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1) 127V vs 120V is easy: they're nearly the same, no conversion needed. If you measure your outlet, you'll probably see bigger variations than that. 2) Liability. Yeah pay attention to other posters, I suppose. 3) Batteries. LOL. LMAO. You are so far beyond practical battery capacity that the previous two points become irrelevant. Give up now and save yourself some time and money. e: also health inspector will get mad if it's not NSF ryanrs fucked around with this message at 05:19 on Feb 17, 2023 |
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Feb 17, 2023 05:10
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Build your own solid state relay with fancy $$$ parts because you don't care about BOM costs because this isn't a commercial product. 1) Massively overspecced $4 mosfet so you don't need a heat sink. Nexperia PSMN1R9-40PLQ NFET, 40V, 1.7mOhm 2) Fancy $3 photovoltaic output optoisolator so you don't have to think about gate drive. Toshiba TLP591B(C,F) Inside is an IR LED and a string of tiny solar cells. Output is 7V, 24uA, just enough to turn on the mosfet. Pros: Small, rugged, runs cool. Cons: Costs $7. (Let me know if you want me to draw a schematic.)
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Mar 2, 2023 21:52
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Pic of the corrosion and age of the microwave?
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Mar 2, 2023 23:02
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kid sinister posted:I'd say 5-10 years? Sorry, I didn't take pictures and I already cleaned the corrosion off and put it back together. Seems like a decent service interval. I'm not sure that warrants greasing up the power supply. Check the enclosure vents aren't blocked and moist air isn't being trapped. But if you do, at least use something nonflammable and nontoxic. If you search for food grade dielectric grease, you'll find some silicone based products. These should be fine. Brush on a thin coating, don't goop it everywhere.
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Mar 2, 2023 23:19
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Toshiba: Basic Electrical Characteristics and Application Circuit Design of Photovoltaic Couplers for MOSFET Drive for Relays Yes, photovoltaic optocouplers are slow. They are good for power switching, but not PWM. For example, you can't use them to drive the main mosfet in a switching power supply. Turn on/turn off speeds are in the <10ms range. In this case: MOSFET gate charge Qg = 120nC @ 5V Photovoltaic output = 24uA 120nC / 24uA = 5ms This is slow for an optocoupler, but fast enough that I don't think you have to worry about the printer's rise time requirements or stuff like switching losses.
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Mar 3, 2023 00:28
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DC to Daylight posted:I bet a lot of power MOSFET's would be unhappy spending a couple milliseconds in the linear regime. Especially if the rep rate were high. Yeah but that big-rear end PSMN1R9-40PLQ can do 20A @ Vds=10V for 10ms.
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Mar 3, 2023 01:07
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Amazon: Perf Board Amazon: More Perf Board
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Mar 6, 2023 09:27
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6-100V to 5V Regulator I need to regulate 6-100V down to 5V@50mA to drive a buzzer. This is an overvoltage/reverse polarity alarm, so I'm not going to build something complicated like a switcher just to drive the buzzer. The circuit should be simple and cheap, though constrained by the requirement to dissipate 5W for at least several seconds.  Will this circuit behave like I'm expecting? It relies on the LDO's 500mV dropout to operate in the linear region of the depletion FET. As the difference between Vin - Vout increases to 2-3V, the FET turns off. The idea is the big FET withstands the high input voltage and high power dissipation. In my application it just powers a buzzer, so I don't care much about how "good" a regulator it is. Things like e.g. PSRR are unimportant, but I hope it's at least stable and won't oscillate. IXTY1R6N50D2 N-ch 500V 2.3ohm depletion TO-252 DPak MCP1754S 5V LDO Also, is there a name for this topology? I guess it's a cascode?
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Mar 24, 2023 05:10
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IKR? 1.2V regulator with a 12V dropout, wtf is going on inside that chip?
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Mar 24, 2023 18:06
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I kinda want to go through Digikey's catalog and correct all the depletion mosfet that are incorrectly listed as enhancement mode. The selection of depletion mode mosfets is sparse enough without that kind of parametric search headache. Anyone have a comprehensive depletion mosfet part list? Digikey lists depletion fet manufactuers as: Microchip (Supertex), Infineon, and IXYS. Taiwan Semiconductor has 1 depletion part. Do you know of any other depletion mfgs carried by Digikey that perhaps have all their fets mislabeled? e: silicon only, not GaN ryanrs fucked around with this message at 22:20 on Mar 30, 2023 |
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Mar 30, 2023 22:18
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I feel like I am missing out on cool transistors because they don't show up in parametric search. For example, BSS139 won't show up in a search for depletion mosfets because the only in-stock part is miscategorized. (I am willing to do this free work for Digikey because their parametric search is so much better than the semiconductor manufacturer's own sites. I figure it will take a several hours.)
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Mar 30, 2023 23:01
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 work in progress 300W Power Converter 9-36V in 8-24V @ 20A out (300W max) I'm working on a new project: a rugged 300W DC-DC step-up/step-down power supply for working with cars and power tool batteries. Basically, I want to run high-power automotive stuff like tire inflators and my ham radio using a Milwaukee M18 chainsaw battery. I'd also like to use the M18 battery to recharge my car battery in an emergency (it's not powerful enough to turn the starter, but it can put a superficial charge on a dead car battery). Features: Digital output voltage control. ADCs measure input and output voltage, output current. Power, Charge, Energy monitoring on output. Robust to electrical faults, incorrect hookup. Audible alarm for reverse polarity, overvoltage. Temperature sensors. 5V 1A housekeeping power supply. 100% controlled over I2C. Core chip: LT8390 60V Synchronous 4-Switch Buck-Boost Controller TDK i7C2W020A120V-003-R is a power supply module based on the LT8390. It's very similar to the circuit on pg 28 of the LT8390 datasheet. This is the heart of my device. The input voltage passes through a fuse and a pair of big back-to-back FETs controlled by a LTC4365 Overvoltage, Undervoltage and Reverse Supply Protection Controller. It should survive +100V overvoltage and -40V reverse polarity. The output is also protected with back-to-back FETs, though under GPIO control, so they will not have as fast a reaction time. But they will prevent sparking when connecting/disconnecting cables, because they isolate the large output capacitors from the output connector until the microcontroller turns it on. A LTC2946 Wide Range I2C Power, Charge and Energy Monitor sits on the output, with its own current shunt downstream of the output filter caps. It's a DC-DC swiss army knife, designed to be controlled by an Arduino.
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Apr 3, 2023 00:22
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ante posted:I've used a TDKi7 module before. Make sure your heat sinking is good Heatsink? I was just going to blow on it with a little fan. I will have a temp sensor glued to the TDK module, so I can monitor the temp in operation. (Is this good enough? I don't see provision for a real heatsink.)  There's also this ominous footnote in the TDK docs:  I think this has something to do with the LT8390's loop compensation (see LT8390 pg 25). I guess it depends on the values of the Rs and Cs TDK put on the LT8390 Vc pin? I was planning on putting 1600 uF of aluminum polymer caps on the output, but maybe that is a bad idea? TDK support didn't respond to an email, but maybe I haven't bugged them enough. ryanrs fucked around with this message at 05:02 on Apr 3, 2023 |
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Apr 3, 2023 05:00
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Speaking of massive loads, it'll be an opportunity to try out an active load I built a couple years ago. I designed it in EAGLE + python scripts to gently caress around with polar coordinates. Historical context: At the time, people were making fun of Pence for saying 'lodestar'
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Apr 3, 2023 07:25
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Wait why are you replacing diodes and inductors with massively larger versions? Is the theory that the power supply is grossly undersized, not malfunctioning? And that a bigger diode will fix that? (I admit I only skimmed the thread tho)
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Apr 4, 2023 04:45
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Aren't all schottky diodes fast? I didn't think they had the soft vs fast recovery variations that you see in silicon pn diodes.
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Apr 4, 2023 15:01
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It sounds like you are afraid to run a continuous duty solenoid 24/7/365. But it's an electromagnet. It's not going to wear out or something, just get a little warm.
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Apr 5, 2023 17:38
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lol that's a big solenoid. Just hook it up to the master power switch and make sure it has some clearance for natural airflow, if possible. e: His Divine Shadow posted:I was looking at solenoids since they also seem like they can provide some decent force. I don't want something weak here, needs to provide forceful engagement as well as speed. Overkill option: Teknic ClearPath MC Servo. $500 gets you sophisticated motion control and enough speed and power to break fingers. You probably don't want this, but it is neat to know it exists. ryanrs fucked around with this message at 18:19 on Apr 5, 2023 |
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Apr 5, 2023 18:08
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I bet a pneumatic piston would make cool noises. (not sure if that's a deciding factor, but keep it in mind)
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Apr 6, 2023 03:14
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Ugh I need to rip up and place this bit again, because I don't have enough space for a nice silkscreen legend. To make matters worse, KiCad is slowing down and basic poo poo like dragging a trace has stopped working (I think the DRC is having seizures). Do people design big circuit boards in KiCad? Seems pretty hosed that I'm hitting noticeable performance issues with a 17 sq in board and 150 components.
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Apr 8, 2023 05:16
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Are there non-obvious things I should be doing, like turning off filled zones, or closing the 3D window when I'm working in the PCB editor? (I made those up, but are there pitfalls like that?)
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Apr 8, 2023 05:30
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Antialiasing is off, if that's what you mean. I'm running KiCad 6 on a Mac.
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Apr 8, 2023 05:47
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I don't see that option. OK, if 7.0.1 is generally stable without showstopper bugs, I will upgrade. e: Oof, no. It sounds like my hardware is no longer supported unless I want to build KiCad from source. ryanrs fucked around with this message at 06:02 on Apr 8, 2023 |
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Apr 8, 2023 05:57
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It seems to be behaving better now without the 3D window in the background. I don't know if that was the actual issue or what. But I will definitely try KiCad 7 if/when I get Mac OS 11 working on my older hardware. I suppose the hackintosh crew has something fairly functional by now, but I am loathe to mess with that stuff unless really forced to.
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Apr 8, 2023 06:09
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longview posted:Also FWIW I will just not have all components marked in silk for tight boards; no way I'm sacrificing electrical performance just to get some text on there. I have the space, and only this small bit needs to be tweaked. I don't think layout is super critical for this circuit (400 kHz 5W switching regulator). I mean, it matters, but not so much that I can't make room for a little text (I hope). This board uses 0603 passives. I did notice that with 0402s, the silkscreen was limiting density more than the actual resistors and capacitors, which isn't great.
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Apr 8, 2023 17:26
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How much should I fear soldering this 5x6 QFN? I've never soldered a QFN before, and this board will be the first pcb I reflow at home. I will be using a stainless steel stencil, an electric skillet, and a hot air station to add heat to larger components if necessary. I have an excellent microscope, and the usual electronic technician tools. The board is 140x80 mm, and I only need to make one. I wonder how much hassle/risk I'm creating for myself with this chip vs a TSSOP-20 I am using now. But the QFN chip will let me increase the switching frequency to 2 MHz, putting it above the AM broadcast band. This is for a 5W aux power supply. The main switcher on the board will be running at 250 kHz, so it's 3rd and 5th harmonics will be still be in-band. Maybe I should stick with the TSSOP at 750 kHz, in the shadow of the big regulator, ha.
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Apr 9, 2023 23:47
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Ok, sounds good. My main concern was stacking too many ‘first time’ experiments onto this one board. But it sounds like it’s not that bad.
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Apr 10, 2023 00:28
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but it's a $12 analog devices chip 
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Apr 10, 2023 01:45
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Ferrite vs metal inductors for switching supplies. Is there some frequency rule of thumb for switching supplies? I guess at 2 MHz, I'm now solidly in ferrite-land, is that right?
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Apr 10, 2023 05:34
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I thought you were supposed to sprinkle beads over your circuit to ward off EMI, like ferrite holy water?
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Apr 13, 2023 01:12
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Forgot to mention! For extra fun, the board is double sided: I feel like those ceramic caps really, really want to be on the back of the board, close to the switcher module pins. I guess I should add thermal reliefs on the backside copper fills, since I will be reflowing with hot air only (and maybe a soldering iron)? I did not put thermal reliefs on top-side SMT components because they will be reflowed on a skillet. All through hole components have relief, except the switcher module which runs 30A through a single pin. PCB stackup is 2.4mm thick, with 2 oz outer layers and 1.5 oz inner. Rework will be way more annoying than on a normal pcb.
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Apr 13, 2023 02:11
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    Board is almost done!  Bottom-side capacitor thermal reliefs. Some issues remain, like what is going on with the U9 QFN paste stencil? The aperture looks pretty under-pasted, especially with 6 vias wicking away solder. I downloaded the footprint from SnapEDA, so I better double-check it. OTOH, solder bridges under the chip would be a real pain in the rear end, so maybe a sparse paste pattern is intentional? 
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Apr 14, 2023 02:56
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That particular board will cost about $320 for the pcbs (PCBWay, 5 boards min order) and $200 in parts from Digi-key. But this is an expensive PCB (thicker fiberglass core, extra thick copper) with fancy, expensive chips (esp. Analog Devices). If I wanted the pcb factory to also do the soldering, that would add maybe another $100 or so. For a simple, little 2-layer board with a couple cheap chips, you could get 10 copies manufactured and tested for maybe under $100 (<$10/ea). I'm not sure where the floor is, but it's something like that when you're talking 5 or 10 units. If you want 100 or 1,000 the per-unit cost goes way down. These prices are for PCBWay and JLC (cheaper). Both are in China and produce good quality boards, have good English support, etc. e: I have some posts in my AI thread with detailed cost discussion. https://forums.somethingawful.com/showthread.php?threadid=3961355&userid=0&perpage=40&pagenumber=23#post526879563 https://forums.somethingawful.com/showthread.php?threadid=3961355&userid=0&perpage=40&pagenumber=24#post527070332 https://forums.somethingawful.com/showthread.php?threadid=3961355&userid=0&perpage=40&pagenumber=25#post527890652 https://forums.somethingawful.com/showthread.php?threadid=3961355&userid=0&perpage=40&pagenumber=26#post528301104 ryanrs fucked around with this message at 03:46 on Apr 14, 2023 |
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Apr 14, 2023 03:24
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For 1 or 2 boards, the real tradeoff is do you want to solder them, or do you want to write up the specs and instructions and and BOM spreadsheets to have someone else solder it?
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Apr 14, 2023 03:52
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Zero VGS posted:I've seen online services that let you design a pcb cheap [..] FYI, don't use some pcb manufacturer's bespoke web app to design boards. That locks you into their production (and higher prices). Design your boards in KiCad, which is free and better than some manufacturer's app, then get your boards made literally anywhere in the world.
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Apr 14, 2023 05:38
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SOT-23FU
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Apr 14, 2023 06:13
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Design an actively-balanced common mode choke, with a 3rd winding (w/ higher turn ratio) to cancel the current imbalance, ha ha.
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Apr 14, 2023 17:59
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Yeah anything looks crazy when sped up 10x.
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Apr 15, 2023 20:51
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Splode posted:a few cents of additional BOM cost I'm working on the BOM for that power supply board I posted on the previous page. $61.18 for capacitors.  Though that's mostly for fancy hybrid polymer caps and flex term 1210 ceramics, not bypassing.
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Apr 16, 2023 07:29
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| # ¿ May 9, 2024 14:32 |
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Splode posted:I just use a soldering iron to get the enamel off, you may need to bump up the temperature a little bit first That's gotta be how the manufacturers do it, right? It's not like they're stripping the strands individually or whatever.
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Apr 16, 2023 16:37
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