external gate driver's don't they? Did you use them?
11:07 PM Jak_o_Shadows: Also, if you need more cooling, you could totally put a heat pipe through the middle of that aluminium bar. Maybe expensive, but probably effective.
11:08 PM Jak_o_Shadows: enthdegree, I think the people suggesting that sort of design books are right. It seems similar to camshaft design.
11:09 PM Jak_o_Shadows: To optimise it, I think you'd be looking at some kind of genetic algorithm.
11:09 PM Jak_o_Shadows: Also, rue_bed, I got that universal motor working - about 8 of the joints needed rework, but now I have a free trim router!
11:14 PM rue_mohr: ah good
11:15 PM rue_mohr: I used the 4081 fet drivers direct
11:15 PM rue_mohr: it should be ok for cooling, the fets I'm using are 3mR and I'm running at 20A peak
11:16 PM rue_mohr: hah, its a trimmer eh?
11:16 PM rue_mohr: yea 5 of the 10 hip4081 I got from china were bugus
11:16 PM rue_mohr: oops, didn't pay enough
11:19 PM Jak_o_Shadows: aha. Oh well.
11:19 PM Jak_o_Shadows: I think you're probably right without external gate drivers, that's only for fast switching speed eh?
11:27 PM rue_mohr: yea, I'm switching under 1khz
11:27 PM rue_mohr: well under 2 for sure
11:27 PM rue_mohr: I have discrete fet drivers that I can run up to 3Mhz
11:28 PM rue_mohr: my top on isolators is 1.5Mhz, but I might have something about 20Mhz that I cant figure out how to test just yet
11:29 PM rue_mohr: wow, sometimes twitter just halts, dead quiet
11:30 PM rue_mohr: gonna go take a shower