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Newbie question: I've just taken a handful of inductors and transformers off of a TV PCB. The only markings on them are on stickers of the form: 19.40 054.011 LSE 0204 Anyone know what these numbers mean? Or more generally, how do I find an unmarked inductor's inductance and power rating?
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Oct 23, 2009 19:15
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| # ? May 21, 2024 21:49 |
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Ha, amusingly enough, this ad was at the top of the page when I read your post:
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Oct 23, 2009 19:45
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Hey guys, I have a question. Let's say I want to build a heating element, using a 120 v power source, and I want that heating element to have 100 watt power. 100watt = 120volt x 0.83 amp 0.83 amp = 120volt /141ohm So I would need a 141 ohm resistance right? So heres my question, how do I build a heating element of that precise resistance out of nichrome wire? According to this site: http://www.wiretron.com/nicrdat.html I would need like 17 feet of 31 ga nichrome wire. Isn't that a bit much? Would using a smaller gauge wire help? I need to insulate that nichrome wire, from the rest of the device and from itself, how would I do that? Some sort of insulating tape? Would that last long term? How do consumer-intended electricals do it? And lastly, If i want this heating element to have a solid surface (about the size of a dollar coin), I'm assuming I'll need to make a ceramic base for it. Does anyone have any experience with that? I only need this to get around 300f hot, so I could basically use any sort of ceramic. Would I need to have it fired or can I just file down a piece of terracotta? Is there any place that sells custom ceramic for a cheap price? Thanks.
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Oct 26, 2009 18:50
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Lower your diameter to get the size down, it increases the resistivity of the wire. You'll probably need only a thin (but structurally weaker) piece. If you're looking for something really small, you will have to look into coiling it or using different material (coiling isn't too bad). Keeping the wire from shorting becomes a bigger issue then. I would be very cautious sticking low resistance things into electrical outlets, getting shocked is no fun. Why do you need such a large amount of thermal power in a small spot anyways? Trying to emulate a Pentium 4?
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Oct 26, 2009 22:43
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And since you need heat in a small area could you use a peltier junction instead? You can find 100w+ peltiers for <$10 and 150w (to have some headroom) for $20ish. Just need a simple power supply to run it off 120.
obso fucked around with this message at 00:56 on Oct 27, 2009 |
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Oct 27, 2009 00:53
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Thanks for the answers.clredwolf posted:Lower your diameter to get the size down, it increases the resistivity of the wire. You'll probably need only a thin (but structurally weaker) piece. If you're looking for something really small, you will have to look into coiling it or using different material (coiling isn't too bad). Keeping the wire from shorting becomes a bigger issue then. That's what I thought. I think I'll drop the idea because manufacturing my own ceramic casing+ insulating the coiled wire sounds like a clusterfuck waiting to happen. obso posted:And since you need heat in a small area could you use a peltier junction instead? You can find 100w+ peltiers for <$10 and 150w (to have some headroom) for $20ish. Just need a simple power supply to run it off 120. Great idea, thanks. Yeah, I specified 120v because I want this thing to run out of an outlet. I haven't given much thought to the power supply bit yet. About these Peltier junctions, how easy is it to stack them? I'm looking online and I have trouble finding 150 watt ones. Maybe you have a better source than me? I'm in need of something that can hit as high as 450f certifiably.
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Oct 27, 2009 02:58
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Archives posted:I'm in need of something that can hit as high as 450f certifiably. 450 is a bit of a step from 300. This one Will get you just shy of 400f. I thought I've seen them rated higher but I don't see any listed.
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Oct 27, 2009 03:22
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obso posted:450 is a bit of a step from 300. This one Will get you just shy of 400f. I thought I've seen them rated higher but I don't see any listed. http://www.thermoelectricsupplier.com/tec-modules.php these guys (shady rear end thai website) http://www.tecoolers.nl/index1.html And these ones (I don't speak dutch.) Edit: I think the max temp on the first website is for high-heat+stacked modules, and on the second one is just saw the temperature I have no idea of the context.
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Oct 27, 2009 06:05
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Help me goons! I'm hooking up to an old piece of equipment from 1979 that expects your grandpa's RS232. I need a really beefy RS232 level converter. The CMOS-level side needs to be 3.3v compatible, and the RS232-level side needs to supply at least +/- 10v at a few milliamps. All of the Maxim ICs I've seen so far have been "EIA standard" +/- 5v or 6v, which is way too low for my application.
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Oct 27, 2009 11:20
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I need some simple 2.5mm and 3.5mm jacks and plugs and I found what I need from DigiKey but how can I tell what size wire I'm supposed to use? Here's an example of what I need: http://search.digikey.com/scripts/DkSearch/dksus.dll?vendor=0&keywords=CP-2520-ND ...and here is the datasheet: http://www.cui.com/pdffiles/MR-2501.pdf It gives measurements for the opening but I'm not sure how they translate to wire gauge.
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Oct 27, 2009 13:32
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I found an old tube reel-to-reel recorder in good condition. I'm not totally sure if it works since I don't have reels, but the monitor speaker buzzes and mechanically everything seems alright. All the tubes light up. However, something is making a burny smell. I think it's the transformer, which might also be making a crackling noise. It does have 2 or 3 leaky caps, which is the only obvious thing wrong with the circuit, so I'm going to fix them and see how it behaves after that I guess. I know some people are obsessive about what caps you should use for audio equipment, but if I just want this to work I can replace the wax caps with plain electrolytic right? The .1uf caps in it now are the size of AA batteries. Bonus: the tubes include 2 mullard 12au7s and a mullard 12ax7, which are worth like 5x what I paid for the recorder. It also has a full schematic pasted to the bottom. Thanks 60's guys.
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Oct 27, 2009 17:19
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Yeah electrolytic replacements are typically fine. Just be careful of your voltages, especially on the tube feed side. Stuff them into your old wax cap cans to keep it looking authentic.
obso fucked around with this message at 17:48 on Oct 27, 2009 |
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Oct 27, 2009 17:32
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Mill Town posted:Help me goons! I'm hooking up to an old piece of equipment from 1979 that expects your grandpa's RS232. I need a really beefy RS232 level converter. The CMOS-level side needs to be 3.3v compatible, and the RS232-level side needs to supply at least +/- 10v at a few milliamps. All of the Maxim ICs I've seen so far have been "EIA standard" +/- 5v or 6v, which is way too low for my application. The old "True RS232" chip numbers are 1488 and 1489, the driver and transmitter are separate chips and require a bigger supply then the RS232 compatible chips. Maxim (and I'd imagine other companies like Intersil) do still make pin compatible versions of these. Maxim's is the MAX1488E and MAX1489E: http://www.maxim-ic.com/quick_view2.cfm/qv_pk/1022 Digikey sells them for around $3 each in DIP form: http://search.digikey.com/scripts/DkSearch/dksus.dll?Detail&name=MAX1488EEPD%2B-ND Keebler fucked around with this message at 19:42 on Oct 27, 2009 |
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Oct 27, 2009 19:38
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Keebler posted:The old "True RS232" chip numbers are 1488 and 1489, the driver and transmitter are separate chips and require a bigger supply then the RS232 compatible chips. Maxim (and I'd imagine other companies like Intersil) do still make pin compatible versions of these. Maxim's is the MAX1488E and MAX1489E: Ah, thank you. The only downside is that those need +/- 12v from the power supply. I guess maybe I could steal power from the device I'm talking to...
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Oct 27, 2009 22:45
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Is it better to buy one of those 150-in-1 solderless circuit builders to practice on, or just buy a simple circuit design like an Atari Punk Console kit to get started?
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Oct 29, 2009 02:40
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greg_graffin posted:Is it better to buy one of those 150-in-1 solderless circuit builders to practice on, or just buy a simple circuit design like an Atari Punk Console kit to get started?
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Oct 29, 2009 03:46
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Radio Shack (or "The Source" as they're called here now) wants 5 bucks for a 555 timer but the local electronics and hobby warehouse outlet sells packs of two for a dollar. See if you have something like that near you. Digikey is also really amazing for selection, prices and shipping cost but they don't hold your hand so if you don't know what you want right now you should avoid it.
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Oct 29, 2009 03:59
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BattleMaster posted:Radio Shack (or "The Source" as they're called here now) wants 5 bucks for a 555 timer but the local electronics and hobby warehouse outlet sells packs of two for a dollar. I would kill for a local electronics type store that wasn't RS. 
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Oct 29, 2009 04:36
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obso posted:I would kill for a local electronics type store that wasn't RS. That's funny, there's a european distributor called RS that's really cool http://radionics.rs-online.com/web/ 
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Oct 29, 2009 19:44
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What kind of products that might be sitting on the curb have supercapacitors (specifically, something like a 1F 5.5v goldcap or a 2.5v, etc) in them? My local electronics shop doesn't have any - mostly a stock of stuff from the early 1980s, which is fine for resistors but not so hot for other stuff.
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Oct 30, 2009 21:02
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I'm designing a circuit to power electronics on an older snowmobile. The voltage output by the machine varies from about 6V to 16V depending on RPM. Here's my current plan: Voltage from the snowmobile-->rectifier-->filter-->5V regulator-->charge pump(x3)-->12V regulator. Here's my reasoning. I need 12V to power accessories but the 12V regulator (7812) needs 14.6V input to maintain line regulation. The 7805 only requires 7.5V. This way, the circuit will work as long as the snow machine is outputting 7.5V, which it should most of the time. My problem is that I can't find a charge pump IC that can output 15V and supply 200-300mA. Does anybody know of one? If I built a charge pump from basic components, would it be easy to meet my requirements? On top of all that, is there a simpler solution that I'm missing? What I want is a nice regulated 12V supply that will work over the greatest possible voltage input range with expected values being between 6V and 16V. Thanks for any help.
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Oct 30, 2009 21:05
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One solution would be to use a buck-boost converter, controlled to a fixed output voltage of 15V. Voltage from the snowmobile-->rectifier-->filter-->buck/boost-->12V regulator. That will work all the time.
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Oct 30, 2009 22:46
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catbread.jpg posted:One solution would be to use a buck-boost converter, controlled to a fixed output voltage of 15V. I'd recommend that you get rid of the 12V regulator and just use a regulated buck-boost converter that outputs 12V directly. That will be more efficient, and also simpler. Edit: Something like this looks like a good place to start. Mill Town fucked around with this message at 01:54 on Oct 31, 2009 |
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Oct 31, 2009 01:48
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Mill Town posted:I'd recommend that you get rid of the 12V regulator and just use a regulated buck-boost converter that outputs 12V directly. That will be more efficient, and also simpler. There's regulation and then there's regulation. Linear regulation will have a higher rejection of input noise. It depends on the tolerances of the application as to what is suitable. That looks like a pretty good design to work with.
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Oct 31, 2009 11:36
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Alright circuit gurus, I'm looking for some help on a circuit I'm making. It needs to make a motor run in the positive direction for a number of seconds, hold for a number of seconds, and then run the motor in reverse. Here's a schematic with what I've come up with so far:  Click here for the full 1600x1200 image. The idea is that the button press will start a routine on the PIC. It'll set one of the output pins high which will put the transistor into saturation and switch the relay from ground to +12v. Then the software will do the same for the other output pin. I can handle the software for the PIC fine, but is this a sound idea for what I'm trying to do?
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Oct 31, 2009 19:25
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catbread.jpg posted:One solution would be to use a buck-boost converter, controlled to a fixed output voltage of 15V. There we go, there is something out there that I've never heard of that offers up a great solution. I'm not sure if I'll need to add the 12V regulator but I can if I have to. It's pretty simple and I have access to some 7812s. Thanks for your help, catbread and Mill Town.
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Oct 31, 2009 19:56
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Holy Diver posted:
Looks fine. May be a typo, but your top relay will need to be switching +12v (hooking it up to -12v would make both relays run the motor the same direction)..
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Oct 31, 2009 21:46
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What are you using it to drive, and how sensitive is it to voltage ripple? If you want to use that circuit, I would recommend using the provided PCB layout or making your own, as opposed to making it on a breadboard. The parasitic inductances will kill the switching performance. I might just download Eagle to take a look at the schematics, for interests sake. A SEPIC is an interesting choice of topology. You might be better served finding a design for a standard buck/boost, which will only require one inductor for one thing. Unless of course you're going to be using the chassis as a common ground, in which case a SEPIC topology would make more sense.
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Oct 31, 2009 21:54
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Holy Diver posted:Alright circuit gurus, I'm looking for some help on a circuit I'm making. It needs to make a motor run in the positive direction for a number of seconds, hold for a number of seconds, and then run the motor in reverse. Do you really need to use relays? Just how much current do you expect to be going through the thing? If you're not running some big fuckoff motor you can probably get away with an H-bridge IC.
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Nov 1, 2009 05:37
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I'm kind of new to all this. I want to know how you can get 30V+ from a 9V battery. My very limited knowledge suggests I would have to go DC->AC->Tranformer. Is there an easier way. For reference I'm looking at how the "tens" machines work.
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Nov 2, 2009 12:19
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You could certainly do it that way, but you would typically use a boost converter, which is a type of switching power supply. From that wiki page: The key principle that drives the boost converter is the tendency of an inductor to resist changes in current. When being charged it acts as a load and absorbs energy (somewhat like a resistor), when being discharged, it acts as an energy source (somewhat like a battery). The voltage it produces during the discharge phase is related to the rate of change of current, and not to the original charging voltage, thus allowing different input and output voltages. So in a way you are making the initial DC voltage into a sort of AC voltage then feeding it through an inductor and smoothing things with a cap. This is extremely generalized, and you would do better to read the wiki page on it. Don't worry if the theory behind it looks hard, practical use of these is pretty straightforward, and most manufacturers of boost ICs have sample schematics for typical uses.
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Nov 2, 2009 22:29
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BattleMaster posted:Do you really need to use relays? Just how much current do you expect to be going through the thing? If you're not running some big fuckoff motor you can probably get away with an H-bridge IC. It'll be controlling a pump and cylinder for a car hatch, so peak currents of 60A and average currents of 30A.
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Nov 4, 2009 18:42
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Holy Diver posted:Alright circuit gurus, I'm looking for some help on a circuit I'm making. It needs to make a motor run in the positive direction for a number of seconds, hold for a number of seconds, and then run the motor in reverse. Here's how I have used logic signals to drive a 24V relay. This should work for a 12V relay as well. It's pretty close to what you were doing:
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Nov 4, 2009 18:52
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Time for what I think is a retardedly simple question. I got halfway through building my circuit (the one quoted above) today and realized: aren't I going to need two power supplies to accomplish what I'm doing? One for the +12V and one for the -12V? There has to be a simple way to switch the voltage around. I remember seeing a circuit at work consisting of nothing but 3 relays and two switches. One switch ran the motor in the positive direction, the other in the negative. Can someone explain the best way to do this, because clearly my brain isn't working right now.
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Nov 5, 2009 06:43
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Holy Diver posted:Time for what I think is a retardedly simple question. You don't need -12V, you just need to switch the current direction. Replace the -12V at the top with +12V. Connect the motor across the common terminals of the relays. When only the top coil is energized, current flows in one direction and vice versa. When both are energized, nothing happens.
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Nov 5, 2009 07:19
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Holy Diver posted:Can someone explain the best way to do this, because clearly my brain isn't working right now. I told you above you didn't need -12v. if you are using standard relays this schematic should make it easy. Just replace the actuators with your motor and lock/unlock with forward/backward.
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Nov 5, 2009 07:43
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Thanks guys
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Nov 5, 2009 12:51
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I feel dumb for not knowing this, but could someone elucidate the differences between small signal transistor circuits versus large signal, ie, power amplifier transistor circuits? I'm looking at my electronic devices textbook and I don't really understand why small-signal circuits are in one chapter and power circuits - where they introduce class A, B, C amplifiers - are in another. It seems like an artificial distinction. I mean, I can build a voltage-divider bias circuit and stick a power transistor in it, can't I? Conversely, the power circuits all look like small-signal circuits, except they stick transformers in various places and call them by different names.
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Nov 6, 2009 05:10
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Cyril Sneer posted:I feel dumb for not knowing this, but could someone elucidate the differences between small signal transistor circuits versus large signal, ie, power amplifier transistor circuits? You can do that, but power transistors typically have different signal characteristics (speaking of SCRs/GTOs here), and/or have rather non-linear response curves. That's fine when you're doing PWM control of a motor, not so much in an analog small-signal amplifier. Power transistors use vastly simplified versions of the small signal equations, so while the difference is arbitrary, it makes things much easier for people using solely high-power systems. Especially since such things tend to be on or off, the middle range so useful in small signal matters so little with high power stuff. There are also several kinds of transistors used for power that you'll never see in the small signal world. IGBTs, IEGTs, SCRs, GTOs, etc; all are pretty much only used in high-power applications.
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Nov 6, 2009 05:35
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| # ? May 21, 2024 21:49 |
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Cyril Sneer posted:I feel dumb for not knowing this, but could someone elucidate the differences between small signal transistor circuits versus large signal, ie, power amplifier transistor circuits? Signal amplifier circuits are primarily designed for high linearity, and low noise. Power circuits are primarily designed for a low output impedance, i.e. the ability to drive a load, which of course compromises the previously mentioned goals.
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Nov 6, 2009 07:25
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