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Marsupial Ape posted:Well, when I no longer live in a desolate rural area where we don't even have a convenient Goodwill or the like and no longer have to rely on shipping for everything, I'll take your advice. I'm going to go delve my dad's garage later , but my sourcing options are incredibly limited and that's why I try to get the right thing the first time, everytime. Oh. Well in that case, electronics salvagers/closeout stores are great for things like transformers. Because they don't produced at nearly the same scale these days in addition and the material costs (metal) to make them have shot way up, I find they can be considerably less expensive that way. Dunno if you've found one somewhere already that's cheaper, but this seems like it'd be about what you're after and even has three screw terminals instead of a barrel plug. https://www.allelectronics.com/item/actx-12167/12vac-1.67-amp-screw-terminal-wall-transformer/1.html
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May 28, 2021 17:21
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Forseti posted:Oh. Well in that case, electronics salvagers/closeout stores are great for things like transformers. Because they don't produced at nearly the same scale these days in addition and the material costs (metal) to make them have shot way up, I find they can be considerably less expensive that way. That is very helpful, thank you! I’m on the lookout for a 18v version so I can squeeze everything I can out of the preamp, but that is definitely what I need. Now that I have the proper search terms I am seeing a lot more options and solutions. Ideally, I’d love to find some kind of ac-to-ac PCB mounted power supply because I could mount it under the preamp using acrylic panels and standoffs, but that is just aesthetics. Again, thank you.
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May 28, 2021 18:25
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Marsupial Ape posted:That is very helpful, thank you! I’m on the lookout for a 18v version so I can squeeze everything I can out of the preamp, but that is definitely what I need. Now that I have the proper search terms I am seeing a lot more options and solutions. What about that one I yanked the other day. I think it's 18v, I'd be glad to send it for free, WTF. ED: oh sorry, I'm seeing it's 24, not 18. Sorry. petit choux fucked around with this message at 19:31 on May 28, 2021 |
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May 28, 2021 18:37
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Marsupial Ape posted:That is very helpful, thank you! I’m on the lookout for a 18v version so I can squeeze everything I can out of the preamp, but that is definitely what I need. Now that I have the proper search terms I am seeing a lot more options and solutions. No problem! They have a bunch of those things with various ratings, but that one seemed closest to what you were looking for at a quick glance. Also holy poo poo you can tell I edited the second sentence but didn't read it back  Here's a short list of the electronics surplus sites I like to browse off the top of my head:
I tend to use the top two the most often though, especially Electronics Goldmine who have crazy deals on random crap all the time that I like to waste money on and put in drawers
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May 28, 2021 18:39
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petit choux posted:What about that one I yanked the other day. I think it's 18v, I'd be glad to send it for free, WTF. Thanks, but you're already being too generous with my dumbass as it is. In fact, I accidently bought two of these pre-amps and send you one as Monkey's Paw. When I get to the water plant, tonight, I'll rummage through the junk pile. I don't think they've thrown away a single telemetry meter or piece of lab equipment in the last 30 years after upgrading or replacing. I do believe the life lesson here is that I should double check power supply documentation and stick with AC to DC. Which means I'm finally going to convert this old ATX power supply into a bench top power supply... Forseti posted:No problem! They have a bunch of those things with various ratings, but that one seemed closest to what you were looking for at a quick glance. Also holy poo poo you can tell I edited the second sentence but didn't read it back Thanks for the resources. I love crazy deals on weird things. I can't wait for flea markets, again. Anyway, every thing I am doing right now is in service of of eventually building a completely DIY DML panel speaker system. The speakers themselves are dirt simple and cheap to make. The trick is finding a decent amp kit. More on that, later.
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May 28, 2021 19:19
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Shame Boy posted:Sure but like, we're talking about stuff that connects to wall power here, something you really really do not want to gently caress with directly unless you have to. Like I've been doing this for years and it still makes me kinda nervous when I have to do it. If you really really want to do it anyway, at least include a fuse, run it from a GFCI outlet, and don't leave it plugged in and unattended.
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May 28, 2021 21:41
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Foxfire_ posted:Seconding this. Mains power is not a good first learning project because the failure modes can be hazardous shock/fire instead of just not working or destroying your project. And don't forget to clean your clothes dryer's lint trap. ...never said I was going to kit bash my own step down transformer out of a fork and a chain of diodes, guys. I just wanted to know what my options were so I wouldn't have any types of failures or injury. I apologise for asking electronics questions in the "learning electronics" thread.
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May 28, 2021 21:56
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Oddly aggressive response for someone suggesting that designing your own mains powered device as a beginner project has a high chance of very negative outcomes. You did imply you were going to do that, so it's a valid warning. Also nothing like nagging you to clean out the lint trap. Because we use electricity every day, it's easy to get complacent and forget that it can kill you, or for beginners to assume that the danger is overblown, and multiple professionals have already chimed in to say that they are very nervous when working with mains
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May 28, 2021 22:14
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You seem kind of touchy. Everyone here is trying to help and it wasn't clear from your original post what your skill level was, how much hacking around you were comfortable with, or how much access you have to electronics parts. I assumed: low skill, wants to hack, has what you'd expect to find in an average city. Some of those were wrong, I guess. Like, finding an appropriate wall wart and opening it up and wiring it into your project is about as simple as it gets (mains voltage concerns aside). If you live in a place where wall warts aren't available, or you don't want to take anything apart, cool, there are ready-to-go AC-out transformers you can buy instead. That's not really "learning electronics" though, that's just sourcing a part. It's also not really clear what your goal is. You started out saying you wanted to power this amplifier but now you're saying you want a bench supply. These are two very different things. Do you just want the amplifier to work, or do you want to hack around with the electronic aspects of it? What is the purpose of the bench supply? Can you get any parts locally? Are you okay with maybe screwing things up now and then as part of the learning process? Sagebrush fucked around with this message at 22:31 on May 28, 2021 |
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May 28, 2021 22:25
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Asking questions is fine. But if you ask a question about doing something with some inherent danger, the correct answer is (or, at minimum, includes) "this is dangerous. Please don't do it as a beginner project." Try to remember that you're not the only person reading the answer to your question. There may be other beginners in the thread who would be very poorly served by an air of complacency around working with mains electricity, to put it lightly.
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May 28, 2021 22:30
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ante posted:
When, exactly, did I say that? I asked what my buying options I had for equipment, either preassembled or not. I never suggested I was going to bread board a transformer. I'm not the one suggesting I wrap my own ferrite rings, for chrissakes.
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May 28, 2021 22:30
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Marsupial Ape posted:When, exactly, did I say that? I asked what my buying options I had for equipment, either preassembled or not. I never suggested I was going to bread board a transformer. I'm not the one suggesting I wrap my own ferrite rings, for chrissakes. Christ's sake dude you just said this on the last page when someone told you to just buy an appropriate adapter: Marsupial Ape posted:The easy way is not the fun or educational way. Do you just want to buy an adapter and be done with it, or do you want to mess around with electronics?
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May 28, 2021 22:34
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Sagebrush posted:Christ's sake dude you just said this on the last page when someone told you to just buy an appropriate adapter: I meant that in regards to finding a purpose built device for this particular instance instead of going the route of simply buying a wall wart. If that’s where you’re getting that I want lick a wall socket then, fine, that’s the misunderstanding. I’m just getting agitated at being accused of being stupid/unsafe by the same people who told me to break open an old wart or cable wrapping a ferrite core by hand. So if it’s a misunderstanding of intent, then, fine. Let’s move on.
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May 28, 2021 22:50
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Cool Here's that horrifying flesh coloured PCB I mentioned making earlier 
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May 28, 2021 23:05
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Mmm... forbidden caramel.
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May 28, 2021 23:12
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ante posted:Cool That is some Cronenberg poo poo, right there. Edit: I just realized that it looks like it has a bite taken out of it on the left side. This thing is SCP entry inspiring. Marsupial Ape fucked around with this message at 23:28 on May 28, 2021 |
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May 28, 2021 23:14
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Edit: wrong thread, sorry
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May 28, 2021 23:17
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Marsupial Ape posted:I meant that in regards to finding a purpose built device for this particular instance instead of going the route of simply buying a wall wart. Well I can try to answer that I guess, realistically your options for benchtop low voltage AC are an isolation transformer + a variac (kinda bulky and expensive for what you're trying to do but it'd work), some lab-grade low voltage isolated AC power supply (i'm sure they exist but they're not exactly something common so they'd probably be expensive), buying a transformer like the one you mentioned before and wiring it up yourself (still kinda dangerous but manageable), or getting a wall wart (safest but makes an assumption that the circuit you posted is actually two AC connections and GND, not AC / center tap / AC, and I don't think I can tell from the pictures). Sorry if I came off as calling you an idiot or unsafe, I didn't mean that at all. Personally I stress the wall power safety stuff with everyone, even if I already know they know what they're doing. Like I even do that with my dad and he's been doing this for nearly 50 years now. The reason is, I've had a probe wire explosively vaporize in my hand before while I was probing a part of a circuit I thought (but didn't verify) was grounded. Scared the poo poo out of me, felt like I was holding a firecracker right in front of my face and I was incredibly lucky I didn't lose a finger in the process. Really, being electrocuted is the most tame possible danger when working with wall power. I'd rather come off as a bit annoying and saying obvious stuff everyone already knows than have me or you or anyone else experience that cuz their thinking lapsed for a moment like mine did. But anyway yeah sorry, I hope I / we didn't discourage you from doing cool electronics stuff or feeling like you're free to ask questions in this thread or anything.
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May 29, 2021 01:34
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I'm done rehashing it. I will say that after going back reading response that were edited after I responded, there is either some willful misunderstanding or skim reading going on. I never said I was going to build a variable AC bench top supply. I said I was going to convert an ATX power supply into a DC desktop power supply and avoid AC powered devices in the future. I'm done with it and will not respond to any more conflict on the matter. Anyway, after reading the documentation on a Velleman amp kit that uses stepped down AC, they had a list of suggested power supplies, which turned me into actual torrodial transformers meant for the task. I will be getting some thing like This. I've seen others that are wired for ground on the primary side and may go with that. Interestingly, I did find a YouTube video by an (I guess) engineer who has the very same preamp and explains then why and how of converting it to DC. I may pursue that if I catch another preamp super cheap.
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May 29, 2021 04:21
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Marsupial Ape posted:Anyway, after reading the documentation on a Velleman amp kit that uses stepped down AC, they had a list of suggested power supplies, which turned me into actual torrodial transformers meant for the task. I will be getting some thing like This. I've seen others that are wired for ground on the primary side and may go with that. Neat! I had suspected it was a 24VAC center-tap! This is just based on Art of Electronics old-school opamp design with the +-15VDC rails. Old logic chips took all kinds of crazy "high" voltages compared to modern ones, and 24VAC was basically ubiquitous in every household: the aforementioned HVAC controls, doorbell transformers, all manners of small isolated clocks and things.... That's why a lot of those audio circuits are based around 24VAC with center tap: you get a pair of 15V rails, which is about the power supply limit for chips of the day, so you could get as wide as possible an amplification range out of your just-barely-integrated circuits. Rail-to-rail opamps and especially single-sided full-range IC opamps are super rare in tiny cheap audio designs. Elegantly stated thus: M_Gargantua posted:Almost everything in the audio world makes me either sad, or in cases of poor engineering practice that is merely a carryover from yee-olden days that continues to get used, just angry edit: if you ever find an audio circuit with a neon lamp ANYWHERE in it, just pass it by. ESPECIALLY if it's on the secondary side of a transformer, but ESPECIALLY if it's on the primary side of the transformer and not just parallel with the fuse.
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May 29, 2021 05:52
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babyeatingpsychopath posted:edit: if you ever find an audio circuit with a neon lamp ANYWHERE in it, just pass it by. ESPECIALLY if it's on the secondary side of a transformer, but ESPECIALLY if it's on the primary side of the transformer and not just parallel with the fuse. Heheh voice of experience there. The rare neon lamp/audio amp combo.
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May 29, 2021 11:27
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Does anybody know of any current production electret mics that approach the quality the quality of the now discontinued Panasonic WM-16A? I know about the JLI-61A, I can’t find a source that won’t skin me on shipping. I’m making some lavalier mics as gifts for friends.
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May 29, 2021 12:00
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Maybe a dumb question, but would this 12 volt light ballast work for my preamp, or do I need an actual 24volt transformer because it is 12-0-12?
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May 29, 2021 21:40
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Ballast is such an imprecise term. I'm not sure what's going on inside that. It might be a lot different than just a transformer. Flourescent tube ballasts do a ton of power conditioning, for example
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May 29, 2021 21:51
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ante posted:Ballast is such an imprecise term. I'm not sure what's going on inside that. It might be a lot different than just a transformer. Ah. Good to know. I am literally just looking for what I can get in the next town over. My dad’s garage may have just come through. Bless that old horder, he had a 12 volt charger to a flashlight he lost in the early 00s. Edit: I got the transformer out fairly easily, but it is not center tapped. At least I have a part for later. Marsupial Ape fucked around with this message at 23:10 on May 29, 2021 |
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May 29, 2021 22:08
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Marsupial Ape posted:Ah. Good to know. I am literally just looking for what I can get in the next town over. Find a second one. Wire them together. Get your project powered to see something work. Do not despair. Tinker, experiment, be careful, wary, and quick to jerk back and pull the plug. I'm not sure how in-the-sticks you are, but hardware store doorbell transformers will get your circuit powered. This is not High End Audio yet. This specific power application is not the final form of the project. I want to urge you to not let "exactly what I want, perfectly, the first time" get in the way of "something working," since down that path is frustration. This hobby is not easy, because there are so many options. However, getting center-tapped 24VAC into a circuit is a problem that was solved in the 1920s, and that tech lingers on well into the 2020s.
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May 30, 2021 04:01
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babyeatingpsychopath posted:Find a second one. Wire them together. Get your project powered to see something work. Do not despair. Tinker, experiment, be careful, wary, and quick to jerk back and pull the plug. I'm not giving up on it, I'm just working on my next project as I regroup for this one. I am currently putting together an Elenco bench top DC power supply, but adding the very simply mods of a on/off switch and a digital voltage display. Lovely way to spend an evening while listening to podcasts. I'm attempting a simple reflow on the completed PCB board, right now. I pre-warmed my oven to 200 (using two different thermometers to make drat sure), turned it off, and placed the PCB to sit while it cools. We'll see if I totally hosed it up. You got a tutorial on wiring two transformers in series? Also, yes, I l know the Elenco DC regulator kit has a center tapped transformer in it perfect for my needs. That is not lost on me.
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May 30, 2021 04:57
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Marsupial Ape posted:I'm not giving up on it, I'm just working on my next project as I regroup for this one. I am currently putting together an Elenco bench top DC power supply, but adding the very simply mods of a on/off switch and a digital voltage display. Lovely way to spend an evening while listening to podcasts. I'm attempting a simple reflow on the completed PCB board, right now. I pre-warmed my oven to 200 (using two different thermometers to make drat sure), turned it off, and placed the PCB to sit while it cools. We'll see if I totally hosed it up. Not much gets past this ape.
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May 30, 2021 05:40
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Marsupial Ape posted:You got a tutorial on wiring two transformers in series? Not really; I know from basic electrical theory how transformers work, and how "in series" is a very strange way of describing your problem. Let's take a transformer. Good old 120VAC -> 12VAC.  Ok. Now let's take two transformers and wire them in series. Should give us 120VAC -> 24VAC, right?  Oh. So two in series is still 120VAC -> 12VAC, but now we have two 6VAC outputs with respect to the newly-manufactured "center tap." This could be useful. Not right now, we want "12VAC complementary outputs." Something like this: we wire the primaries in parallel, and the secondaries in series.  Oh. Well. That's not actually a complementary waveform. It appears as though they're both in-phase with each other? There's more than one parallel in AC, though! BEHOLD:  Now the waveforms are complementary. It's a miracle granted us by Faraday or Culoumb or Gauss or Maxwell or someone. But, like who cares, right? It looks like both of those things are positive.... I thought we wanted "complementary" which means a positive and negative? Oh, right, our circuit that we actually care about takes the center tap as its zero-volt reference, thus:  Amm, it still looks like both of those are positive with respect to the ground. They have the same relative polarity at every point in time. This may be what the circuit wants. however, with the other way of wiring our primaries, we get this:  Which is a positive voltage in one leg while there's a negative voltage in the other. The waveforms are in-phase, but SO WHAT?! The DC on the output probably doesn't care. Unless it does, which is why the manufacturer is specifically asking for "12VAC center-tap with complementary outputs." Even though that phrase is fraught with ambiguity, as we've seen. Regardless, anything on the left side of the coils pictured can kill you dead, so be careful about what you're touching while it's plugged in. If you can hold the bare transformer in the palm of your hand, it PROBABLY can't output enough energy to kill you dead with anything on the right side of the coil. If you hook it up backwards, then it'll REALLY HURT and possibly burn you, and maybe paralyze your arm for a while, but it probably won't kill you dead unless you've got a dicky heart. Be careful and don't let the smoke out.
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May 30, 2021 06:54
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Hey great post! I mean I'm not looking to gently caress with wall power anytime soon but this is good to know. Any more tips to keep from shocking yourself? Would it help to wear gloves?
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May 30, 2021 07:18
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Cory Parsnipson posted:Hey great post! I mean I'm not looking to gently caress with wall power anytime soon but this is good to know. Any more tips to keep from shocking yourself? Would it help to wear gloves? General rule is to try to find a way to work with it when it's not powered up. If you gotta work on it when it's powered:
My usual process for working on live stuff is to use alligator clips to clip my meter on to whatever I'm gonna measure, then power the thing up once I'm fully clear, take measurements, power it down again, repeat. If I need to probe around while it's powered up, I'll clip on to one thing (the neutral line for example) and then that way I can probe using one hand with the other in my pocket. It's a little fiddly and annoying to have to switch things on and off and work around it like that but you get used to it and it's not that big a deal after a little bit.
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May 30, 2021 08:07
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Wow. That was fantastic. I meant ‘parallel’ instead of ‘series’, so you’re going to have to scrap it and start over, but, wow. Seriously, that was informative, but don’t worry about me playing with AC any time soon. I completed the Elenco DC regulator and have thoughts and comments. The PCB survived the oven and my soldering did look much more uniform. I had cleaned the completed board with soapy water and a isopropyl alcohol rinse before the oven, too. The power supply works as advertised and I did not gently caress it up. The added on/off switch makes me feel much safer. Testing with the multimeter shows that the maximizing out put is 17.8 volts instead of just 15. I’m glad I wired in the LCD voltage meter. One hick up, though. Why I was soldering on the power indicator LED, both the drat solder pads came off when I desoldered it to adjust the height. Lacking and copper tape or epoxy, I scrapped the silk screen off the copper leads with a razor blade, cleaned with alcohol. They tinned right up and the LED jointed in fine on both new contacts. I should have multimetered it, but I figured I’d dodged a bullet. Of course, the LED doesn’t come on when the unit powers on. It’s currently 2 am, so I am going to leave the disassembly and trouble shooting for tomorrow. Here are my current hypotheses: 1. Tinning the leads did gently caress all and I just don’t have a power LED, now. 2. I put the LED in backwards after stressing over the lifted solder pads. 3. The LED was ruined by the oven. It was only 200f and was turned off to cool as soon as I put the board in, but I now now that those little LEDs have a max temp of 140f. 4. I had to use an LED from my own supply because the original was cut too short…and I grabbed one of the duds from when I playing with an AA battery. 5. I’m bad at this and should quit. Otherwise, I had a blast putting together a new tool.
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May 30, 2021 08:26
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Re that LED, it should be possible to diagnose it with a multimeter. You can check the voltage across the leads. If it's the full supply voltage you know it's an open circuit and the LED has gone bad or is connected backward. If it's 0V you know something isn't connected or the led is shorted, internally or on the board. And you can trace the voltages through the resistor to the supply to see where the problem is. If the resistor has the full supply voltage across it, the LED is short. If it has 0V across it, something's open.
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May 30, 2021 13:17
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Marsupial Ape posted:Otherwise, I had a blast putting together a new tool. babyeatingpsychopath posted:Not really; I know from basic electrical theory how transformers work, and how "in series" is a very strange way of describing your problem.
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May 30, 2021 15:46
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BTW, the little program I used to make those diagrams is Falstad Circuit Simulator. There's an offline java version that's a couple of revisions back, but still (obviously) plenty useful for getting a feel for normal things. It's got transistors and diodes and 555s in it, too.
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May 30, 2021 16:27
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petit choux posted:Which is more or less what I thought I'd be getting with that train power supply the other day. I don't know if my being tired of digging through crates for the right power supply is enough to motivate me to build one of these but it is tempting. What does the oven phase do? The kit is only $30 or so depending on where you get it. If you’re needing a quick and dirty (but safe) power supply, get one of those adjustable voltage wall adapters that comes with changeable plug heads. They can have multiple setting from 12v down. Snip the head off the cord and you can attach the positive and negative wires to the posts of a breadboard or into the terminals of your project. Or solder alligator clips onto the ends. Go nuts…just don’t let them touch, of course. The oven phase is to reflow the board after my initial soldering. The idea is that the solder will flow just enough to make the best joints possible and then cool in place as the oven cools. It’s actually part of the manufacturing process in electronics plants. Some people even hack toaster ovens with Arduino controlled thermocouples to get it just right. Honestly, I do it because when I am done with a board, I scrub it with a tooth brush and dish soap and rinse with isopropyl alcohol or distilled water. This cleans off all the flux and residue to make sure up don’t get shorts and the like. A cooling oven is a safe way to dry it. And my LED problem was that both the 2.2k resistors were bad! Fucker was putting 21v through the LED. Yikes. I put desoldered and replaced them and now my new DC power supply is fully functional. I learned a lot about trouble shooting and my multimeter this afternoon.
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May 31, 2021 01:58
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You don't have to snip anything, they usually come with adapters that you can get to having a screw terminal. Also, they aren't very good. If you need the actual voltage and not somewhat close to the voltage, just get an actual power supply. The one I've got would sometimes be nearly half a volt off from what it should be. It also causes weird artifacts with a microcontroller I have that doesn't happen with my bench power supply.
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May 31, 2021 06:30
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Cojawfee posted:You don't have to snip anything, they usually come with adapters that you can get to having a screw terminal. Also, they aren't very good. If you need the actual voltage and not somewhat close to the voltage, just get an actual power supply. The one I've got would sometimes be nearly half a volt off from what it should be. It also causes weird artifacts with a microcontroller I have that doesn't happen with my bench power supply. Haven't had that many wall warts that didn't vary by at least 1V from their stated voltage.
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May 31, 2021 14:44
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Transformer-based wall warts can be pretty accurate if they're properly loaded. Remember that a lot of them were designed for old relatively inefficient electronics, so they'd be pulling a decent amount of current in use. Take your 2A wall wart from an old answering machine and use it to power an Arduino that draws 15 mA and you might find it's quite a bit higher than the nominal voltage.
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May 31, 2021 15:06
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Sagebrush posted:Transformer-based wall warts can be pretty accurate if they're properly loaded. Remember that a lot of them were designed for old relatively inefficient electronics, so they'd be pulling a decent amount of current in use. Take your 2A wall wart from an old answering machine and use it to power an Arduino that draws 15 mA and you might find it's quite a bit higher than the nominal voltage. Hey! Maybe that helps explain it. I always just assumed low QC and a lot of gear having wider tolerances than stated. I think I like your explanation a lot better.
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May 31, 2021 15:10
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