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What I meant was use the remote operated switch part of the power strip to switch on a connection between the exposed wires.
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Nov 21, 2010 05:10
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Anyone know a good source for small super cheap displays? I'd like something 2-3" square. Monochrome, LCD or whatever technology is cheapest. Probably need 100 of them. Nothing fancy but places seem to want 10$ per part for even the bottom of the barrel. I'd be willing to use surplus stuff if I can get enough.
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Nov 23, 2010 05:19
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apparently previous generation ipod nano displays are hella cheap?
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Nov 23, 2010 09:42
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Hey there guys, just picked up a NerdKit which seems to be a more newbie friendly Arduino in that its based around the Atmel Atmega168. I am just getting into electronics and read electronics for dummies which I'd highly recommend for a little bedside reading. So far I have managed to blink an LED and output whether it is on or off (hooray) and make it read a temp sensor all with code written by someone else. Awesome. Reading "C for Dummies" now. ValhallaSmith posted:Anyone know a good source for small super cheap displays? I'd like something 2-3" square. Monochrome, LCD or whatever technology is cheapest. Probably need 100 of them. Nothing fancy but places seem to want 10$ per part for even the bottom of the barrel. I'd be willing to use surplus stuff if I can get enough. Would a regular ol dot matrix LCD work? http://www.bizoner.com/arduino-1602-lcd-module-black-char-green-backlight-p-188.html AnomalousBoners fucked around with this message at 13:23 on Nov 23, 2010 |
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Nov 23, 2010 13:19
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ValhallaSmith posted:Anyone know a good source for small super cheap displays? I'd like something 2-3" square. Monochrome, LCD or whatever technology is cheapest. Probably need 100 of them. Nothing fancy but places seem to want 10$ per part for even the bottom of the barrel. I'd be willing to use surplus stuff if I can get enough. Sparkfun has some good deals on monochrome LCDs. This one is only $3 but you need to source one of those annoying rubbery connector strip things to use it: http://www.sparkfun.com/products/9924 This one is the same, but mounted on a PCB so you don't need to buy the connector. $8. http://www.sparkfun.com/products/10168 Ninja edit: They are $2.36 and $6.36 in quantities of 100, respectively.
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Nov 23, 2010 18:29
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Have any of you ever run into something you could not de-solder? I was trying to remove a jack from an Insipron 1545 and unlike most other systems, this jack was on a small daughterboard. The jack would NOT come loose, I removed as much solder as possible, wetted the pins with some fresh solder and wiggled back and forth a little, then tried to pry up on it a bit, but nothing. Eventually the jack just broke off with the pins still in the holes. I have never run into anything this difficult to remove so far. Any suggestions?
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Nov 25, 2010 17:52
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Happens a lot. Big ground pour nearby, the part itself is a big heatsink, aluminum pcb, whatever. Just add more heat. A lot of the time it's easier to add a LOT more solder and just bridge every pin (lay your iron sidways) into a big blob instead of wicking each leg one by one. And more heat, always more heat.
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Nov 25, 2010 19:26
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I have a little project in mind as a way to get back into RC (well, except for the radio part) and learn a little about electronics. Basically, I'd like to be able to control some kind of vehicle with my iPhone using the accelerometers. I think what I've decided on is to start with one of these: http://www.robotshop.com/dfrobotshop-rover-tracked-robot-basic-kit.html. Eventually I'd like to be able to build my own vehicle from an RC kit or something but for now that's the less interesting part for me. Anyways, I'd then combine it with one of these: http://www.asynclabs.com/store?page=shop.product_details&flypage=flypage.tpl&product_id=29&category_id=6. Am I going to be able to do what I want to do with this? My eventual goals are to add lots of random instrumentation including video and any other useless data that sounds fun (temperature, light, whatever) to the thing and displaying it all on the iPhone. Once I get point to point working I'd then also like to hook it up to my home network and torment my cat while at work or something. Or mount lasers to it and use it for home defense. I'm an experienced programmer so nothing on that side really worries me except for having never worked on the iPhone before. Any gotchas there?
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Nov 27, 2010 01:48
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Quick, someone convince me that the whole PIC family isn't completely worthless. I've been having nothing but problems. SPI doesn't seem to work properly with my 18F4610. Google reveals that this is a common problem.
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Nov 27, 2010 04:07
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PICs work perfectly for me and peripheral pin select is the best feature on microprocessors since, uh, anything ever. So yea PICs own. But I use pic24s.
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Nov 27, 2010 04:19
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guenter posted:I have a little project in mind as a way to get back into RC (well, except for the radio part) and learn a little about electronics. Basically, I'd like to be able to control some kind of vehicle with my iPhone using the accelerometers. If you can handle C/Object-C then Embedded C should be no problem! http://www.nerdkits.com/videos/rc_car/ EDIT: PS if the NK is too much to swing the components individually from digikey are like $20. AnomalousBoners fucked around with this message at 04:50 on Nov 27, 2010 |
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Nov 27, 2010 04:33
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Does anyone know of a good tutorial for hooking up power relays? I need to set one up for an electrical pump that just plugs into a wall socket with your typical three pronged plug.
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Nov 29, 2010 15:10
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What exactly do you need the relay(s) to do?
Do you need to limit the rpms of the pump's motor? Is the motor big enough that you have to redirect current through special starter windings? Were you planning on using water (or whatever fluid) levels/presures to control the pumps operation?
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Nov 29, 2010 16:21
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As I understand it you want a 120V relay that will switch on your pump. Is the pump also 120V? Or are you saying the pump plugs into a typical 3 prong 120V wall outlet and you want to use a secondary relay to control it?
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Nov 29, 2010 16:26
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Thanks for the display suggestions guys. Might get one of them. Anyone else enter that Renesas design contest with the free devkit? Finally got mine in via fedex. With the almost 900 page hardcover book included I think it might actually be a better deal if they just gave you a wifi kindle with all their documents on it. ValhallaSmith fucked around with this message at 18:49 on Nov 29, 2010 |
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Nov 29, 2010 17:45
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The pump takes 120V and 50mA. I just need to be able to switch it on and off electronically to demonstrate a microcontroller (so it doesn't really matter how fast the pump is going), but I have no idea experience using/installing relays.quote:Or are you saying the pump plugs into a typical 3 prong 120V wall outlet and you want to use a secondary relay to control it? This. It has a power cord (no transformer) that plugs into a wall outlet.
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Nov 30, 2010 16:59
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Find an NPN BJT and connect the output of the micro to the base. Connect the Emitter to ground and the collector to one side of the relay coil. Connect the other side of the relay coil to VCC. Break the hot lead in the pump power cord and connect one side to the relay's common terminal and the other to the NO (normally open) terminal. Driving the output connected to the BJT high will energize the relay, connecting C to NO, and turning on the pump. This is simplified, if you want it more robust you should add a flyback diode and probably some resistors like a 10k between B and E on the NPN.
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Nov 30, 2010 19:51
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ValhallaSmith posted:Thanks for the display suggestions guys. Might get one of them. y'know, if you had told us about it when there was still devkits available to get, i bet more people would've entered 
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Dec 1, 2010 16:12
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Hillridge posted:Find an NPN BJT and connect the output of the micro to the base. Connect the Emitter to ground and the collector to one side of the relay coil. Connect the other side of the relay coil to VCC. Break the hot lead in the pump power cord and connect one side to the relay's common terminal and the other to the NO (normally open) terminal. Driving the output connected to the BJT high will energize the relay, connecting C to NO, and turning on the pump. Thanks. After tripping the breaker and watching sparks form inside the relay a few times I got everything working.
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Dec 1, 2010 18:25
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Frobbe posted:y'know, if you had told us about it when there was still devkits available to get, i bet more people would've entered It was pretty widely advertised. There was a thing on most of the major "maker" sites, eevblog, etc.
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Dec 1, 2010 22:25
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longview posted:I know this is a long-shot but does anyone know a way of getting NEC service manuals? I've been calling all day to their German headquarters as well as the Swedish repair centre, and they plain refuse to send them to outsiders. I did some digging and pinging and, I'm sorry to say I really don't think this stuff exists anymore. At least not digitally in the US or Japan. It maybe in a printout in some long-ago laid-off guy's file cabinet in Europe, but that's like finding a needle in a stack of needles. I mostly know/have access in US and Japan, and can't really help much with Europe, but it sounds like you already tried those guys. Do you have a name/contact of someone (English or Japanese speaking) in Europe that you think has the manual you need and just won't share it externally? If so PM me and I'll give it a go. Short of that (and it's a long shot), sorry! If I hear anything good I'll let you know, but I just wanted to chime in and encourage you to seek whatever alternatives you might have.
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Dec 2, 2010 08:29
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I know very little about wiring, and I have a stupid question about using a pair of switches to control power on/off and forward/reverse for a small motor powered by a battery. One switch would be SPST to just interrupt power... then what? How would a second switch be used to change polarity to the motor? What kind of switch is needed? If someone could help me with a simple diagram I would be forever grateful. Basically I'm imagining it like: Battery->SPST (on/off)->?(second switch, forward/reverse)->motor How would I actually wire this up?
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Dec 2, 2010 18:29
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Use a single DPDT switch instead. Get one with three positions and it'll have an 'off' position too. edit: 
Zo fucked around with this message at 18:48 on Dec 2, 2010 |
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Dec 2, 2010 18:36
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sirbeefalot posted:I know very little about wiring, and I have a stupid question about using a pair of switches to control power on/off and forward/reverse for a small motor powered by a battery. H-bridge. Replace transistors with the DPDT switch below vvv Remember to alternate the terminals! If the motor doesn't move when you flip the switch you are shorting your power supply out!
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Dec 2, 2010 18:41
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Zo posted:Use a single DPDT switch instead. Get one with three positions and it'll have an 'off' position too. Is there any way to do it with two or is it way over-complicated? I've done a couple drawings for a prototype for someone and they like the look of individual switches. I've suggested a single one but they'd like to see both options. :/ e; Duh, left the reply window open. 
sirbeefalot fucked around with this message at 19:02 on Dec 2, 2010 |
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Dec 2, 2010 18:58
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You can do it with two, just treat the above drawing as two SPDT rather than one DPDT. you will have a couple combinations where nothing happens though (+ to +, - to -).
Hillridge fucked around with this message at 19:30 on Dec 2, 2010 |
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Dec 2, 2010 19:22
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sirbeefalot posted:Is there any way to do it with two or is it way over-complicated? I've done a couple drawings for a prototype for someone and they like the look of individual switches. I've suggested a single one but they'd like to see both options. :/ In that case use a two-position DPDT switch for directional control (the same as the drawing in my above post but without the middle positions marked with X's), then add another normal switch anywhere that breaks the circuit for on-off.
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Dec 2, 2010 19:32
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Zo posted:In that case use a two-position DPDT switch for directional control (the same as the drawing in my above post but without the middle positions marked with X's), then add another normal switch anywhere that breaks the circuit for on-off. Cool, I figured this was the case. Thanks!
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Dec 2, 2010 19:39
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Do any of you know what the internal pullup in a Cyclone II is? I suspect it's around 15k because it was overpowering my 10k pulldown, but not by much.
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Dec 2, 2010 21:18
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Hillridge posted:Do any of you know what the internal pullup in a Cyclone II is? I suspect it's around 15k because it was overpowering my 10k pulldown, but not by much. It's in the datasheet - page 94. http://www.altera.com/literature/hb/cyc2/cyc2_cii5v1_01.pdf Looks like it can range from 10k - 50k if you're using 3.3v IO
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Dec 2, 2010 21:27
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Theoretically, is therre any difference between this: and this: https://www.youtube.com/watch?v=k4xsqw463Hs ?
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Dec 4, 2010 02:09
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The Scientist posted:Theoretically, is therre any difference between this: Yes - they operate on completely different principles. A microwave emits RF energy at around 2.4 GHz, which is absorbed by various polar molecules (such as water or fats in the case of food) through a process called dielectric heating. This basically causes the polar molecule to rotate (NOT vibrate) producing heat. An induction furnace uses very high magnetic fields to induce eddy currents in the metal to be heated. Additional heating in magnetic materials is caused by magnetic hysteresis, which causes the atomic dipoles to rapid flip. Either way, it's caused by magnetically coupling the the material to be heated and is very different than dielectric heating.
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Dec 4, 2010 03:05
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Thanks, very well explained. Why is it that the part can have so much voltage induced across it, but still be safe for the dude to hold with his bare hand? Is it only the fact that he's not providing a path to ground that he's not getting a 17.5 kv shock? Also, does this mean that you could not heat like a laminate ferrite core of a normal transformer as much as the piece in the video?
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Dec 4, 2010 03:16
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Has anyone ever messed around with ultra wideband stuff?
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Dec 4, 2010 05:56
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I'm currently trying to teach myself how to make circuits and solder and what not. I've done a few tutorials and kits from sparkfun, and feel like I have the super very basics down (but am still quite overwhelmed--this stuff is hard!). Right now I'm trying to construct a circuit and I'm just unsure of how to do a few things. My many nights of googling has helped a little, but I'm still having a few issues. If anybody could point me in the right direction that'd be great. Pardon my layman's terms/ignorance. Problem 1: Is there some sort of component that has a higher forward voltage than the minimum .7 that I seem to see on most resistor/diodes? Or maybe some sort of component that is specifically for "filtering" or something? I just want my circuit to work if it's being supplied with > 10v or something like that and for it to ignore anything < 10v. I'm totally lost on this, as it seems everybody wants their stuff to work with minimal power. What would I use? Problem 2: Are there any sort of capacitors that "leak" charge? I want to charge one up but I don't want it to remain indefinitely. Or alternatively a way to slowly drain the charge from one. would i just use a really low resistor hooked up to it constantly, and then use a switch to connect it to the rest of the circuit when it reaches a certain level? Problem 2.5: Is there a way to measure how much charge a capacitor currently has? or maybe something else like that?
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Dec 4, 2010 22:42
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crabrock posted:Problem 1: I'm am very much a beginner as well, and I don't mean this to be condescending, but: Ehhh.... Wut? A resistor has a [relatively] constant resistance. If there is a difference of voltage between one lead of the resistor and the other, the exact voltage drop of that specific resistor is a function of the voltage of the entire circuit, the resistance of the entire circuit. For instance, if you have 3 lamp bulbs in series (that is, in a row, one lead of one lamp touching one lead of the next; such that any one electron has to flow through all bulbs during the course of traversing the circuit), the exact drop in voltage you see across each bulb is bulb 1's resistance divided by the circuit's entire resistance, mutliplied by the entire circuit's voltage. Like this: R1/RT * VT Now, what you described DOES seem like a valid understanding of forward bias voltage. A diode is simple a junction of 2 dissimilar semiconductors. In order to overcome the gap in that junction, between the 2 dissimilar semiconductors, a certain voltage is needed. The junction presents resistance, and a specific minimum voltage is required to overcome that resistance. There are semiconductors with different characteristics, among those different forward bias voltages. Although this is not what, from your description, it sounds like you need, here's an example of a diode that behaves differently than the normal, run of the mill variety: Zener Diode You don't actually need a diode your objective. A diode is most commonly just for controlling the direction of voltage - letting positive voltage through, but showing a large resistance to any negative voltage. You've got a circuit that you only want to work if it sees more than 10 volts. Does the circuit require over 10 volts to work? or does it need only the voltage left over once you subtract 10 volts? quote:Problem 2: A capacitor will drain its stored voltage as long as it has a complete circuit to a point with a lower potential. You know, like one terminal of a battery when referenced against the opposite terminal. So if you have the positive terminal of a battery with a wire running to the positive terminal of a capacitor (some capacitors are polar, they have a specific terminal for positive and for negative. Some don't), then the negative terminal has 2 wires hooked up to it. One of the wires branches off to a resistor, and on the other side of the resistor is another wire that goes straight to the other battery terminal. The other wire branching off from the capacitor goes to an on/off switch, then to the other battery terminal like the first. So, when the switch is on(closed, so current can flow), any charge that has built up in the capacitor dissipates back to the other battery post. For our purposes, this is basically instantaneous. If we assume that the wires in our circuit have a resistance of basically 0 ohms, this is true. However, we know a resistor resists current flow. If only 1 amp of current, for example, can flow through a resistor as opposed to 2, it would take 2x as long to achieve a total flow of 2 amps. This is self explanatory. So, how fast the charge in a capacitor drains is a function of the resistance it has to overcome for the electrons to flow to where they want to be. The higher the resistance, the less current can flow at any one time, so the slower the capacitor drains. There is a term that describes the relationship between a resistor and a capacitor: RC Time Constant
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Dec 4, 2010 23:32
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crabrock posted:I'm currently trying to teach myself how to make circuits and solder and what not. I've done a few tutorials and kits from sparkfun, and feel like I have the super very basics down (but am still quite overwhelmed--this stuff is hard!). Assuming this means you want your circuit to be off if it isn't receiving enough voltage. You want a voltage regulator with a low voltage cutoff. Or use a switching chip to do it. crabrock posted:Problem 2: All capacitors leak charge. I believe TVs and such that have very high capacity capacitors have high value resistors across them to drain them off within 15 minutes. Thats probably changed with newer TVs. crabrock posted:Problem 2.5:
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Dec 5, 2010 03:10
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Krenzo posted:Has anyone ever messed around with ultra wideband stuff? What are you tryng to do? Cognative radio? Or just a very high bandwidth link? Generally it's all done with FPGAs since you have to acquire and process very large amounts of data.
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Dec 5, 2010 04:23
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SnoPuppy posted:What are you tryng to do? Cognative radio? Or just a very high bandwidth link? I'm trying to do time of flight stuff: send out a single pulse from a transmitter and time how long it takes to reach the receiver. I have several FPGAs and have built a test circuit that can time the travel time of a square pulse through a wire to within about 100 picoseconds (I'm planning to reduce the noise to get a more accurate timer). The next part is to construct a UWB transmitter and receiver to replace the wire that the pulse travels through. However, the difficult part I'm having to deal with is figuring out how I'm going to troubleshoot any problems I may encounter with such narrow pulses (ones that will register in the >3 ghz range). To even be able to see the pulse with an oscilloscope would take a very expensive one. I'm currently trying to ask electrical engineer grad students at my school to figure out if the university has any fast scopes I could get some time with. I hate the idea of getting into this project and not have any concrete feedback as to what's going on, ie if things are really operating how I planned them to.
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Dec 5, 2010 09:54
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Krenzo posted:I'm trying to do time of flight stuff: send out a single pulse from a transmitter and time how long it takes to reach the receiver. I have several FPGAs and have built a test circuit that can time the travel time of a square pulse through a wire to within about 100 picoseconds (I'm planning to reduce the noise to get a more accurate timer). The next part is to construct a UWB transmitter and receiver to replace the wire that the pulse travels through. However, the difficult part I'm having to deal with is figuring out how I'm going to troubleshoot any problems I may encounter with such narrow pulses (ones that will register in the >3 ghz range). To even be able to see the pulse with an oscilloscope would take a very expensive one. I'm currently trying to ask electrical engineer grad students at my school to figure out if the university has any fast scopes I could get some time with. I hate the idea of getting into this project and not have any concrete feedback as to what's going on, ie if things are really operating how I planned them to. Why do you need UWB? Or do you plan on scanning through specific frequencies? One thing you might consider is just using dirt cheap DBS LNBs for your transmitter and receiver. It would be easier than building a UWB from scratch and have less need for a high speed RF scope. http://www.youtube.com/watch?v=vDyo_OQFdAc is Jeri Ellsworth's take on modifying a LNB.
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Dec 5, 2010 11:28
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