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Bistromatic posted:I've been looking at rolling ball tilt switches recently and while i get the general principle i haven't been able to find out how the behaviour differs for the variants with one ball, two balls and two differently sized balls. All googling has just led me to pages selling them without explaining the finer points. Two ball variants are less prone to random disconnects as they're moved about, because the balls lodge against two points. If you've ever had a trunk light in an older car that flickers if you jiggle the lid, that's either a mercury or one ball switch.
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Mar 1, 2019 18:33
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KnifeWrench posted:I don't have a recommendation off hand, but I know that there it's relatively common for accelerometers to have a "shake-to-wake" sleep mode that will send an interrupt on motion. Thanks for the knowledge on terms. Shake to wake does sound like what I'm aiming for. CopperHound posted:Is battery life a concern? If so you'd probably want to explore the direction of tilt switches so you can leave the device in a power down sleep to be awoken by digital interrupt. You could also set up a voltage reference trigger on an analog input with a little more power draw. Ultimately, yes. This will be shrunken down in the end (assuming I can do it haha), and the point of all this is to make a battery in a watch last longer than normal. I did not know that tilt switches could be used in this manner. I'm worried with a tilt switch that it will only recognize large tilts as opposed to, say, picking the watch up off a table.
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Mar 1, 2019 18:33
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If you can define how it's going to be picked up every time (like, it's always sitting flat on a table with the same side facing up, and people are going to just grab it to pick it up and not gingerly lift it or anything) you can just use one or more tilt switches oriented so that they will tilt when jostled from the default "up" direction. If it needs to be more arbitrary than that you'll probably want to go with a 3-axis accelerometer and just look to see change in any direction above a certain threshold.
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Mar 1, 2019 18:36
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Shame Boy posted:If you can define how it's going to be picked up every time (like, it's always sitting flat on a table with the same side facing up, and people are going to just grab it to pick it up and not gingerly lift it or anything) you can just use one or more tilt switches oriented so that they will tilt when jostled from the default "up" direction. If it needs to be more arbitrary than that you'll probably want to go with a 3-axis accelerometer and just look to see change in any direction above a certain threshold. Unfortunately yeah, it'll be pretty arbitrary. The idea is that when you don't wear the watch for 30+ minutes, the mechanism stops but it digitally still keeps time. When the watch is picked up to be worn again, it rotates the hands to what the current time is, without any winding. I looked into vibration sensors (as suggested) and that might work as well?
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Mar 1, 2019 18:38
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Claes Oldenburger posted:Ultimately, yes. This will be shrunken down in the end (assuming I can do it haha), and the point of all this is to make a battery in a watch last longer than normal. I did not know that tilt switches could be used in this manner. I'm worried with a tilt switch that it will only recognize large tilts as opposed to, say, picking the watch up off a table. Is this a particularly large watch or are you trying to cram a full microcontroller and accelerometer assembly into a normal wristwatch alongside the mechanism already in there? Because the latter would be very hard if you don't have access to like, full industrial assembly systems that can handle teeny tiny parts...
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Mar 1, 2019 18:38
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Shame Boy posted:Is this a particularly large watch or are you trying to cram a full microcontroller and accelerometer assembly into a normal wristwatch alongside the mechanism already in there? Because the latter would be very hard if you don't have access to like, full industrial assembly systems that can handle teeny tiny parts... Right now I'm just trying to make a prototype that works the way I want it to. It's kind of a 50/50 learning project but also something that could work (a mechanism like this already exists, albeit in a very expensive watch). In the end, I would be custom making the watch movement to include all these parts, but tbh mostly this is for fun and (can I do it) rather than an actual serious project I want to finish and bring to market ASAP.
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Mar 1, 2019 18:43
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I'm dumb and didn't actually research any accelerameters. It looks like some have interrupt outputs so you can use one in combination with a powerdown sleep: https://www.adafruit.com/product/4097 CopperHound fucked around with this message at 18:54 on Mar 1, 2019 |
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Mar 1, 2019 18:43
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mewse posted:I'm slowly working my way thru a youtube series called "getting to blinky" about making a schematic + board layout using kicad He (Chris from Contextual Electronics) has quite a few good videos on his channel related to KiCad. Well worth checking out for anyone getting started with it.
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Mar 1, 2019 18:45
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Queen Combat posted:Two ball variants are less prone to random disconnects as they're moved about, because the balls lodge against two points. If you've ever had a trunk light in an older car that flickers if you jiggle the lid, that's either a mercury or one ball switch. Thanks, that makes sense!
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Mar 1, 2019 18:49
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CopperHound posted:I'm dumb and didn't actually research any accelerameters. It looks like some have interrupt outputs so you can use one in combination with a powerdown sleep: Thank you! Something to look into anyways.
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Mar 1, 2019 19:06
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One Legged Ninja posted:Hopefully I'm misunderstanding, but if those pushbuttons are your piezo buttons, the microcontroller doesn't have enough analog inputs to read them all. They'll still only be on/off. Yeah this one is just push buttons on digital. When I implement the piezo buttons I will have to get a different board or use a multiplexer.
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Mar 1, 2019 20:58
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A student came in today with her guitar amp and asked me, as the Professor Who Knows Electronics, to take a look at it. I don't know a whole lot about audio electronics specifically but we opened it up anyway. It's a transistor amp -- inside is just a ton of of capacitors and resistors, some TO-220s that I assume are the output stage, and a number of ICs on carrier boards, with a rack of potentiometers on the front end as the equalizer. Forgot to get the part numbers of the ICs but I assume they're the actual amps. I didn't see any popped capacitors, burnt components, or loose solder joints. The symptom is that it works fine when first turned on and if she only plays low notes, but when she gets higher up the scale it suddenly starts to get "crunchy" and then gets stuck in that state. Something about going to a high frequency messes it up. It sounds to me like a problem with one of the IC boards, because if it were an analog component going bad it should probably go back to normal as soon as she plays low notes again, right? Anyway I don't know what's going on but it's a curious puzzle now and I wonder if anyone here has the experience to know what might be going on?
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Mar 1, 2019 21:35
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Sagebrush posted:It sounds to me like a problem with one of the IC boards, because if it were an analog component going bad it should probably go back to normal as soon as she plays low notes again, right? CopperHound fucked around with this message at 22:11 on Mar 1, 2019 |
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Mar 1, 2019 22:05
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Are you sure it's not just warming up over time and the problem appears once it's up to temperature? I assume you've tried just immediately playing the high note and it happens right? Once you've triggered it, does it constantly emit crunching sounds, or is it just audible when you play a note? With no input, is the amp quiet? Does it still happen if you play it very quietly? Does the volume control affect it at all?
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Mar 1, 2019 22:30
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Does it sound cool? You might have something there
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Mar 1, 2019 22:31
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Shame Boy posted:Are you sure it's not just warming up over time and the problem appears once it's up to temperature? I assume you've tried just immediately playing the high note and it happens right? That was my first guess/question, too, and she says that it happens as soon as she plays the high notes regardless of when that is, but that she didn't check if it also screws up without playing the high notes if you just leave it for a while. So it's definitely frequency-related but temperature isn't completely ruled out. I don't know if there is some kind of frequency/power relationship that might lead to that kind of behavior. CopperHound posted:My shot in the dark would be some analog component latching-up. Maybe Something is definitely latching, based on what she described, but yeah I dunno what in the amp could cause that behavior. None of the passives should do anything like that to my knowledge, though your idea about something getting driven too hard and going past its breakdown point etc could be something to look at. ante posted:Does it sound cool? I haven't heard it, but she is a for-real musician (I think she played SXSW last year) so if she says it's not right then probably it's not interesting enough to use.
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Mar 1, 2019 22:48
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Rule out temperature with a quick (though long enough to discharge caps) off-on. It won't cool instantly, but it will unlatch if it's something purely electrical
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Mar 1, 2019 23:14
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Was just mucking around with ElectroBOOM's "taser" experiment and got a very educational reminder that high voltage don't give no fucks about thin insulation. http://i.imgur.com/P6l8fdq.gifv
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Mar 1, 2019 23:57
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Sagebrush posted:A student came in today with her guitar amp and asked me, as the Professor Who Knows Electronics, to take a look at it. I don't know a whole lot about audio electronics specifically but we opened it up anyway. It's a transistor amp -- inside is just a ton of of capacitors and resistors, some TO-220s that I assume are the output stage, and a number of ICs on carrier boards, with a rack of potentiometers on the front end as the equalizer. Forgot to get the part numbers of the ICs but I assume they're the actual amps. I didn't see any popped capacitors, burnt components, or loose solder joints. smells like some analog part is going into oscillation at a freq above audible range and locking up doing all its work up there. I'd check bypass caps (lil' ceramics) and filter caps. Feedback networks in amps are usually relatively low current, so I don't think it's a fried resistor.
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Mar 2, 2019 19:35
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Parts Kit posted:Was just mucking around with ElectroBOOM's "taser" experiment and got a very educational reminder that high voltage don't give no fucks about thin insulation. Oh wow, that video made me laugh. Is his stuff always like that?
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Mar 5, 2019 16:06
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Saul Kain posted:Oh wow, that video made me laugh. Is his stuff always like that? Dude is a master of deadpan humor. His first video is one if my all time favorites, but it might have helped that I wasn't expecting it to be so funny: https://youtu.be/RtlYi1yLTVQ
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Mar 5, 2019 16:29
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Saul Kain posted:Oh wow, that video made me laugh. Is his stuff always like that? You should check out more of his videos, they are pretty entertaining. He is always shorting things out and hurting himself for educational purposes.
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Mar 6, 2019 00:02
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Yeah electroboom is great. He's very smart and competent but also knows how to make things entertaining without being awkward or cringey. He shows stupid ideas, but then explains how they're stupid (or not) so you learn about electricity and safety. His most recent one where he builds a thermostatically controlled seat heater with an oven element and a couple of wires connected to a meat thermometer is the  est thingThis is my personal favorite though https://www.youtube.com/watch?v=TwIvUbOhcKE
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Mar 6, 2019 00:47
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Sagebrush posted:Yeah electroboom is great. He's very smart and competent but also knows how to make things entertaining without being awkward or cringey. He shows stupid ideas, but then explains how they're stupid (or not) so you learn about electricity and safety. His most recent one where he builds a thermostatically controlled seat heater with an oven element and a couple of wires connected to a meat thermometer is the This guy is a clown in a bad way.
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Mar 6, 2019 00:50
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If you want to see someone put themselves in danger with electricity this is the way to go: https://www.youtube.com/watch?v=HUW7dQ92yDU https://www.youtube.com/watch?v=B_olmdAQx5s
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Mar 6, 2019 00:52
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Novo posted:You should check out more of his videos, they are pretty entertaining. He is always shorting things out and hurting himself for educational purposes. I take his videos as educational. As in I never trust a loving thing he says until I research it myself. The heated chair thing is of interest as I am building an alcohol still and somewhat fine temp control of an element is of interest.
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Mar 6, 2019 13:56
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Humphreys posted:I take his videos as educational. As in I never trust a loving thing he says until I research it myself. The heated chair thing is of interest as I am building an alcohol still and somewhat fine temp control of an element is of interest. controlling anything with heat is hard as poo poo, it takes way too long for the kettle wash to respond b/c its buffered by all that thermal mass. control reflux instead 
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Mar 6, 2019 22:57
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Humphreys posted:I take his videos as educational. As in I never trust a loving thing he says until I research it myself. The heated chair thing is of interest as I am building an alcohol still and somewhat fine temp control of an element is of interest. Oh for sure. He's clearly knowledgeable, but I thought it was obvious that pretty much all his projects (even the ones that work) are poorly conceived and executed (aka "jokes"). That's the entertainment for me. I shudder to think of anyone actually trying to learn electronics from his channel.
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Mar 7, 2019 20:30
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Learn electronics, maybe not, but learn about some interesting project ideas, maybe..
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Mar 7, 2019 21:04
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Can y'all do a quick double-check of my RF layout before I send it out to get made? Here's what I got: I've turned off all the layers but the top one since in this area there's only stuff on the top anyway. The only non-RF bit here is the reset button in the upper left, I figured it would be ok there because most of the time it'll be doing nothing, and any interference it generates when you push it really won't matter because, well, the thing will be resetting. R7, C12 and L4 are injecting power into the antenna line to power active antennas, I've done that part exactly like in the datasheet so I'm pretty sure it'll be fine. Similarly C13 is a DC-blocking capacitor matching the specs of the one in the datasheet. All the standard components are 0603, except R7 which is 0805 since it needs to dissipate slightly more heat. I fiddled with the SMA connector footprint to just run the same width of track right to the edge. I also tried to make the SMA/U.FL solder jumper as small as I could but it's still much thicker than the trace, I hope that's not going to be a problem... The trace width is 0.35mm, the separation from the ground on either side is 0.2mm, dielectric thickness is 0.2mm and dielectric constant is 4.6. According to this calculator, that should give me an impedance of 49.84. Did I do that right?
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Mar 8, 2019 19:28
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Are you sure you can solder that center pin? It looks like a really thin pad with very close ground fill. Wrt. the bias feed: R7 is largely irrelevant to performance since it's isolated by the inductor. Choosing a good inductor is key, a good capacitor is secondary. My guess is if you have any notable input losses, they are likely to occur right there, not in the traces. Most wirewound inductors are probably fine, ferrite core based ones can be pretty lossy. With the length of your traces there I doubt you'd have noticed anything at all if you skipped all of the research and just did whatever, but it's good practice and learning so I can't hate on it  If you were truly concerned about shielding the signal you'd probably want to run the trace on an inner layer with ground fill on top, but that's probably not worth the effort since putting the entire thing inside a metal box will work even better. Coupling to a 4 layer PCB like that is probably minimal anyway. Also FYI in general when a PCB manufacturer actually does an impedance matching for high end (non RF but high speed digital on FR408) boards with coupons and stuff, the impedance is only guaranteed to +-10% - I don't know how close they actually get in practice though. The following applies to active antenna systems only, for passive antennas you're absolutely right to care: With an active antenna, you don't need to care much at all about impedance matching or losses, you need to care about the system noise figure/link budget. Insertion losses in your receiver are irrelevant if your antenna has enough gain vs. the cable losses and your actual receiver noise figure. When this is designed properly, the sensitivity/noise floor of the receiver system is (almost) entirely determined by the first antenna+LNA noise figure and gain. For example: Spectracom Epsilon GPS clocks work fine when installed as specified, with ~10 dB excess gain (i.e. if you have a 20 dB gain antenna, you can have around 10 dB cable loss leaving 10 dB excess gain). They require this because the 5V bias feed in those clocks has 6-7 dB loss (it's really bad, don't know why they did it that way).
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Mar 8, 2019 20:14
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The separation between your antenna trace and the ground plane seems really small, but if you've used a calculator it is probably right. I assume you've got an unbroken ground plane underneath
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Mar 8, 2019 23:08
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longview posted:Are you sure you can solder that center pin? It looks like a really thin pad with very close ground fill. Yeah I've soldered pins that small in the past. To make it a bit easier I made sure it extends out past the end of the center pin of the SMA connector. I plan on laying down solder paste, soldering the ground connectors first to provide rigidity, then heating the whole thing up on my reflow heater thing and melting it with a heat gun. Then if I need more solder I can put some at the very end and it should wick itself under via capillary action. longview posted:Wrt. the bias feed: R7 is largely irrelevant to performance since it's isolated by the inductor. Choosing a good inductor is key, a good capacitor is secondary. My guess is if you have any notable input losses, they are likely to occur right there, not in the traces. While I designed it to support an active antenna, I'd like it to be able to use a (reasonably good, large) passive antenna as well if I can get away with it, so I did my best to keep everything short and small and hopefully if I need to I can just leave out L4 and maybe bridge the DC blocking cap pads and be fine. I guess I'll see if that actually works out  Splode posted:The separation between your antenna trace and the ground plane seems really small, but if you've used a calculator it is probably right. I assume you've got an unbroken ground plane underneath Yeah it's a 4-layer board and the layer right under the top is ground plane. I made the gap that small since it's the same distance away from the trace as the thickness of dielectric between the trace and the ground plane, which seemed like a good place to start and the calculator says it should be fine 
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Mar 9, 2019 20:36
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The same layer spacing to ground can in practice probably be smaller than your manufacturing process allows and still have very little effect since it's such a tiny area interacting with the ground around it. Especially compared to a typical 4 layer stackup with internal ground planes. Incidentally I've been looking at doing a GPS receiver board using a uBlox receiver myself (since yesterday). I found some Trimble Acutime Gold pole mount GPS receivers on eBay (+ a Symmetricom one) a week or two ago, plan is to use one for NTP and possibly make a little board to convert the NMEA messages to Motorola binary (OnCore UT+ compatible) to feed to a Lucent RFTG-u clock. The pole mount receivers aren't terrible (12-16 channels, better than the 1996 vintage 8 channel job in the Lucents) but it's tempting to gut one of them and put in a NEO-M8T timing receiver to get GLONASS + Galileo as backup systems. Will have to see what the antennas are like though, if they're passive then the original L1 antennas might be broad enough to get GLONASS as well but if they're active I'll have to replace or modify them. When testing the NEO-M8N I had in my drawer here today I found that it tracks 8-10 GPS satellites when my old systems only tracks 4-5 so things have definitely improved (and that's using the same antenna with an active splitter). Also found out that my M8N is unsurprisingly counterfeit when I tried to update the firmware (so no Galileo reception for me today), I'll be buying my modules direct from uBlox in the future.
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Mar 9, 2019 22:26
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longview posted:When testing the NEO-M8N I had in my drawer here today I found that it tracks 8-10 GPS satellites when my old systems only tracks 4-5 so things have definitely improved (and that's using the same antenna with an active splitter). drat that reminded me I have an old LEA-6H module sitting in the back of a drawer for an old project.
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Mar 14, 2019 11:58
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After my latest solder tip literally crumbled in the middle of a project, I'd like to know what tips y'all use and how you take care of them.
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Mar 15, 2019 02:14
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I use genuine Hakko tips and I take care of them by not overheating the iron or using it to poke holes in plastic objects. Also don't accidentally buy acid-core solder and don't try to scrape off oxides with a knife or sandpaper -- only brass wool. Beyond that, I dunno. Tips are consumables, but just doing the above should get you at least years of hobbyist use.
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Mar 15, 2019 02:43
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Unperson_47 posted:After my latest solder tip literally crumbled in the middle of a project, I'd like to know what tips y'all use and how you take care of them. I can't comment on private use, but I've been soldering pretty regularly at work for the past twenty years at three different places. I've never seen a tip disintegrate so badly it had to be replaced. The current station I use has had the same tips on the pen iron and the vacuum sucker for 6-7 years. The stations are powered on only when needed, use rosin core lead solder, and get cleaned with brass wool and/or a wet sponge.
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Mar 15, 2019 02:51
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Yeah, people run their irons way too loving hot. Leaded solder works fine at 300C/580F, on the high end. Use genuine tips on low temp with brass wool and they'll last years. If you want to abuse a tip for some reason, get the lovely 12 pack for $8 and use that.
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Mar 15, 2019 03:08
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I need some help. I need some little plastic or fibre washers to use on an expansion board for an rpi zero. The nylon spacers that came with it are < 1mm too short so if I tighten the nylon nuts it bends the Pi Zero over the pogo pins. I absolutely cannot work out what they are called so I can't look for them. Suggestions or alternatives?
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Mar 15, 2019 10:09
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