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Bad Munki posted:Anyhow, if my understanding is correct, the power induced in the coil will be AC, but will be oscillating super duper fast, meaning the LED will have like a 50% duty cycle but at something like 150khz at least so that should be okay (150khz is just the value from the plans I'm working off of...sounds like it can be much, much higher. That's okay too, I think.) I guess I could add some stuff to convert it to DC but I want to keep this as absolutely dirt simple as is possible. How big is the capacitor you're putting in there? I think it would be elegant to use the LED itself as the diode in a half-wave rectifier, with an appropriately sized capacitor to keep it from sagging too much. Just make sure that the LED is rated to take the largest reverse voltages you're expecting.
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Oct 27, 2013 04:00
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I'm not sure how big the cap is yet. Apparently that and the frequency are intertwined, and I haven't gotten even close to figuring out appropriate values for each. But then, that (assumedly) lends me some leeway, in that I can pick a "good" value for the cap for my purposes and hopefully tune the frequency to best work with that...or at least work well enough. e: Does anyone know if OSH Park will do non-rectangular shapes? Just wondering if I need to go somewhere else for my circular board. ee: Nevermind, looks like they will. Here's what they're currently making of my submission. I haven't ordered anything yet, I don't think I'm really anywhere near that point, but this will (eventually) be the first time I've actually ordered a "real" board so I'm excited.  Top render:  Bottom render:  Top copper layer:  Bottom copper layer:  Top solder mask:  Bottom solder mask:  Board outline:  Drills: 
Bad Munki fucked around with this message at 05:47 on Oct 27, 2013 |
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Oct 27, 2013 04:02
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You should probably calculate what size capacitor you need before committing the design, that obviously tunes the loop for your operating frequency, and I don't think it's hard to calculate from the loop dimensions to get a ballpark figure. Is putting a second LED in an option? You could put two back to back and prevent reverse voltage being a problem. Flicker won't be a problem at 150 kHz, and you'll utilize all the power available. If you can't, you should be putting a normal signal diode like a 1n4148 back to back to prevent the reverse voltage damaging the LED, resonant circuits can have some surprisingly high voltages at times, especially with nothing loading them down. Since you're (presumably) designing a generator for this as well, you could make these boards land wherever they land (within reason) and put a manual tuner (like a variable capacitor) on the excitation loop in the board. These boards are likely to be very narrowly resonant (and may even require capacitor matching/presision caps to all provide the same current) so it's very likely you'll need to be able to fine tune frequency for the transmitter in order to hit that sweet spot.
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Oct 27, 2013 08:06
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Based on my experience building etched RF coils, I'd say you're looking at 30-40uH of inductance. I strongly suggest leaving more space for bigger capacitors (or an array of little ones). You want to use a nice NP0 ceramic cap, but your not going to find a 30nF one in a 0603 package. Raising the frequency would help with that though. And putting a high impedance choke in series with the LED will probably increase efficiency as well. If the LED is in parallel with the resonant cap, then reverse voltage shouldn't be a problem, since the reverse voltage should never exceed the applied forward voltage (if the circuit Q is high). Preventing overcurrent is probably the greater issue. ANIME AKBAR fucked around with this message at 13:16 on Oct 27, 2013 |
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Oct 27, 2013 13:14
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I'm pretty sure I could stuff an 0805 under the LED like that as well, and that opens up my capacitor options a lot. It'd be a little cozier, but I'm pretty sure it'd fit. Need to double-check on that, though. If anyone has an 0805 package they could stick between the leads of a 5mm LED (such that they would be connected in parallel) would you mind testing that fit?
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Oct 27, 2013 14:10
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Rotary encoder question: I currently have a unit with 16 detents per revolution. I'd like to replace it with a smaller one that has 30 detents per revolution. Am I understanding the internal operation of these little gizmos well enough to think that it wouldn't affect the operation of the equipment, aside from not having to turn the knob as far to get the same results? Does my question even make sense? I haven't had a lot of coffee yet this morning.
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Oct 27, 2013 15:35
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Acid Reflux posted:Rotary encoder question: I currently have a unit with 16 detents per revolution. I'd like to replace it with a smaller one that has 30 detents per revolution. Am I understanding the internal operation of these little gizmos well enough to think that it wouldn't affect the operation of the equipment, aside from not having to turn the knob as far to get the same results? Does my question even make sense? I haven't had a lot of coffee yet this morning.
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Oct 27, 2013 15:43
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It's the program/BPM selector on a Korg Kaoss Pad, which just cycles through the available settings. After looking at the KP itself, it also has a 30-step encoder. The 16-step one is part of a remote controller kit I'm installing in a guitar. Neither relies on absolute position, so I'm going to guess incremental.  Every time I jump into a new project there seems to be one component involved that I don't know nearly enough about. Thanks for the info!
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Oct 27, 2013 16:00
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I need to replace a blown cap in a fan speed controller for an air filter. 1000uf 6.3v. Due to a lack of proper electronics shops in my area, I'm going to have to order online which sucks for one cap. I have in my possession from another project two caps that may fit the bill. 2200uf 10v 1000uf 25v My Googling says that you can usually replace caps with a higher rating and be fine. The 2200uf cap is closer in physical dimension to the existing blown cap which is helpful, but my gut says I should use the 1000uf since it's closer to the original specced part. I'm under the assumption this cap was used as a filter. Before it failed completely, the brightness on the LED display would pulse up and down. Now that the cap is so far out of spec, the whole thing flashes on for a brief moment then shuts down immediately. Thoughts?
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Oct 27, 2013 19:32
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SynMoo posted:I need to replace a blown cap in a fan speed controller for an air filter. 1000uf 6.3v. Due to a lack of proper electronics shops in my area, I'm going to have to order online which sucks for one cap. I would guess the 1000uf cap will work okay. There cap is going to have some sort of design trade-off to get the rated voltage higher, but without knowing more I can only guess that your circuit will be okay with the substitution of a close part; "fan speed controller for an air filter" doesn't sound like a particularly touchy device. What do you mean by "the cap is so far out of spec" though? Is that behavior with one of the new caps or with the blown cap?
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Oct 27, 2013 19:55
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I was speaking about the behavior of the circuit with the blown cap. I went with the 1000uf 25v. It was a tight fight physically, but the circuit is now operating as new. Thanks for the advice!
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Oct 27, 2013 20:37
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tonberrytoby posted:It would be a lot easier to solve that as an S-Parameter expression. That one would be closed form too. Oooooh, nice find. Thanks!
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Oct 27, 2013 20:41
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Has there been any success using old iPhone screens in DIY projects? Last I checked there was a distinct lack of data on the interface, etc. Wondering if that's changed recently or not. I've got a dead 3G that I'd like to pick apart.
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Oct 27, 2013 20:42
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Stabby McDamage posted:I did classic MIDI for simplicity/cheapness. I'm using a USB MIDI converter to the PC, but I didn't want to integrate the converter it because it cost a few bucks and seemed reusing. Also I may want to the Nickelphone with other classic MIDI gear in the future. Which MIDI->USB interface?
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Oct 27, 2013 23:54
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ANIME AKBAR posted:Based on my experience building etched RF coils, I'd say you're looking at 30-40uH of inductance. I strongly suggest leaving more space for bigger capacitors (or an array of little ones). You want to use a nice NP0 ceramic cap, but your not going to find a 30nF one in a 0603 package. Raising the frequency would help with that though. And putting a high impedance choke in series with the LED will probably increase efficiency as well. So using 35uH and 30nF, that'd put me at about 150khz, that seems pretty reasonable and totally do-able. e: Using this equation from wikipedia: 
Bad Munki fucked around with this message at 02:56 on Oct 28, 2013 |
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Oct 28, 2013 02:52
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Bad Munki posted:I'm pretty sure I could stuff an 0805 under the LED like that as well, and that opens up my capacitor options a lot. It'd be a little cozier, but I'm pretty sure it'd fit. Need to double-check on that, though. If anyone has an 0805 package they could stick between the leads of a 5mm LED (such that they would be connected in parallel) would you mind testing that fit? An 0805 package is 0.08" long, a T-1 3/4 LED has a 0.1" pitch. Should fit just fine (well, the footprints will overlap with the LED annular rings). I would put footprints for two 0805 caps in parallel.
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Oct 28, 2013 03:00
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Yeah, I was looking at my design up there and I could very easily fit another two caps, one to the north and one to the south, and just extend the pad a bit to have them all in parallel, as needed. Or just scoot one cap north and setting another to the south to make a centered pair. Whatever I need, it looks like there's space. I did find some NP0 caps (well, they call it "C0G(NP0)" for that manufacturer, I think that's the same, just that manufacturer's naming scheme?) in an 0805 package at 27, 33, and 39 uF, so if that's actually the right value, I can do it with one. Is there a benefit to doing it with more caps instead of one? Really appreciate the input, by the way. I know I'm way out of my field here, but it's something I've been wanting to do for a long time, so reasonableness be damned.
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Oct 28, 2013 03:36
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NP0/C0G are basically interchangeable terms. Having more footprints just gives you more possible overall values to work with, in case you have to work at a specific frequency.
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Oct 28, 2013 03:58
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Oh, okay, gotcha. I'll probably order a bunch in the mid-30uF range, then. Those NP0 ones are more expensive, but we're still only talking 30 cents a pop for singles.
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Oct 28, 2013 04:02
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Delta-Wye posted:Which MIDI->USB interface? This one.
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Oct 28, 2013 04:40
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Delta-Wye posted:Hello blue smoke thread. I made a thing. From the thumbnail it looks like you made your own Lament Configuration.
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Oct 28, 2013 13:40
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Stabby McDamage posted:Hey, thread, I just finished a thing. http://hackaday.com/2013/10/28/the-nickelphone/ 
Delta-Wye fucked around with this message at 23:06 on Oct 28, 2013 |
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Oct 28, 2013 21:35
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I'm looking to build a light bulb contraption for a halloween costume. Basically a light bulb that gets mounted above my head and can be lit up as if I had an idea when I press a button. The contraption would need to be portable so I could walk around and then press the button to light up the bulb. It was suggested in the basic questions thread that I build an LED type circuit and place it into a hollowed out bulb. Is this the best solution? If so, what kind of LED should I be looking for and power?
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Oct 29, 2013 14:46
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How bright do you want it to be? EDIT: Go to your local CVS and buy this: http://www.cvs.com/shop/product-detail/InstaBulb-The-Stick-Up-Light-Bulb?skuId=890705 You should be able to take it apart and extend a button to switch it on/off, and it's already battery powered. n0tqu1tesane fucked around with this message at 17:36 on Oct 29, 2013 |
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Oct 29, 2013 17:11
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n0tqu1tesane posted:How bright do you want it to be? Oh wow, that is perfect! Time to cannibalize, thanks!
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Oct 29, 2013 20:04
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Bad Munki posted:Well, I finished the frame for my little keypad doodad. Need to put a case on it to hide the LED channels & bezel mounting screws and house the rest of the guts and all, but that won't really change the dimensions at all, just make it prettier. So I finally got this thing installed and working. It's super cool looking, really happy with the results: https://www.youtube.com/watch?v=LsFqkeSp4Y4
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Oct 31, 2013 03:25
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Ha, yeah. It's been picked up by all these international blogs from that -- I keep seeing my name embedded in Russian and Turkish tweets...kinda weird.
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Nov 1, 2013 16:14
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So I'm working on a system of bicycle lights using electroluminescent wire and tape. This stuff needs to be driven with high-frequency AC, maybe 200v and 3kHz. Ideally, I'm shooting to have six different channels of lights driven by a single inverter, switching them on and off with triacs. If all the channels are disabled, though, there'll be no load connected to the inverter output and the voltage will spike, damaging it, right? That's what I have been told about these inverters anyway. I could program it to never have all the channels disabled, but I'd rather have the flexibility to do so if possible. I assume that I can solve this just by connecting a capacitor across the inverter output so that it's always got something to push against and stabilize its output. Will that work? If so, how can I calculate an appropriate value for that capacitor, and what type should I use?
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Nov 3, 2013 01:43
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Sagebrush posted:So I'm working on a system of bicycle lights using electroluminescent wire and tape. This stuff needs to be driven with high-frequency AC, maybe 200v and 3kHz. Ideally, I'm shooting to have six different channels of lights driven by a single inverter, switching them on and off with triacs. If all the channels are disabled, though, there'll be no load connected to the inverter output and the voltage will spike, damaging it, right? That's what I have been told about these inverters anyway. I could program it to never have all the channels disabled, but I'd rather have the flexibility to do so if possible. I didn't have problems with running my inverter with no-load when I was messing with EL wire. Maybe this is an issue for certain EL wire inverter topologies, or maybe it's just an issue over time.... Regardless, if this is actually an issue, you could use just about any ceramic cap (with a resistor) to create a load...However, since this is just an AC inverter, you would be better off using just a load resistor. That will act as a simple load, and should work fine. FAKE EDIT: I took a look at the comments on the EL wire sequencer I got from Sparkfun, and someone asked the question about the no-load condition. They claim that they tested it and didn't have any problems with the inverter they sell (which is the one I used), but that this might not be the case for other inverters.
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Nov 3, 2013 02:56
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Hmm. I've also had no real problems running other EL inverters with no load before, but every place I can find online suggests that it's a bad idea and these ones came stamped with a warning. So I really do want to have some sort of protection circuit in place just in case. I realized that my multimeter has a capacitance function I've never actually used! I tested a few of the lengths of the EL tape and a meter averages around 40-50nF. So at least that value's easy; 47nf should do fine. When measuring for resistance...there's no continuity between the two contacts, obviously. Measuring along the length of one wire, by probing the contacts on each end (I assume this is the core) gives me 15k resistance for the 1-meter length. The other wire (which I assume is the corona) reads 1.5 megaohms. What should I do? Just hook a 1.5M over the output and call it a day, or do something more complex?
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Nov 3, 2013 03:38
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Sagebrush posted:Hmm. I've also had no real problems running other EL inverters with no load before, but every place I can find online suggests that it's a bad idea and these ones came stamped with a warning. So I really do want to have some sort of protection circuit in place just in case. If you haven't seen this guy's adventure's with EL wire I'd give it a read. There's tons of fascinating information. Regarding the load. Adafruit and a few other places indicates that depending on the design of the inverter the capacitance of the wire might be used to stabilize it, so a pure resistive load may not be the best standby load. On the other hand, your particular inverter may not even need it.
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Nov 3, 2013 05:08
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EL inverters probably use transformer coupled outputs? I've been warned that running transformer coupled audio amplifiers with no load can destroy them, but the exact mechanism was never explained. Some electricians also warned me against running a door-bell transformer with no load, citing a case where one caught fire, I still think they just wired it in backwards. If the output transformer was designed to drop voltage across its windings in normal operation (which is probably a bad idea) I could see how the open circuit voltage might cause arcing, but that would be a bad design IMO.
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Nov 3, 2013 08:24
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longview posted:EL inverters probably use transformer coupled outputs? At moments like this I regret going Computer Engineering instead of EE. My program was only about 4 courses different than E.E. and one of those courses dealt with magnetics (I've recently been dealing with transformers so this has been on my mind). The other reason is that Computer Engineering confuses people with C.S. On the other hand when I got a job I knew how to actually bring up a CPLD or Microcontroller on a board (sort of).
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Nov 3, 2013 16:14
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longview posted:EL inverters probably use transformer coupled outputs? So there is lots of current running through the hot coil. Which can make it overheat if it is designed badly. Or the current can make the end stage of your source overheat. If you are worried about that sort of thing, put in a fuse.
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Nov 3, 2013 16:29
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longview posted:EL inverters probably use transformer coupled outputs? The ch00ftech pages I linked earlier indicates that the output is transformer coupled. It also indicates that most of the drivers are self resonant tank circuits. If it's using the el wire as an element as the C element in the LC resonant circuit, removing it will naturally drastically change the operating mode.
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Nov 3, 2013 23:39
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Just ordered a bunch of stuff from Mouser for a CMOY pocket amp for my girlfriend and as a warmup for building my b22.  What are some "buy this you idiot" things I should buy for any electronics project, because I'm an idiot? I have a Weller soldering iron with an SP7 tip in the mail, a pound of Kester 63/37 .031 solder, helping hands, a $5 multimeter (my friend stole and lost my good one  ), wire strippers, various dykes, Hakko tip cleaner, solder suckers... anything hugely important I'm missing? Any tips? I don't wanna mess too much up 
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Nov 5, 2013 04:49
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Flux and breadboard wire. Also breadboards. If you're like me, you also probably want to get some lead solder from China because gently caress tin solder.
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Nov 5, 2013 04:54
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Get extra flux and some solder wick. And chisel tips work better for soldering irons than conical, so if you can get one for your iron get it.
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Nov 5, 2013 05:23
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Wish I thought to check here before I went and bought all this stuff I'm yet another goon trying to make sense of solderless crimps for the first time. The crimps I have are these ones from Molex, after finding the housings first and backtracking through data sheets. The crimper I got from amazon since Mouser kept wanting to sell me some $300 expense account crap. From what I can tell:
I saw the tool linked a few pages ago when discussing this same topic. I've got smaller wire, but I'd prefer to keep the crimper and find the right die for it.  
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Nov 6, 2013 21:54
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This may not be correct for your setup but I've found it's nearly always much easier to leave them on the metal strip they come attached to until [i]after[\i] you crimp.
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Nov 6, 2013 22:15
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