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ANIME AKBAR posted:supervisor basically hands me a paper by some MIT physics professor about inductive coupling for magnetic energy transfer and says "hey try to make this work, only make it more efficient." I tell him his demands are physically impossible and he basically says "yeah, well try anyways." This happens to me all the god damned time. This one person I work with wants me to simply make a 100hz 60V@200mA source weigh less then 10 grams. She doesn't realize its physically impossible; she too is a chemical engineer. Don't go in to research. Especially if you are the only EE in the building. Gah.
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Jul 6, 2009 04:17
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Twerpling posted:This happens to me all the god damned time. This one person I work with wants me to simply make a 100hz 60V@200mA source weigh less then 10 grams. She doesn't realize its physically impossible; she too is a chemical engineer. That's totally possible! Just present her with a proposal to make a custom, mixed signal ASIC. I bet you could do the whole thing for less than a million!  Or you could always try asking for something equally nonsensical back in return...
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Jul 6, 2009 04:22
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What's your input voltage? That may be actually be doable. Why does it need to be so light? Is it being shot into space or something?
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Jul 6, 2009 15:10
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Twerpling posted:This happens to me all the god damned time. This one person I work with wants me to simply make a 100hz 60V@200mA source weigh less then 10 grams. She doesn't realize its physically impossible; she too is a chemical engineer.
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Jul 6, 2009 22:25
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So what exactly is your job now?
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Jul 6, 2009 23:45
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ANIME AKBAR posted:There's actually a senior EE I answer to, and when I told him the demands were realistic he basically said "oh come on, where's your sense of adventure!" or some such bullshit. I'm literally the only person in the entire company who can interpret the paper's methodology, and it absolutely supports my objections. I'm basically going to end up turning in a 30 page report spelling out in terms they can understand that they've been wasting both my and their time. That senior EE was right. That's a fun sounding project. I'd love an excuse to play around with something like that. Who cares if the end product will actually work or not? You'll learn a lot and it'll be neat.
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Jul 7, 2009 03:23
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I cannot believe someone is giving you money to experiment and screw around, and I can not believe you are complaining about it. What is wrong with you?
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Jul 7, 2009 03:41
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Cyril Sneer posted:That senior EE was right. That's a fun sounding project. I'd love an excuse to play around with something like that. Who cares if the end product will actually work or not? You'll learn a lot and it'll be neat. Or as I once heard it put, "Aim for the stars and be happy when you end up with the moon." Although, if what your trying to do is physically impossible, then it's not quite as much fun knowing you're going to fail.
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Jul 7, 2009 03:43
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catbread.jpg posted:So what exactly is your job now? I work at a company called alphamicron, whose proprietary thing is liquid crystal shutters for use in sunglasses/visors/windows/etc. Cyril Sneer posted:That senior EE was right. That's a fun sounding project. I'd love an excuse to play around with something like that. Who cares if the end product will actually work or not? You'll learn a lot and it'll be neat. Corla Plankun posted:I cannot believe someone is giving you money to experiment and screw around, and I can not believe you are complaining about it. What is wrong with you? here's the gist of it, just to give you some perspective. The paper I'm working with claims that with a certain part of coils spaced a certain distance (call it D) apart, it's possible to get some nominal transfer efficiency. This is assuming absolutely ideal conditions. My task is to take the same setup and make it work with the same efficiency but at ten times the distance. Efficiency is proportional to the inverse of distance cubed. Get it? ANIME AKBAR fucked around with this message at 04:04 on Jul 7, 2009 |
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Jul 7, 2009 03:58
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ANIME AKBAR posted:I work at a company called alphamicron, whose proprietary thing is liquid crystal shutters for use in sunglasses/visors/windows/etc. You should talk to this guy, he's looking to do something like that on the cheap. Got any slightly damaged engineering samples around?
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Jul 7, 2009 04:05
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ANIME AKBAR posted:
only with an omni-directional radiator
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Jul 7, 2009 04:09
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Mill Town posted:You should talk to this guy, he's looking to do something like that on the cheap. I can hardly get a decent sample to work with myself. Plus this is some serious intellectual property, so no. SnoPuppy posted:only with an omni-directional radiator
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Jul 7, 2009 12:22
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ANIME AKBAR posted:magnetizing inductance approximately follows the inverse cube for distances much greater than the radius of each coil. So you're working in the far-field. Use high frequencies and a non-omni-directional antenna. Cyril Sneer fucked around with this message at 04:39 on Jul 8, 2009 |
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Jul 8, 2009 04:36
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Cyril Sneer posted:So you're working in the far-field. Use high frequencies and a non-omni-directional antenna. no, it's midrange field coupling, not radiating. here's one version of the paper itself.
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Jul 8, 2009 06:41
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ANIME AKBAR posted:no, it's midrange field coupling, not radiating. Your boss just wants some kind of long distance power transmission scheme; he's not expecting a replication of the paper - he just thought it might be useful to that purpose.
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Jul 8, 2009 14:27
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Cyril Sneer posted:Your boss just wants some kind of long distance power transmission scheme; he's not expecting a replication of the paper - he just thought it might be useful to that purpose. This is probably true. In general, it's less about how it gets done, and more about does it work/meet requirements. While you're boss might have some ideas about solving the problem, they may or may not be the best/most applicable. Part of the job of a good engineer is the ability to effectively communicate the best solution for the problem. And simply saying "Can't be done" isn't a solution. Anyway, I vote for two microwave horns and a magnetron!
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Jul 8, 2009 15:25
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Cyril Sneer posted:Your boss just wants some kind of long distance power transmission scheme; he's not expecting a replication of the paper - he just thought it might be useful to that purpose. SnoPuppy posted:In general, it's less about how it gets done, and more about does it work/meet requirements. While you're boss might have some ideas about solving the problem, they may or may not be the best/most applicable. This is not a problem of engineering, it's a problem with physics. There may surely be some completely different method suitable to these specifications, but I don't think it exists yet, and I'm not exactly arrogant enough to think I can second guess MIT eggheads on this stuff. Also another thing that really irks me about this job is that they don't provide the equipment necessary. Just a TDS220 scope, a couple bench supplies, a couple multimeters, and a scant assortment of discrete components. Not even a drat function generator, which is pretty critical when I'm dealing with resonances with quality factors in the thousands. ANIME AKBAR fucked around with this message at 16:13 on Jul 8, 2009 |
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Jul 8, 2009 16:00
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But one neat thing that occurred to me while working on this was that coupling between coils that are either coplanar or concentric (the paper discusses coplanar) is pretty weak, but coupling between coils that are both concentric and coplanar is relatively good. I'm imagining the source coil as encircling an entire room, embedded in the walls. Possibly a pair of hemholtz coils so that the field inside the room is very uniform. Even if the receiver is much smaller than the transmitter, it will see relatively good flux linkage, and using the resonance techniques might make it far better. I'm going to toy with the idea for a while before doing anything with it. It definitely doesn't meet my boss's specs, but he might be interested anyways. But on the other hand, if it looks very promising I might keep it to myself...
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Jul 8, 2009 16:10
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ANIME AKBAR posted:Yes that's all well and good, but it literally can't be done to specification, so saying anything other than that would be lying. Right, the method which your boss suggested can't be done. However it seems like the real problem is "send power". Which is further restricted to "send power without wires." Which is further restricted to "send power without wire using method x." If the most restricted version can't be done ("using method x"), investigate the next level up and present those findings. If that can't be done, go even further up the chain, until you have a solution. Realize that sometimes people ask the wrong question, but it's still up to you to give the right answer. That way you're not the guy that can't solve problems, you're the guy that gives answers.
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Jul 8, 2009 16:23
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SnoPuppy posted:Right, the method which your boss suggested can't be done. However it seems like the real problem is "send power". Which is further restricted to "send power without wires." Which is further restricted to "send power without wire using method x." Yes, this. The overall point here is that telling your boss "it can't be done" just does not come off well. A good engineer should always be able to finagle a solution at some level.
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Jul 9, 2009 00:23
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What about using a device-tracking directional antenna?
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Jul 9, 2009 09:31
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I'm repairing a power supply and have found what I think is a bad diode. It has 0 resistance on my multimeter regardless of polarity. However I'm confused as the symbol on the circuit board isn't your typical diode symbol. It's labeled as D6, but the symbol is not your typical triangle with a line.  The part number is KIV44D with lines above the 4 and the D, but I can't find a datasheet from any of the usual websites. Anyone think they know more about this part? What can I replace it with?
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Jul 10, 2009 01:14
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I recently got a job as a radio technician, but quickly discovered I'm not that good at it. I did a years worth of general technician's level electronics in my lovely local college, but then spent 6 months less than sober in Europe and then another few intoxicated at home and forgot most of what I had barely learned in the first place. I'll be re-reading some of my textbooks, but can anyone recommend any specific reading for troubleshooting and repairing newer radios? You'll be saving a few rear end in a top hat truckers hundreds of dollars, as currently every time one of them comes in with a blown PA (probably) I'll just sell them a new radio rather than investigate further and verify the problem. Sorry if something like this was already answered. I read through the first 10 pages, scanned through the next 15 and then jumped here.
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Jul 10, 2009 07:45
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SnoPuppy posted:If the most restricted version can't be done ("using method x"), investigate the next level up and present those findings. If that can't be done, go even further up the chain, until you have a solution. If you have any ideas, though, I'd love to hear them. quote:Realize that sometimes people ask the wrong question, but it's still up to you to give the right answer. I also found the experimental report that the MIT guy put out on his demonstration in which he claimed to power a lightbulb with 60W at a distance of 2 meters at 45% efficiency. Catch they calculated efficiency by only measuring current and calculated losses from theoretical models. And even worse is they didn't factor in the efficiency of their driving circuit. They used a colpitts oscillator (precisely what I tried at first, actually), which is about 15% efficient itself. 45% efficient my rear end. I'm thinking a well designed class E amplifier would work much better though.
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Jul 10, 2009 19:17
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RivensBitch posted:I'm repairing a power supply and have found what I think is a bad diode. It has 0 resistance on my multimeter regardless of polarity. However I'm confused as the symbol on the circuit board isn't your typical diode symbol. It's labeled as D6, but the symbol is not your typical triangle with a line. Well looking at your picture of the board it appears to have been in parallel with the input into a bridge rectifier. This suggests that it's actually a bypass capacitor, though it could also be a bidirectional TVS diode. It it's either one of these, then the supply will likely work okay without it, though it may be more vulnerable to transients on the input line. The symbol on the board is ambiguous. Almost looks like a varactor symbol, but that's certainly not it. And the polarity band is also strange. It certainly shouldn't be a normal unidirectional diode, or a polarized capacitor. Could you post a high-res image of the board again, showing a bit more of the surrounding circuitry? I'm kind of curious now. And of course you could always look for service manuals for the supply itself. ANIME AKBAR fucked around with this message at 19:27 on Jul 10, 2009 |
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Jul 10, 2009 19:21
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I can add some hi res photos later, but whatever D6 is, it's preceded in the circuit by the AC input (J1), the fuse, a few capacitors and resistors, and a transformer. The bridge rectifier then feeds the rest of the circuit. When I isolate this part of the circuit from everything else (including D6) I read 120V AC from the traces that feed D6, so I'm not sure what the transformer is doing other than maybe providing some coupling/isolation? When I reconnect D6, the fuse blows, every time. This makes sense to me as I'm reading no resistance across D6, so it is shorting the circuit. I'm going to try powering the circuit without D6 and see if the fuse blows again. Also this board is from a Pioneer CLD-D504 Laserdisc player and I can't find any manuals on the player or the supply. The model # on the PSU board is VWR1246-A. RivensBitch fucked around with this message at 21:12 on Jul 10, 2009 |
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Jul 10, 2009 21:06
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Looking forward to these pictures. This stuff is fun. make sure you post the front and back sides of the PCB. My guess is that the circuit is probably a transient supressor diode, like a TVS with cutoff at 200V or something.
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Jul 11, 2009 00:26
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ANIME AKBAR posted:I'm not aware of any "level" above this. The limitations I'm facing aren't the quality of components or cost of materials or anything like that, but the laws of physics themselves. Radiative methods, including microwave, laser, and acoustics, cannot give the required efficiency without being directional, and directionality is explicitly not acceptable. Capacitive coupling is certainly out due to matters of safety and practicality. This is the perfect application for a half-bridge resonant converter (parallel/series loading is not entirely applicable, as the load is the resonant tank itself, but it will basically behave like a series load). Not sure about the receiver end, is that usually passive, or do they tend to have an active oscillator there too?
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Jul 11, 2009 07:10
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catbread.jpg posted:This is the perfect application for a half-bridge resonant converter (parallel/series loading is not entirely applicable, as the load is the resonant tank itself, but it will basically behave like a series load). quote:Not sure about the receiver end, is that usually passive, or do they tend to have an active oscillator there too? The guys at MIT didn't address this at all, and they used a "calibrated" lightbulb as their load. It's perfectly happy to run off of 9.9MHz AC, so that works for it, but not for me. ANIME AKBAR fucked around with this message at 13:21 on Jul 11, 2009 |
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Jul 11, 2009 13:15
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I had looked up class E amplifiers, they use a similar principle to achieve ZVS (the 1st order topology commonly in use seems to be that of a series-parallel loaded converter, a more advanced converter design which avoids higher resonant currents when not fully loaded), I was just thinking that you might be able to learn some other things by looking at that class of circuits from a power electronics point of view. I think the solution to a more generalised receiver is to use an identical half-bridge resonant circuit, allowing two-quadrant operation. Achieving the Q required is another matter...
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Jul 11, 2009 15:10
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 Pieced together from many pictures, hopefully it makes sense. The PCB is single sided so with the symbols this is actually pretty complete. I can post values of specific resistors and caps if requested. Also CN1 is american 110V 50hz power. All of the J connections are metal jumpers which I think are meant to help diagnose problems of the circuit (at least that's what I'm using them for). The problem is that fuse F1 keeps blowing. I disconnected all of the jumpers (some I desoldered, some I clipped) to isolate and troubleshoot, and F1 didn't blow. I reconnected just J25 and J26 and the fuse blew. I removed D6 (as pictured) and powered up the board, and F1 still blew. I've removed C11 and C12 and verified that they're still good (C11 is 220uF 250V, C12 is 1uF 50v). I've also replaced C20 and C21, which are both 2200uF 50V. My next thought is to isolate the "primary" part of the circuit from the "secondary" by removing T1, D20 and C7, plug it in and see if the fuse blows. RivensBitch fucked around with this message at 00:33 on Jul 12, 2009 |
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Jul 12, 2009 00:24
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Erm, those jumpers are there to connect together parts of the circuit that other traces get in the way of. It's not going to work like normal with them removed. They aren't for troubleshooting. Edit: Also, judging by the fact that the diode is placed directly across the AC line, I'm going to say that's a bidirectional transient voltage suppression diode. No idea what the specific rating or replacement part is though. Mill Town fucked around with this message at 07:44 on Jul 12, 2009 |
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Jul 12, 2009 07:37
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J25 and J26 can't serve any purpose other than to let you isolate that part of the circuit from everything else, there are no components or traces in their way. You're probably right about some of the other jumpers though, I honestly don't have much experience at repairing electronics so I figured isolating different parts of the circuit would be a decent starting point in the troubleshooting process.
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Jul 12, 2009 08:08
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Considering how awesome the metcal stations I had where I used to work, I was considering looking for one on ebay. Is getting a full setup under $150 realistic, or should I just go for a weller?
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Jul 12, 2009 19:11
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catbread.jpg posted:I had looked up class E amplifiers, they use a similar principle to achieve ZVS (the 1st order topology commonly in use seems to be that of a series-parallel loaded converter, a more advanced converter design which avoids higher resonant currents when not fully loaded), I was just thinking that you might be able to learn some other things by looking at that class of circuits from a power electronics point of view. I've looked into ZVS/ZCS topologies a bit and they're pretty neat, but I don't think they would work for my application since I'll need to allow the source and receiver to ring for hundreds or thousands of cycles in a row to transfer a decent amount of energy, and the LC tank needs to have very low resistance (like in the milliohms) so putting the switch in that path won't work either. It brings up a very relevant point though, which is that the specific point in time the LC tank is "charged" will affect efficiency and power considerably. Ideally I would switch it during a zero-voltage condition, like the ZVS topology does. I'm considering a few methods of doing this. I'd likely have to put some zero-crossing detector on the source voltage, which would trigger a charging cycle. Thing is, I'm likely going to see hundreds of volts peak on the source, so that makes it kind of tricky.
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Jul 14, 2009 02:08
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https://www.pupman.com Look up what the tesla guys do on their solid state coils. Zero-triggered crossings with long ring-downs at very high power are exactly what they design for.
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Jul 14, 2009 15:18
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Cyril Sneer posted:https://www.pupman.com I'm well aware of how solid state tesla coils work. After all I just finished helping some classmates build a one megavolt musical coil for the cleveland ingenuity festival. It used class E amplifiers in a split-phase configuration (based roughly off of steve ward's techniques), but that's not plausible for this application. ANIME AKBAR fucked around with this message at 22:55 on Jul 14, 2009 |
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Jul 14, 2009 22:50
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ANIME AKBAR posted:I'm well aware of how solid state tesla coils work. After all I just finished helping some classmates build a one megavolt musical coil for the cleveland ingenuity festival. It used class E amplifiers in a split-phase configuration (based roughly off of steve ward's techniques), but that's not plausible for this application. How about instead of saying everything is impossible, tell us what exactly the distance requirements are (and WHY they are what they are), and what exactly it is that needs to be powered remotely.
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Jul 15, 2009 03:44
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at least ten milliwatts with least 10% efficiency. Distance must be over one meter with receivers/transmitters under 15cm in diameter. The load can be anything so long as it is DC (an led or a resistor or a battery charger or whatever). The link must be work regardless of position (within one meter) but it's okay for orientation to be fixed.
ANIME AKBAR fucked around with this message at 04:06 on Jul 15, 2009 |
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Jul 15, 2009 04:03
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That's a pretty high efficiency requirement for 10 mW. Sure, it would be important if you wanted to extend it much further than 1 metre. If you were sticking to a 1m design range, surely 0.1% efficiency would be tolerable for that power level.
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Jul 15, 2009 05:28
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