#garfield Logs

Sep 07 2020

02:07 AM polprog: i notices the same thing about netflix
02:13 AM polprog: there are some good movies but they are hard to find
02:13 AM polprog: and the only series we are watching on it is better call saul
02:48 AM rue_bed2: switching cases again
02:48 AM rue_bed2: back to the orig that was on the shelf, but with smaller meters and the 19V supply
02:48 AM rue_bed2: I think everything will fit
02:48 AM rue_bed2: but I need to do a bunch of loud cutting that Icant right now cause its 1am
04:14 AM Tom_L: just put some bacon on and when they look over the fence offer them some
05:30 AM polprog: https://twitter.com/polprogpl/status/1302911356216250368
05:30 AM polprog: 74hc04 amplifier
05:30 AM polprog: input needs to be biased right in the middle of the undefined logic level range, and then I can just ac couple some audio signal
05:31 AM polprog: three inverters in paralell can drive a 2.7 ohm speaker easily, through a 220u cap
05:32 AM polprog: and when the input doesnt hit either logic level the sound comes through pretty clean!
12:38 PM rue_mohr: :)
12:39 PM polprog: what's up?
01:22 PM aandrew: are HC unbuffered?
01:30 PM polprog: i think they are, datasheets shows 3 inverters in serie as one unit
01:31 PM polprog: but it still has this linear region
01:32 PM polprog: i wonder if i can make a buck converter this time, using the fact that hc04 will pull its output high if the input is < ~2.0V
01:33 PM polprog: id preferably use a 74xx14 for that though
02:04 PM polprog: it sorta works
02:04 PM polprog: 04 is better for that
02:05 PM polprog: but i need to chain 3 in serie to force it to switch, otherwise it just becomes a linear regulator
02:24 PM polprog: hmm, cant make a boost converter though
02:24 PM polprog: maybe i should try with a ring oscillator, rather than direct feedback
02:41 PM rue_shop2: dont recall what that looks like inside
02:42 PM rue_shop2: remember that adjusting vcc on a ring buffer changes the freq a lot
02:43 PM rue_shop2: vco ;)
02:52 PM polprog: yeah its not exactly part 15 compliant :v
03:46 PM aandrew: :-)
03:46 PM aandrew: you're so far away from the FCC you wouldn't have to worry about it
04:00 PM polprog: we have our own radio police here :P
04:00 PM polprog: nighters
05:36 PM rue_shop2: power supply
05:36 PM rue_shop2: I'm doing another transparent faceplate
05:36 PM rue_shop2: I like how the other one came out
05:37 PM rue_shop2: but this project has a power indicator
05:37 PM rue_shop2: I'd lined up a jewel type indicator last time for this
05:37 PM rue_shop2: but, as the faceplate is transparent (paint mask) I dont technically need it
05:37 PM rue_shop2: so
05:38 PM rue_shop2: I'm fumbling on how to do the power indicator
05:38 PM Tom_L: wish i had a dpdt contactor
05:38 PM Tom_L: i'd add it to the power switch
05:39 PM rue_shop2: why dt?
05:39 PM Tom_L: one for the cnc and one for the vfd
05:39 PM Tom_L: well dt isn't a requirement
05:39 PM rue_shop2: but you dont need dual throw...
05:39 PM rue_shop2: right
05:39 PM rue_shop2: well
05:39 PM Tom_L: right
05:40 PM Tom_L: just used to getting them that way just in case
05:40 PM rue_shop2: from the scrapper, a rooftop heating unit will have a big 24V contactor
05:40 PM rue_shop2: 2 or 3 poles
05:40 PM rue_shop2: ?
05:40 PM Tom_L: din rail would be awesome
05:40 PM rue_shop2: it might be
05:40 PM Tom_L: 2 pole might be ok
05:41 PM rue_shop2: lots of them are universal
05:41 PM Tom_L: both hot going one to each device
05:41 PM Tom_L: i've got a 3phase contactor on my compressor
05:41 PM Tom_L: only using 2 poles
05:41 PM Tom_L: 220v
05:41 PM Tom_L: way oversize but used and cheap
05:43 PM Tom_L: better to be 110v instead of 24
05:48 PM Tom_L: to use 24v one would have to power before the other
05:49 PM Tom_L: rue_shop2, if i gave you a pn or data sheet could you tell me if the relay is big enough to handle the vfd?
05:49 PM Tom_L: given it's parameters too
05:53 PM Tom_L: allen bradley #700-HK32Z24
05:53 PM Tom_L: https://www.rexelusa.com/usr/Root-Category/Control%2C-Automation/Relays/Ice-Cube-Relays/8-Blade-Relay/Allen-Bradley-700-HK32Z24-Relay%2C-Ice-Cube%2C-Slim-Line%2C-8-Blade%2C-2PDT%2C-8A%2C-24VDC/p/54881
05:54 PM Tom_L: you think the contacts would be big enough for that vfd @ 120vac
05:54 PM Tom_L: i've got 2 spares of those with din mounts
05:56 PM Tom_itx: Input Voltage: AC110/220VAC, 50/60Hz,
05:56 PM Tom_itx: Continuous Output current: 8A, suit for less than 1500W brushless motors
05:56 PM Tom_itx: Max. Output current: 15A,
05:56 PM Tom_L: but that doesn't say the max input current
05:58 PM Tom_itx: DC bus line terminal in driver, rated power 315V
05:58 PM Tom_L: does that mean the motor runs at 315v?
05:59 PM Tom_L: i'm lost when it comes to BLDC
06:08 PM Tom_L: https://www.ideadigitalcontent.com/files/11994/ID-SPE-v1-700-td552_-en-p.pdf
06:13 PM Tom_L: i don't wanna burn up the relay...
06:14 PM Tom_L: i have a 24v center tap on one of the transformers i could hook the relay to and wire the vfd thru it but the cnc supply would be up before the vfd which might be desireable anyway
06:16 PM Tom_L: problem is, i don't know how current out relates to current in on those
07:00 PM rue_mohr: they have to have a higher dc bus casue to the peak voltage of the AC and stuff
07:01 PM rue_mohr: oh dont disconnect the motor from the vfd
07:01 PM rue_mohr: just pull the power from the vfd
07:01 PM rue_mohr: disconnecting the motor could casue flyback that would kill the vfd
07:05 PM aandrew: I wonder what I can convince rue_mohr to be distracted by tonight...
07:08 PM Tom_L: rue_mohr, the plan was to switch the input 110vac to the vfd
07:09 PM Tom_L: they also said don't swap motor wires around
07:09 PM Tom_L: i just need to know if you think that relay is big enough
07:11 PM Tom_L: i also have din mount fuse blocks i could put on it
07:11 PM rue_shop1: yea, let the vfd do the reverse
07:12 PM rue_shop1: an input power contactor is just fine
07:12 PM rue_shop1: the LV control is isolated anyhow
07:12 PM rue_shop1: (typically)
07:12 PM Tom_L: you think 8A is enough?
07:12 PM Tom_L: on the relay contacts
07:13 PM Tom_L: i could double them up and run the DP on the 'hot' side of the 110v
07:14 PM rue_shop1: how big is the motor?
07:14 PM Tom_L: Input Voltage: AC110/220VAC, 50/60Hz,
07:14 PM Tom_L: <Tom_itx> Continuous Output current: 8A, suit for less than 1500W brushless motors
07:14 PM Tom_L: <Tom_itx> Max. Output current: 15A,
07:14 PM Tom_L: that's the vfd rating
07:15 PM rue_mohr: 8A isn't enough
07:15 PM Tom_L: ok
07:15 PM Tom_L: not even if i double up on the contacts like i suggested?
07:15 PM rue_mohr: yer looking to load it (I know you will) to about 12.5
07:15 PM Tom_L: switch one side
07:15 PM rue_mohr: so you want a 20A prefably
07:16 PM Tom_L: i may just plug the vfd into the wall then
07:17 PM Tom_L: i don't have a 20A relay
07:22 PM rue_mohr: you know you CAN get one
07:23 PM Tom_L: yeah
07:23 PM Tom_L: do they make em with 120v coil?
07:23 PM Tom_L: or typically 24v?
07:25 PM rue_mohr: both can be found
09:56 PM Tom_L: i'll check my local motor guy and see if he has one
09:57 PM Tom_L: DPST should do
10:17 PM rue_mohr: shutdown relay for his VFD
10:17 PM rue_mohr: input power
10:17 PM rue_mohr: almost out of time :(
10:18 PM rue_mohr: need to get this power indicator
10:31 PM aandrew: it doesn't have an e-stop input?
10:31 PM aandrew: if you really want to open the input potentially under load you're gonna want an AC3 rated input contactor
10:58 PM Tom_L: rue_mohr,
11:00 PM Tom_L: https://www.amazon.com/Packard-C230B-Pole-Contactor-Voltage/dp/B07C1X6SHD
11:00 PM Tom_L: something like that work?
11:00 PM Tom_L: undecided on the coil voltage but same thing in 24v coil as well
11:02 PM Tom_L: https://www.amazon.com/C240A-Contactor-Pole-Amps-Voltage/dp/B07G8Q2QBJ
11:09 PM rue_mohr: thats what ya want
11:09 PM rue_mohr: could be smaller
11:09 PM rue_mohr: sometimes they just down the ratings tho