#garfield Logs

Jun 15 2025

12:48 AM rifraf: scary thing is i am finding it right more often than not
01:03 AM rifraf: just picked up a bunch of kiln bricks for $25, the guy had 4 kilns for sales :/ big bigger than i can fit though but still tempted
01:41 AM rue_mohr: it might seem right, but its not...
01:43 AM rifraf: kiln for $500 rue? about 500x500x500 inside, manual programmable timer
01:45 AM rifraf: i think it could save alot of timer, about 600x600 on outside, asking for pics now, the guy had a shed so full of just and has about 100 marketplace listings , but not the kilns, i reckon its worth it for the box and elements even if i have to add new controllers
01:45 AM rifraf: could fit 4 or 6 crucibles inside, and do heat treatment etc, am so temped
01:46 AM rifraf: was gonna drop 600 on a tiny aliexpress one that fits a single crucible
01:46 AM rifraf: but the ali one still not programmable, would need to rewire anyway
02:12 AM rue_mohr: 500mm?
02:19 AM rifraf: like 1/2 a meter
02:19 AM rifraf: 20" or so square
02:21 AM rifraf: i was in a rush, it was in a wall of junk with other kilns and stuff, he made bicycle frames, i guess you need to temper some parts after welding or?
02:22 AM rifraf: his shed was way fuller than yours even, just a little walkway between stuff piled to the roof, would love to spend a few hours in there
02:24 AM rifraf: he is gonna pull it out tomorrow ands then send the details
02:25 AM rifraf: even the cheapest new rubbish kiln like $400 so is almost a no brainer if it works, will make room, will throw out the rest of the old mechmate cnc
02:26 AM rifraf: or i should try sell the parts, was many hours of work put into the mechmate
02:41 AM rifraf: just layed out the 40mm thick tiles i got for $25, is enough to make a 400x400x400 internal kiln, but elements and controllers will cost almost as much again, and after adding the time i think a used kiln might be better option, will see if he gets it working tomorrow, he was electrician and said he could wire it up however i wanted, but that would
02:41 AM rifraf: be extra, but i know a few electricians, like yourself
02:43 AM rifraf: used to work for the main electric element manufacturer in AU, so could get kanthal wire or old not selling elements pretty easy, decisions decisions
02:45 AM rifraf: this guy has some good advice, https://www.youtube.com/watch?v=7FalYyVASyw , making knives though
02:45 AM rifraf: at least 3 of the tiles already have grooves to put elements in
08:04 AM aandrew: https://www.tomn.co.uk/posts/2025/May/08/pcb_cnc/
08:05 AM aandrew: that's pretty nicely done actually
08:05 AM aandrew: 0.1mm trace/space is better than what I aim for in general (5mil)
11:16 AM rue_mohr: hahah right around the outrunner, why not!?
11:17 AM rue_mohr: trapped parallel linear rails is a bad idea tho
11:17 AM rue_mohr: looks good tho
11:18 AM rue_mohr: 300pound!? how did it cost that much!?
11:39 AM aandrew: I'm assuming that linear rails and 2020 extrusion is expensive in UK
11:39 AM aandrew: but yeah I also liked the belt around the outrunner like that :-)
11:40 AM rue_mohr: using a reversed timing belt is cute too
11:40 AM aandrew: I also liked the spindle design, it seemed really elegant
11:41 AM rue_mohr: so, robot power supplies
11:41 AM aandrew: I assume it was simply becuase you don't care if the drill slips a little (and it really shouldn't ever slip since you're not really cutting deep
11:41 AM rue_mohr: I have an idea
11:41 AM rue_mohr: that I got from an OLD phone system
11:41 AM aandrew: what kind of power do you need for the robot
11:42 AM rue_mohr: it basically works like this, you make one powerfull square wave pushpull supply off your main source and just distribute that, everything that wants a [different] voltage supply uses its own transformer
11:42 AM rue_mohr: and honestly, you CAN just regulate by switching your transformers output on and off
11:42 AM aandrew: oh, that's very similar to the distributed supply idea I wanted to put in the house here
11:43 AM rue_mohr: well, I might need 5v there, and 3v there and some isoltated 15volts there for fet drivers and and and
11:43 AM rue_mohr: so, everyone could just parallel into the "raw square wave supply"
11:43 AM rue_mohr: if the distribution is twisted pair, the noise shouldn't really be that high
11:44 AM rue_mohr: I'm failing hard on the "little" smps design I'm trying to do
11:44 AM rue_mohr: if I drop the efficiency idea, I could probably just use royers
11:44 AM aandrew: I have a single run of cat5 going around every door and window (in the gap between the window and the wall) -- 2 pairs for comms (CAN/RS485/etc.), 1 pair for 48VAC and one spare pair, maybe used as a dry contact
11:44 AM rue_mohr: but I like this buss thing and am wondering
11:45 AM rue_mohr: yup
11:45 AM aandrew: each "node" on the bus can then take that 48VAC and do what it needs, but most likely use is just rectify + buck down to 3.3V
11:45 AM rue_mohr: yup, are you having any issues finding converters for the 48V?
11:45 AM rue_mohr: when I was using 48 for the run to my driveway lights, I found out that almost all smps chips stop at 36
11:46 AM rue_mohr: so the peak 52V you get on a 48V bus is a bit of an issue
11:46 AM rue_mohr: and the converters I was finding had efficiency issues
11:46 AM aandrew: well the idea never got past the wire in the wall so I haven't had to worry about that, but I have a favourite regulator for that: Rohm BD9G341
11:46 AM aandrew: 12-76V input range, up to 3A
11:46 AM rue_mohr: https://www.digchip.com/datasheets/search.php?pn=BD9G341
11:47 AM aandrew: I found it when I was looking for a regulator that I'd be happy using in automotive for the load dump case
11:47 AM rue_mohr: oh integrated
11:48 AM aandrew: I use it on my irrigation controller too; 24VAC input, rectified - the cheaper converter I used before exploded because of some transient or something, but so far the BD9G341s I have put in place have been very rbust
11:48 AM rue_mohr: oh smol
11:48 AM rue_mohr: hmm 12V up
11:49 AM rue_mohr: so, the power converter I want to make, I want for 3-24V range
11:49 AM aandrew: it's also pretty decent in the sense that it's SOIC8 yeah and also you can adjust the switching frequency from like 50-800kHz or so so you can play with different inductors
11:49 AM rue_mohr: oh hmm
11:49 AM aandrew: it doesn't do synchronous rectification but for the little loads I tend to need it hardly matters not to be *that* efficient
11:49 AM rue_mohr: I need to learn how to better manipulate boost controllers into pushpull
11:50 AM rue_mohr: those diodes can be a big hit
11:50 AM rue_mohr: % wise anyhow
11:51 AM aandrew: it's also not awesomely efficient at light loads (~50% with high VIN) but generally speaking it's not a problem
11:51 AM rue_mohr: so how much do these cost?
11:51 AM rue_mohr: % is not a particularly good measure
11:52 AM rue_mohr: so, for 24V to 5V @100mA I'm using linear a bar, about 2w loss
11:55 AM aandrew: there are tons of these on digikey actually. MP948x, LM5169, LMR380x...
11:56 AM aandrew: these are like $4.50 in onesie-twosie which is not cheap (all the others I mentioned above are cheaper), but this is for higher current, the cheaper ones are down in the 500-800mA range
11:57 AM aandrew: MP4514 for example is $1.70 and up to 30Vout 800mA, still SOIC but synchronous rectifier
11:57 AM aandrew: and ~80% efficient with 48Vin and 200mA out
11:58 AM aandrew: rises to about 85% at full load
11:59 AM aandrew: I want to play with spin-coating UV soldermask and selectively hardening with the 3D printer UV
12:00 PM rue_mohr: oush
12:00 PM rue_mohr: ouch
12:01 PM rue_mohr: $1/chip bites
12:07 PM rue_mohr: I also want my generic supply to be isolated, with two outputs, so I can use it for floating fet drivers
12:07 PM rue_mohr: or li-ion chargers
12:10 PM rue_mohr: even from ali the BD9G341 are $1.30ea ahhah +$7 chipping
12:11 PM aandrew: I guess I look at it as "compared to what" -- $1/chip, no diode, flexible options and less screwing around seems a reasonable tradeoff
12:11 PM aandrew: well your generic supply could use everyday pulse transformers for isolation
12:11 PM rue_mohr: I would like to use up the ferrite I have around
12:12 PM rue_mohr: but the success of ethernet transformers has spoiled me
12:12 PM rue_mohr: I might break down and cut apart one of the tiny dc-dc modules I got from china
12:14 PM rue_mohr: aliexpress.com/item/1005006647887769.html
12:14 PM rue_mohr: I got a few, not cheap tho
12:14 PM rue_mohr: I have some from ewaste too
12:15 PM aandrew: I've been playing with ultrasonic distance sensors to watch the sump water level as a way to detect when the iron filter/softener are regenerating
12:16 PM aandrew: https://ibb.co/k2QjsYyd
12:17 PM aandrew: nothing crazy, it just takes 16 measurements, throws away any bad ones (so far only zeroes) and averages the rest, then computes distance based on that average
12:17 PM aandrew: does this every 15s and posts the measurement to MQTT where I can see it with Home Assistant
12:18 PM rue_mohr: hmm