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Anybody have experience with the Tektronix 2246 'scope? I'm looking to pick up an old analog scope for projects at home since I won't be able to just use the stuff in the lab at my university soon. I've found that in a few projects having more than two channels is a big plus, and the 100MHz is very nice headroom but not strictly necessary. I looked through the Craigslist and a guy is selling one of these locally for a pretty reasonable price compared to ebay, and he claims to have calibrated it already. I'm going to go check it out tomorrow, but anybody have any advice beforehand? Also, anybody got any recommendations for a variable power supply, preferably with two outputs) or function generator that are easy to get in the US? Preferably fairly cheap, $100-$200 is my preferred max, although if I need to go higher I'll just save up for a while.
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Aug 19, 2012 04:38
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FSMC posted:I have a Tek 2445A. It's quite good for what it does but it has the limitations of being an analogue scope. Although four channels are nice, four monochrome signals on the small screen just got confusing. I found that I needed fancier triggering, the ability to freeze the frame, etc, so I ended up getting a digital scope. So it really comes down to what you are going to use the scope for. Thanks! It turned out the guy was a guy who got old electronics tech and fixed it as a hobby, then sold it on eBay/CL. I looked through his stuff and found one that he hadn't listed yet, a 2230, which is a dual-function digital-analog scope. Only two channels, but oh well, it's worth it. I also picked up a function generator, a 1MHz Simpson 420 (hurr  ) for a pretty reasonable price off him.taqueso posted:We have a couple supplies from Mastech at work and have been happy with them. http://www.mastechpowersupply.com/ Thanks! I was actually kind of looking at those, but I wasn't sure. I'll probably pick one up once my poor college student wallet recovers from the scope + function generator. Next up on the list after that is a non-poo poo soldering iron, xacto knife set, hot glue gun, and bigger/better component & tool boxes, probably in that order. I already managed to get a Fluke 87V for free, which is rather nice.
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Aug 20, 2012 00:39
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sharkytm posted:A local guy is selling: I bought a new scope just recently - what I found in my research is that the Tek 2213 is a pretty decent entry-level analog scope. Make sure you know the difference between analog and digital going in - if you want to look at digital communication signals or logic circuits, an analog scope probably isn't what you want. Otherwise, it's probably just fine for whatever you're doing. $100 is a pretty good price for that one, I saw a couple going for about $150. Assuming it's in good condition, with everything working properly, of course. Find a good signal generator to check that it's still calibrated, too if you can. They aren't too hard to calibrate, just open the cover and tweak a few pots, but it's nice if it's at least reasonably close. Fake edit: this episode of the eevblog is a pretty good example of what to look for when you're examining a used analog scope. Don't know anything about the Ideal. I used one of those Fluke bench meters at school my first year and it was really good to me. Looks to be going for about $200 on ebay, so I'd say that's a pretty reasonable price. Fluke stuff in general is pretty drat awesome too.
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Aug 23, 2012 05:07
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Cockmaster posted:I've decided I'd like to get an oscilloscope for working wih digital electronics, as well as potentially doing automotive diagnostics. I'd like either a handheld scope or a USB interface (an average size benchtop scope would be kind of unwieldy in my work area). Handheld scopes are either expensive or lovely, usually both. USB scopes are almost exclusively the latter. There may be good, cheap ones but if there are I haven't found any. As far as brands... Fluke, Tektronix, and Agilent are all generally good, reliable companies that make (or made in the past) handheld scopes. Looking at ebay the old Tek ones seem to be going to not too far above your price range, although most of the ones I saw were "for parts/as-is". Usually for digital work, depending on the speed you need, 50-100MHz is fine, maybe a bit less if you aren't going to work with anything particularly fast. Don't know much about automotive stuff though, but I wouldn't think you'd need any more than you would for digital.
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Aug 25, 2012 04:32
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nobody- posted:But does TI provide a good, non-crippled toolchain for it? Well, TI might not (although they've usually been good about un-restricting their toolchain, if only for launchpads IIRC), but since it's based on ARM you'll probably be able to use GCC for ARM with it. And if not somebody will figure it out and post a how-to on Hackaday 2 days after launch or something.
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Sep 3, 2012 20:33
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Hidden Under a Hat posted:About PCB design: a pad that the pin of the component goes through connects to both sides right? I have a series of pad through-holes, but some of them I want to connect to the bottom layer, and while I can specify that the traces are on the bottom layer, I can't do the same with the pad. I just want to be absolutely sure that traces on both layers can connect to the same pad through-hole. With through-hole stuff, yeah, the holes connect to both sides. If you're using surface mount stuff, then you can have pads that are on one side only.
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Sep 13, 2012 20:54
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Hidden Under a Hat posted:This is separate from that project. What I'm illuminating will be sensitive to the off-and-on nature of PWM dimming. No, we're fine answering your questions, it's just that you have some very strange requirements. It would have been better to ask "I need to dim some LEDs without PWM because the environment I'm working in is sensitive to extremely high frequency flashes, what's the best approach? I was thinking about this solution with relays..." rather than "How do I use relays to dim LEDs?". The latter is a silly question because 99% of the time that's a bad solution to the problem. The former is a perfectly valid question even if you can't say anything more about that environment, though thank you for explaining that. Now, the question is, is it sensitive to constant illumination with an extremely small ripple? In that case, you could use filtered PWM as is being discussed in the context of a DAC above. If it is sensitive to that small a fluctuation, then if you need very lower power, using a digital potentiometer would be the simplest solution, or if you need to power more than ~>5 small LEDs, then yeah, rolling your own with mosfets would be the way to go.
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Sep 17, 2012 03:19
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Krenzo posted:So I'm at a point in my electronics project where I need some custom fabrication for a large, mostly flat piece of material to mount antennas on. I need to fabricate something that is 2 ft x 2 ft x ~2 in with hinges to hold antennas that will sit perpendicular to the flat piece. I was thinking at the very least it could be a flat board (any strong non-metallic material) with precision drilled holes and then hinges that will screw in there to hold the antennas. Can anyone recommend any sort of CNC fabrication service or point me to a thread that may hold the answer? These type of services seem very expensive at first glance, as in it would be more worthwhile to just buy your own CNC machine. Why do you need this CNC'd? Like, why can't you just go to Home Depot and buy a wooden board, some hinges, and a drill and do it yourself? Maybe I'm being thick but just from what's in your post it sounds really simple.
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Sep 19, 2012 23:16
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sighnoceros posted:See I think it's that polarity that is messing me up. Because if you look at D1, the wiring on both sides of it is "charged", so in my mind, why does it matter which side you connect D3 to? How does the charge change before/after D1? The current is still flowing in the same "direction". I could even put another LED after it in series, so what changes such that I can't connect D3 to it after the charge passes through an LED? If I'm understanding your question correctly, which I may not be: Current can only flow one way through a diode - it's like a valve. Current can flow through it the direction the "arrow" is pointing, but not the other way. LEDs are still diodes, so they have that property too. (In a perfect diode - at some high enough voltage current will start to flow "backwards" through it but you don't really need to pay attention to that part for this circuit.)
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Oct 17, 2012 08:11
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sixide posted:Low 700s for 63/37 or around 800 for RoHS solder, generally speaking. You'll get a good feel for the appropriate temperature with practice. You'll surely need to adjust to the situation. Soldering a through-hole transformer to a 4" square with no thermal relief is vastly different from soldering 0402 resistors to pads with proper relief. This is in Fahrenheit, just to be clear. Most digital soldering irons I've seen have their temperatures in C by default.
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Oct 23, 2012 01:07
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BattleMaster posted:So I've started drawing European resistors instead of American ones because it's just so much easier. Especially for these resistor-solving questions in my electric circuits class. Seriously why would anyone build these nutty circuits??? The American resistor drawing is literally just squiggling your pencil, you can do it without even lifting your hand. Laziest symbol ever. To answer your question though, it's to get you good at the process, which is useful because complex impedances combine in pretty much the same way. And if you're doing frequency-dependent stuff, you'll need to take stray impedances into account. Basically, every circuit you build is also accidentally a filter and sometimes you need to account for that.
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Nov 2, 2012 07:34
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Zaxxon posted:does anyone know where I could find some of those silicone LED/Button covers like on monomes/bliptronics? If 4x4 or 2x2 sizes work, Sparkfun has some: https://www.sparkfun.com/products/7835
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Nov 5, 2012 13:20
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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 |
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Nov 17, 2012 05:55
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priznat posted:It makes me mad when the doofuses at my work treat the Fluke meters & leads like poo poo because they're great and also expensive Don't worry, they're made so you can treat them like poo poo and they'll keep working just as perfectly. It does piss me off when people gently caress up the probes though, those aren't quite as tough. Unless you're talking about the bench meters, those are still durable but aren't built for nearly the same pounding and are even more expensive.
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Dec 9, 2012 05:33
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movax posted:With the variations inherent in manufacturing resistors and LEDs, I feel like using LED controller ICs / constant current drivers, whilst driving up cost, would be a better way of achieving some kind of reasonable uniformity among the LEDs. True, but if he's just trying to make a one-off project work, a resistor would do the job and be a lot simpler as a kludge fix. Also, on a note which will surprise few of us, engineers are cold, emotionally dead shells of human beings. Arcsech fucked around with this message at 04:45 on Jan 22, 2013 |
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Jan 22, 2013 04:37
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Delta-Wye posted:Usually my problem is getting rid of the oscillator I accidentally made I'm in my final year of university for EE, and looking at the job market I'm definitely seeing people talk about how hard it is to find people who know what they're doing with RF or high frequency analog. Sadly, that's not me - I'd like to learn, but I don't know how. My university doesn't offer any serious classes in that area, we kind of talked a little bit about it in one class but nobody really understood it (I don't know if the professor did, even). I took a "Wireless Communication Systems" class, but it was all stuff about path loss, link budgeting, network layout, and so on. Not a word was breathed of antenna design or anything like it, other than looking at some data sheets for existing antennas.
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Feb 19, 2013 18:59
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I can't speak to this myself for sure, but one of my friends recently disassembled an automatic Nerf gun and was very confused about a cap in the same place as that C7. I think what he eventually found out was that it's a diode in a package that looks a lot like a cap (and possibly mislabeled?), which makes more sense as it would prevent anything from happening if you put the batteries in the wrong way.
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Feb 28, 2013 07:10
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JawnV6 posted:I don't understand what problem that's solving. That too many stupid people have money to burn on Kickstarter projects. There's already a tiny FPGA dev board designed for the maker crowd, the Papilio One. It even comes preloaded with an AVR soft processor, so you can use the Arduino software to write programs for your FPGA  (Admittedly, it might be pretty interesting to dissect as a learning experience, but still) Arcsech fucked around with this message at 18:45 on Mar 18, 2013 |
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Mar 18, 2013 18:36
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Otto Skorzeny posted:So today I found out that my ADC's internal buffer, when enabled, increases the INL from about .003% to about .15%. gently caress my life. TJ Rogers is the reincarnation of Hitler. Yeah even on the PSoC 3 the internal ADC buffer is poo poo. The PSoC is sort of a jack-of-all-trades-master-of-none type device. If you need something really flexible but don't need it to do any one thing particularly well it's about what you need.
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Mar 26, 2013 03:41
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Bad Munki posted:Can someone tell me if this is an okay regulator by which to power an atmega328p (and the associated bits to make a barebones arduino, i.e. a few caps, a resistor, and a crystal)? Looks good to me. Voltage regulators are pretty straightforward. The only other thing I'd take into consideration is that if you're planning on powering it on the higher end of that and using a lot of current it might get pretty warm, but you should be fine if you're powering it off a 9V or whatever.
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Aug 5, 2013 04:34
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For something between the 11X and the 87, look at the Fluke 177 or 179. The accuracy specs aren't quite as good, but it's a good bit cheaper than the 87, has all the functions, is built like tank, and is as safe as they come. Don't use those cheap Chinese crapmeters unless you're never measuring more than 5V, most of them don't have adequate safety measures and will blow up if you try to measure high voltage with it (there's even anecdotes about some of them actually blowing up at 120v, although you have to get really cheapass ones for that). A name-brand meter like Fluke or Agilent will keep you safe up to like a dozen kV surge. See also: https://www.youtube.com/watch?v=M-FZP1U2dkM Also, I can definitely endorse the Hakko soldering irons, they're on the expensive side but they work great.
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Sep 10, 2013 20:19
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ANIME AKBAR posted:I've been looking around at high end multimeters, and does anyone know of a handheld one that has excellent accuracy, like 100ppm or better? Also a kelvin sense ohm meter would be nice. It doesn't do kelvin sense resistance, but the Fluke 289 has voltage/current specs better than 100ppm. If you want AC specs that good, you'll be hard pressed to find it in a handheld I think, and it's resistance specs is 0.15%, which isn't quite as good as you want but it's the best I can find in a handheld DMM. You might be able to get better in an LCR meter, but that's kind of a different category.
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Sep 11, 2013 00:31
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peepsalot posted:What is the most efficient way to run a large ultracapacitor in a battery-like application (to get near constant voltage output for as long as possible, rather than a characteristic capacitor discharge curve). Is a buck boost converter the best thing for this? Yeah, a boost regulator would be your easiest bet I think. If you need to switch between that and an external power supply look at something like the the LTC4412, which is a power supply OR with a ~20mV drop. Edit: Maybe not exactly that chip considering it only lets the "battery" go down to 2.5V but something like that.
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Sep 13, 2013 23:07
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longview posted:The funny thing for me was that I discovered that around 1% of the bags were empty, but a further 1% had two transistors. One of my friends did something like that. We had a school assignment to design a voltage buffer out of discrete BJTs and characterize it. This guy, being a somewhat lazy smartass took the LM741 schematic and built it on a breadboard. The professor was impressed, but made him redo it anyway.
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Oct 17, 2013 02:13
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The Royal Scrub posted:Seems like that second equation would indicate a voltage gain over the resistor. Whether it's a gain or a drop is just dependent on current direction. It may be a negative gain (a drop) or a negative drop (a gain) depending on the circumstances. It's all the same absolute value, whether you call it a gain or a drop and what the sign is depends on the direction you arbitrarily draw your current arrow.
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Feb 20, 2014 23:30
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Illusive gently caress Man posted:Yo, I want to build a thing ~for a project~ and I'm wondering if it's something I can do myself, or maybe I should find someone experienced to design it (how much would this even cost?). I want a board with a bunch of PCI-E sockets. The data/clock lines don't need to be connected, but the sockets need to be fully powered and a microcontroller on the board needs the ability to turn power to each individual socket off/on. I guess there needs to be some kind of power supply on board too. So all you need it to do is distribute power? That should be easy enough, sounds like all you need is a/a set of regulators, a microcontroller, and a bunch of FETs to switch the power. How much power will the things be drawing, and how many different voltage levels do you need?
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Mar 1, 2014 19:35
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Stabby McDamage posted:Okay, I think I put too many rambling words in my previous post, so let me try again. None of them. There aren't even too many expensive small oscilloscopes that are any good. You're going to have a slow sampling rate and likely a very low analog bandwidth for any price below at least several hundred to a thousand dollars. If you're looking for something to use in the audio range, then I think Adafruit sells one that's kind of okay, but what you're looking for essentially doesn't exist. Edit: And all of them, even the expensive ones from Fluke and the like, have godawful interfaces. Arcsech fucked around with this message at 04:43 on Mar 18, 2014 |
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Mar 18, 2014 04:40
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theperminator posted:Stupid question I know, but When it comes to diode specifications, is the Voltage Forward figure the voltage drop across the diode? The voltage drop over a diode will remain more or less constant no matter how much current you push through it* - but if you try to push too much you'll overheat the diode and burn it out. How much current that is, is dependent on forward voltage drop and how much heat the diode can dissipate. *(This is not true on the very low current end, and it will change but not nearly as much as, say, a resistor)
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Apr 16, 2014 03:03
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Parallel Paraplegic posted:So what's the big difference between them and regular capacitors, rather than their absurd capacity? Is there a reason why every filter cap in every system isn't rocketing towards the Farad range (other than price)? Are they not great at filtering and are only meant for power storage? There are a few reasons you don't use huge caps for filters/bypassing. The first is cost - caps in the uF range cost basically nothing, as in less than a cent per in volume. They're also really tiny - 0603s or 0402s,which makes it possible to use them in portable electronics. Supercaps are getting a lot smaller, but definitely not that small. The second is power-on time and inrush current - with low value caps, they charge up really fast with a relatively low current draw. With a mondo cap, you'd have a longer charge time and a higher current draw, meaning your power supplies have to be beefier and your thing takes longer to power on. And all that wouldn't buy you a whole lot. Smaller caps even out power rail spikes pretty well, and if your rail is dirty enough that you need a Farad-range cap to even it out it probably has bigger problems.
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May 27, 2014 05:09
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sixide posted:I think we'll see an inversion at some point in my lifetime. The general-purpose computing guys will start working like video-encoder, etc. developers and start squeezing bits of efficiency out of the hardware while the embedded (microcontroller, not smartphone) guys will get progressively more sloppy as the hardware becomes non-limiting. Hell, this is probably already starting. The second part definitely is. Unless you're in hardcore cost or power crunch mode, SOP is now just chuck an ARM in and run Linux on the thing. Hell, I remember reading an article about how some hard drive controllers do exactly that, just because it covers a lot of bases for you.
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Jun 8, 2014 22:07
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SoundMonkey posted:tl;dr it's getting really affordable to be lazy That's just the thing - it's getting affordable enough that even in (semi)large scale manufacturing, if using the ARM-based Linux system means a shorter dev cycle and less engineering resources needed to get the thing out the door, it's often preferable to go with the more expensive IC. Edit: Design effort is a very real consideration in any project, even personal ones. Given that a 555 timer and an ATTiny cost effectively the same (~$0.20 difference, until you get to ultra large scale manufacturing this almost doesn't matter), the only reason to go for the 555 timer is aesthetics. Which, if that matters to you then go ahead, but I'd kinda rather just get poo poo done. The argument could even be made that the ATTiny is the better solution, considering that it takes up less board space, there's no passives to worry about, and it's easier to change the behavior later if you need to. Arcsech fucked around with this message at 00:31 on Jun 9, 2014 |
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Jun 9, 2014 00:21
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kid sinister posted:As a circuitry noob, I want an oscilloscope so bad and I'm not sure why. So... what exactly can they do? They're like a multimeter, except instead of reporting a steady voltage, they plot it over a typically very short amount of time. This works best (or for analog scopes, only works) with a repeating signal. They're good for checking how stable a power supply is, measuring the frequency of AC stuff, that sort of thing. Digital scopes can also be used to check logic circuits or catch intermittent problems, because they can essentially "freeze time" when they see certain voltages or patterns. Beaten, really hard. Anyway, in my opinion it's worth getting a digital oscilloscope over an analog one when starting out because, even though they're more expensive, being able to freeze and look at non-repeating signals is super super useful. Arcsech fucked around with this message at 05:37 on Jul 9, 2014 |
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Jul 9, 2014 05:34
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Buffis posted:On capacitors, is it feasible to replace a tantalum cap with a electrolyte cap? IIRC tantalum caps are used mainly for low ESR or high temp applications. So your main concern would be those. For a bypass cap it shouldn't really matter unless you're really trying to squeeze every last drop of accuracy you can out of the ADC, you should be fine using an electrolytic.
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Jul 27, 2014 22:17
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PDP-1 posted:Here's a kind of interesting problem that came up at work the other day: Suppose you have a DC signal somewhere in the +/-10V range with a 10Hz, 0.2V AC sine wave superimposed on top of it. What is the simplest circuit you can build with an output that gives only the DC component to within 1-2% when sampled at a random time? The solution that comes to mind immediately is to sample at an integer multiple of the frequency you want to drop and average over an integer multiple of the frequency you want dropped. So for example, sample at 20Hz, 40Hz, etc. and average over 2, 4, etc samples. Multimeters use this technique to attenuate 60Hz/50Hz noise in DC mode, in addition to a low-pass filter.
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Sep 14, 2014 05:25
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