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I'd definitely take a look at assembly (looks like they have most of the parts) but the total part cost is fairly high and I only really need 1 unit ultimately. If I wanted 10+ I'd for sure consider it. I think for me part of the problem is I'm fairly slow to design boards and perfect them before ordering, so trying to design something and then have jlcpcb go out of stock of a part would be pretty infuriating. If the setup cost was low enough it might almost be worth having them solder the one or two QFN parts to all 5 boards even if I only end up finishing one but I'll have to consider that. I'll keep that in mind with the paste. Small tubes of chip quik paste are only like $11-13 from digikey, so in reality it's not bad even if I only get one use out of them. EDIT: Good god, 50x50mm four layer boards with a specified impedance stackup and assembly for two loving dollars (not counting parts of course). I mean.... the gently caress? Rescue Toaster fucked around with this message at 03:24 on Oct 16, 2023 |
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Oct 16, 2023 03:16
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Shelf life on solder paste is usually "We guarantee that it will be good at least this long", not "It won't last much longer than this".Example from a datasheet posted:Shelf Life: Refrigerated >12 months, Unrefrigerated >12 months *See notes below: Non-refrigerated paste is pretty similar price, and being able to ship ground often makes it effectively cheaper
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Oct 16, 2023 03:19
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PCBWay will also do assembly, and at least last time I tried it they could assemble both sides if necessary and would do throughhole if requested. I'm actually surprised JLCPCB won't as I assumed they all used the same actual factories behind the scenes. Good to learn re: solder paste, though, I ended up never trying any mass SMT (e.g. BGA) at home because I'd be worried about huge amounts of paste just going to waste, but if it's not actually that bad I might get some.
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Oct 16, 2023 03:22
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The one time I ever tried using a stencil it only kinda worked and a bunch of the paste didn't like, stick to the board so idk I guess I did something wrong.
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Oct 16, 2023 03:55
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Charles Ford posted:PCBWay will also do assembly, and at least last time I tried it they could assemble both sides if necessary and would do throughhole if requested. I'm actually surprised JLCPCB won't as I assumed they all used the same actual factories behind the scenes. PCBway is more expensive for 4 layer boards though Foxfire_ posted:Shelf life on solder paste is usually "We guarantee that it will be good at least this long", not "It won't last much longer than this". this is great to know! I ended up just getting a tube and letting it lie around at room temperature anyway, good to know that it'll be fine
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Oct 16, 2023 11:04
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I have some solder paste from 2014, should I deep six it or what
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Oct 16, 2023 14:28
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Bad Munki posted:I have some solder paste from 2014, should I deep six it or what I mean I've had solder paste go bad after just two years so yeah prolly, unless it's still completely sealed or something.
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Oct 16, 2023 14:36
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It’s just a little 2oz tub or something, no clue what it cost me or relatively how much is left but I’m not too broke up about it. I understand getting solder paste and flux in handy little syringes is a thing, anyone got a rec for those two things in small quantities?
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Oct 16, 2023 14:52
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Bad Munki posted:It’s just a little 2oz tub or something, no clue what it cost me or relatively how much is left but I’m not too broke up about it. I just use these until they start to "feel" wrong (like the flux in them starts behaving...differently? it takes too much heat to melt the solder, idk how to describe it it just feels bad when I try to use it) and then I get another one. They usually last about a year or two, and I write the date I open it on the tube with a pen so I can keep track. https://www.amazon.com/dp/B00M1RC0YY Also the needle it comes with is enormous and next to useless for fine work, so I bought a bunch of thinner dispensing needles to use. If you're just gonna squeeze a bunch out for use with a stencil though it should be fine. e: As for flux idk, I have a syringe of it but I rarely use it, I mostly either just don't use flux at all (since solder paste is already drenched in it) or I use a flux pen. Shame Boy fucked around with this message at 15:07 on Oct 16, 2023 |
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Oct 16, 2023 14:59
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Oh and for the record I don't just throw away the old syringes since they're, y'know, full of lead. So far I've just been collecting them and one day I'll figure out how to dispose of them properly but they're small enough that it's not like they're taking up a huge amount of space just keeping them in a drawer either.
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Oct 16, 2023 15:02
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Cool, thanks. Looks like a standard syringe so I can get a variety of tips for it, my wife keeps a drawer full of that poo poo for work.
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Oct 16, 2023 15:10
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Hi ok, this is one of those project posts where I realize I'm making a lot of mistakes, and I'm embarrassed by the output, but if I don't solicit feedback I'll never learn. What I'm posting isn't in any way representative of "ok here's what I have and I'm ready to send it for production", but more of a "here's where I am, and I'm making a LOT of mistakes, but I need feedback to get better" Here is the contextual goal of the project: I have a retro PC, a NABU, which has a PSU I am looking to swap for a Mean Well equivalent. I have the option of simply dropping in the Mean Well and wiring everything directly to it, but I decided to use the opportunity to learn a little KiCad. Other people have done this by simply hacking up the OEM wiring harness and wiring it directly to the PSU, or creating a little breakout board to only translate the PSU to the OEM harness. My primary success criteria: 1. It mechanically supports the Mean Well PSU on the standoffs which housed the original PSU, since there is no "good" way to mount it. Only one of the PSU's mounting holes lines up with the OEM standoffs. 2. It acts as a "distribution board" for the Mean Well, taking AC in from the mains and power switch, routing it to a header near the Mean Well. And similarly taking the PSU output and routing it to a header for the OEM NABU wiring harness. 3. Provide a 5v fan header for a replacement DC fan. My secondary success criteria which influenced some of the design choices I made in my head: 1. Be as "drop in" as possible, require as little cutting of the original wiring as I can get away with. Right now the only wiring modification I think I need to make this work is the power button routing. ... actually since my secondary criteria are driving a LOT of my decision I'm not sure it's fair to even call them secondary, but I guess here we are. --- The schematic I mocked up is this:  I made the conscious decision to take AC and route it on the PCB rather than wire directly to the Mean Well PSU. I don't have a strong reason for doing this other than I wanted the PSU to feed into and out of the PCB rather than be wired to mains directly, just for consistency. Everything else is fairly straightforward, I think. --- The PCB I have mocked up is roughly this (pcb extends past screenshot but no components exist there):   - PCB is 18cm x 10cm and the two mounting holes near the right edge of screenshot is meant to bolt the PSU chassis to the PCB mechanically, no other purpose. - The screw terminal takes earth and neutral as direct inputs and live is routed through the existing fuse on the metal case, through a power switch, and the output of the switch feeds into the remaining screw terminal. - The PSU_AC and PSU_DC footprints are located by hand where they are because they roughly line up in front of the PSU's AC input and DC output. A (very) small wiring harness will extend from the PSU and connect to both headers respectively. - I am 100% certain that I am using the wrong footprint for PSU_AC. My gut tells me that a 2.5mm pitch molex connector isn't appropriate for 120v mains, but I haven't yet figured out how to choose something more appropriate without randomly going through KiCad's library. - I am 100% certain that the autorouting is inappropriate for mains AC but I don't yet know how to properly configure parameters to create appropriate traces. So yeah, That's my ugly baby. At this point I think I'm looking for feedback on my approach of routing AC on the PCB, but I also don't know what I don't know, so I'm very wiling to hear other feedback which I'm certain is necessary. - Routing mains AC on the PCB vs directly wiring the mains cable/power switch to the PSU. Is this just a stupid idea for a beginner to mess with? I don't mind just wiring directly to the PSU, I was just trying to be consistent in my "everything connects to the PCB" approach. - Choosing an appropriate connector and wiring gauge for mains AC to PSU. I also didn't really put a lot of thought into how this is grounded other than the wiring block does connect to mains earth and passes that on to the PSU. I'm not sure what other considerations I should be making here. And apologies, not sure if there's a better way to get screenshots or files out of KiCad. Very much a learning process for me. some kinda jackal fucked around with this message at 17:18 on Oct 16, 2023 |
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Oct 16, 2023 17:13
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I've been fixing up an old sewing machine. I had it plugged in while I was working on something else, and it randomly started running by itself! Then some magic smoke came out of the back. I opened it up and found a cracked and blown capacitor on the power lines. It's a 250v 0.1uF metal-foil model. This is a 50-year-old machine with essentially zero electronics -- this capacitor, a larger capacitor on the motor, a discharge resistor, and a couple of diodes, and that's it -- so I assume based on that and the burned capacitor's specs that it's a filter for EMI from the brushed motor. I took it out and the machine appears to work perfectly fine without it. Am I correct in my assumption, or is there some other reason it might be in there? I think I can find an equivalent part, but should I even bother to replace it?
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Oct 16, 2023 21:10
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"running by itself" says to me that the cap may have been part of a snubber in parallel with the power switch or pedal or whatever, to keep the switch contacts from arcing when you shut it off. Just in case that's what it's for I'd either avoid using it until you've replaced the cap or replace the cap and switch at the same time.
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Oct 16, 2023 21:47
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Sorry OP it's ghosts
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Oct 16, 2023 21:55
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I would expect a 50 year old sewing machine to have little-to-no consideration for EMI. My alternate guess would be that a big cap would be part of a motor starting circuit and that maybe it's turning with lower/bumpier torque or higher heat now.
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Oct 16, 2023 22:18
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Foxfire_ posted:I would expect a 50 year old sewing machine to have little-to-no consideration for EMI. The 1970s was when the FCC started started clamping down on interference.
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Oct 16, 2023 22:55
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Foxfire_ posted:I would expect a 50 year old sewing machine to have little-to-no consideration for EMI. My alternate guess would be that a big cap would be part of a motor starting circuit and that maybe it's turning with lower/bumpier torque or higher heat now. Couldn’t it be both? I’d expect people 50 years ago to be pissed that the sewing machine was messing with their AM radio listening
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Oct 16, 2023 23:54
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Looking into it further, it is a special X2-rated fire-resistant type, so that makes me a little more concerned about its importance. And yeah despite the machine seemingly working correctly, it's bothering me that it isn't right. The capacitor wouldn't be in there for no reason. I found an identical part (different manufacturer) on Digi-Key and, knowing how fast they ship, will probably have it installed by Wednesdays night or something.  Foxfire_ posted:I would expect a 50 year old sewing machine to have little-to-no consideration for EMI. My alternate guess would be that a big cap would be part of a motor starting circuit and that maybe it's turning with lower/bumpier torque or higher heat now. It's not a big cap. It's 0.1uF. Could still be part of a starter circuit I guess idk. The "wiring diagram" I found is a picture of the terminal blocks with instructions of where to screw things in and I'm too tired to interpret it right now. namlosh posted:e: ^^^^^^^^^ That was my thinking too originally. Yeah it might emit more EMI now, but I don't have anything in my house anymore that's super sensitive to EMI. Sagebrush fucked around with this message at 02:17 on Oct 17, 2023 |
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Oct 17, 2023 02:04
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I have a bluetooth speaker with an extremely dead 18650 that I want to replace with just a plug-in power supply, but the board won't run off of USB power alone. It's also one with three wires (+3.7v, ground, temperature sensor?) so I don't know if I need to do some magic to make the temperature sensor happy. It's going to be living in my garage, which isn't insulated, so swapping the battery isn't really an option since it will have to survive -30c. I tried just feeding it 5v through a (modified  ) usb cable but it wouldn't turn on, so I assume I either have to give it more current, or I've over-volted it and it's decided to die (is 3.7-4.2v being given 5v enough to kill it? It seems like it should be within tolerances) Worse case scenario, I can just shunt some other audio output to the speakers, but the board itself has some LED controls I'd like to use if possible.
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Oct 17, 2023 14:27
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DHO914 showed up today. Compared to my old LeCroy 9310A it's almost TOO nice. Not a massive fan of the touch UI and small questionable UI elements but what else would you expect in the year 2023 on an android-based device? Waveform refresh is super fast. I have memories of waveform updates being sluggish on software scopes and old old LCD based DSOs but that's a thing of the past I guess. Really happy with this device whose capabilities I'll use, generously, 5% of.
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Oct 19, 2023 12:13
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some kinda jackal posted:
I would not use a screw terminal to terminate a stripped AC power cord. The risk of one of the wires slipping out is just too high. {edit} The industry term for such a cable is a "suicide cable" btw. some kinda jackal posted:- I am 100% certain that I am using the wrong footprint for PSU_AC. My gut tells me that a 2.5mm pitch molex connector isn't appropriate for 120v mains, but I haven't yet figured out how to choose something more appropriate without randomly going through KiCad's library. I would agree with your gut. Check the connector to ensure its rated for 120VAC. You can use a 2.5mm pitch connector if you happen to have them, but consider having an empty position between the AC lines to give it more clearance. some kinda jackal posted:So yeah, That's my ugly baby. At this point I think I'm looking for feedback on my approach of routing AC on the PCB, but I also don't know what I don't know, so I'm very wiling to hear other feedback which I'm certain is necessary. The typical way to do these types of things is with a "power entry module" which is panel mounted on the enclosure. These usually have spade terminals then that connect to corresponding studs on a PCB. In this case, I would suggest terminating the wires from the power entry module onto ring terminals screwed directly to the PSU. Routing 120VAC on a PCB is fine. There's lots of rules and guidelines depending on the application but one general rule of thumb is to keep 5mm of space between AC traces and anything else. Ne Cede Malis fucked around with this message at 03:24 on Oct 22, 2023 |
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Oct 19, 2023 16:42
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Looking at the CV/CC circuit in 29 and can't figure it out. https://www.ti.com/lit/ds/symlink/lm350a.pdf?ts=1697608614954  Not sure how to complete the circuit. There is incoming 35V (DC) from a power supply but where do you connect the return to the power supply's negative terminal? How would something be powered by this circuit? Only output is specified but it's not clear for me how I complete this circuit. The pins 4 and 7 from the op-amp leave me confused as to their purpose as well, are they just not used, or part of the circuit? Like pretend I wanted to power a lightbulb by this circuit. Where would the return from the bulb go? Back to the negative terminal power supply itself, to pin 4 or something else?
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Oct 20, 2023 09:15
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I don’t know poo poo about stuff, but…wouldn’t it just be ground?
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Oct 20, 2023 13:57
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The return for the load is ground, yes. This doesn't have to really be earth grounded or anything. It's just shorthand for the side of the supply that is at 0 volts by convention. There is a problem here, though: This schematic says nothing about how to power the op-amp (pins 4 and 7). It needs two additional supply voltages, one positive (like the 35V, with its negative terminal on ground) and one negative (with its positive terminal on ground), and how these should be made isn't shown in the schematic.
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Oct 20, 2023 14:43
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Ah I was wondering about that, but thought that's probably wrong. I thought the op-amp might not have needed those since they weren't included in the schematic. Weird to make a schematic that doesn't function.
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Oct 21, 2023 07:27
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Are beginner questions OK here? Trying to kludge together something and could use a little advice. Never learned electronics properly and just combining various schematics, would appreciate some help. I'm trying to use the output of a 4040 binary counter into a 4070 XOR IC to get Gray code.  Each of the 'bits' drives an LED and individual bit output, and all of them go to an R-2R DAC. However I'm not quite sure how to correctly handle the most significant bit (output of 4040's Q3 here) in context. Is it OK to just directly connect it to both the 4070 and the R-2R ladder/output section, or do I need some kind of buffer? The output of this whole section is buffered by an opamp afterwards at least. Sorry if the answer's super-simple, I don't really have the vocabulary to know how to ask properly.
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Oct 21, 2023 19:41
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His Divine Shadow posted:Ah I was wondering about that, but thought that's probably wrong. my man never read a ti datasheet
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Oct 21, 2023 20:29
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free Trapt CD posted:Are beginner questions OK here? Trying to kludge together something and could use a little advice. Never learned electronics properly and just combining various schematics, would appreciate some help.  free Trapt CD posted:I'm trying to use the output of a 4040 binary counter into a 4070 XOR IC to get Gray code. It's fine without a buffer. Your 4040 can source like 0.5mA and you're only loading it with ~0.01mA. The xor is not a significant load (check out the input currents in the datasheets, they're less than a microamp) and the 2n3904s already act as buffers for the LEDs.
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Oct 21, 2023 20:44
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free Trapt CD posted:Are beginner questions OK here? Trying to kludge together something and could use a little advice. Never learned electronics properly and just combining various schematics, would appreciate some help. Coming from a beginner myself, this thread is super beginner friendly… What’s a “Gray code”?
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Oct 21, 2023 21:21
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namlosh posted:Coming from a beginner myself, this thread is super beginner friendly… Wikipedia has an article, but it's basically a way to ensure that each incremental value only changes one bit, so if you mis-receive e.g. a digital radio signal, you're only a wee bit off instead of changing the meaning of the number altogether. e: as well as radio, it's good for things like code disks (which is what I've used it for) for measuring angles because as you rotate, only one sensor will change state and you won't get weird edge cases where only one of multiple sensors is meant to be changing state resulting in similar weird numbers. Charles Ford fucked around with this message at 21:28 on Oct 21, 2023 |
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Oct 21, 2023 21:25
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Stack Machine posted:
Thank you so much! This is very reassuring. Looking forward to getting it together on the breadboard later. namlosh posted:Coming from a beginner myself, this thread is super beginner friendly… Charles Ford has explained it well! In my case I'll be using it to switch audio signals on/off in sequence, and using Gray code means that with each step through the pattern I'll only be 'adding/removing' one signal. The resulting changes are a lot less abrupt than using the binary equivalent to control the switching. (Plus it makes a pretty pattern with the LEDs!)
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Oct 22, 2023 04:26
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I need to ground my network stack in my closet (my switch has a dedicated grounding lug for it since otherwise everything uses isolated power brick supplies) and I'm trying to figure out a good way to do that. The difficulty is there's only one wall outlet in there, and it's being taken up by the UPS power cable. I guess I could plug something like this into the UPS: But that would use up a precious UPS outlet. Is there anything out there that's like... a cheater plug, but instead of letting you defeat the earth pin it just lets you tap off it? I'm not really sure what to search for, "grounding plug" just gets me things like that one in that picture and a bunch of new-age woo devices that are the same exact thing but marketed by telling you to connect it to your bed so you can feel more "grounded" and let earth's healing energies flow through you or whatever.
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Oct 23, 2023 15:54
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Just run some 16 ga over to your bathroom sink
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Oct 23, 2023 16:19
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Shame Boy posted:I need to ground my network stack in my closet (my switch has a dedicated grounding lug for it since otherwise everything uses isolated power brick supplies) and I'm trying to figure out a good way to do that. The difficulty is there's only one wall outlet in there, and it's being taken up by the UPS power cable. I guess I could plug something like this into the UPS: Put a ring terminal on the grounding lug for the outlet and run it out the side of the outlet. Its a tad wonky but meh who cares if its your closet networking stack.
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Oct 23, 2023 16:44
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Sagebrush posted:Just run some 16 ga over to your bathroom sink The days of plumbing being a reliable source of ground are long gone.
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Oct 23, 2023 16:47
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Bad Munki posted:The days of plumbing being a reliable source of ground are long gone. This place was built in the 70's but yeah still. CarForumPoster posted:Put a ring terminal on the grounding lug for the outlet and run it out the side of the outlet. Its a tad wonky but meh who cares if its your closet networking stack. Difficulty: apartment.
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Oct 23, 2023 17:08
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Shame Boy posted:This place was built in the 70's but yeah still. Sure, there are a ton of places it’ll work, and it’s probably still more likely than not, but it’s not a blanket expectation these days, that’s all.
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Oct 23, 2023 17:24
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Shame Boy posted:This place was built in the 70's but yeah still. It takes less than 5 minutes and maybe $15 worth of tools Crimp a ring terminals on a wire. Shut off breaker to outlet. Remove faceplate. Unscrew outlet. Screw ring terminal onto grounding lug of outlet. Screw other end's ring terminal onto grounding lug or screw on case of rack. Check ground connections with multimeter. No idea what residential specs for ground wire resistance are but 1 ohm from screw to ground pin of outlet is prob fine. Reinstall by reversing this process. When you move out, remove it. EDIT: My original phrasing was dumb of me CarForumPoster fucked around with this message at 18:38 on Oct 23, 2023 |
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Oct 23, 2023 18:26
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What function are you trying to accomplish with the grounding? - fault current path for electrocution safety? - drain esd voltages? - short transients away from the device?
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Oct 23, 2023 18:37
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