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movax posted:That, and I've posted about it before, but after doing one blinky LED project, they run around without a basic understanding of electronics as "makers" who "love to teach" others about what they (haven't) learned. To be fair, there are some significant downsides with the MSP430 launchpad: 1. Big IDE to install, with a much more complicated build procedure. 2. Faaaar less idiot-proof tutorials 3. A lot of the target ICs have poo poo for flash memory 4. No prewritten libraries I mean, these are not really hurdles for anyone who wants to learn embedded systems, but to someone who just wants to "make" something in 30 minutes, without any background, it kinda is.
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May 29, 2012 17:42
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Has anyone else here taken advantage of the ST Microelectronics free STM32 F0 (ARM Cortex M0 based uC) eval board? I got mine during finals week and haven't poked anything with it yet in the chaos of graduation and moving, but I'm thinking an OBD-II sniffer.
Blotto Skorzany fucked around with this message at 19:46 on May 29, 2012 |
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May 29, 2012 19:43
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My Rhythmic Crotch posted:Probably not the right place to post this, but I don't really think we have a better thread for it. This single image manages to capture what I hate so much about the Arduino "movement". And this is why I hate the old school electronics mentality. Elitism works both ways, hating on Arduino because it's overkill is just as silly as that dude's mustache. Arduino has dramatically lowered the barrier of entry and exposed a world of electronics to people who would have never before even considered making something on their own. Who cares if they never get past the point of a blinking a bunch of LEDs that respond to their twitter feed? It sure is as a whole hell of a lot better than playing farmville all day.
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May 29, 2012 19:45
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Otto Skorzeny posted:Has anyone else here taken advantage of the ST Microelectronics free ARM evaluation board? I got mine during finals week and haven't poked anything with it yet in the chaos of graduation and moving, but I'm thinking an OBD-II sniffer.
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May 29, 2012 19:51
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Fatal posted:And this is why I hate the old school electronics mentality. Elitism works both ways, hating on Arduino because it's overkill is just as silly as that dude's mustache. Arduino has dramatically lowered the barrier of entry and exposed a world of electronics to people who would have never before even considered making something on their own. Who cares if they never get past the point of a blinking a bunch of LEDs that respond to their twitter feed? It sure is as a whole hell of a lot better than playing farmville all day. YES. I can see being amused at someone having an attitude that's like "hey dudes, I'm an electronics expert!", when they don't know much of anything, but to get elitist on them? Please. They made something! Why do you care if they don't have an EE degree or understand electronics in a deep, meaningful way?
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May 29, 2012 21:46
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Slanderer posted:To be fair, there are some significant downsides with the MSP430 launchpad: That's true; the only reason I got my MSP430 stuff done in 30 minutes without ever having used it before is because I have years of experience with other micros, and knew what to look for in the datasheet. And yeah, the IDE is obnoxiously huge (and requires registration  ), but I think mspgcc might be a little smaller (certainly not as friendly).Thermopyle posted:YES. The problem (to me) is the blind leading the blind. loving up little circuits just smokes some digital ICs, but I've had to stop people from killing themselves interfacing an Arduino with AC power/relays. Basic understanding of basic electronics is all I ask (they can completely ignore EE disciplines like signals/controls/etc). I mean, I have really basic welding experience, and I know that I'm nowhere near qualified to weld anything that might be responsible for safety in the smallest way. I guess I get stabbed by own sword though, as I get made fun of sometimes by greybeard old-school guys who roll their eyes and then show me how I could do the same thing with like a dozen op-amps. I like it though, because analog artistry is getting rarer and rarer, and you learn some cool tricks. peepsalot posted:Don't know about that board, but if you wanna play with OBD, i would just use a chip specifically designed for it such as ELM327. You can get a whole device with connector and bluetooth and usb for like $12. It shows as a serial device so you can just play around sending AT commands etc from a terminal. Really easy to write communication software for it. There's a "new" similar chip to that (also PIC-based, even the datasheet is Microchip-style) the STN1110 which if I recall, claims ELM327 compatibility or something as a feature.
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May 29, 2012 22:05
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movax posted:There's a "new" similar chip to that (also PIC-based, even the datasheet is Microchip-style) the STN1110 which if I recall, claims ELM327 compatibility or something as a feature.
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May 29, 2012 22:09
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peepsalot posted:Yeah I would hav mentioned that, but I think those devices stil cost a lot more. Not a whole lot of extra useful functionality as far as I can tell besides a higher UART rate. Ah, ok, I had just briefly noted the existence of the STN1110, didn't know anything about pricing. Here is the comparison between the two, but it's written by the STN1110 company, so take with a grain of salt I guess.
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May 29, 2012 23:05
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peepsalot posted:Yeah I would hav mentioned that, but I think those devices stil cost a lot more. Not a whole lot of extra useful functionality as far as I can tell besides a higher UART rate. Worth it right there, actually. ELM327 scan rate is verging on frustratingly slow. An STM32-based OBD2 scanner would probably be a worthwhile effort, if you really want to learn OBD2. Otherwise that STN1110 looks really good.
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May 30, 2012 15:14
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Okay, back to voltage regulation. If you're trying to get something like 12v down to 3.3v, there seems to be a pile regulators to do that sort of thing, but even with high efficiency, once you try to pull something like an amp or 2 through them, they get ridiculously hot at that sort of voltage difference. Are you really supposed to slap on a giant heat sink and fry some eggs, or is there a better way to do that sort of thing?
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May 30, 2012 22:24
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bobua posted:Okay, back to voltage regulation. You use a switching supply; the 78xx drop-in replacements from Murata's Okami series are rated up to 1.5A, but they (any many other company) make larger capacity modules if you don't want to roll your own. Your switching elements (FET/JFET/etc), plus inductor and (flywheel)diode scale with current. Monolithic regulator ICs will be limited by the current capability of their internal FETs. The modules are limited by whatever the company put on them. e: This guy seems solid. movax fucked around with this message at 22:37 on May 30, 2012 |
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May 30, 2012 22:35
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Auh, I think I've been pointed in that direction before, wasn't worried about heat back then so I didn't do enough reading on switching vs linear. Thanks!
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May 30, 2012 23:09
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Do standard diodes affect the amperage passing through them? I want to prevent current flowing in a certain direction in some LED circuitry in which I've spliced together several different components, but I need the current to remain constant. Here is what I mean:code:code:That way, current can't be redirected from one of the 1 A current drivers in case one of the rows has a failed connection, but the current from the 350 mA driver can still be split between both rows. But I need to make sure those diodes won't actually affect the current going through them, or prevent current from being split evenly between the two circuits.
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May 31, 2012 19:29
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Goddamnit, how do you keep making this more convoluted!? Proper LED drivers would have been the correct solution so many pages ago.... Regardless of LED open-circuit failures, placing constant current sources in parallel, as in the top diagram, is a terrible idea, and bound to be unstable at some point, I'd think....with the diodes in place, however, the two drivers will be essentially isolated, and there shouldn't be any weird behavior in the feedback loops of the drivers. And with the 350mA driver, keep in mind that you can't control the current to each set of LEDs, so there is absolutely no guarantee they will be the same brightness (especially at low brightness, when your eyes will be most sensitive to differences). Lastly, make sure you factor the voltage drop across the diodes into the calculation for the minimum input voltage, as well as picking diodes that can dissipate the correct amount of continuous power.
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May 31, 2012 19:54
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Slanderer posted:Goddamnit, how do you keep making this more convoluted!? Proper LED drivers would have been the correct solution so many pages ago.... I don't know what you mean by this, my problem has always been needing to have two different brightness ranges for my LEDs because simple PWM control at one current was not giving me my full necessary range. I contemplated using a relay-controlled resistor to divert a bunch of current when I wanted, but now I decided it would be easier to just have high current drivers on each row on one setting, and one low current driver on all the rows at a different setting, even though that means adding a lot of expense to the project since I'll need many more drivers. Unless they make variable output current drivers that can be computer controlled, I don't know what you mean by "proper LED drivers". I've always been using 350 mA, 700 mA, or 1000 mA BuckPucks in my design. I wish there was an easier way to have an automated system that can go from 1 uE/m2/s all the way up to 2000 uE/m2/s. Anyway, I'm planning on using this diode: http://www.digikey.com/product-detail/en/1N4001/1N4001FSCT-ND/1532742 There's enough spare voltage to cover the forward voltage drop and it can handle 1 A while I'll only be passing 175 mA through it. Slanderer posted:Regardless of LED open-circuit failures, placing constant current sources in parallel, as in the top diagram, is a terrible idea, and bound to be unstable at some point, I'd think Also this is totally unavoidable because one array will have 96 LEDs on it and there's no way I can have one current driver per row of 6 Hidden Under a Hat fucked around with this message at 20:34 on May 31, 2012 |
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May 31, 2012 20:27
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As far as variable output LED drivers, the first hit I got was for these guys: http://www.rapidled.com/mean-well-eln-60-48p-dimmable-driver/ http://www.rapidled.com/mean-well-hlg-185-42b-dimmable-driver/ One of those hooked to any sort of USB->i/o interface (like an arduino*) which made me think: sorry for not wanting to go back and reread your old posts, but the places where you have parallel LED strings--they are the same, right? Same # + color? *gently caress you guys, it's totally a cost-effective solution for a premade interface. Yeah, you could do the I/O directly with one of FTDI's chips or something, but in terms of time + money, this is the cheapest + quickest
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May 31, 2012 21:05
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Slanderer posted:As far as variable output LED drivers, the first hit I got was for these guys: The parallel rows all have the exact same type of LED and number. I've even made sure they're form the same manufactured batch. I know they don't all have the same intensity, but we're mainly concerned with an overall average light field from the combination of all 96 LEDs, so minor variations row-to-row or LED-to-LED are ok.
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May 31, 2012 21:20
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Otto Skorzeny posted:Has anyone else here taken advantage of the ST Microelectronics free STM32 F0 (ARM Cortex M0 based uC) eval board? I got mine during finals week and haven't poked anything with it yet in the chaos of graduation and moving, but I'm thinking an OBD-II sniffer. Oh man I got right on this and it came in the mail today. I'm thinking of putting in a CompactFlash interface so I can learn how that works. I have a CF 10/100 ethernet adapter I could get going and turn it into an internet enabled weather monitor or something. I love the whole "here's a protoboard, make your own drat shield" concept it's got going for it.
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Jun 1, 2012 01:04
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Looking at the schematic for a filter from a UK company we're dealing with, it's got a circuit symbol on it that nobody here has ever seen: Those...things...on the right-hand loop, looks like a chassis ground connected to a capacitor, what the hell does that signify? Does that mean that the circuit runs between the plates of a cap, the cap is grounded, but the cap actually isn't in the filter circuit? Why the hell would you do that? Or is it some weird UK thing suggesting that there's, I don't know, a grounded shield around just that part of the circuit. Huh? Help? SnoPuppy posted:I believe it's either an explicit indication of a transmission line or a microstrip structure. Low, the line input's actually DC, this filter's there to prevent any EMI out on the load side from making its way back out onto the DC supply bus. Phanatic fucked around with this message at 20:27 on Jun 1, 2012 |
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Jun 1, 2012 20:02
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Phanatic posted:Looking at the schematic for a filter from a UK company we're dealing with, it's got a circuit symbol on it that nobody here has ever seen: edit: removed incorrect guess SnoPuppy fucked around with this message at 22:43 on Jun 1, 2012 |
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Jun 1, 2012 20:22
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The dual inductor with a "C" is a common mode choke. The funny capacitors are feedthrough (three terminal) capacitors. This looks like a pretty typical line filter, there's no real magic going on.
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Jun 1, 2012 20:51
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sixide posted:The dual inductor with a "C" is a common mode choke. The funny capacitors are feedthrough (three terminal) capacitors. This looks like a pretty typical line filter, there's no real magic going on. Okay, thanks. Like I said, none of us here had seen that symbol before.
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Jun 1, 2012 21:02
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I am a high school physics teacher as of two months ago. The school needed a quick replacement for a teacher who had to leave, so I stepped in. Yesterday was the last day of classes, and two of my students came up and asked me to be the adviser for the robotics team. I said hell yes, because robots are awesome. My degree is in engineering, and I took an EE course in college, but I am pretty clueless about building robots. I can solder and I have a solid understanding of the AP-level E&M topics (resistors, capacitors, AC/DC, induction, etc), but it has been a very long time since I fooled around with a breadboard. Where should I start? I have all summer and a ton of equipment (oscilloscopes, power supplies, function generators, a huge budget from the school for physics supplies, and my classroom where I can leave poo poo sitting out), but I'm at a bit of a loss as to what it means to make a robot and what I will need to help the students learn it as well. The "we all learn it together! Yay!" method doesn't sit right with me. I want to be prepared with activities for students to do for the first semester to really learn what they need to know. They don't build the actual robot for the competition until second semester, so I have the first half of the year to teach them neat poo poo about electronics for about an hour a week.
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Jun 2, 2012 17:52
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Valdara posted:I am a high school physics teacher as of two months ago. The school needed a quick replacement for a teacher who had to leave, so I stepped in. Yesterday was the last day of classes, and two of my students came up and asked me to be the adviser for the robotics team. I said hell yes, because robots are awesome. My degree is in engineering, and I took an EE course in college, but I am pretty clueless about building robots. I can solder and I have a solid understanding of the AP-level E&M topics (resistors, capacitors, AC/DC, induction, etc), but it has been a very long time since I fooled around with a breadboard. I don't have experience with any of them, but Google for "school robotics kits". There's lots (several?) of them geared for this type of stuff.
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Jun 2, 2012 18:57
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Thermopyle posted:I don't have experience with any of them, but Google for "school robotics kits". There's lots (several?) of them geared for this type of stuff. I've already done that, but most of them are "here is a list of parts and a list of instructions. Follow the instructions and BAM! Robot!" rather than actually teaching them about electronics and components. I don't want them to only be able to follow an algorithm. I want them to be able to reason using electronic components and understand how they work.
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Jun 2, 2012 20:05
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Valdara posted:I've already done that, but most of them are "here is a list of parts and a list of instructions. Follow the instructions and BAM! Robot!" rather than actually teaching them about electronics and components. I don't want them to only be able to follow an algorithm. I want them to be able to reason using electronic components and understand how they work. Look for some of the FIRST or BEST oriented stuff. As the rules of the contest change year by year, much of the information out there is oriented around how to create a new design to solve the problem, rather than how to follow a set design. There are some good books out there, and some great postmortems.(even a book on postmortems) In addition, many (all?) competition robots are designed around the same chassis. Putting together one of these could be a good way to do the first half of the year. Looking at such a chassis would start giving you the ideas for the interrelationships between mechanical and electrical systems. If what you're working on is for one of the robotics competitions, I'd see if you could one chassis over the summer yourself, and put that experience towards having the class build the second. Two chassis let you do all kinds of experiments with refining different elements while still leaving you with a good base to work with in the mean time. If you're talking more about BEAM robotics, I don't really have much in the way of advice though. Much of the complexity of the large robotics competitions is in the mechanical side, as they are basically large remote controlled devices. Electronics and programming is mostly in the form of motor and solenoid controls, automation is typically very limited, subsystems and the like. BEAM robotics have all the mechanical challenges combined with the learning curve of electronics. You could look in the robot thread. It's not that busy though. More activity would be a good thing.
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Jun 2, 2012 21:12
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Valdara posted:I am a high school physics teacher as of two months ago. The school needed a quick replacement for a teacher who had to leave, so I stepped in. Yesterday was the last day of classes, and two of my students came up and asked me to be the adviser for the robotics team. I said hell yes, because robots are awesome. Robots are awesome! What are they doing competition-wise? Is it a big competition like FIRST, is it remotely operated or autonomous?
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Jun 3, 2012 09:20
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Delta-Wye posted:Robots are awesome! What are they doing competition-wise? Is it a big competition like FIRST, is it remotely operated or autonomous? It is FIRST. I have kinda browsed around the website, but I have not done any real research on what it requires. That is on my list of things to do this summer, though!
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Jun 3, 2012 23:24
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Valdara posted:It is FIRST. I have kinda browsed around the website, but I have not done any real research on what it requires. That is on my list of things to do this summer, though! Oh gently caress dude, you just volunteered yourself for a huge timesink. You need to find a good core of volunteer parents, fast. Machinists, engineers, programmers, etc etc (not just technical folk...you need/can get kids involved in marketing for your team, participating in the video competitions, etc). FIRST can get absolutely insane during the season.
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Jun 4, 2012 05:37
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movax posted:Oh gently caress dude, you just volunteered yourself for a huge timesink. You need to find a good core of volunteer parents, fast. Machinists, engineers, programmers, etc etc (not just technical folk...you need/can get kids involved in marketing for your team, participating in the video competitions, etc). FIRST can get absolutely insane during the season. Eh. I have a philosophy of not killing myself to make these things happen. If the kids are interested and motivated, then it's up to them to make it happen. I will advise, I will help, I will organize, but I will not make myself crazy over a damned robot. The legwork is on them.
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Jun 5, 2012 06:21
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Valdara posted:I will not make myself crazy over a damned robot.
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Jun 5, 2012 14:03
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Dielectric posted:An STM32-based OBD2 scanner would probably be a worthwhile effort, if you really want to learn OBD2. I was thinking of doing this but gently caress it for now I'll just throw together an instantaneous MPG sensor thing with the stn1110. It's moderately lame that cars don't (generally) report instantaneous fuel usage btw.
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Jun 5, 2012 22:59
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ok, so i have a max232 chip on a circuit that I was powering from a dc power supply. Everything was great. I could communicate over serial at a good 200ft of cat6 no problem. I hooked it up via a battery(12v car battery, not in a car) and lost communication. First thing I did was check the power. The circuits good, everything is powering up ok and getting the correct voltages. Second thing I did was swap the 200ft cord for a 6ft. Still no communication. I suspected something to do with ground. I don't really understand what would be different between a bench power supply and a battery in that respect, but I shorted the ground pin on the pc's serial port directly to the ground pin on the battery and it started working. Can someone explain what's going on?
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Jun 6, 2012 06:06
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Otto Skorzeny posted:I was thinking of doing this but gently caress it for now I'll just throw together an instantaneous MPG sensor thing with the stn1110. It's moderately lame that cars don't (generally) report instantaneous fuel usage btw. A lot of newer cars do exactly that. I've heard it's more common on trucks. Some of the newer nissans including my 2011 370Z reports fuel consumption, instantaneous, trip average, estimated miles till empty, etc.
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Jun 6, 2012 06:22
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Can/should I use any ole' DC-to-AC inverter in a vehicle for charging NiCd and lithium ion power tool batteries or is there something in particular I should look for when purchasing one?
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Jun 6, 2012 18:16
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Thermopyle posted:Can/should I use any ole' DC-to-AC inverter in a vehicle for charging NiCd and lithium ion power tool batteries or is there something in particular I should look for when purchasing one? Lithium Ion batteries are totally different beasts and you definitely want a charger that understands the 3 phases of proper charging. 1) 0.1C constant current until voltage exceeds 2.5V. 2) 1.0C constant current until voltage reaches 4.2V (of a 4.2V-rated cell) 3) Constant 4.2V charge until current drops below 0.1C I've charged some small 50mAh Lithium Ion cells using a 4.2V source and a resistor, but I'd recommend getting a real charging circuit if you plan on charging unattended. I use a MCP73831-2 when I need to build a Li-Ion charging circuit. Also remember you shouldn't charge multiple batteries in parallel with a single charge monitor, as different batteries will charge at different speeds. Super-cheap dealextreme chargers usually have one charge monitor for all batteries which is just an accident waiting to happen. NiCd batteries I believe release hydrogen when the reach full charge...
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Jun 6, 2012 21:12
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^ I think he's asking about a car inverter that a standard tool battery charger can be plugged into. Thermopyle posted:Can/should I use any ole' DC-to-AC inverter in a vehicle for charging NiCd and lithium ion power tool batteries or is there something in particular I should look for when purchasing one? You shouldn't need anything fancy, really, just something rated for enough power. Unlike a power tool (for instance), a charger won't be creating huge spikes of current, and should be pretty steady (typical Li-Ion chargers use a constant current - constant voltage scheme wherein they limit both the maximum charge current and the maximum charge voltage. First the charger puts out just enough voltage to put the maximum current into the battery. After it's about 90% charged, the charger will have increased it's output to the maximum voltage, at which point the current drawn by the battery will be diminishing). What this means is your inverter doesn't need to be rated much higher than the listed input power of the charger (there is a word for this that I completely forget....), whereas you'd probably want to do so for like an AC air pump or something. Or at least, that's what makes sense to me. Never had to use an inverter. Obviously something from Harbor Freight will be must more likely to mysteriously stop working than one from sears, but you can probably get something that is both reliable and reasonably priced from Amazon. Also, might want to make sure that it has user-replaceable fuses.
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Jun 6, 2012 21:45
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Really cheap DC-AC inverters put out square waves with the proper RMS voltage; these are godawful and won't work right with sensitive AC devices. For stuff like laptop power supplies, they are usually fine. I'm not sure where a charger sits on that continuum. Would it be possible to get a battery charger that will run off of 10-14V DC directly?
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Jun 6, 2012 22:06
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Slanderer posted:^ Yeah. Slanderer posted:good info Thanks. Delta-Wye posted:Really cheap DC-AC inverters put out square waves with the proper RMS voltage; these are godawful and won't work right with sensitive AC devices. For stuff like laptop power supplies, they are usually fine. I'm not sure where a charger sits on that continuum. Would it be possible to get a battery charger that will run off of 10-14V DC directly? Ahh, yes. A quick Amazon search shows the pure sine wave inverters are probably what I need. I have power tools from like 4 different manufacturers. While they probably all make DC-to-DC chargers, they're around $100 bucks from each manufacturer. I've already got the AC battery chargers and a pure sine wave inverter looks to cost around $150 for the wattage I'd need. I wonder how hard it would be to build a DC-to-AC inverter myself? Good beginners electronics project?
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Jun 6, 2012 22:11
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Delta-Wye posted:Really cheap DC-AC inverters put out square waves with the proper RMS voltage; these are godawful and won't work right with sensitive AC devices. For stuff like laptop power supplies, they are usually fine. I'm not sure where a charger sits on that continuum. Would it be possible to get a battery charger that will run off of 10-14V DC directly? I'd imagine that chargers with linear regulators wouldn't care *that* much about the harmonics, but simpler switching regulators might--I'm no expert on that, though. Laptop power supplies are generally pretty sophisticated, though, so I can see why they could handle a really lovely waveform....yet I'd really be hesitant to do it, though. Thermopyle posted:I've already got the AC battery chargers and a pure sine wave inverter looks to cost around $150 for the wattage I'd need. Wait, really? Are you connecting up multiple battery chargers at once or something? That's just a lot more than I would've expected this to cost you... Thermopyle posted:I wonder how hard it would be to build a DC-to-AC inverter myself? Good beginners electronics project? Nope! Power electronics are never good for beginners, due to a bunch of added requirements (proper component ratings for the required power, proper temperature ratings for the components, just heat in general, not starting a fire in your car, etc...) It doesn't help that DC-AC is somewhat complicated to do correctly--modern inverters are waaaay out of hobby league in terms of design, and require knowledge of a bunch of different subject areas. Making a simple AC-DC converter using a transformer, full wave rectifier, and a linear regulator is dead simple, on the other hand.
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Jun 6, 2012 22:27
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