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It's not that the external capacitor versions are faster (232/233 and 232A/233A run at the same speed as the counterpart with the A being faster), it's that they're much cheaper.
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Feb 6, 2009 20:48
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It's 4 extra caps too, of the most common cap value known to man. It's not exactly like they're asking for gold-plated thermoresistive ionic couplers or a still-beating human heart. Plus the MAX232 is second soruced to heck and back, so you can find them anywhere for cheap. Digikey lists some for 90 cents a pop. For the money saved between it and the cheapest MAX233 I found ($7.45 on digikey for 1). Since 0.1uF through hole caps are 16 cents a pop *or less* you can buy several MAX232s and caps for what one MAX233 costs.
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Feb 8, 2009 08:21
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You can often get free samples of smaller/common ICs from the manufacturer websites. Maxim will send you a couple of free 233s no problem (or any of their other transceivers). Microchip are also very generous at giving out PICs, even some of the higher end models.
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Feb 8, 2009 13:00
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Does any one know of good schematic creation tools (just high level diagrams) for Mac OS X. I'd rather not use Eagle, but if that's my only choice, I'll do it.
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Feb 11, 2009 02:10
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OS X compatible CAD programs are pretty rare, unfortunately. You might be able to find a SPICE simulator with a schematic capture, but chances are eagle is your best bet. I haven't found anything better that isn't terribly expensive.
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Feb 11, 2009 06:36
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I posted this thread earlier http://forums.somethingawful.com/showthread.php?threadid=3075756 , tldr is that a me and a few mates came across a traffic light and we've now managed to get it powered up. At the moment, all 3 lights are shining constantly, and we want to change that. I had the idea to modulate the light intensity by a musical input, maybe even to have the green light modulated by bass, yellow by mids, and red by treble. Problem is, my knowledge of electronics is pretty basic and I wouldn't know where to start with this! The setup is an ipod connected to the phono input of a hifi with a converter cable. Would it be possible to solder a few wires onto this connector to siphon off some of the voltage to use as an input for the circuit? Or would we need to use a microphone? If anyone could point me in the directin of some resources for this or could give me advice themselves that would be much appreciated. Thanks!
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Feb 11, 2009 21:36
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Auspex posted:At the moment, all 3 lights are shining constantly, and we want to change that. I had the idea to modulate the light intensity by a musical input, maybe even to have the green light modulated by bass, yellow by mids, and red by treble. Problem is, my knowledge of electronics is pretty basic and I wouldn't know where to start with this! Before doing any of the signal conditioning stuff, you should decide what you use to switch power to the lights. Triacs or SCRs are probably your best bet. Just be very careful when handling the AC lines. I strongly advise the first thing you do is get an isolation transformer and run everything from that. ANIME AKBAR fucked around with this message at 23:38 on Feb 11, 2009 |
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Feb 11, 2009 23:34
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On the topic of breakout boards a couple pages ago, I was looking for an MLP-16 4x4mm breakout board, but I can only find 3x3mm. Is there a keyword I'm missing? I'm just not talented enough to solder that small without overheating the chip. I'm still working on that FAN5609 LED dimmer. I wish there was a SMT socket for breadboarding.
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Feb 12, 2009 14:31
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Since I wasn't able to get into a college I liked back when I had time (might be moving out-of-state where credits probably won't transfer), I decided to buy this book called Electronics Self-Teaching Guide. I'm a few pages into it so far and it's pretty neat, though it's really reminding me that I'm horrible at algebra. My question is how much is this book going to teach me (provided I soak up everything in it) compared to an entry-level electronics course? When I get into a university, will I be able to (in theory) ace my first few courses and have a good springboard into more advanced stuff? edit: I'm also having problems calculating the impedance of two resistors of different ratings when they're wired in parallel, and this goes back to me sucking at math. I know the formula is R = 1/(1/R1 + 1/R2), but I can't ever seem to get the right answer because I guess I don't know where to flip the numerator and denominator. 
scuz fucked around with this message at 16:51 on Feb 12, 2009 |
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Feb 12, 2009 16:45
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scuz posted:Since I wasn't able to get into a college I liked back when I had time (might be moving out-of-state where credits probably won't transfer), I decided to buy this book called Electronics Self-Teaching Guide. I'm a few pages into it so far and it's pretty neat, though it's really reminding me that I'm horrible at algebra. My question is how much is this book going to teach me (provided I soak up everything in it) compared to an entry-level electronics course? When I get into a university, will I be able to (in theory) ace my first few courses and have a good springboard into more advanced stuff? Kirchhoff's node current law Kirchhoff's voltage loop law Thevanin equivalents Source transformations Mesh current/Loop current method And that just covers basic current/voltage sources and resistors, so they're nothing but algebra. Once you get to stuff like inductors and capacitors and filters, the math steps up quite sharply. You'll want things like: Complex exponents Laplace transforms Fourier transforms Though you can usually get by without having to actually compute these by using simplifications. Knowledge of advanced calculus is by no means necessary. Also, for computing equivalent resistance of parallel resistors use Req = (R1*R2)/(R1+R2).
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Feb 12, 2009 17:29
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ANIME AKBAR posted:Also, for computing equivalent resistance of parallel resistors use Req = (R1*R2)/(R1+R2). I flipped through the table of contents (which you can do on amazon.com, I just figured out) and didn't see Kirchhoff's node current law, Kirchhoff's voltage loop law, Thevanin equivalents, Source transformations, or Mesh current/Loop current method stuff anywhere, but that doesn't mean that it's not in there, just that it doesn't have a chapter devoted to it. Thanks for the guidelines!
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Feb 12, 2009 17:47
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ANIME AKBAR posted:that's pretty feasible. Split the buffered audio signal (whether it comes from a microphone or a cable) into three paths, bandpass each path to the desired audio ranges, then rectify the outputs to get voltages proportional to signal strength. Then use those voltages to control the brightness of each light using some kind of dimming circuitry. Ok, i've had a root around on the internet and I've come up with a general idea for the circuit but I'm still having a bit of trouble. Heres the diagram (excuse the fact that its on mspaint, i'm on a friends computer and he doesn't have anything else!)  Click here for the full 875x740 image. As far as I can tell, the voltages across the 3 diode bridges should be fully rectified copies of the music, filtered to the frequencies I select via the RC value of the filters. The trouble I'm having is im unsure how to connect this to the triac that's connected to the mains. The areas I'm talking about are circled in red on the diagram. There are two outputs from the rectifier and the triac gate is only one input, and I'm not too sure what I need to do. Like I said, my electronics knowledge is pretty basic and I'm probably missing a load of stuff on this so if anyone could have a look over this and point out where I'm going wrong it'd be much appreciated. Thanks! fake edit: Where would the isolation transformer go in that diagram?
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Feb 12, 2009 18:11
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scuz posted:Ugh, that is a life-saver! I was pretty discouraged when I couldn't figure out simple poo poo, but that's so much easier for me. It's probably in there, it would be weird if it's not called that by name though. Read over the Lessons in Electric Circuits site posted in the OP, should give you a primer on those simple techniques (particularly chapters 6 and 10 in the DC section): http://openbookproject.net//electricCircuits/ If anything you'll know what to expect. It's pretty tricky at first, but over time it gets easier (especially since problems written for Kirchhoff laws and source transformations in general seem to be written by sadists). Two mantras that help with the laws: -'Voltage is the same across parallel elements' -'Current is the same across series elements' if you think about it, it's the same is 'voltage is across, current goes through'. Also, node voltage analysis is an extremely robust way of analyzing circuits, especially when funky things like opamps start getting thrown in. clredwolf fucked around with this message at 21:39 on Feb 12, 2009 |
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Feb 12, 2009 21:30
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scuz posted:Since I wasn't able to get into a college I liked back when I had time (might be moving out-of-state where credits probably won't transfer), I decided to buy this book called Electronics Self-Teaching Guide. I'm a few pages into it so far and it's pretty neat, though it's really reminding me that I'm horrible at algebra. My question is how much is this book going to teach me (provided I soak up everything in it) compared to an entry-level electronics course? When I get into a university, will I be able to (in theory) ace my first few courses and have a good springboard into more advanced stuff? Take a look at The Art of Electronics by Horowitz and Hill. It gives a practical introduction to electrical engineering with just enough theory/math to get the essentials across. It may be a good way to get into some of the ideas behind the subject without drowning in the details. It's often used as a text for 'electronics for non-electrical engineers' classes so if you knew everything in that book you'd be in a good spot to start taking harder courses. If you are seriously thinking about going into electrical engineering and you're finding that your algebra is rusty I'd also recommend looking into a refresher math course. University EE classes will assume that you have a solid knowledge of calculus in addition to matricies, complex-valued functions, and a shitton of algebra. It gets much, much worse than parallel resistor laws.
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Feb 13, 2009 00:44
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clredwolf posted:if you think about it, it's the same is 'voltage is across, current goes through'. Yeah, this. My brother works at an LED lighting shop and he's been calling me a lot recently with some "I've got these LEDs and I need to drop some extra voltage, where's it going?" type questions, and I've basically been repeating this to him. "Voltage is across things, current is through things."
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Feb 13, 2009 06:23
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Does anyone know of a place where you can get a 110v-Primary to about 1600 volt-secondary step-up transformer. We need something to provide power to our coil gun (senior design project) and have exhausted all options other than building our own transformer.
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Feb 13, 2009 06:38
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Did you look at neon sign transformers? 1.6kv might be a bit low for those though.
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Feb 13, 2009 06:50
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Auspex posted:Ok, i've had a root around on the internet and I've come up with a general idea for the circuit but I'm still having a bit of trouble. Heres the diagram (excuse the fact that its on mspaint, i'm on a friends computer and he doesn't have anything else!) the isolation transformer comes directly off the AC line. That means nothing is connected directly to the outlet except the transformer. Also there will only be two outputs to the transformer, so no earth ground. In your circuit you are switching (I assume) on the hot side of the lights. You want to switch on the low side. If you use an isolation transformer then it doesn't matter which line is used as ground and which is hot. And I doubt that the output of your audio line will be enough to switch a triac reliably. You'll likely need some simple amplifying circuitry to provide enough current. Triacs are driven by sourcing or sinking current into their gate. Easiest way to do it is to put one of the main terminals at a fixed potential (ground) and drive the gate positive or negative via a resistor or something, like how you'd drive an LED. Also keep in mind that when I say "ground" I don't necessarily mean earth ground. The point of an isolation transformer is mainly so you don't need to earth ground anything on the secondary side.
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Feb 14, 2009 01:53
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Ham Session posted:Does anyone know of a place where you can get a 110v-Primary to about 1600 volt-secondary step-up transformer. We need something to provide power to our coil gun (senior design project) and have exhausted all options other than building our own transformer. You're likely looking at something like a neon sign transformer or a photoflash transformer. Find a junkyard and start digging... Making transformers is actually pretty interesting though. If you have a decent grounding in physics it's a pretty cool applications. Only tough part really is obtaining the right core material and making sure it won't saturate.
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Feb 14, 2009 01:56
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So I am messing around with microcontrollers and everything I have read said to buy BJT transistors. But the first post in this thread says MOSFETs are better. So just wondering why all the talk recommending BJTs...is it because BJTs cost about $.10 each while MOSFETs cost $2? Also, are they implemented the same way in a circuit?
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Feb 14, 2009 02:59
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MOSFETs are usually used for high-current applications like motors and power switching. You don't need them for low-current applications such as logic and LEDs.
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Feb 14, 2009 03:17
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The construction of BJT's and FET's are wildly different. BJT's are just two diodes back to back. They're input (the gate?) is low impedence, and low capacitance. This means when you shut off the power to the gate, the transistor turns off very, very quickly. Their base-collector resistance is fairly high. The control current bleeds out through the collector. FET's input are high impedance, and high capacitance. It takes very little electricity to turn a FET on. And keep it on. This also means it takes a FET some time to bleed off power in the gate. The power applied to the gate, doesn't actually bleed off through the rest of the device. That's why it's a "field effect" transistor. FET's also have very low resistance, and I think very low voltage drop across the base and collector. (I am no expert, and I get confused often...)
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Feb 14, 2009 06:00
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InediblePenguin got a proper bass amp today (she had been using a tiny guitar amp), so the first order of business, of course, was to build an overdrive box to make it sound like it did on the lovely guitar amp. Er, wait . . . oh well, any excuse to tear apart a lovely amp and tinker with the guts! I found a nice simple overdrive circuit with a breadboard layout provided and set to work, with some rearranging to make it fit my particular breadboard and substitution of a few resistors because I didn't have the exact ones. Long story short, it didn't work. I tried moving things around, swapped out the diodes for a different kind, tried three different op-amps because I had all but the one specced, and eventually got it to work for exactly one note before it went back to a quiet hum and nothing else. And then the 100uF cap blew. The magic smoke stinks. Here's a picture of the two amps, shortly before the tiny one was gutted, desoldered, and reassembled:  Click here for the full 620x800 image.
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Feb 14, 2009 10:53
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Bad Angus! Bad!
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ozziegt posted:So I am messing around with microcontrollers and everything I have read said to buy BJT transistors. But the first post in this thread says MOSFETs are better. So just wondering why all the talk recommending BJTs...is it because BJTs cost about $.10 each while MOSFETs cost $2? Also, are they implemented the same way in a circuit? For what it's worth, as a newbie I find it vastly easier to reason about MOSFETs. Apply voltage -> switch turns on, as opposed to having to put the BJT at its working point.
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Feb 14, 2009 10:56
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ozziegt posted:So I am messing around with microcontrollers and everything I have read said to buy BJT transistors. But the first post in this thread says MOSFETs are better. So just wondering why all the talk recommending BJTs...is it because BJTs cost about $.10 each while MOSFETs cost $2? Also, are they implemented the same way in a circuit? check out my post here: http://forums.somethingawful.com/showthread.php?threadid=2734977&userid=0&perpage=40&pagenumber=21#post351068809 If you're looking for logic and switching circuits, stick with mosfets. If you want analog amplification or instrumentation, go with bjts. If you're not sure what you need, feel free to ask. Also in terms of price mosfet's are perhaps a bit more expensive, but not by much. Decent ones can be had for less than $0.50 each. ANIME AKBAR fucked around with this message at 14:56 on Feb 14, 2009 |
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Feb 14, 2009 14:39
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Delivery McGee posted:InediblePenguin got a proper bass amp today (she had been using a tiny guitar amp), so the first order of business, of course, was to build an overdrive box to make it sound like it did on the lovely guitar amp. Er, wait . . . oh well, any excuse to tear apart a lovely amp and tinker with the guts! as for testing the thing, I'd get a decent multimeter that can measure both AC and DC current and voltage, then check the following in this order: 1. Verify you get about 9V DC at the supply of the op amp 2. Verify you get about 4.5V (9V/2) DC at the bias point. Then apply some signal (preferably a stable one) then check the following with AC measurement: 1. You get a signal at the noninverting input of the op amp 2. You get the same signal at the inverting input of the op amp 3. You get a proportionally larger signal at the output of the op amp. 4. You get a smaller (than the last one) signal at the output of the whole thing. It's likely to be some really lame mistake like forgetting to apply power to the op amp or something. When diagnosing signal conditioning stuff, you just have to start probing at the early stages and keep checking that your signals look right until you find a problem spot. Also bonus tip: for fun, try putting variable resistors (like 50K range) from the clipping diodes to ground (so from the cathode of D1 to ground and the anode of D3 to ground). This should give control over the hardness of the clipping at the output. Let me know if it works, too.
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Feb 14, 2009 14:55
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Also I just wanted to say that I recently finally forced myself to learn LTspice and holy poo poo it is easy and useful. If you aren't familiar with LTspice it's linear tech's own freeware spice engine, but instead of having to type up netlists yourself, it derives the netlist and everything from schematic capture, which is incredibly convenient. Only problem is I haven't quite figured out how to import parts from other manufacturers. So basically if you want to get into simulation, stop dicking around get this program you dumb jerk.
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Feb 14, 2009 15:06
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Quick question: I've got a circuit built on a breadboard that I want to make permanent--can I just blob some hot glue over the components and encase them? It's nothing too high-current. I know that using a proto board and soldering everything is the pro way to go but I don't have the time or my iron with me.
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Feb 14, 2009 15:55
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Hey I found this site the other day http://octopart.com/ It describes itself as a search engine for electronic parts but you can also build a list of parts for projects and stuff. I searched the first few / last few pages of the thread to see if it was mentioned but I didn't see anything so I thought I would share.
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Feb 14, 2009 23:39
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Plexiwatt posted:Quick question: I've got a circuit built on a breadboard that I want to make permanent--can I just blob some hot glue over the components and encase them? It's nothing too high-current. It seems like that should work, but 1) it's an expensive solution and you'll probably never get the breadboard back and 2) if something fails or comes loose it'll be a bitch to find and fix it. Just run out and buy a soldering iron and a perfboard. You can get ones with the same trace arrangement as the solderless breadboard so you can just transfer everything over to exactly the same spots. ozziegt posted:So I am messing around with microcontrollers and everything I have read said to buy BJT transistors. But the first post in this thread says MOSFETs are better. So just wondering why all the talk recommending BJTs...is it because BJTs cost about $.10 each while MOSFETs cost $2? Also, are they implemented the same way in a circuit? The other cool thing about MOSFETs is that they don't need a current-limiting resistor on their gate (the equivalent of a transistor's base). In a circuit with a lot of outputs, this can save you a lot of soldering time. The other uncool thing about them is that they're static sensitive so you have to be careful about handling them.
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Feb 15, 2009 01:47
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Mill Town posted:It seems like that should work, but 1) it's an expensive solution and you'll probably never get the breadboard back and 2) if something fails or comes loose it'll be a bitch to find and fix it. Just run out and buy a soldering iron and a perfboard. You can get ones with the same trace arrangement as the solderless breadboard so you can just transfer everything over to exactly the same spots. Funny enough I did try that before posting, and I learned the hard way that cheap soldering irons suck tremendously. I went with the breadboard (which I don't need back anyway) after this excitingly damaging cheap-iron experience.
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Feb 15, 2009 02:03
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bbq posted:Hey I found this site the other day http://octopart.com/
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Feb 15, 2009 03:27
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ANIME AKBAR posted:check out my post here: My take on the matter from my experiences: BJTs - Super cheap (you can find 2n3904s ANYWHERE), easy to find in discrete packages, harder to understand but have several advantages that make them very useful. Advantages
Disadvantages:
Good for:
Now for MOSFETs: Advantages:
Disadvantages:
Uses:
clredwolf fucked around with this message at 21:30 on Feb 16, 2009 |
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Feb 16, 2009 16:22
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Hey, I have a question bout filtering out RF noise. I'm a bit into photography and recently bought a set of wireless flash triggers to use my external flash off camera. Now, the triggers I bought are very sensitive to interference and the electronics in my particular flash unit are infamous for transmitting RF noise. This means that whenever I connect the receiver to the flash unit the receiver stops functioning. The electrical connection between the two somehow carries a lot of noise that drowns the radio signal from the transmitter out completely. What I need to do is make sure the connection between the receiver and flash unit does not carry this RF noise. This is where I need a bit of guidance. Low pass filter? Or something else? Where do I start? The triggers operate at 433MHz, the connection only requires on/off and I'm not a afraid to use my soldering iron.
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Feb 16, 2009 19:43
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Wow that's weird. Any articles about this phenomenon? From what you've said, it sounds like some kind of interference is coming down the flash through the shoe into the receiver. If that's the case, the flash shoe doesn't have to be all that fast, so you may be able to make some progress by decoupling the shoe on the receiver. I'm warry to give advice without knowing more about what's going on, but if that's the case you should be able to put a cap between signal and ground of a relatively small value (maybe 10nF or so) and get rid of the high frequency noise. Again, link us to some kind of description of what's going on so we don't give you advice on screwing up your flash beyond all recognition...
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Feb 16, 2009 21:29
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I'm looking for an ultra-low cost wireless transceiver. I don't care about bit rate or range (as long as it's over 4 feet), just power consumption and cost. All I need to transmit is a simple on/off signal, and the closest I've come have been these guys from sparkfun: http://www.sparkfun.com/commerce/product_info.php?products_id=8948 But the transmitter and receiver are separate devices, and together they're both larger and more expensive than the rest of my project. Any ideas?
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Feb 16, 2009 21:47
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There are some threads on different photography forums. Two examples: http://flickr.com/groups/strobist/discuss/72157605172686282/ http://www.fredmiranda.com/forum/topic/699706/0 The symptoms of this error are spontaneous random fires and of course missed fires. I have solved the first problem by using a hot shoe adapter and a 12" cord to get the receiver a bit further from the flash unit. I have tried a ferrite bead around the cord and I even jury-rigged a longer cord, about 3', but no perceivable difference. There is still interference blocking the signal as long as the receiver is physically connected to the flash. I gave the capacitor trick a try but the only values i had was a 22pF and a 0.01Pf (if I have read the coding correctly) but these did not do the trick. I have a limited understanding on how a capacitor might help but I don't know how a to big or to small a value might affect the situation. This is really frustrating since my old 70's flash works just fine but my modern flash with all the bells and whistles just fails miserably.
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Feb 16, 2009 22:14
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Ok, here's what I'm seeing: -Longer cord helps. The long cord acts like an inductor, which lets low frequency signals pass but stops high frequency signals. -Capacitor doesn't help, is a small value. That tells me your value is too low, and is missing the radio interference that is screwing up your signal. -0.01pF sounds too small. Sure that's not 0.01uF? -Toroidal core may help. It would look like this. You wrap the cord around it a whole bunch of times tightly, and it makes an inductor. I don't know if this is something you can get at Radio Shack though. This would be more effective than a ferrite bead. Your flash 'trigger', if I understand right, is just an 'off' is no flash, 'on' is flash', and that 'on' needs to be fast but not radio frequency fast. Have you tried a combination of the cord and the capacitor (placed on the side of the receiver, away from the flash)? If that doesn't work, move up to a 1uF cap. Work up to 10uF until it works (don't use polarized caps). If *that* doesn't work, then it's time to bring in the big guns... clredwolf fucked around with this message at 06:33 on Feb 17, 2009 |
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Feb 17, 2009 06:31
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Question, where do you get a whole bunch of those 0.1" (2.54mm) breakaway connectors for cheap? You know, these guys (only those are overpriced as crap)?
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Feb 17, 2009 06:33
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clredwolf posted:Ok, here's what I'm seeing: As for the capacitor idea, it may work. Ideally you'd have both series inductance and parallel capacitance. If you place a capacitor, do so as close to the sensitive receiver as possible. clredwolf posted:Question, where do you get a whole bunch of those 0.1" (2.54mm) breakaway connectors for cheap? You know, these guys (only those are overpriced as crap)? They're on digikey, but I don't see what's too unreasonable about sparkfun's price. Zuph posted:I'm looking for an ultra-low cost wireless transceiver. I don't care about bit rate or range (as long as it's over 4 feet), just power consumption and cost. All I need to transmit is a simple on/off signal, and the closest I've come have been these guys from sparkfun: If your transmission distance is just 4 feet, then maybe something besides RF, like infrared, would work? ANIME AKBAR fucked around with this message at 06:57 on Feb 17, 2009 |
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Feb 17, 2009 06:50
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