#robotics Logs

Aug 03 2020

12:23 AM zhanx_ is now known as zhanx
05:09 AM fling_ is now known as fling
09:14 AM Phrkd is now known as Phreaked
11:19 AM veverak: hmm
11:20 AM veverak: rue_mohr: by any chance, do you have some nice 6v->5v stepdown circuit that can handle raspberry? (so it has to be pretty good and able to handle up to 3amps)
11:20 AM veverak: or anybodyelse
11:20 AM veverak: ^^
11:21 AM Tom_L: a diode would do that
11:21 AM Tom_L: maybe 2
11:21 AM Tom_L: .6v drop across a junction
11:21 AM veverak: I was told that dioed would produce a lot of heat
11:22 AM Tom_L: why?
11:22 AM Tom_L: shouldn't... try one
11:22 AM Tom_L: get a power diode
11:22 AM Tom_L: don't have a rpi supply?
11:23 AM veverak: (it's complicated)
11:23 AM veverak: (I have 6V UBEC from ESC)
11:23 AM Tom_L: https://www.amazon.com/gp/product/B07XTQL6YZ/
11:23 AM Tom_L: i got that one that came with a supply with an inline switch
11:24 AM veverak: again, no
11:24 AM veverak: I have 6V power source, stick with that
11:24 AM Tom_L: you're gonna have more loss on a smps buck supply than a diode would give you
11:24 AM Tom_L: ie it's gonna require more voltage to drop to 5v
11:24 AM veverak: hmm
11:25 AM Tom_L: that's why i suggested a diode
11:25 AM Tom_L: 2
11:25 AM Tom_L: 1 wouldn't be quite enough
11:27 AM Tom_L: when i was testing my avr programmer i kept adding diodes to the supply to see how low a voltage i could program at.
11:27 AM Tom_L: i went from 5v down to 1.7 using diodes
11:28 AM Tom_L: i could have gone lower but at that point i couldn't see the test led blink anymore
11:29 AM veverak: yeah, but how much current can the dioeds handle?
11:29 AM Tom_L: alot
11:29 AM Tom_L: some are rated for 25-30A
11:30 AM Tom_L: get the right size of course
11:30 AM veverak: hmm
11:32 AM Tom_L: https://www.amazon.com/pcs-1N5404-Diode-Rectifier-400V/dp/B00I6IDQXQ
11:32 AM Tom_L: 3A 400v
11:32 AM veverak: 1.2V vdrop
11:33 AM veverak: I wonder how will rpi react to 4.8V
11:33 AM Tom_L: yeah that would give you 4.8
11:33 AM Tom_L: i don't see why not
11:33 AM Tom_L: there is leeway in electronics tolerance
11:34 AM veverak: hmm
11:34 AM veverak: I also suppose that some capacitators would be nice
11:34 AM Tom_L: smooth it up a bit
11:35 AM Tom_L: https://www.amazon.com/5-amp-diode/s?k=5+amp+diode
11:35 AM Tom_L: 5A 60v if you're worried
11:36 AM Tom_L: https://www.amazon.com/BOJACK-Rectifier-KBPC5010-Electronic-Silicon/dp/B07Q5MJBJD/ref=sr_1_8?dchild=1&keywords=5+amp+diode&qid=1596472500&sr=8-8
11:36 AM Tom_L: i put similar on my cnc mill supply
11:36 AM Tom_L: those are full bridges though
11:38 AM veverak: hmm
11:38 AM veverak: ok, I've got conviced for diode
11:38 AM Tom_L: use 2
11:39 AM veverak: why?
11:39 AM veverak: also, parallel or series?
11:39 AM Tom_L: series
11:39 AM Tom_L: 1 might not be quite enough drop
11:39 AM Tom_L: i'd start on the safe side with 2
11:40 AM Tom_L: ---|>--- ---|>---
11:42 AM Tom_L: off my 48v supply i used the centertap with 1 diode and a cap to get my 24v supply
11:42 AM Tom_L: not even a full bridge
11:43 AM Tom_L: http://tom-itx.no-ip.biz:81/~webpage/cnc/psu/caps1.jpg
11:43 AM veverak: wait
11:43 AM Tom_L: that was the main supply
11:43 AM veverak: it's 1.2V drop per one diode
11:43 AM Tom_L: is it?
11:43 AM veverak: yes
11:43 AM Tom_L: they vary some
11:43 AM Tom_L: smaller ones may be .6
11:44 AM Tom_L: check it before connecting
11:44 AM veverak: yeag
11:44 AM veverak: https://cz.mouser.com/productdetail/on-semiconductor/1n5408?qs=y2kkmE52mdMWjAxtkc1EGw%3D%3D
11:44 AM veverak: interesting
11:44 AM veverak: it says 1.2V on other website for the drop :D
11:45 AM Tom_L: http://tom-itx.no-ip.biz:81/~webpage/cnc/psu/control2.jpg
11:45 AM Tom_L: the cap in the middle is the 24v supply
11:45 AM Tom_L: the diode is shrink wrapped in the wire
11:46 AM veverak: I see
11:46 AM Tom_L: it's just used to supply the smps on the left above the buss
11:47 AM Tom_L: 48v was a little too much for it
11:47 AM veverak: I see
03:01 PM rue_mohr: veverak, 6->5 @3A is a trick
03:01 PM rue_mohr: has to be a synchronous buck, the diode drop would be too much otherwise
03:01 PM rue_mohr: I havn't done a synchronous yet
03:02 PM Tom_L: off today?
03:02 PM rue_mohr: its a holiday of some kind
03:02 PM Tom_L: you don't think a diode would do it?
03:02 PM rue_mohr: prolly not close enough
03:03 PM Tom_L: too close together for a buck converter
08:15 PM rue_mohr: not a synchronous one
09:02 PM flyback: bmcc
09:02 PM flyback: rue_mohr, how did the whole i-wire hvac system end up turning out?
09:39 PM rue_shop1: ... hu?
09:39 PM rue_shop1: Tom_L, good show, how was the stability?
09:40 PM Tom_L: great
09:40 PM Tom_L: just like you'd be using a lathe
09:40 PM rue_mohr: ??
09:40 PM rue_mohr: k
09:40 PM Tom_L: stability on what?
09:40 PM rue_mohr: the rotary while cutting
09:41 PM Tom_L: yeah
09:41 PM Tom_L: other channel is why i wondered
09:41 PM Tom_L: it's as solid as the vise
09:41 PM Tom_L: i have a tailstock for it i haven't mounted yet
09:42 PM Tom_L: more to make sure the calcs were right
09:42 PM rue_mohr: nice
09:43 PM Tom_L: i should make a plate for the chuck for my lathe
09:43 PM Tom_L: different threads
09:43 PM Tom_L: it's got a 4jaw now
10:27 PM rue_shop1: Tom_L, so the cnc must have been a benifit when it came to aligning the work
10:28 PM Tom_L: yeah
10:28 PM Tom_L: i aligned the base first
10:28 PM rue_shop1: too bad you cant get it to compensate the job for the rotary being off xy axis
10:28 PM Tom_L: then the angle head
10:28 PM rue_shop1: how close could you get the base?
10:28 PM Tom_L: i used an indicator in the spindle?
10:28 PM Tom_L: and ran it across the side
10:29 PM rue_shop1: how close did it come out
10:30 PM Tom_L: best i could tell within .001"
10:30 PM Tom_L: or less
10:30 PM rue_shop1: nice
10:30 PM Tom_L: my dial was acting up a little
10:30 PM Tom_L: not sure why