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Mill Town posted:I'm in need of a logic analyzer that can do up to 500kHz (fortunately I only need 2 channels, I'm analyzing a proprietary serial protocol). Can anyone recommend a PIC or AVR based solution? I've seen a few plans on the Internet but I'm not sure what's good. It needs to be able to store a lot of samples (at least a few seconds worth) and I don't know which design to pick. Thanks! hobbesmaster posted:The HC11 is the best microcontroller in existence. Do I know you? That is one way to get me all riled up - I'm currently taking a HC12 (9S12) based course and really, goddamn, it most certainly is not the best microcontroller in existence. The 90s called, and they want their cutting edge processor designs back.
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Mar 17, 2009 04:02
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Delta-Wye posted:Sparkfun sells [what sounds like] a really nice USB Logic Analyzer, which is overkill for what you're doing now but it might be worth investing in for the long run. I know I've been looking to invest in one since I first saw it. I've basically got a pile of AVRs and PICs at my disposal thanks to the local hackerspace, hence my desire to roll my own. This one does look pretty nice, though, and I'll consider it if I can't find anything else. Thanks!
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Mar 17, 2009 04:11
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SnoPuppy posted:I assume you were being eetrolled   quote:And I would be surprised that your school doesn't have any design classes. I know mine had several, ranging from analog stuff to embedded systems. Generally they are junior/senior level though. Hillridge posted:If the economy pulls out of the crapper enough for us to lift the hiring freeze by the time you graduate (and you feel like moving) I'll refer you to HR where I work. ANIME AKBAR fucked around with this message at 05:27 on Mar 17, 2009 |
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Mar 17, 2009 05:20
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Mr Anime, what classes are you taking exactly? It sounds like a strange program. I'm really glad of the really broad 200 level program at my university, we were programming AVRs off parallel ports (with hand-soldered parallel port connectors that fell apart at a gust of wind because of clumsy soldering...), as well as getting a good grounding in electronics, power systems, signal processing, and software development. I've been planning to specialise fairly early on, and it's worked out pretty well. This year, 400 level: Power engineering applications (nitty gritty power engineering, turbine governors, system planning etc.) Power systems (power system analysis, load flow, protection) Power electronics II (focus this year is on HF switching converters) Computer hardware (more micros, FPGAs, and DSPs) Engineering management (cynical marketing inside) Project (sweetness) The synergy between power, power electronics, and hardware is really cool, I'm glad I chose it. With any probability, I'll be working in power engineering in the consulting sector, but it's good to know that I could easily go into power electronics if I wanted.
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Mar 17, 2009 06:29
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Delta-Wye posted:Do I know you? That is one way to get me all riled up - I'm currently taking a HC12 (9S12) based course and really, goddamn, it most certainly is not the best microcontroller in existence. Woah woah woah, now, let's just settle down now, let's not get crazy now, Seriously though what's your beef with the venerable HC11
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Mar 17, 2009 06:34
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catbread.jpg posted:Mr Anime  This semester is pretty vanilla. Semiconductor theory, discrete time signals, control systems (basically signals with emphasis on modeling), senior project II, and a dumb technical communications course. But I want to emphasize that aside from getting requirements for graduating, my courses aren't a big deal to me (though I always hope to find some rewarding ones). Like I said, most of what I know wasn't learned in a classroom. But then again, I've been incredibly lucky. When I first came to CWRU, I intended to be an anthropology major, and minor in EE. I had already started to tinker with electronics at that point, so I went into the lab and asked if I could have some space to experiment. Immediately I was given a toolbox, storage space, and free 24/7 access to a lab with awesome equipment and an enormous cache of components free for use. There's even an employee whose main purpose is to act as a consultant to students on anything they want to do (What, you want to build a 6kW tesla coil? Awesome lets draw some schematics...). I hadn't even declared my major/minor yet. Basically I can attribute a lot of my experience to the absurd amount of resources that were thrown at my feet. After seeing this, switching majors was a pretty easy decision. Delta-Wye posted:Do I know you? That is one way to get me all riled up - I'm currently taking a HC12 (9S12) based course and really, goddamn, it most certainly is not the best microcontroller in existence. ANIME AKBAR fucked around with this message at 06:59 on Mar 17, 2009 |
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Mar 17, 2009 06:52
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Delta-Wye posted:Do I know you? That is one way to get me all riled up - I'm currently taking a HC12 (9S12) based course and really, goddamn, it most certainly is not the best microcontroller in existence. 90s? More like 70s. You just have to get into the 70s mindset of CISC and whatever was logical to Motorolla engineers. Its rather... annoying to get into that mindset when you're used to RISC architectures from the 80s/90s such as PIC and AVR. Different things made sense in the 70s than do now. I think I've dropped myself from consideration from two jobs by visibly shuddering when they said something about HC11 development. I need to get rid of that response.
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Mar 17, 2009 14:12
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hobbesmaster posted:I think I've dropped myself from consideration from two jobs by visibly shuddering when they said something about HC11 development. I need to get rid of that response. I've observed poo poo like this in a lot of my friends' jobs. That is, there employers know jack poo poo about electronics, but rather than refer to their employees' expertise, they insist on silly methods and goals. A friend of mine took a job specifically to build a temperature sensor for some guy that does manufacturing control or something. Thing is manufacturer insists that it give an analog output. The friend, named Roy, asked my opinion on the project, and I told him he should ask his boss if that's necessary, since it's likely that whatever system it interfaces to is going to digitize it later on. Sure enough, not only was this the case, but the sensor would have to be a long ways from the system it connects to, meaning good analog performance would require significant concern over interference, hence shielding and differential driving, etc. Complete bullshit since the sensing element he's using gives a digital output. So Roy literally has to convert digital to analog, drive the analog over a long line, only to have it digitized again. Completely silly, and his employer just won't here any ideas. And also just yesterday another friend remarked on how his boss, who hired him to redesign some poorly done circuits, theorized that maybe the problem was that "the resistors were in backwards."
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Mar 17, 2009 14:38
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ANIME AKBAR posted:And also just yesterday another friend remarked on how his boss, who hired him to redesign some poorly done circuits, theorized that maybe the problem was that "the resistors were in backwards." Does he work at monster cable?  Both of the jobs I were referring to were in the automotive supply industry; both emailed me to say that they eliminated the positions. This was back in October... hobbesmaster fucked around with this message at 15:00 on Mar 17, 2009 |
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Mar 17, 2009 14:57
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ANIME AKBAR posted:I've observed poo poo like this in a lot of my friends' jobs. That is, there employers know jack poo poo about electronics, but rather than refer to their employees' expertise, they insist on silly methods and goals. A friend of mine took a job specifically to build a temperature sensor for some guy that does manufacturing control or something. Thing is manufacturer insists that it give an analog output. The friend, named Roy, asked my opinion on the project, and I told him he should ask his boss if that's necessary, since it's likely that whatever system it interfaces to is going to digitize it later on. Sure enough, not only was this the case, but the sensor would have to be a long ways from the system it connects to, meaning good analog performance would require significant concern over interference, hence shielding and differential driving, etc. Complete bullshit since the sensing element he's using gives a digital output. So Roy literally has to convert digital to analog, drive the analog over a long line, only to have it digitized again. Completely silly, and his employer just won't here any ideas. ANIME AKBAR posted:And also just yesterday another friend remarked on how his boss, who hired him to redesign some poorly done circuits, theorized that maybe the problem was that "the resistors were in backwards." You know all those people in your classes that seem like idiots, but still graduate? They get jobs too. It's like the old joke: Q: What do you call the guy who graduates medical school at the bottom of his class? A: Doctor. I'm lucky enough to work at a place that likes to reward good technical decisions and tends to make fun of people who say/do stupid things (assuming they should have known better).
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Mar 17, 2009 15:22
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hobbesmaster posted:What do FPGAs have to do with analog circuit design? My electrical engineering classes went Programming -> Digital Logic -> FPGAs -> Circuit Design. He's clearly a wizard at circuit design, so not knowing about the beginner stuff is very strange to me... like someone who can't tie their shoes but knows how to build them from scratch. Nobody is coming into the dork forum and reading the dork thread just to troll the poo poo out of the 6 other dorks in the thread. Stop being so paranoid you weirdos.
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Mar 17, 2009 16:09
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Corla Plankun posted:My electrical engineering classes went Programming -> Digital Logic -> FPGAs -> Circuit Design. He's clearly a wizard at circuit design, so not knowing about the beginner stuff is very strange to me... like someone who can't tie their shoes but knows how to build them from scratch. You can get out of my school's EE program without ever touching an FPGA.
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Mar 17, 2009 16:25
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Corla Plankun posted:My electrical engineering classes went Programming -> Digital Logic -> FPGAs -> Circuit Design. He's clearly a wizard at circuit design, so not knowing about the beginner stuff is very strange to me... like someone who can't tie their shoes but knows how to build them from scratch. Did you do a computer engineering track? My school's EE program was ordered with circuit design as the very first core coursework we took. Three quarters of analog design, up to the point of op-amp butterworth filters and Laplace transforms. Next we took a few quarters of digital coursework (computer logic, intro to computer architecture, advanced digital logic). Next we took a bunch more theory courses (signal processing, DSP, device physics), and then a couple of more advanced analog design courses. Finally we got into electives. The only mandatory FPGA class in my track was advanced digital logic, and truthfully we only used FPGAs for the last couple of labs. No lectures or coursework on FPGAs. I didn't start getting into FPGA design until I was out of school and working. Poopernickel fucked around with this message at 17:00 on Mar 17, 2009 |
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Mar 17, 2009 16:52
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Corla Plankun posted:My electrical engineering classes went Programming -> Digital Logic -> FPGAs -> Circuit Design. That's pretty interesting. If one is set to take a digital concentration, then this path seems pretty smart. Analog circuitry classes, even basic ones, usually require a fair bit of math to get into. At my university the basic circuits class required calc up to differential equations, which takes three or four semesters, so even prospective circuit design students usually didn't learn poo poo until late sophomore year. But digital is a lot easier to get into without knowledge of math or circuits, so it makes sense to get those out of the way first rather than later. Was "circuit design" for you on practical implementation, or was it just a crash course in op amps/transistors/etc? Was it a requirement for your degree, and what is your concentration? quote:He's clearly a wizard at circuit design, so not knowing about the beginner stuff is very strange to me... like someone who can't tie their shoes but knows how to build them from scratch. hobbesmaster posted:You can get out of my school's EE program without ever touching an FPGA. ANIME AKBAR fucked around with this message at 17:18 on Mar 17, 2009 |
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Mar 17, 2009 17:09
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Hey all. I've been itching to start a small (possibly large) project. So what I'm looking to do is create a custom controller for gaming (perhaps eventually a full cockpit-style layout...) and I'm having a bit of trouble finding what I want. Basically I'm just looking to make a fancy keyboard, as in a typing kind of keyboard. Now being fairly new at all this I suspect that I just don't know what to look for. I've been doing searches on google and what-not for "keyboard controller boards" and not finding much besides musical keyboard construction kits, and tutorials for dismantling old keyboards and using those. That's an option, but my soldering skills are basically non-existent, and the contacts for those things seem awfully close together. So, what I'm wondering is if anyone can point me to a keyboard kit or controller board that is easy to work with for making a nonstandard, typing keyboard?
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Mar 17, 2009 18:04
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You can make a standard USB HID (keyboard, mouse, joystick, etc.) device with a PIC18F4550 and some firmware provided by Microchip that does the hard stuff for you. I think they sell a demo board with that part on it, too, but it doesn't require very much external hardware to run (A crystal and some capacitors) so you can easily make a compact DIY solution. Not the easiest way to go about it (easier than cutting up an existing keyboard though) and probably not recommended if you've never worked with a PIC before, but it's fairly well documented and only requires a single chip and a few other parts to make whatever you want. BattleMaster fucked around with this message at 18:30 on Mar 17, 2009 |
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Mar 17, 2009 18:16
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I have not worked with a pic before, but I've been looking at them quite a bit lately trying to find an excuse to learn more... This seems as good a reason as any, I must do some research. Plus, using the PIC should let me get a bit more creative. Hmmmmm, yes, thank you very much for that!
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Mar 17, 2009 18:31
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ANIME AKBAR posted:Hmm, now I'm starting to see why our FPGA class is considered one of the most difficult, yet rewarding classes in the department. I didn't realize it was normal for general EE students to work with FPGAs. The degree is electrical engineering afterall, not electronic. To not deal with FPGAs in my department would mean that you are very familiar with our machine lab and power distribution.
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Mar 17, 2009 20:34
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lord_daeloth posted:I have not worked with a pic before, but I've been looking at them quite a bit lately trying to find an excuse to learn more... This seems as good a reason as any, I must do some research. Plus, using the PIC should let me get a bit more creative. Hmmmmm, yes, thank you very much for that! There are software USB stacks running on AVRs, too. Check AVR-USB if that's your style. Demo projects with source are provided.
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Mar 17, 2009 22:27
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Are there not AVRs with hardware USB? Doing it in software like that is kind of gross.
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Mar 17, 2009 22:49
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BattleMaster posted:Are there not AVRs with hardware USB? Doing it in software like that is kind of gross. I think you misspelled awesome On a serious note: There are, but I have no experience with them, and a cursory glance shows them to be slightly more difficult to obtain, more expensive and probably overkill for this implementation. Since you can get an ATtiny for pocket change, I know what I'd use for a personal project. E: then again, I'm a complete newbie at this sort of thing 
Snaily fucked around with this message at 23:11 on Mar 17, 2009 |
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Mar 17, 2009 23:07
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For only a couple of dollars more you get a lot more functionality, though. That software USB implementation only supports low speed USB operation and requires a whole bunch of external hardware. Maybe it would be worth it if you were mass-producing keyboards and wanted to save money, but I'm not so sure if it's a good choice for a hobbyist project aside from the novelty value. I don't know about the equivalent AVRs, but the PIC18F4550 has a built in 3.3 volt regulator so it can be plugged directly into the +5v USB power, as well as a built-in transceiver and pull-up resistors. It also has a really flexible oscillator system that lets you derive low speed and full speed clock rates from any crystal that's a multiple of 4MHz, has 1KB of dual-port RAM for configurable buffers simultaneously accessible by the CPU and USB module, and a parallel port that allows the USB module to bypass the CPU entirely for streaming data. What I mean to say is you'd have to be really desperate for that dollar or two you'd save to pass up all that. Hell you might just make it up by not having to add in an external voltage regulator. BattleMaster fucked around with this message at 23:28 on Mar 17, 2009 |
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Mar 17, 2009 23:24
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BattleMaster posted:For only a couple of dollars more you get a lot more functionality, though. That software USB implementation only supports low speed USB operation and requires a whole bunch of external hardware. Maybe it would be worth it if you were mass-producing keyboards and wanted to save money, but I'm not so sure if it's a good choice for a hobbyist project aside from the novelty value. I think the the minimal amount of external hardware is like two Zener diodes to (in a really ugly, "what's a voltage regulator?" kind of way) drop to 3.3V on the data lines, and three external resistors. Your point still stands, though - throughput, reliability and ease-of-use are vastly higher. Nonetheless, I think the software solution is a valid one if one can live with the downsides. I can't find any of the USB-capable AVRs in a through-hole package, though, so depending on your solder-fu that may be a dead end. Go with the PIC.
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Mar 17, 2009 23:37
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hobbesmaster posted:90s? More like 70s. You just have to get into the 70s mindset of CISC and whatever was logical to Motorolla engineers. Its rather... annoying to get into that mindset when you're used to RISC architectures from the 80s/90s such as PIC and AVR. Different things made sense in the 70s than do now. Yes, an architecture with two registers and a million instructions is not a good design  EDIT: Wait, there are three registers! But the third points at the first two so whatever Delta-Wye fucked around with this message at 23:48 on Mar 17, 2009 |
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Mar 17, 2009 23:41
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catbread.jpg posted:Mr Anime, what classes are you taking exactly? It sounds like a strange program. I'm really glad of the really broad 200 level program at my university, we were programming AVRs off parallel ports (with hand-soldered parallel port connectors that fell apart at a gust of wind because of clumsy soldering...), as well as getting a good grounding in electronics, power systems, signal processing, and software development. Jesus christ. Does nobody study RF/E&M anymore?
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Mar 18, 2009 04:39
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Cyril Sneer posted:Jesus christ. Does nobody study RF/E&M anymore? I did and I actually specialized in it. That being said, I was the only one in my class of 60 or so to take all the E&M/RF/Optics courses. Everyone else went for the electronic or programming tracks.
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Mar 18, 2009 04:46
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Cyril Sneer posted:Jesus christ. Does nobody study RF/E&M anymore? My school takes care of that issue by having the worst teacher in the department always teach the required undergrad EM class. The sad thing is that one of the best teachers then has an elective antennas class. Too bad a ton of people are scared off before then...
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Mar 18, 2009 06:53
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Cyril Sneer posted:Jesus christ. Does nobody study RF/E&M anymore? Optional and passed over. The EM courses at my university seem to me to be completely useless unless you have a compelling reason to design RF waveguides. The 400 level electronics course goes into RF (last year was almost entirely audio frequency amplification, I didn't take that either). The mandatory 300 level signal processing and control theory course was by far the most challenging but probably the most useful.
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Mar 18, 2009 07:06
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Twerpling posted:I did and I actually specialized in it. That being said, I was the only one in my class of 60 or so to take all the E&M/RF/Optics courses. Everyone else went for the electronic or programming tracks. I specialized in it as well. Your description sounds exactly like my experience; they've cancelled a bunch of courses too because not enough people signed up for them (I complained bitterly about that).
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Mar 18, 2009 14:21
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Cyril Sneer posted:Jesus christ. Does nobody study RF/E&M anymore? I am. Holy poo poo I'm really starting to love RF/Mixed Mode design. I do admit most of the classes have 'bend over' written somewhere into the course description, but I just can't get enough analog design. I'm taking a 'beta test' class now (special topics) in high frequency amplifier circuits and it's absolutely fascinating. Covers Agilent Design Studio, Gallium Arsenide Transistors (pHEMT and HBT), stability and noise with smith charts, line matching, etc. I was able to make a 1/4 wave transformer the other day out of aluminum foil and scotch tape, and using ADS burn a huge hole in my microwave's glass plate. (Yes, I was very bored, and yes, Guinness was involved). I'm also taking semiconductor physics. Really not my thing, but I think I better understand how transistors/diodes work. I just hope I can pass the drat course... Why do I always have to do things the hard way?...
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Mar 18, 2009 17:54
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hobbesmaster posted:My school takes care of that issue by having the worst teacher in the department always teach the required undergrad EM class. Hey, my department too. Moreover, the signals and systems course (Fourier transforms, Review of Laplace transforms, and pretty much every other precursor to DSP) is taught by a rotating cadre of visiting professors. The one I had got a grand total of 4 weeks into a 16 week syllabus by the time the semester ran out. Everything I know about Fourier transforms I was self taught, which pretty well kills my confidence for trying to take any DSP classes.
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Mar 18, 2009 18:11
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Man this economy must be bad if Bob Pease got the axe: http://www.edn.com/blog/1700000170/post/1030042103.html Dude is an analog circuit master Jedi. He invented the LM317!
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Mar 18, 2009 20:52
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Is there a reason I shouldn't file a new wedge point on my ancient weller tip? The local stores don't carry replacement tips, and I don't want to spend $10 on one from amazon.
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Mar 18, 2009 21:18
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oxbrain posted:Is there a reason I shouldn't file a new wedge point on my ancient weller tip? The local stores don't carry replacement tips, and I don't want to spend $10 on one from amazon. It'll probably be ok, but you'll want to keep it well tinned so it doesn't corrode. Worst case, you have to spend $10 on a new one.
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Mar 18, 2009 21:24
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oxbrain posted:Is there a reason I shouldn't file a new wedge point on my ancient weller tip? The local stores don't carry replacement tips, and I don't want to spend $10 on one from amazon. it depends. I had a weller once and I tried that, but apparently the tip had a core of different material, so when I filed deep enough it exposed it. And whatever that material was wouldn't flow solder well at all. Pretty much ruined it. I'd just recommend not going overboard.
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Mar 19, 2009 00:53
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I filed the tip to a roughly 3/32 wedge, cleaned with flux, and tinned it. I haven't tried it out yet, but it looks good so far. I also filed down the retainer screw to fit nearly flush and hopefully not catch on the holder as much.
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Mar 19, 2009 03:02
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Hillridge posted:Man this economy must be bad if Bob Pease got the axe: quote:He invented the LM317! The LM10, on the other hand, is a really neat part and a fantastic example of ingenious analog design, though I've never found a practical use for it in my projects (not enough bandwidth).
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Mar 19, 2009 14:07
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OK, can someone help me figure out what bonehead problem I'm having with building a buffer for an audio circuit using an Op-Amp? I'm starting to get into wiring up my own guitar pedals from scratch. I have mocked up some fairly ambitious circuit designs in the Falstad simulator, but I'm trying to wade very slowly into actually implementing the circuits to make sure I'm not overlooking any obvious problems. Step 1: I've got a box which contains 2x1/4" TS jacks (input and output), wired to a 3PDT toggle as a true bypass. In the off position, my signal is passed straight through; in the on position, it goes to two leads which are wired to my breadboard. There is also a ground lead which connects the ground of the input and output cables, which is then wired to the ground of my breadboard. Step 2: Wiring the leads together, I'm getting a clean connection in both on and off states, so my switch seems to be working. Step 3: I have also seemed to wire a very simple passive low-pass filter using a 0.1 uF film cap and a 10K pot. All is well and good (although the effect isn't really all that impressive -- sounds more like a volume control than anything else). Step 4: My problem. I'm trying to build my first active circuit now, which is just a simple OpAmp buffer between the input and the output. I'm using a 4558 dual-OpAmp I got from Small Bear Electronics, and the circuit looks like the following: code:
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Mar 19, 2009 14:11
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Well first of all, your op amp is supplied by nine volts. We'll call the negative terminal of the battery our ground (0V). So your buffer can only work with voltages in your supply range (0-9V). In the real world it can't even do that, and your usable signal range will never reach the supply rails, so you're actually stuck with maybe 1.5-7.5V. If your input signal is not in that range, it will not perform properly. The audio signal going in is an AC signal, meaning it has no DC component. Since its ground connection is made to 0V on your circuit, this means that it will be centered (or rather biased) around 0V. So if your input is 1V in amplitude, the signal seen by the op amp input will range from -1V to +1V, relative to 0V. See the problem yet? That is outside the buffers operating range. What you need to do is bias the input signal into the buffer's operating range. The easiest way to do that is to give your circuit what's called a dual supply. Meaning that it has two voltage sources. So use two 9V batteries in series. This gives you three voltage points. Let's now call the point at which the batteries connect to each other our 0V ground. Meaning at the other terminals of the batteries we get +9V and -9V. Connect these points to the op amp supply (in the correct polarity). Your op amp now has an operating range more like -7.5 to +7.5. Now, connect everything else the same way except connect IN_gnd and OUT_gnd to the 0V point, instead of the negative supply of the op amp. Both the output and input are still biased around 0V. The thing, now your buffer's operating range includes that, due to the dual supply. So essentially, do this: code:
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Mar 19, 2009 14:34
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ANIME AKBAR posted:Well first of all, your op amp is supplied by nine volts. We'll call the negative terminal of the battery our ground (0V). So your buffer can only work with voltages in your supply range (0-9V). In the real world it can't even do that, and your usable signal range will never reach the supply rails, so you're actually stuck with maybe 1.5-7.5V. If your input signal is not in that range, it will not perform properly. Of course, that makes perfect sense. The two-battery configuration worked fabulously (although now there's some hum in the sound, which I assume is coming from the preamplifier not expecting a DC-offset in its input signal). Do you have any suggestions on how I'd go about applying a DC-offset to the input using only a single battery? Every pedal I've ever seen or worked with uses a single bipolar supply (usually either 9v or 12v, unless it has tubes), so I assume there's a fairly simple solution. Looking at some simple schematics online like this one (posted earlier), it seems like they produce a +4.5v source (Vb) using a resistor divider, then somehow use that to pull up the input voltage. I'm not quite clear on how that works, however. So, what do I have to modify to make this work:  (Thanks for the assistance, btw. There's a huge amount of really great resources for learning this stuff all over the internet, but all that bootstrapping turns to crap when something goes minorly wrong and you have no idea what the right questions are to find a solution  )
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Mar 19, 2009 18:01
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