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Sorry if this has already been asked, but how about inexpensive oscilloscopes? I'm just setting up a bench for my hobby projects, but all the good oscilloscopes seem to be hundreds of dollars. I found a few tiny hand-held ones on the cheaps, and a few that interface with a computer instead of having a screen which I might be able to work, but what about quality? Is there a huge difference between cheap oscilloscopes and expensive ones? Do you think I would be able to do the fairly basic stuff I need to do with a cheap (sub-$150) one? I just want to look at waveforms to see how my circuits are doing and to see what other circuits are doing for hacking stuff apart. For context, my specific first project I'm targeting is to build a Geiger counter, as it's not terribly complicated and it's cool enough to keep me interested, but I want to make sure the pulses aren't awful and noisy so I can read them with a microcontroller and I can't really think of a way to do that without a scope. Also I'd like to do some sound-based projects in the future. My dad is an electrical engineer and I grew up around this stuff and did it a bit for fun as a kid so I remember a lot of basic things about parts and how they go together, can tell my resistors from my capacitors and such, but I never really built anything terribly advanced on my own.
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Dec 9, 2012 05:13
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So I'll probably need to save up for something actually good or it's a crapshoot I take it (though I will look into that DSO-203 and the logic analyzer, thanks peepsalot!) Oh well, maybe I can borrow one of my dad's ancient analog CRT scopes while I'm waiting, at least I can pretend I'm a 1950's mad scientist 
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Dec 9, 2012 21:25
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Cool, I'll look into Rigol then. I talked to my dad today, and he said that while he did have an old spare analog scope I could have, it was in pieces as he was replacing the control systems since they were "noisy, worn and getting a bit oxidized with age". He has the new parts, just hasn't gotten around to putting them in yet, so I guess that's out at least for now. Anyway, thanks for your help guys.
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Dec 10, 2012 03:03
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Delta-Wye posted:Okay, plan B. Let's complicated this bitch You know, they could just dump an assload of salt in the water to raise the conductance. Plus this would probably kill the tree, and then they wouldn't have a dirty-rear end tree ruining their perfectly good water sensing apparatus
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Dec 11, 2012 00:06
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priznat posted:This has probably been mentioned before, but the icircuit app is pretty nifty for just seeing how electronic stuff behaves. Looks great, but can I get it on something that doesn't have a tiny screen and that I don't have to poke at with my big greasy fingers? Actually, I've been looking for a good, cheap circuit simulator for the computer for a while too. I tried some free ones out but I didn't really like any of them. I used to have this one back in the 90's that I learned a ton from, but I can't remember the name of and I'm pretty sure the company went out of business. It had a "rocket" component and a "car" component for some reason, which was enough to keep my 8 year old self interested in learning about poo poo. It was a full-fledged circuit simulator though, not just a kid's program, and I remember it had a pretty straightforward UI and I liked it.
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Dec 13, 2012 01:27
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but nicely done and can be helpful for visualizing what is going on. Shows you where the current is flowing, etc.
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timb posted:It's available on the Mac App Store so that certainly fits the bill. I've got it on both my iPhone and Mac; it's pretty great for I didn't see that, but I don't have a mac. Thanks anyway  EDIT: I'm trying out LTSpice (yeah it's still free) and that seems to be fine, thanks tonberrytoby. Shame Boy fucked around with this message at 03:44 on Dec 13, 2012 |
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Dec 13, 2012 03:39
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SnoPuppy posted:I'll put in another vote for LTSpice - don't think that just because it's free, it's a lesser tool. I went ahead and bought that app for my android phone to play with when I'm bored at work, it's designed well enough to use on my phone comfortably so I can get some fun out of it. But yeah, I'll be using LTSpice on my PC (and I'm actually running it under WINE and it works fine).
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Dec 13, 2012 05:01
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I got this neat geiger counter kit for christmas and managed to put it together in just under two hours. I'm quite satisfied with it as it worked the first time I turned it on, and now it's happily clicking away in the corner. Anyway, I'm going back over the circuit to try to understand exactly how it works, and I've gotten most of it (the detector circuit, the microcontroller, etc) but I have no idea how the high voltage supply works. Here's the schematic: A 555 timer, inductor, two transistors and a bunch of resistors, capacitors and diodes? Huh? What does the 555 even have to do with anything, I thought that was just for making signals, timing, switching etc? Sorry if this is kinda a basic question but I've never encountered a HV supply quite like this in my electronics hobbying before 
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Dec 27, 2012 00:17
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Delta-Wye posted:http://www.ledsales.com.au/kits/nixie_supply.pdf Ah thanks, that makes sense.
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Dec 27, 2012 00:39
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Delta-Wye posted:http://www.amazon.com/Weller-WLC100-40-Watt-Soldering-Station/dp/B000AS28UC/ I got this one for Christmas and it works great. My dad has almost the same model which he bought twenty years ago and it still works fine even though he's assembled countless projects with it (though he replaced the tips a few times I think)
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Dec 27, 2012 09:41
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Double post, sorry 
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Dec 27, 2012 09:42
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Powdered Toast Man posted:I'm thinking about building a multi-station USB charger with micro-USB connectors. I've sourced some durable-looking PC mount connectors from Digi-Key and I've been looking at the pinout/specs for USB...do I need to do anything other than provide constant, regulated 5V? I'll be charging stuff like cell phones or accessories that have their own batteries and charging circuitry built-in. I did something like this once, and yeah basically you just need a good steady 5V and ground and most things will just suck as much juice as they can. You might want to be careful in this regard as having many devices connected will suck a surprisingly high amount of current. The USB spec is only supposed to go up to 500 mA but some things can take as much as 5 loving amps when charging if they just try to suck up whatever is available, according to Wikipedia.
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Dec 28, 2012 18:43
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orange sky posted:I don't know if this warrants its own thread, so here goes: You can't just do some kind of band-pass filtering to filter out low frequencies and only accept high frequencies, then feed that to an amplifier and some kind of logic that would only trigger on sufficiently "strong" signals? I mean if you want this to be really accurate and only respond to specifically her voice that would take some fancy programming, but if you just want it to respond to a certain range of frequencies and not others that's somewhat easy to do even without a microcontroller, I believe.
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Dec 31, 2012 02:27
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Slanderer posted:The problem is that even a lower pitched voice will have higher pitched overtones stuffed in there. That, combined with general ambient noise, means that a single bandpass filter isn't really enough. Yeah, I was thinking find a frequency that is very strong in her voice but not as strong in his voice, and then make it so that in normal conversational volume it would trigger for her but not for him. I'm also assuming that this is just some kind of novelty "I built this 'correctness' detector honey, it's specifically tuned for our marriage!" thing, and not something that would need to reliably trigger on her voice but not his in all conditions. Of course I'm still probably underestimating the complexity of the human voice.
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Dec 31, 2012 02:35
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orange sky posted:Thing is, I don't know if I have access to the kind of stuff needed to build/test a band pass filter. I'll try to talk to the electronics guys at my university. And yes, it's just a band pass filter that I need, not something fancy only for her voice. Well don't put too much stock in my answer, I got shot down by everyone who has actual training here so I'm actually doubting the feasibility of it myself now However talking to your electronics buddies would probably be a great place to start, assuming there is a simple solution to this.
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Dec 31, 2012 02:40
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peepsalot posted:You might be interested in this guy's code: There's actually a tutorial about doing FFT in arduino's native C-ish language too. It even has some information on finding specific frequency peaks and doing some basic DSP.
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Dec 31, 2012 03:24
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Martytoof posted:Putting the cart before the horse, I collected way too much surplus electronics gear for my skill level and I'm basically drowning in parts and test equipment and stuff. Total first-world-problem but the disorganization is kind of making me want to not work on electronics when every time I whip out a multimeter probe cable it gets tangled on like 5 other cables. I don't really know why I posted this since this isn't livejournal, but it's just an observation that cleanliness and organization is important in everything Sell some of it. To me. For a very low price.
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Jan 2, 2013 11:35
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Slanderer posted:Holy loving poo poo. Agreed, this guy has basically made every DIY project I've ever done seem like LEGO in comparison.
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Jan 4, 2013 12:41
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I was thinking of building an audio amplifier with digital volume control driven by, say, the Arduino I have lying around. I like the idea of controlling random things around me with my computer and amplifier circuits are fun. I was thinking I would control the volume by building a voltage divider and adjusting the value of one of the resistors, as described here: http://embedded-lab.com/blog/?p=2967 However I was wondering, do I really need the digital potentiometer chip? I was reading elsewhere that for reasonably low frequency circuits you can make a fairly effective variable resistor by using PWM to control a transistor that repeatedly shunts power away from (or into, depending on how you set it up) a normal resistor, the idea being that if you use a 2k resistor at a 50% duty cycle the circuit would only "see" a 1k resistor. I'm just wondering if this would be unacceptably noisy for an amplifier and I should just get some of those digital potentiometer chips, or if I could just smooth it out with a capacitor or otherwise handle it. If I don't need to get those chips, I think I have everything I need to breadboard the circuit right now.
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Jan 10, 2013 03:16
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Aurium posted:Following on this, the default pwm frequency on your arduino is approximately 490 Hz, which is absolutely audible. You'll need to bump it up quite a bit. Wow, I had no idea it defaulted to a frequency that low, I always assumed it was in the mid-tens-of-kHz range for some reason. Thanks! longview posted:My recommendation is an actual pot with a dc motor, that's how commercial products used to do it. I also had no idea that pro models would just use motors to turn pots, I always thought they'd have a more... elegant solution? I guess it makes sense though as it lets you manually adjust the knobs too. I have some research and experimenting to do, thanks guys.
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Jan 10, 2013 13:57
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longview posted:As a matter of fact I do know an ex military communications guy, I might give him a call. I like the electromagnet, if it fails you just wind up with it floating to the surface too early and you try again, whereas if the balloon fails you lose it forever. Of course if you can't demagnetize it enough you also lose it forever, so you better be sure it's a good electromagnet, maybe build in some logic to try the electromagnet a few more times if it doesn't detect itself ascending the first time (in case the scrap metal falls off but then gets stuck to the permanent magnet again once you turn the EM off)
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Jan 13, 2013 03:13
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So I went to the thrift shop today and got a bunch of neat old stuff to break apart and see how it works, harvest for parts, etc. The coolest thing I got was an old Texas Instruments TI-8250 printing calculator from what looks like the early 90's. I took the screen out of it as it has a pretty nice little segment display, but I can't seem to find any datasheets or information on this screen. Here's some pictures of it:  I looked around for "Futaba 11-MT-62G" datasheets (and variations of that) and only found datasheets for other devices that referenced that they USED a "Futaba 11-MT" component, but no sheets for this screen itself. There seems to be a little glass stem on the side of it as well and the whole thing is sealed, does this mean it's some kind of gas discharge thing that I'll need high voltage to drive? VV Yeah I figured I might have to do that, I was just hoping I'd get lucky and someone here would have experience with a similar device. VV Shame Boy fucked around with this message at 04:10 on Jan 14, 2013 |
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Jan 14, 2013 03:50
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Slanderer posted:That's a vacuum fluorescent display. Even compared to many LED displays, they are useful because they have extremely high contrast. They are kinda fun to play around with if you have a power supply or two to figure out the voltage requirements and pinout. This might help--it helped me when I played with some years back. Make sure not to put too much current through the filament--it shouldn't be glowing! The different VFDs intended for DC or AC control can be controlled any way you choose, but will probably not work as well, so keep that in mind. Thanks for the links! I actually did try to figure out the pinout when I first opened it up, and it's not as easy as I would hope. The traces go all over the board, curve in weird ways I've never seen traces curve (it's like some of them were drawn by hand) and connect to a bunch of different things, including some Darlington IC's, this big IC on the back with no writing on it that I assume is the main calculator chip, and these two big traces that go all around the board which I think are the main power/ground lines, but I'm not sure. Nothing seems to connect directly or indirectly to any sort of ground I can identify, it's all going through a bunch of other components before it gets to the power circuitry. I'll go back and see if I can sketch it out tomorrow I guess. EDIT: Now that I know what the heck it is, I managed to find the datasheet to a very similar model that has a very similar pinout that I think I can work with. Thanks! Shame Boy fucked around with this message at 05:03 on Jan 14, 2013 |
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Jan 14, 2013 04:49
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Thanks to that ghetto data sheet, the tutorial-y page Slanderer linked, and my own insomnia I got it to work! Looks like all the segments are nice and bright and functional, and I got them all sketched out and mapped to which segment what pin goes to and what voltages etc to use so I don't have to refer to the ghetto datasheet again  Totally gonna use this in a project some time, it looks great. Thanks guys!
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Jan 14, 2013 06:54
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Rexxed posted:The goal of the project is to not have to check the mouse traps in the basement every day and also not have dead mice fouling up the traps. So there'll be a RF transmitter with a microcontroller on each trap one and a receiver that can just alert me when the transmitter(s) are doing stuff. The Atmega328 is probably overkill for something that will be using maybe two I/O pins but I got an Arduino Uno as a gift and even "too much" microcontroller is still only like $2. Exactly how mouse-infested is your basement anyway 
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Jan 16, 2013 18:29
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Anyone have any tips or tricks for cutting perfboard? I tried to score it pretty deeply (first one side then both sides) and snap it in half on the edge of a table and it just flexed a little and refused to budge. I finally wound up using pliers to crack it off (which was very visceral and snapped in a weirdly disturbing way, like how I'd imagine spines would snap  ), and while it did crack right on the score I had made, half of the piece I was cracking off twisted and broke apart. I managed to save enough to still put my circuit on but it wasted more than I'd like since I had to throw some away. Do I need to score it even more (I think I scored it pretty drat deep but I could be misjudging) or should I just invest in a good Dremel tool? Any other ideas I missed?
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Jan 20, 2013 04:57
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sixide posted:Is this classic phenolic perfboard or some sort of FR4 circuit board in a perfboard layout? It's "Epoxy Fiber". I guess I'll look for the "classic" kind next time.
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Jan 20, 2013 06:14
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Jonny 290 posted:How I cut my boards, with really good success rate: Yeah I basically did this and the fucker cut my hand open but didn't break. I guess I just got the "extra tough" stuff or something
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Jan 20, 2013 22:15
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I think they mean why can't you just connect the LED to yourself (and not connect yourself to anything else) and have it work, because the human body is a pretty okay "ground" for some things (IE static discharge). I'm guessing it doesn't work because your voltage source also has to be connected to the same ground, as "voltage" is only really meaningful as a relative value, so it's "+5 volts with reference to this thing we say is zero (the 'ground')." Since the voltage source is not using you as the zero "thing" itself, the rest of the circuit doesn't have any charge with reference to you and therefore no energy flows. I'm completely talking out of my rear end here so someone with better training could probably explain it better. Shame Boy fucked around with this message at 23:53 on Jan 20, 2013 |
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Jan 20, 2013 23:50
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huhu posted:Just spent the last two hours assembling and troubleshooting the circuit and got everything running smoothly. Except for the fact that I bought lovely LEDs and the color detection system I made doesn't work because the one LED is so much more bright than the others and this leads to a false positive every time. You can't just put some extra resistors or maybe a voltage divider on that one particular LED?
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Jan 22, 2013 03:16
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At least I learned a lot and have a strobe light now!
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So I tried cutting some more of that thick perfboard today by scoring it and putting it under a book and breaking it right on the edge, and it worked perfectly with very little effort. I guess when I was doing it before it was flexing too much and couldn't break. Thanks for the help again guys!
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Jan 23, 2013 04:31
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Bad Munki posted:So I've narrowed it down to five options. The low ESR option isn't available unless I'm buying seven thousand of them, so that's out. With that in mind, do I want high frequency, low impedance, or general purpose? All else apparently the same. I doubt that thing needs to be high frequency if it's just a power supply. Wouldn't low impedance imply low ESR? I'm not really sure but it makes sense that it would.
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Jan 27, 2013 04:17
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icantfindaname posted:edit: Okay, since that last question was fixed, here's another: How the heck do I get wires to stay in the arduino as I'm stuffing the whole thing inside a flashlight casing? I used braided wire to connect everything because the solid wire was way too stiff and the solder joints were falling apart. Would an arduino shield work? Did you tin the ends of the braided wire first? It keeps them from fraying and generally helps keep them in the holes in my experience. You could also probably just electrical tape the wires to the arduino, if you don't care about removing the arduino for other projects. The best way would probably to make a little shield for it, maybe out if perfboard, then solder all the wires to the shield. This would have the added benefit of allowing you to easily remove the arduino later for programming or other projects. Watch out for that arduino spacing error though, it's a bitch to deal with on perfboard if you have to use the full range of pins.
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Jan 29, 2013 05:51
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EDIT: ^^ Basically what they said ^^Moist von Lipwig posted:I was hoping I could get some quick advice here. That copper twisted around the white wire is the ground line which doubles as a shield against interference, some cables have them and some just put the ground line in another wire (probably the white or black wire in the other one, but I'm not certain). If you have access to a continuity checker, you could use that to find out which wires go to which part of the jack (tip, middle or base). Then, assuming you kept the old jack you cut off, do the same to that one to figure out which wires are which and wire up accordingly. If you have a multimeter you could use that as well, or you could probably pick up a cheap continuity checker at Radio Shack, they're just little things that beep or light up when they detect a complete circuit. I wouldn't guess at this, you'd run the chance of shorting out whatever you plug it into (unless someone else here already knows exactly which wires go to what, I have to check whenever I hack a cable apart just for peace of mind )Also it looks like you're wiring a mono headset with microphone to what is usually assumed to be a stereo headphones-type jack (which is fine, it will work) but make sure whatever you plug it into is not expecting stereo headphones and is in fact designed to have a mono headset with microphone plugged into it - otherwise it will try to run sound signals through the microphone and probably destroy it. If you don't need to use the mic you might want to just leave that completely disconnected.
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Feb 1, 2013 02:37
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peepsalot posted:Those component packs look like pretty ripoff prices to me. You could go on mouser and get all that poo poo for probably $50 or something. Yeah, I've found that a lot of people who don't do electronics don't realize that components are mass produced to such levels that a lot of them have absurdly low prices. Some of them are fractions of a cent each. If you go to mouser or jameco etc and just buy the stuff that's in that kit you can probably save a bunch. My last order had about 400 total quantity of items and cost me about $55 shipped. Then just get yourself a good breadboard and some kind of power supply (I use a wall wort that I run through a little board with a 5V regulator and some capacitors on it, really simple to build - here's the same basic circuit though I put bigger caps on it: http://www.instructables.com/id/5v-Regulator/). If I were you I'd just buy the book by itself, then get the parts separately. I definitely recommend buying some of those grab-bags for capacitors and resistors and LED's etc like peepsalot said. Jameco has them, Amazon has them (though it's more expensive from them) or you can get the eBay ones. It's great for fleshing out your supply of some of the most frequently used parts, and they usually come in the most frequently used values. Now keeping all those parts sorted is a bit of a bigger problem. I keep my parts in a big tackle box, but this probably isn't ideal since it's not anti-static. You can buy specifically anti-static containers but they're a bit more. Still probably cheaper than that kit.
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Feb 2, 2013 23:35
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So I'm trying to figure out what the heck I'm doing wrong here. I'm trying to recreate this circuit for a CMOS NAND gate, only using BJT's. So this circuit but with discrete PNP and NPN BJT transistors: Everything seems to be going fine if I build everything (connecting A and B to a pull-down resistor connected to ground) but leave out one of the PNP's. However, the second I connect the missing PNP (which could be either one) the LED I'm using to indicate the output state dims to about half of its normal brightness and the PNP heats up really fast, actually burning my finger and releasing the smoke in one case where I didn't pull it out fast enough. I have no idea how I'm doing this, I have 1k resistors on every possible path to ground (I even replaced them with 100k and it didn't make a difference) and the resistors don't seem to heat up much at all. Some permutation of this circuit should be possible to build with discrete BJT components, right? Am I missing some fundamental "catch on fire" property of BJT's that I don't know about that prevents them from working in this circuit? Shame Boy fucked around with this message at 03:07 on Feb 4, 2013 |
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Feb 4, 2013 03:00
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Yeah I should have posted a schematic, right now I'm just dicking around on the breadboard but I guess "hey guys my thing that kind of looks like this isn't working, help!" is a pretty dumb thing to post. Sorry!  Anyway I had missed a path to ground that I didn't see until I carefully went back over what I had done. Somehow I missed it in all the previous goings-over I did. I am a dumb again, I guess. It's not heating up anymore but it's still not working, probably due to the several reasons you have already pointed out. I did actually have resistors on the bases. I've put an LED between the NPN's and ground to see if they're actually turning power on and off, and they are, but the voltage across the output never changes. I tried lowering the value of the resistor on the NPN's output thinking that if it had a preferential path to ground it might at least drop the voltage across the output, but still nothing. I will draw up a schematic and get back to you guys, sorry I didn't do that to begin with
Shame Boy fucked around with this message at 03:48 on Feb 4, 2013 |
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Feb 4, 2013 03:45
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Okay, here's what I drew up, including the values of resistors I currently have in there while loving around with it. If I switch A and B to low, the MONITOR LED is off and the OUT LED is on. If I switch them both to high, MONITOR comes on, but OUT remains on, and the voltage across OUT remains totally unchanged.
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Feb 4, 2013 04:28
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SnoPuppy posted:I think the problem is the bases of the PNPs and NPNs are connected together. This provides a path for current to flow from the PNP emitter through the base, and into the 220 ohm and base of the NPN transistor, turning it on. It is generally a very bad thing to have high base currents. I added the 1K resistors and no luck. The forward-biasing makes sense, but it's weird that the voltage remains exactly and perfectly unchanged as far as I can tell (down to three decimal places, according to my cheap and unreliable multimeter). I assume that means I can't actually build this circuit with BJT's then?
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Feb 4, 2013 04:52
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asdf32 posted:Ok so based on a second look and reading everything you said your problem still isn't entirely clear. But here are some more points: I'll see if this works, but wouldn't removing the resistor between the NPN's and ground mean that current can flow essentially uninterrupted through the whole thing (effectively bringing back the catching-on-fire issue from earlier?) Should I put a resistor before the PNP's instead? Anyway thanks for everyone's help with this, I never realized the differences between transistor types could make this big a difference. Also, I tried LT Spice a while ago and couldn't get it working (I'm one of those freaks who uses linux, so entirely my fault ), so I'm actually using what I first learned this poo poo on back in the 90's, CircuitMaker (which works perfectly in WINE for some goddamn reason). It's got full SPICE simulation and does most of the things more modern software does, while being an interface I'm already familiar with, so meh.
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Feb 5, 2013 03:29
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