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It's not the easiest way but if you want to email me the file I'll host it on my site. I do this with a few other low-bandwidth goon files that I've got interest in  c.sammis@gmail.com That or maybe Rapidshare? I don't know if that's even considered a legitimate thing to use for normal files and not just 
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Jun 16, 2011 21:18
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Delta-Wye's file "MSP430 example w/ interrupts, timers, and a code listing" is up at http://csammisrun.net/sa/CPEHW1.pdf
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Jun 16, 2011 22:07
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I'm wiring up some custom gauges in my Datsun 510, and I've got a small puzzle that may or may not be an issue: The 510's fuel sending unit gives me a range of 0 ohms (full) to 100 ohms (empty). However, I'm installing a 280z fuel gauge, but the 280z fuel sending unit provides a range of 10 (full) to 80 ohms (empty). I understand that this is going to cause the fuel-gauge calibration to be off by a little, showing that there's still a little bit of fuel when the tank is actually empty, and showing that the tank isn't completely full when it actually is. How do I remedy this? What arrangement of resistors is going to spread the 10-80 ohms out to 0-100 ohms? e: I was corrected below; my actual goal is to take the 0-100ohm sweep of the sending unit and reduce it to a range of 10-80 ohms. jovial_cynic fucked around with this message at 20:58 on Jun 19, 2011 |
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Jun 17, 2011 06:19
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You could add a 20 ohm resistor in series to make it read full but that will really mess up the zero. I would just live with the fact that the fuel reading is off.
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Jun 17, 2011 14:31
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On the subject of MSP430s and Launchpads: Delta-Wye inspired me to get off my butt and write my first program for the Launchpad. I spent last night hammering this out using msp430-gcc on my Macbook - no fine IDE for me so no debugger at the moment  http://codepad.org/Suru41xw There's a problem with it that I'm hoping this thread can help me with (please keep in mind this is my very first shot at writing C for a microcontroller). The LED toggles on the first button press and then every third button press instead of every other. Basically this where the Xs are button presses: code:So now I have myself a very nice waltz counter but that isn't what I was going for. Can anyone give me some pointers to ferret out what's wrong? I feel like maybe I'm not re-enabling an interrupt or clearing a flag where I should be. Update: Success! It turns out that I wasn't clearing the P1 interrupt flags at the end of the debounce timer ISR and that was causing some cruft to miss my case statement in the button ISR. I'm slightly confused as to why I have to clear the entire flag register as opposed to just resetting the single bit for the button. Couldn't that potentially axe a legitimate pending interrupt? Any insights? http://codepad.org/vQbhei0c csammis fucked around with this message at 23:06 on Jun 17, 2011 |
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Jun 17, 2011 17:50
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csammis posted:Any insights? Maybe try swapping these lines in the debounce function? code:
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Jun 17, 2011 23:43
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If I've got a low-side MOSFET with a gate threshold voltage equal to or less than my logic voltage, is there any reason to not drive it directly from a logic output? I notice that they give the gate charge in Coulombs (or rather, nC). I'm guessing if you rapidly switch it, the charging and discharging of it could add up to a big current? Could I just multiply the gate charge by the frequency of the switching to find out the current?
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Jun 18, 2011 05:28
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BattleMaster posted:If I've got a low-side MOSFET with a gate threshold voltage equal to or less than my logic voltage, is there any reason to not drive it directly from a logic output? quote:I notice that they give the gate charge in Coulombs (or rather, nC). I'm guessing if you rapidly switch it, the charging and discharging of it could add up to a big current? Could I just multiply the gate charge by the frequency of the switching to find out the current?
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Jun 18, 2011 05:47
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A series resistor would help with the peak currents wouldn't it? Could I select the resistor using Ohm's law assuming V = logic voltage and I = estimated average current? Though I guess I could just get around to getting some MOSFET drivers and not have to worry about any of that.
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Jun 18, 2011 05:54
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Well you'll have to choose between have good switching speeds on the FET and not stressing the logic gate. If you can't find a good compromise between the two, then consider paralleling several gates, or getting a proper driver IC.
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Jun 18, 2011 06:21
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Cool. Could I estimate switching speeds with the standard RC formulas or is it more complicated than that?
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Jun 18, 2011 06:29
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It's about as good as an approximation as you'll need. But it assumes your gates have no output impedance, which, depending on the logic family, may be a bad assumption. You'll just have to try it.
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Jun 19, 2011 00:27
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Awesome, thanks for all the help. I think I've got enough of it figured out now to get things working.
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Jun 19, 2011 00:57
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jovial_cynic posted:How do I remedy this? What arrangement of resistors is going to spread the 10-80 ohms out to 0-100 ohms? Figured it out. 233ohms in parallel to the sending unit limits the range of the sender from 0-to-100 down to 0-to-70, and then adding a 10-ohm resistor in series bumps the values up to 10-to-80.
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Jun 19, 2011 05:59
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jovial_cynic posted:Figured it out. 233ohms in parallel to the sending unit limits the range of the sender from 0-to-100 down to 0-to-70, and then adding a 10-ohm resistor in series bumps the values up to 10-to-80. You know got got it backwards, right? He has 10-80 and wants it to be 0-100. Which is sorta impossible to do passively.
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Jun 19, 2011 18:00
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Slanderer posted:You know got got it backwards, right? He has 10-80 and wants it to be 0-100. Which is sorta impossible to do passively. He is me. I think I may have explained poorly. The sending unit is a variable resistor with a range of 0-to-100. The gauge that reads the unit is designed to accept values of 10-to-80. Limiting the 100-ohm sweep down to a 70-ohm sweep shouldn't be a problem...
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Jun 19, 2011 20:57
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jovial_cynic posted:He is me. Oh poo poo, yeah, the last line of your original post was sort of misleading. Whoops.
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Jun 19, 2011 21:05
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I'm looking for a connector that an equipment manual describes as being a "mixed-pin DB15" plug that has two oversized pins for drive current and a few smaller pins like this: actual picture:  Googling for DB-* returns so much stuff that finding what you really need is drat near impossible. Does anyone know what that kind of plug might be called, or know any company that manufactures this kind of thing?
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Jun 22, 2011 13:42
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http://search.digikey.com/scripts/DkSearch/dksus.dll?Detail&name=626-1116-ND http://search.digikey.com/scripts/DkSearch/dksus.dll?Detail&name=626-1311-ND Those look like what you want, or should get you close enough that you can find one based on the datasheets. "CONN D-SUB 7W2" is the search term you want to use, then click the "D-sub (xxx items)" link and choose 7 for the number of positions. Hillridge fucked around with this message at 14:12 on Jun 22, 2011 |
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Jun 22, 2011 14:05
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D7W2, I think. http://en.wikipedia.org/wiki/DB_connector shows the connectors with 3 coax and calls it D13W3, so I just guessed and google D7W2: http://www.adam-tech.com/pdf/DRAWINGS%20STARTING%20WITH%20A-D/D7W2-SDP-X.pdf efb
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Jun 22, 2011 14:08
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Yep, those links look like exactly the part I needed. Thanks!
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Jun 22, 2011 17:59
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A belated thanks to Delta-Wye for the MSP430 stuff. Now question time: I want to setup an electronically dimmable spotlight in my room for experiments with artificial dawn type stuff. I know for AC controlled stuff I'd want to use a Triac, but that's as much as I know, since I've never used one. An optocoupled interface might not hurt, either. If I'm doing with a DC spotlight (which is actually probably preferable for the brightness I need. We currently use some to illuminate a sign on our lawn), I'll probably just want to drive the light with an unfiltered PWM, right? Anyone have any idea what frequency range would be ideal? Would a power MOSFET probably be sufficient for this? If not, I suppose I could use parallel drivers, but I would have to remember how to properly do that (since they can do weird things due to mismatches).
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Jun 22, 2011 19:35
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Slanderer posted:If I'm doing with a DC spotlight (which is actually probably preferable for the brightness I need. We currently use some to illuminate a sign on our lawn), I'll probably just want to drive the light with an unfiltered PWM, right? Anyone have any idea what frequency range would be ideal? I think any frequency > 60 Hz will work fine, but I don't think there is a good reason to use a frequency that low. Maybe 500Hz-1kHz? How much current will the spotlight use? I doubt you will have trouble finding a single FET that is large enough, 10-20A can be had in fairly small packages. You will have to figure out how much heat it will dissipate.
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Jun 22, 2011 20:00
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Slanderer posted:A belated thanks to Delta-Wye for the MSP430 stuff. This site has a good description of how the TRIAC dimmers work in general. http://www.epanorama.net/documents/lights/lightdimmer.html At the bottom they have a quick description of how to interface a microcontroller with the triac setup. Basically, you trigger the TRIAC whenever, and then it 'sticks' on until the next zero crossing. Ideally, you would detect the zero crossing, wait some portion of the waveform (defined by your desired brightness level), trigger it, and wait until the next zero crossing. I designed a simple 3 channel dimmer using triacs but got stuck on the zero crossing detector. I couldn't get something that would provide a reliable signal. Plus, the project had a crazy power regulator section and needed to be redone from the ground up. Slanderer posted:If I'm doing with a DC spotlight (which is actually probably preferable for the brightness I need. We currently use some to illuminate a sign on our lawn), I'll probably just want to drive the light with an unfiltered PWM, right? Anyone have any idea what frequency range would be ideal? Usually efficiency goes down as your PWM frequency goes way up. Switching loses, inductive and capactive loses, etc. The big thing is you need it high enough you can't detect the blinking. 60 Hz would be a reasonable minimum, 1 KHz @ 12V is very doable and should be a good target. I don't know how much current you are drawing at 12V, but I am confident you can find a MOSFET solution.
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Jun 22, 2011 21:12
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So, one problem I have with circuitry is that I can't think of ideas. I finally have one. I have a couple of Icom PCR-100 serial-controlled receivers and am not doing anything with either. Going to get an Arduino and use a 16x2 LCD along with some supporting parts to build a controller for it. It won't be that wiring-intensive, really. Stage 2 will have me doing the same thing, but in a gutted antique radio chassis (I'll pick a dead one, don't worry) with Nixie display and IR remote, and perhaps even a low-watt tube audio amplifier. It'll be pretty cool to eventually have an Olde Tyme Radio that can do everything from listen to local AM nutjobs to far-off shortwave to the local cops, with a billion memories and modern stability.
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Jun 23, 2011 21:37
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Ideas are really the hardest part. I've got one that I wouldn't mind some weigh-in. I'd like to make a portable wifi cracker. I'm wondering the best way to do this, there are a few avenues I could use: SoaC with Linux and the Aircrack-NG suite, connected to one of the supported wireless cards. Pros: Should be possible for sure. Minimal software hacking. Cons: Not designed expressly for my needs. Potentially slower and more power-hungry than the other options Arduino ethernet shield/PIC ethernet module of some sort. Pros: Can be custom designed to only do what the cracking requires so it should be faster. Energy efficient(ish). Cons: Probably have to rewrite the Aircrack-ng stuff for PIC/AVR. I haven't looked at this yet, so I don't know how trivial it is. Those are the two extremes of what I could do, there's some mixing and matching possible, too. I'd rather use PIC than an Arduino or AVR, too, but I don't know what ethernet solutions there are. I know there aren't any real questions in this post, but if anyone has any thoughts to add, I'd like to hear them. edit: long and rambling post after a 16 hour day at work 
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Jun 24, 2011 06:02
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I'm not sure if an AVR/PIC would be fast enough and/or have enough RAM for wifi cracking. I could be wrong, but it might be slow as hell, and might involve a lot of recoding work. An ARM board that runs linux shouldn't be hard to find; Other than beagleboard, however, I don't know of any specific recent ones to recommend. As long as the toolchain config and whatnot is well documented, that might be the easier route. If you really, really want to rewrite it, though, I'd still consider rewriting it for an ARM. Also, someone at work has been messing with a lot of wifi modules recently, and they seem to be really hit-or-miss (ie, some flake out at high transmission speeds, others reset, others are basically undocumented, etc).
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Jun 24, 2011 06:52
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Question on re-wiring an alarm clock. I sleep through alarms and I want a louder alarm clock, so I figured why not hook up a bell, buzzer or car/train horn? I figure take out the current speaker/buzzer and replace it with bridge rectifier -> cap -> relay, then hook up whatever up to the relay. Would this work? Am I over thinking this or am I missing something? This video just connects the speaker to the relay, but wouldn't that keep pulsing the relay? Fire Storm fucked around with this message at 07:20 on Jun 24, 2011 |
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Jun 24, 2011 07:08
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Fire Storm posted:Question on re-wiring an alarm clock. I sleep through alarms and I want a louder alarm clock, so I figured why not hook up a bell, buzzer or car/train horn? So, a few things: First, I don't know what the hell their "voltage relay switch" is here, but it doesn't really matter as long as it's not a latching switch or anything. Heck, maybe it's just a fancy mosfet or analog switch, i dunno. Presumably, however, the mechanical switch removed from the water gun was directly between the battery and the motor. The alarm clock in this instance has a speaker, which means it's being driven either by a PWM waveform or some misc. waveform from an analog oscillator. If we consider the "relay" to be fully digital (ie, at some set voltage it switches from fully off to fully on), then whatever the input waveform is, it will become some sort of square wave with the freq and duty cycle being determined by the input. This will be fine for driving the motor, although the power will clearly be lowered as the duty cycle will no longer be 100% as it was when the motor was connected directly to the battery. If the switch isn't fully digital and the switch varies from fully open to fully closed (like w/ a MOSFET's linear region), the waveform will still drive the motor. If you want to rewire an alarm clock, you'll need to determine if it as a speaker or buzzer. If it's a buzzer, it might be a simple piezo, whose frequency (and possibly volume) can be roughly adjusted by changing the signal. Alternatively, it might be a buzzer package that includes an internal oscillator, and just takes power. But let's consider some options on the conversion to another kind of transducer: If you want to hook up to a louder speaker or buzzer, that's easy--a bigger speaker just needs an amplifier circuit. But let's say you do, in fact, want something with a relay. Using a bridge rectifier might be a poor solution here, depending on the voltage (since the diode drops on a 5V output might be annoying). Consider instead a simple comparator, with slight filtering. Then since you want it to stay on for the duration of the alarm pulse, either add a 2nd op amp to make a fancier time delay thing, or more simply, rig up something with a 555 or two. I had a hell of a lot more to say about that last paragraph, but my brain just broke, so if someone doesn't pickup where I left off, I'll continue it when I wake up
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Jun 24, 2011 11:17
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ante posted:Ideas are really the hardest part. I was thinking about doing something along these lines myself. I wanted to pick up a Beagleboard and use this as my first project. Keep us posted and I shall do the same when I can scrape together enough cash to get a board!
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Jun 24, 2011 14:14
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ante posted:Ideas are really the hardest part. Cracking a WEP network requires around 80,000 packets to be captured, and requires a reasonable bit of RAM and CPU power. I'm not sure that a micro would be up to the task, unless it was something heavier duty, like an ARM. There's also the practical problem of being able to capture all the packets on the air - I have no idea if a WiFi shield lets you do raw packet capture, or if it simply throws away packets it can't decrypt. You also might run into the issue that very few people use WEP these days anyway. Now, if you want to crack WPA/WPA2, you definitely don't have enough processing power on an embedded device. There are no public flaws with the standard WPA algorithm (aside from some issues with TKIP, but those don't recover the key), so the only real attack is to try to bruteforce the password. This will take a while. It might be more viable to just create a wifi (or bluetooth) logger that you could place somewhere to grab data. Then you could try cracking it offline using rainbow tables, GPUs, etc.
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Jun 24, 2011 14:52
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Edit:/\/\/\ My house is beset on all sides by "secured" WEP networks. I feel like they are still pretty ubiquitous. I'm thinking about grad school. Do you all have any resources that could help pare down potential schools? My only requirement right now is that they teach in English; I'm comfortable with traveling just about anywhere and I haven't officially chosen my area of specialization yet. My question is manifold: I need help deciding on an area to focus on, and I also have no idea what each school is best at. I am about to embark on a shitload of googling to answer these questions, but I bet some of y'all have already done this and I was hoping you could share your results. Corla Plankun fucked around with this message at 16:17 on Jun 24, 2011 |
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Jun 24, 2011 15:47
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Slanderer posted:I'm not sure if an AVR/PIC would be fast enough and/or have enough RAM for wifi cracking. I could be wrong, but it might be slow as hell, and might involve a lot of recoding work. My thinking is that I could replace some of the algorithms with an FPGA and get the thing really blazing fast. And I haven't looked into it at all, but I bet regular computer RAM is pretty well documented and could be run from a PIC/ARM. This is all long-term stuff, though. I have a few things on the go already.
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Jun 25, 2011 17:03
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ante posted:My thinking is that I could replace some of the algorithms with an FPGA and get the thing really blazing fast. And I haven't looked into it at all, but I bet regular computer RAM is pretty well documented and could be run from a PIC/ARM. Hah, if you're willing to try to redo stuff for an FPGA, than more power to you! Trying to get at computer memory through an avr/pic is probably more work than its worth. An avr couldn't use nearly enough external ram (i dunno, limited addressing or something?) However, that kind of stuff is well documented with mid to high end FPGAS. Still probably cheaper & easier to use an ARM than an AVR though--it's gonna be so much faster, not just because of the clock speeds, but the architecture as well. Question time: Electromagnets! So, I remember building electromagnets with my dad when I was like 8, using lantern batteries, wire, and these hilariously thick nails. I'm sorta interested in making a somewhat more legit one now, but aside from my electronics work, and a semester of e&m (not the freshmen stuff, but the full on classical e&m upperclass stuff. Electric displacement fields and all that), I'm not really sure where to start. Sure, there are programs out there for doing simulations on various shapes and materials, but I'm hoping someone can recommend a text from a more practical point of view. Basically, it's some combination of me wanting to be able to mess around with an enormous magnet, while at the same time understanding a bit better how the big gently caress-off electromaget I used in senior physics lab for the Zeeman effect worked. It looked something like this:  Only it was enormous.
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Jun 25, 2011 23:37
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Slanderer posted:Basically, it's some combination of me wanting to be able to mess around with an enormous magnet, while at the same time understanding a bit better how the big gently caress-off electromaget I used in senior physics lab for the Zeeman effect worked. It looked something like this: So I'm assuming that the area of interest is in between the tips of those two cones, right? What kind of field strength are you looking for, and what kind of volume? Lately people have found that you can use permanent magnets to get incredibly strong (like over 1T) fields in large volumes using proper field guides.
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Jun 25, 2011 23:50
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I was thinking about getting a logic analyzer at some point to help me out with continuing adventures in embedded development and have found http://www.saleae.com/logic/. Does anyone in this thread have any experiences good or bad with it? My needs are not many at this stage - I would like to be able to see PWM output on something other than an LED and a guess at the percentage of brightness, for example.
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Jun 27, 2011 01:31
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ANIME AKBAR posted:So I'm assuming that the area of interest is in between the tips of those two cones, right? Actually, I have no idea. I just know very little about practical magnetic, so I don't know where to start...Especially in terms of materials, field simulations, weird eddy currents, etc... The picture was just an example of a wacky electromagnet shape from lab that I know very little about why It's made that way. csammis posted:I was thinking about getting a logic analyzer at some point to help me out with continuing adventures in embedded development and have found http://www.saleae.com/logic/. Does anyone in this thread have any experiences good or bad with it? My needs are not many at this stage - I would like to be able to see PWM output on something other than an LED and a guess at the percentage of brightness, for example. The logic seems to work fine. Sometimes it got confused by a strange implementation of a protocol, but I usually got it to work. Never used it to measure PWM, though. Not sure why you would---LEDs are hilariously bad for trying to guess at the % with, since your visual response to the duty cycle is logarithmic.
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Jun 27, 2011 02:47
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Slanderer posted:Never used it to measure PWM, though. Not sure why you would---LEDs are hilariously bad for trying to guess at the % with, since your visual response to the duty cycle is logarithmic. Huh, this actually explains quite a bit - I thought I was seeing progressively diminishing increases in brightness as duty cycle % increased but my eyes are not great in the first place. This is why it would be helpful for me, a complete beginner in electronics, to see charts of logic output over time instead of having to hope for the best and learn from offhand comments on forums that my "test" is fundamentally flawed
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Jun 27, 2011 03:09
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csammis posted:Huh, this actually explains quite a bit - I thought I was seeing progressively diminishing increases in brightness as duty cycle % increased but my eyes are not great in the first place. This is why it would be helpful for me, a complete beginner in electronics, to see charts of logic output over time instead of having to hope for the best and learn from offhand comments on forums that my "test" is fundamentally flawed Hah, unfortunately, most people figure it out when they do something like make a potentiometer control the duty cycle, and then notice the shape of the response (hopefully). I thought I had a link saved about it, but I guess I was wrong since I can't find it. Regardless, it's helpful to linearize the response of a PWM'd LED if you want to do something more fancy with it, like make a laptop sleeping fade in fade out sorta thing.
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Jun 27, 2011 03:31
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Slanderer posted:Actually, I have no idea. I just know very little about practical magnetic, so I don't know where to start...Especially in terms of materials, field simulations, weird eddy currents, etc... The kind of application you want will define how you build it. For instance I build my own miniature NMR systems, which require decent field strength (between 0.2-0.4T), but most importantly they have to be very homogeneous fields, which often requires using many additional coils to correct for inhomogeneities.
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Jun 27, 2011 05:39
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