|
Honestly, this is my checklist for stripping electronics, and outside of this, I do not give a single poo poo: -Toroids -Electrolytics -Headers, connectors and jacks -Diodes *with long-ish leads* - I don't pull through-hole diodes unless they have a good 3/8" of leads on both sides -TO-220 voltage regulators and any worthy transistors - you can sometimes skeeze a couple of MOSFETS out of switching PSUs -Socketed ICs that will be useful - proprietary/unlabeled stuff I don't even look at twice. I don't desolder anything SMT for salvage, ever.
|
#
?
Nov 12, 2012 22:33
|
|
|
|
| # ? May 9, 2024 12:19 |
|
|
Bad Munki posted:I have a laptop battery that decided to go all pear-shaped on me, so I ripped it open and pulled out the little circuit board. Aside from a host of ridicu-small resistors and capacitors and diodes and such, it has some things I'd like to further identify. Finally, I can be of assistance! One of our older battery pack designs here uses the bq20z80 gas gauge IC. It's pretty complicated, and the whole line was allegedly developed as a joint project between TI and Sanyo/Panasonic (can't remember which, since they merged). Sanyo doesn't sell their version of the IC, though (they developed radically different firmware), but the hardware is the same. It's pretty cool for a low power processor, but may be something weird like 4-bit. The functions of the gas gauge as way to complex to get into, but they're pretty sweet. The bq29312A is the accompanying analog front end, which contains the ADCs, FET drivers, extra protection hardware, and so on. Not very useful on it's own. The Dale resistor is the 5mOhm current sense resistor, which may or may not be high precision (the AFE is calibrated to correct for the resistor value). The SFH-1212B is a triggerable fuse (not sure of the correct name). It acts as a normal fuse, but is also an active protection device (it contains a heater than can blow the fuse via an external driver circuit). FAKEDIT: Just noticed Delta Wye's post. damnit. The only stuff worth saving are the FETs, and the sense resistor.
|
|
#
?
Nov 12, 2012 23:09
|
|
|
Well, there's also an extremely-low-travel microswitch that still has a nice satisfying "click" to it that I didn't post, I'll probably save that too. On a side note, this is all from a 7-8 year old apple lithium ion battery, if anyone's at all curious.
|
|
#
?
Nov 12, 2012 23:54
|
|
|
Bad Munki posted:So I guess the last question is, is it worth bothering to pull any of these parts? And if so, how best to do so? Hot plate and tweezers? I don't think a hot plate would get hot enough, especially if it's lead-free solder. A hot air gun (the kind for SMD rework) would be best, but I've (very carefully) used a butane torch to desolder surface mount stuff before. I have an aftermarket Apple-compatible battery that went bad myself, and it has an ATMega406 on the controller board. Also what looks like a thermocouple, maybe I should do something with that. Silver Alicorn fucked around with this message at 05:21 on Nov 13, 2012 |
|
#
?
Nov 13, 2012 05:16
|
|
|
Sorry for the lovely photo: Love working in academia. Walking down the corridor today and I find this metric ton of drawers being thrown out of a lab. It's actually twice as long as this photo shows but I didn't want to zoom out any more. A lot of ancient ICs, but also I'll probably never need storage space or resistors again. So many packages of unopened resistors of every type  I'm actually thinking of donating all the stuff + half the drawers to a local hackerspace or something. No way will I ever need (or have room for) all these drawers, and I can already get all the small components I need for free by tacking them onto bigger campus orders.
|
|
#
?
Nov 14, 2012 21:21
|
|
|
Is the PC chassis spec'd to be directly connected to signal ground? Can I/should I connect the mounting hardware of an ISA card slot cover directly to my pcb's ground (which in turn connects to the bus GND)? I am redoing an old ISA card - the old version of the card isolates the slot cover. I have a 3-Com ISA ethernet card I'm using as an example of a professional design - it connects the slot cover directly to bus ground. I checked a few PCI cards and connecting the chassis to bus gnd seems to be the norm. I have Solari's AT Bus Design, but I can't find any mention of the chassis potential in it. I think I probably should connect the slot cover to bus ground, but was hoping you guys had input. e: Chassis, earth, and signal ground are all connected on the couple PCs I checked. taqueso fucked around with this message at 21:35 on Nov 14, 2012 |
|
#
?
Nov 14, 2012 21:26
|
|
|
This ATX 2.2 spec pdf mentions "chassis ground" in a few places, and talks about keepout areas designed to facilitate electrical connections with add-on cards. It doesn't explicitly say what the chassis is connected to though.
|
|
#
?
Nov 14, 2012 21:56
|
|
|
I want to track the rotation of a spinning cylinder (cylinder axis is rotation axis). The cylinder may be spinning up to a few hundred rpm, maybe even upwards of 1krpm. Any thoughts on how to do so? One thought I had was to use the guts of an optical mouse to look at one end of the cylinder (it'll be closed, so one could examine the flat end cap). Not sure what the resolution is on those mice, though, and how fast they are, but I imagine that by putting it closer to the axis of rotation, it'd make for a lower linear speed, which might ease tracking. If I could track it accurately enough to confidently say "this side of the cylinder is up" while spinning at max speed, that'd be awesome. The cylinder will be 6-8" in diameter and spun by hand, but there's no real resistance so it should spin very nicely. Any ideas? Bad Munki fucked around with this message at 15:55 on Nov 15, 2012 |
|
#
?
Nov 15, 2012 15:53
|
|
|
taqueso posted:Is the PC chassis spec'd to be directly connected to signal ground? Can I/should I connect the mounting hardware of an ISA card slot cover directly to my pcb's ground (which in turn connects to the bus GND)? They're all connected, but should be filtered (hopefully) so noise on frame ground/chassis ground/etc doesn't couple onto the digital ground all the logic uses, and to mitigate ESD effects. It should also give you a leg up in EMC testing where some of the tests will purposefully inject noise into your device (say through an external cable), and you don't want that noise to have a direct path to the ground your ICs are using. You could do some large (footprint that is) high-voltage capacitors between GND/FGND (say 0.1uF/0.01uF combo maybe) or have a single point where all of FGND connects to GND. This is what we do on industrial CompactPCI / PCIe peripheral boards (CompactPCI defines ESD shapes for the PCB anyway).
|
|
#
?
Nov 15, 2012 16:08
|
|
|
Bad Munki posted:I want to track the rotation of a spinning cylinder (cylinder axis is rotation axis). The cylinder may be spinning up to a few hundred rpm, maybe even upwards of 1krpm. Any thoughts on how to do so? I've done similar things before with a hall effect sensor and one or several magnets attached on the perimeter of the cylinder like so:  You then trigger an interrupt on your uC on the rising edge of the hall effect sensor's output and check a timer in your ISR if you want to track speed too. Boom. 
Blotto Skorzany fucked around with this message at 16:14 on Nov 15, 2012 |
|
#
?
Nov 15, 2012 16:10
|
|
|
movax posted:They're all connected, but should be filtered (hopefully) so noise on frame ground/chassis ground/etc doesn't couple onto the digital ground all the logic uses, and to mitigate ESD effects. It should also give you a leg up in EMC testing where some of the tests will purposefully inject noise into your device (say through an external cable), and you don't want that noise to have a direct path to the ground your ICs are using. Is FGND = "Frame Ground"? I get what you mean, just wondering what it stands for. Are you saying you use a single connection point on the PCIe boards? Anyway, I rounded up more PCI cards and looked more closely. I found a crappy video card and a sound card that have the chassis directly connected to ground. The others all have separate grounds connected by 1 to 3 caps. I think I will go with the capacitors. taqueso fucked around with this message at 18:25 on Nov 15, 2012 |
|
#
?
Nov 15, 2012 18:06
|
|
|
Bad Munki posted:If I could track it accurately enough to confidently say "this side of the cylinder is up" while spinning at max speed, that'd be awesome. The cylinder will be 6-8" in diameter and spun by hand, but there's no real resistance so it should spin very nicely. If you want information about speed AND position, you will need something like a grey code rotary encoder (http://en.wikipedia.org/wiki/Rotary_encoder) although if you need fine-grained position information you're kind of hosed because things get complicated and impractical if you need more than 45 degree resolution
|
|
#
?
Nov 15, 2012 19:01
|
|
|
I don't explicitly care about speed, really just position (angle). Of course, with high-resolution positional (angular) determination, I can calculate speed more accurately than I even need, but that extra information is still incidental. But yeah, I need that angular determination to be, say, correct within an inch on the outer circumference. So with an 8" diameter cylinder, that'd be about 25" of circumference, so 360/25 would be about 14 positions as my final resolution. More would be better, but that would likely suffice. I feel like that should be do-able, but again one of the key factors is the speed of that reading. If I could determine which of those 14 positions it's in a thousand times a second, I'd be content (as long as the read isn't cumulative, i.e. miss a couple steps and it gets "lost." In other words, I want an absolute measurement, not a relative one.) If I could double both those numbers, I'd be ecstatic. Bad Munki fucked around with this message at 19:19 on Nov 15, 2012 |
|
#
?
Nov 15, 2012 19:07
|
|
|
taqueso posted:Is FGND = "Frame Ground"? I get what you mean, just wondering what it stands for. Are you saying you use a single connection point on the PCIe boards? Yeah, frame ground. We don't use a single conn point on the PCIe boards, I think we mostly go with the capacitor approach there (plus ESD strips on the edges) as our defence/filtering mechanism. Sounds like the latter PCI cards are the ones you want to model after; I have seen some where there may even be 1M+ ohm resistor between GND/FGND, but I'm not sure what the "best" is.
|
|
#
?
Nov 15, 2012 19:28
|
|
|
Bad Munki posted:I don't explicitly care about speed, really just position (angle). Of course, with high-resolution positional (angular) determination, I can calculate speed more accurately than I even need, but that extra information is still incidental. Either a 4 bit rotary encoder, or one magnet that rotates with the cylinder and >14 fixed position hall effect sensors should give you what you want, and both will be measures of absolute position (error will be non-cumulative); the latter scheme is used by some ABS systems, incidentally.
|
|
#
?
Nov 15, 2012 19:49
|
|
|
Or a quadrature encoder (so you know number of pulses and direction) with some sort of zero you pass occasionally to reset the count (so error doesn't accumulate, assuming you make a full rotation occasionally). The zero can be a hall effect, or an additional optical input.Otto Skorzeny posted:...one magnet that rotates with the cylinder and >14 fixed position hall effect sensors should give you what you want, and both will be measures of absolute position (error will be non-cumulative); the latter scheme is used by some ABS systems, incidentally. This is also good, and can be done optically.
|
|
#
?
Nov 15, 2012 20:18
|
|
|
Here's how automotive crank position sensors work http://www.megamanual.com/ms2/wheel.htm Toothed wheel, hall effect, and a missing tooth or two in one spot to for absolute positioning. Depending on how crucial positioning is at low rpm, or how quickly your object is changing rotational velocity, you might be able to get away with a single sensing point, using led+photodiode and reflective or absorptive stripe on the surface to see when it passes by. Assuming you're using a microcontroller, count the time elapsed on the previous rotation and apply that as a prediction of the progress through the current rotation. If you need only resolution of 1/14 rev(~7%) or whatever, then as long as you are not accelerating/decelrating more than 7% in a single revolution, then a single "tooth" or other sensing point would be adequate. Is this for a persistence of vision project?
|
|
#
?
Nov 15, 2012 22:06
|
|
|
Delta-Wye posted:This is also good, and can be done optically. peepsalot posted:Is this for a persistence of vision project? Bad Munki fucked around with this message at 22:11 on Nov 15, 2012 |
|
#
?
Nov 15, 2012 22:07
|
|
|
Just out of curiosity, how many of you guys consider yourselves hobbyists and feel you fully understand what is happening in this video: https://www.youtube.com/watch?v=XiiXSCQqVYg I don't mean this in any trolling way, but I'm trying to ground my understanding of all these basic parts and while I understand the basics of what is happening in a transistor, the second they introduce ... maths ... I sort of go cross-eyed. I realize it's important to understand the math behind it (and believe me, I am going to struggle to do so), but I'm legitimately curious how many people are getting by just knowing "eh a transistor does X" and not much more.
|
|
#
?
Nov 16, 2012 02:34
|
|
|
Martytoof posted:Just out of curiosity, how many of you guys consider yourselves hobbyists and feel you fully understand what is happening in this video: I'm of the "ehh, it does X" for most transistor circuits because I only use them as switches. I make sure I can get to saturation or cutoff with what I've got, and that's it. I don't design amplifiers or anything; discrete parts are better at it than I. I just like current-controlled or voltage-controlled nonmechanical switches. This goes for BJTs and FETs of all flavors.
|
|
#
?
Nov 16, 2012 03:08
|
|
|
Martytoof posted:Just out of curiosity, how many of you guys consider yourselves hobbyists and feel you fully understand what is happening in this video: What is the last math class you felt comfortable in? I would be happy to explain it if you tell me what you know. I have an EE degree so I'm not exactly a hobbyist, but I do remember the struggle to understand wtf transistors are doing.
|
|
#
?
Nov 16, 2012 03:14
|
|
|
I'm strictly a hobbyist and don't have any formal EE education, but I was physics student (i.e. dealt with a lot of math and electromagnetism), and I've spent some years doing analog synthesizer stuff, where it helps to really understand bipolar transistors. Voltage control in analog music relies on bipolar transistor behavior. Understanding transistors was definitely a struggle, though, and I do think a lot of hobbyists take a "cookbook" approach of dealing with well-known circuits. Most of the people who would actually sit down and design a VCO are EEs off the clock.
|
|
#
?
Nov 16, 2012 03:24
|
|
|
What helped me more than anything (professional EE/CpE) was sitting down and solidifying the fundamentals as much as possible; so, lots of physics. Understanding electrons and semiconductor physics helped me kind of get an intuitive feel for what passive and active components did. At some point though, you work with all the components enough where they simply become tools in your arsenal in the battle to control nature :battle101: As well as getting to know / memorizing some basic circuits that are frequently used.
|
|
#
?
Nov 16, 2012 03:27
|
|
|
Thanks guys. I will definitely post questions about transistors later on, but those who called out a lack of maths/physics fundamentals are definitely right. I legitimately have not taken a math class since last year highschool because apparently getting a sweet well paying job out of school was an awesome thing for a teenager to do instead of getting an education like a normal person so you don't try to learn transistors at 33 and nearly hang yourself when they start introducing "letters" into math again  Uphill struggle, but I'm not above putting in some elbow grease. I'm going to have to go pick up some fundamentals books soon. I'm getting by by pulling bits and pieces out of a toolbox and thankfully I don't work with enough bits where if you forget a resistor or hook a transistor up wrong you will literally be sorry, but I'm trying to fast-track some of this and it seems like there's no real "fast track" to this material for a reason. It's stuff you need to know and understand. I'll definitely be back here asking dumb questions so bear with me
|
|
#
?
Nov 16, 2012 03:48
|
|
|
In my opinion, the math for EE gets really critical/involved when it comes to communication systems and controls. You can get away with a basic understanding of calculus and algebra for microelectronics / circuits with it not being the end of the world. Sure things get a little trickier when talking imaginary numbers, but that's nowhere near switching domains for signal analysis or calculating transfer functions. Seriously no one in this thread should feel dumb / useless for wanting to do electronics stuff without math knowledge; it's not the end of the world at all. Especially with math resources on the web like Khan Academy now, it'll be easier to pick up on the math you will need to know. The best part is all the basic parts you need for experimenting are so damned cheap there's no need to feel bad about blowing stuff up (aside from the initial regret at dooming an innocent IC because you're swapped VCC and GND  ).
|
|
#
?
Nov 16, 2012 05:37
|
|
|
movax posted:Seriously no one in this thread should feel dumb / useless for wanting to do electronics stuff without math knowledge I think the main advantage of being a math nerd is confidence when you encounter some, not actual mad math skills.
|
|
#
?
Nov 16, 2012 05:43
|
|
|
Oh yeah, I definitely didn't mean to sound emo over the math or anything. I'm having a great time figuring this stuff all out. I think I legitimately found something I am excited about learning, only I'm like 15 years too late to actually get into it and make it a career choice. But I guess it should say something that I'm actually as excited about learning this as I am about what I've considered my dream career field all this time. (It's network engineering. I'm the guy who loves to do networking  )
|
|
#
?
Nov 16, 2012 06:05
|
|
|
movax posted:The best part is all the basic parts you need for experimenting are so damned cheap there's no need to feel bad about blowing stuff up (aside from the initial regret at dooming an innocent IC because you're swapped VCC and GND I once made a PCB with VCC and VEE swapped for one of the opamps, not my proudest moment.
|
|
#
?
Nov 16, 2012 09:47
|
|
|
Anyone have any experience using (bluetooth) modems using the AT command set (or something close enough)? I've used them in the past, but now at work I'm trying to implement something more complex--specifically, I need to send and receive commands (in the form of text strings). The commands need to be parsed, but it's been years since I had to write a parser in intro to C, and even then it was a chore. Anyone have any suggestions on where to look for examples/ideas?
|
|
#
?
Nov 16, 2012 16:00
|
|
|
I don't think the AT command set is particularly complex. If I didn't care too much about extensibility, I would just handroll a state machine and hardcode the whole thing.
|
|
#
?
Nov 16, 2012 16:35
|
|
|
taqueso posted:I don't think the AT command set is particularly complex. If I didn't care too much about extensibility, I would just handroll a state machine and hardcode the whole thing. Yeah, pretty much this. Brush up on your C string functions and enjoy debugging the inevitable off-by-one where you lose '\0' 
|
|
#
?
Nov 16, 2012 16:37
|
|
|
Martytoof posted:Oh yeah, I definitely didn't mean to sound emo over the math or anything. I'm having a great time figuring this stuff all out. I think I legitimately found something I am excited about learning, only I'm like 15 years too late to actually get into it and make it a career choice. But I guess it should say something that I'm actually as excited about learning this as I am about what I've considered my dream career field all this time. Don't sell yourself too short. For the past 50 years or so, it has become less and less popular to focus on hardware component electronics, due to Asian mass-production, automated assembly and the SE Asia engineer explosion. However, now there is virtually nobody around who can troubleshoot and fix things. Niche markets are holding strong, and it's easier than ever to get started blowing up transistors and hooking up the wrong resistors. Back when I was learning this poo poo in the early 90's, we had to work out of mail-order catalogs (operator, please stop calling me ma'am, i'm twelve, not a woman). Now you can either Amazon up some poo poo to tinker with the next day, or get literally any random gizmo or circuit board you want out of China with a couple weeks mail-delay. Get a good understanding of the laws (Ohm's, Kirchoff's, and the power law) and how common 3-pin semiconductors work, and you are basically ready to start building and fixing things. You don't have to know how many transistors are in that opamp (though learning the basics of opamps is strongly recommended). Jonny 290 fucked around with this message at 17:37 on Nov 16, 2012 |
|
#
?
Nov 16, 2012 17:24
|
|
|
Sounds good. Well, I've been basically diving in headfirst every day and learning a ton of new stuff every time I do, so I'm pretty stoked with the whole process, still. Question of the day: Today I made it my mission to understand how voltage regulators and voltage regulator circuits and power supplies work. It's actually a lot simpler than I ever imagined once I figured out what diodes and rectifiers and regulators are. So my question is: Armed with my newfound knowledge I obviously immediately tried to examine any and all power supplied devices I own (and are open for me to look at), which meant my Arduino Uno is a perfect candidate. I managed to trace down the 5v regulator really easily, but I'm trying to figure out where the 3.3v rail is generated. Without a magnifying glass I can't really trace down any of the smaller components, and I'm still really green at reading schematics so I tried to figure it out here (http://arduino.cc/en/uploads/Main/Arduino_Uno_Rev3-schematic.pdf), and while I found the 5v relatively easy to find, I'm having trouble locating a 3.3v regulator. Unless the 3.3v is generated by some other means. This might be an arduino specific question, but I mean it more as a general "how the gently caress" type of thing. I'm not actually interested in this arduino per se, just how it's implemented.
|
|
#
?
Nov 17, 2012 05:25
|
|
|
Martytoof posted:Armed with my newfound knowledge I obviously immediately tried to examine any and all power supplied devices I own (and are open for me to look at), which meant my Arduino Uno is a perfect candidate. I managed to trace down the 5v regulator really easily, but I'm trying to figure out where the 3.3v rail is generated. Without a magnifying glass I can't really trace down any of the smaller components, and I'm still really green at reading schematics so I tried to figure it out here (http://arduino.cc/en/uploads/Main/Arduino_Uno_Rev3-schematic.pdf), and while I found the 5v relatively easy to find, I'm having trouble locating a 3.3v regulator. Nope, that's the same type of thing. It looks like the 3V3 net is coming out of the LP2985-33 IC in the middle of the page, and Googling the part number turns up this TI LDO voltage regulator. Edit: Although 3.3V is pretty neat because in a pinch you can just stick 2 AA batteries in series in a pinch. Arcsech fucked around with this message at 05:57 on Nov 17, 2012 |
|
#
?
Nov 17, 2012 05:55
|
|
|
Marvellous, thank you Now that I look at it, it was a LITTLE more obvious than I made it out to be, but now I know! 
|
|
#
?
Nov 17, 2012 06:30
|
|
|
I'd like to set up one of these in my Prius: http://www.priups.com/misc/multisupply.htm Basically use the hybrid battery as an emergency generator. While drawing power, the engine will automatically kick on every few hours to top off the battery. I could some help figuring out what I need. I have one of these: http://www.amazon.com/Cobra-CPI-1575-Power-Inverter/dp/B00126IDDC I can't run the inverter straight off the hybrid battery because the inverter expects 12V DC and the hybrid battery is 48V. So I have two options: 1. Convert 220V to 12V. I don't know what exactly this entails, if it is possible, if there are dangers, etc. I'm skeptical if this would work since the PriUPS site doesn't even mention commerical 12V inverters. 2. Ignore the inverter and set up the PriUPS "Medium System" as it's listed. I'm having trouble figuring out where to find a "Cherokee 48V 30A switcher". Any help would be appreciated on either front. Thanks. Let me know if there's a better thread for this. SurgicalOntologist fucked around with this message at 22:41 on Nov 18, 2012 |
|
#
?
Nov 17, 2012 20:50
|
|
|
I am pretty sure that much power could actually kill you so it might be a good idea to let a professional handle it and not do anything based on internet forum advice. Furthermore, that guy in your link doesn't seem to have the aforementioned expertise: capacitors are not typically measured in pounds, and systems with "no batteries" do not usually include UPSes with batteries in them. Please be careful.
|
|
#
?
Nov 18, 2012 00:06
|
|
|
I want to murder whoever came up with the resistor colour scheme. Browns that look like purples under certain light, oranges that look like reds, silver and golds that are virtually indistinguishable from each other under any sort of light. Is that white or really light blue? And then when you pull out your meter and the actual ohms read nothing even remotely close to what the chart says.
|
|
#
?
Nov 18, 2012 01:11
|
|
|
Martytoof posted:I want to murder whoever came up with the resistor colour scheme. I'm partially color-blind, the stripes all say "hey, I'm a resistor!" and I measure everything. Of course, these days I also need a giant magnifying lens to read the numbers on capacitors, so...
|
|
#
?
Nov 18, 2012 01:16
|
|
|
|
| # ? May 9, 2024 12:19 |
|
|
Martytoof posted:And then when you pull out your meter and the actual ohms read nothing even remotely close to what the chart says. One trick with this - it's tempting when measuring a resistor to mash both leads against your ohmmeter probes with your thumbs to get a good contact. The problem with that is your body becomes a part of the circuit, looking like a ~10kOhm load* in parallel with whatever you are measuring, and you end up throwing your reading off making you think you read the bands wrong. I usually mash one lead down with my thumbs on one probe and then use the natural springiness of the other lead as a contacting force on the opposing probe to get a good reading. But yeah, those lovely color bands can be hard to read. I also hate it when some black IC package has it's part number printed on it with dark brown ink. Why would anyone do such a thing?  *This value varies with how moist your skin is, how hard you press against the probes, etc.
|
|
#
?
Nov 18, 2012 02:15
|
|
