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Probably the same reason you see capacitors listed as 330,000 uF instead of 330 mF. (ie: none)
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Jun 10, 2013 05:03
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Since the previous two posts weren't really clear on it, the reason the antenna is necessary is because the power for the passive tag you're reading comes from the reader. The antenna in the reader and the antenna in the tag are tuned to each other, and basically form an air-core transformer; powering the reader creates an EM field that induces a few microamps of current in a nearby tag's antenna, and that tiny current is enough to power the chip and tell it to read back its ID number. So, if you cut the antenna off, you won't just be "losing range", you'll be ruining the carefully tuned system that allows the reader to transmit power to and activate any nearby tags.
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Jun 13, 2013 04:04
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Put it in a faraday cage! 
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Jun 18, 2013 04:55
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Slanderer posted:However, I would probably ignore the flex PCB and repair the traces manually. Those 3 traces go to 2 passives and an IC,and look like you should be able to tack on wirewrap wire to the existing solder joints and then run those wires to wherever the flex circuit terminates. Along the way, you'd tack the wires to the flex circuit in a few places with silicone adhesive or something. Wirewrap wire is really thin, but may still be too big to work here... Just thought I would say that this is exactly my suggestion, too. Don't try to fix the flexible traces...you'll melt the substrate and lift the traces and it will be a giant mess. Running Kynar wire-wrap wire from the components at each end is a much better idea. I think with a good iron tip and a steady hand you should be able to to make the joint.
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Jun 24, 2013 23:09
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Delta-Wye posted:Tons of good information there. I guess I was mostly talking about the "lets just plug this in and see what happens" breadboarding at my desk. Nothing wrong with that. There's too much good practice in this thread anyway; don't keep that magic smoke all cooped up inside all the time!
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Jun 26, 2013 00:46
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Rescue Toaster posted:a bridge too far 
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Jun 30, 2013 04:51
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I like Fritzing 
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Jul 2, 2013 22:07
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I have a Hakko 936/907 and use the T18BL for small stuff like SMD resistors (http://www.amazon.com/Hakko-T18-BL-Soldering-FX-8801-Conical/dp/B00762AGTA), and it works well for that, but to solder the little fine-pitch ICs I think you'd want something in a similar size but with the oblique tip that looks like they sliced the edge off a cone at an angle. I've never tried soldering an SMD IC before so I dunno though.
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Jul 3, 2013 03:02
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I was going to say that your battery is dead, because that sounds exactly like what happens to cheap multimeters when they have dead batteries. Not that the Extech is cheap -- I have a 330 and it's excellent -- but I've only ever seen that mystery failure mode with cheap ones because the expensive ones have a low battery warning indicator that comes on before they start to screw up. Are you sure the batteries are good? If that's not it, did you do something kinda dumb like try to measure a high voltage when you were in current mode? Some of the modes connect the meter's probes to a huge internal resistor and some have effectively no resistance, so it is certainly possible to burn the meter out if you hook it up the wrong way in certain modes. Also check the internal fuse. If it's blown, replacing it may or may not fix it, but at least it'll tell you that you did a no-no at some point.
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Jul 13, 2013 01:23
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I think the usual way of building an anemometer is with a small DC motor with the little paddles on it. Build a voltage divider to get the value down to the 0-5v the Arduino can handle, and don't forget the diodes.
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Jul 14, 2013 05:22
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I'd love to see some pictures of those, if you have any. Sounds super cool.
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Jul 20, 2013 22:32
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A hobby radio-control grade lithium polymer pack is the ideal mix of size, weight and energy density. I power the various lights and electronics on my biycle  with the Zippy 20C packs from HobbyKing and they work great.However, the thing about lithium packs is that they have to be charged carefully so that you don't blow them up. If you used regular heavy old nicads or nimh cells, you could essentially just hook them up to the dynamo with a diode and go. With lithium cells you need to regulate the charge with something like this unit from Adafruit: http://www.adafruit.com/products/280 That unit will only charge single cells (for safety reasons), so you're limited to the nominal 3.7v provided by a li-poly cell. If you're planning to drive a phone charger or run a 5v microcontroller you'll need a boost converter to bring the voltage up to the proper level: https://www.sparkfun.com/products/10255 As an aside, in my case, I actually use 3-in-series (11.1v nominal) li-poly packs rather than the single-cell type. The ~12v source lets me run things like electroluminescent wire inverters at higher efficiency; to power the central microcontroller I have a little 5v buck converter, and the head and taillamp LEDs are all running on their own constant-current driver boards that accept the 12v in with about 80% efficiency. I don't have any generators or dynamos and just charge the packs with a regular balancing charger. e: the charger that you linked to is pretty poorly constructed (a perfboard just sitting out in the open on the wheel in San Francisco weather?) and will be inefficient at high speeds. The linear regulator is an especially poor choice if he's seriously producing 30 volts at the generator going downhill but needs 5v for the phone. If you want to build something like that, at least put it in a good waterproof case please, and there are much better options (buck converter) for bringing the voltage down more safely and efficiently. Sagebrush fucked around with this message at 04:20 on Jul 21, 2013 |
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Jul 21, 2013 03:49
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Do consider that a 9v battery has something like a 200mAh capacity already, and burning up nearly half of that as waste heat will mean incredibly lovely battery life. Is it worth the $3 to not have to replace batteries all the time? e: looked it up and typical power consumption for an ATMega328 running code is roughly 12mA, so add that to whatever else you'd be driving off the board (a single 5mm LED: 15-30mA) and I think you can see the problem. Sagebrush fucked around with this message at 01:32 on Aug 6, 2013 |
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Aug 6, 2013 01:26
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When I need a little buck converter for an electronic project, I tend to use these: http://hobbyking.com/hobbyking/store/__15212__HobbyKing_Micro_UBEC_3A_5v.html They're designed for radio control usage and so are pretty small and light. Not a great package if you're trying to make a PCB, obviously, but for hackery stuff where you're just going to cram it in an Altoids tin they're fine. Cheap, stable and pretty efficient (70-90% depending on draw and input voltage). Also note that that unit will source up to 3A vs. that TO-220 drop-in replacement's 0.5A -- much better if you're going to be running little motors, strings of high-powered LEDs, etc. As asdf32 says, boost converters are a little harder to find, but here's one designed to take 3.2-4.2v from a single lithium-polymer cell and boost it to 5v for your Arduino or whatever. Same sort of package as the buck above but still nice and compact. Very nice for when you don't have a whole lot of power requirement but need to squeeze as much energy from your battery as you can. http://hobbyking.com/hobbyking/store/__11784__TURNIGY_Voltage_Booster_for_Servo_Rx_1S_to_5v_1A_.html Sagebrush fucked around with this message at 04:31 on Aug 6, 2013 |
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Aug 6, 2013 04:29
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That seems right to me. I bet you could also do a neat timed restart by adding some circuitry to power the relay with a capacitor connected to the line.
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Aug 14, 2013 00:25
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I'm thinking you should get that powerswitch tail and hook it up to an Arduino with an xbee, then build a second Arduino + xbee into a box with a button on it and put it wherever you want. Then you have the flexibility to reprogram it whenever you want.
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Aug 15, 2013 06:16
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demonachizer posted:http://makezine.com/projects/Sous-Vide-Immersion-Cooker/ If you have literally zero experience, try this: http://learn.adafruit.com/sous-vide-powered-by-arduino-the-sous-viduino/sous-vide You don't get the aquarium pump water circulator (though you can easily add one), but the rice cooker has much better insulation than that plastic container he's using. The design is also actually more modular than it looks because the complicated part, the PID controller, is all separated from the heater and vessel, so if you want to upgrade later to something bigger it's quite straightforward.
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Aug 31, 2013 02:44
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reading posted:Heat shrink tubing makes my stuff look so pro if I trim it nicely.  62.5 volts into a 7805? Don't put it on any flammable surfaces!Yes, your best option here is an appropriate switching regulator. You aren't going to get a whole lot of efficiency stepping the voltage down that much, but at least you won't be burning up 93% of the energy as heat and instantly detonating your poor 7805. Out of curiosity, what on earth uses a 62.5 volt battery? The only things I can think of are those really old portable ham radios and the like that needed the high voltage before boost converters or charge pumps were invented.
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Sep 4, 2013 21:23
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Here's a $6 driver circuit that only needs the one wire: http://www.hobbyking.com/hobbyking/store/__18002__HobbyKing_Red_Brick_10A_ESC.html
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Sep 4, 2013 21:57
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Bridgeport posted:So I need some advice regarding a new soldering iron and multimeter. I'd like to try building up a headphone amp, and I have an electric R/C car and an R/C heli that I'd really like a meter for troubleshooting. Soldering station: Weller WES51 or Hakko 936 (currently discontinued, so get one on eBay, or if you need something new it's been replaced with the goofier-looking but arguably even-more-functional FX-888). Both are heavy-duty temperature-controlled stations that will be able to handle 8ga wires just fine if you use one of the larger tips. I personally like analog controls but the WES51 also comes in a digital variant. There are Chinese knockoffs of each that you can get for pretty cheap, but having tried a few I'm not totally sold on the build quality. The Wellers and Hakkos will last the rest of your life. Multimeter: I don't own any Flukes so I can't speak to those, but my everyday meter is an Extech EX330 and it works just fine for everything I've done so far. It goes down to microamps, it's fast, has automatic or manual ranging, and it has an audible continuity tester which is great because when you're building stuff that's the function you'll be using like 80% of the time.
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Sep 11, 2013 01:13
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For #1 I agree with Stabby McDamage (there's a sentence that has never before been uttered) -- get whatever is available on eBay. Shipping an epacket from China is usually a week or two but they'll do the job fine. If you have Amazon Prime and want something fast, this is a good deal: http://www.amazon.com/Bluecell-White-Electronics-Ultra-Bright/dp/B005ONQ41W/ For #2, it's probably going to be easier to solder the LEDs when they're glued in place...but if you screw up, it's a lot easier to fix if they're all still discrete parts. You choose. For #3, the differences are complicated but I'd prefer the AA or AAA route just because the batteries are cheaper and you'll waste less power for various physics reasons. 9-volts are really expensive for what you get. Also, regarding resistors...the standard values that are available are selected so that if you can't find the exact resistance you need, you pick the next closest value and you'll never be off by more than 10%. +/-10% is perfectly fine for something like an LED. You want 87 ohms, the next closest is 82 ohms, but 100 will also be fine.
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Oct 2, 2013 03:32
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If you're mechanically-inclined, you might be able to make some kind of system to push the LED in and out of contact with the battery to turn it on and off, but no, there aren't any better ways of adding a separate switch than soldering one in place. It's the best way of bonding metal to metal short of actually welding. Soldering really isn't too hard to pick up, though soldering wires to a coin-cell battery can be tricky. A $15 radio shack starter kit would probably do fine -- I wouldn't recommend one if you were wanting to get into electronics as a hobby, but a soldering iron is a good thing to add to your toolbox if you don't already have one.
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Oct 6, 2013 21:50
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Zero Gravitas posted:Need your help, goons. This isn't a software thing at all, it's hardware. It's a simple 3-pin potentiometer, right? Left lead to +5v, right lead to GND, center lead to the analog input. The potentiometer functions as a voltage divider, and you're probing the center point between the "two" resistors it forms as you turn the dial. If the numbers still float in that case, then maybe you have a broken board, yes, but I bet it works fine in that case. e: and to expand on the above, if you need to convert the value from one range to another, try this int Res0 = 0; float Var0 = 0; Res0 = analogRead(0); Var0 = map(Res0, 0, 1023, 0, 100); //where 100 is the maximum value you want as an output Serial.println(Var0); also don't capitalize your variables
Sagebrush fucked around with this message at 19:05 on Oct 11, 2013 |
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Oct 11, 2013 19:01
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Check the potentiometer. Get your multimeter and set it to an appropriate range (probably the 2k or 20k range if it's not auto-ranging) and probe between the center pin and either one of the side pins. Turn the dial slowly and make sure the resistance goes smoothly from 0Ω to 10kΩ or whatever the maximum value is. It's a linear pot, right? Not an audio pot? That wouldn't cause the values to change randomly but it would give you an unexpectedly bizarre output.
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Oct 11, 2013 19:26
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It's not enameled magnet wire, is it? That stuff behaves as you describe but it's supposed to be that way. If you mean they're the little patch cables with solid pins on each end, and the supplier put plastic insulation over each pin, wow. Just wow.
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Oct 11, 2013 21:53
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Depends on the battery chemistry. Some (lead-acids, nicad, NiMH) you can just stick on a constant-current charger at some low value forever and they won't be harmed. For instance, you can happily maintain a car battery on a 12v 250mA wall wart with stripped wires. Other kinds of batteries (mostly lithium chemistries) are really bad at handling overcharge and need to be carefully monitored when they reach the end of the cycle. The best smart chargers out there usually have a three step process: 1) Charge at constant current equal to ~1C (1x the capacity per hour; a 2.2Ah battery charging at 1C draws 2.2 amps) until the battery voltage reaches its peak. For a completely dead battery this will be around an hour. 2) Switch to constant voltage mode and maintain the battery at peak voltage, decreasing the current as needed to prevent the voltage from rising. How long this takes depends on self-discharge, ion mobility within the battery, and a whole pile of other things. 3) Depending on the chemistry, either continue reducing the current until it's a trickle charge that matches the self-discharge rate (best practice for lead-acid, etc); or continue charging until the charge current is about 2% of the peak current, at which point you call it charged and terminate the cycle to avoid starting fires. I don't know of any chargers that are smart enough to figure this out on their own so you usually have to at least tell them whether it's a lithium battery or not. When your iPhone does its fast charge thing that brings it from dead to 80% in an hour, it's basically just doing step (1) and maybe even boosting above 1C depending on how confident the Apple engineers were in their battery supplier's quality control. The remaining hour and a half it takes to get to 100% is steps (2) and (3). I've built constant-current and constant-voltage power supplies before, but I'm kind of foggy on the schematics right now so if you're asking how the electronics specifically work someone else can probably answer that better than I.
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Oct 22, 2013 07:07
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There's generally also a regulator in there somewhere, since the alternator speed depends on engine speed (in my motorcycle, the rotor is literally mounted on the crankshaft) so when you rev it up high the voltage goes sky-high too. Without the regulator you can easily see 30-40 volts at the rectifier, plenty high to boil off all your electrolyte. e: though I think more modern vehicles that have more space use energized rotor windings, so that you can vary the magnetic field and hence the voltage more efficiently than a chop-off regulator Sagebrush fucked around with this message at 07:26 on Oct 22, 2013 |
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Oct 22, 2013 07:22
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Laserface posted:to summarise: Coils are wound in the factory by spinning the coil while a spool of wire moves around it. It's sort of like a weaving loom: https://www.youtube.com/watch?v=6lvm3FGTHSI You can do stuff like this yourself, although more slowly, with a power drill and some cleverness. The more turns in a coil, the more powerful the magnetic field. You can also increase the field by increasing the current, or by making the coil itself smaller (narrower radius). The gauge of the wire doesn't directly affect the field strength, but it does affect indirectly through the number of turns you can fit into a given space (larger wire = fewer turns) and the amount of current the coil as a whole can carry (larger wire = more current). I don't remember the laws exactly but there are lots of quadratic functions so the tradeoffs get fairly complicated.
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Oct 25, 2013 00:07
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Bad Munki posted:Anyhow, if my understanding is correct, the power induced in the coil will be AC, but will be oscillating super duper fast, meaning the LED will have like a 50% duty cycle but at something like 150khz at least so that should be okay (150khz is just the value from the plans I'm working off of...sounds like it can be much, much higher. That's okay too, I think.) I guess I could add some stuff to convert it to DC but I want to keep this as absolutely dirt simple as is possible. How big is the capacitor you're putting in there? I think it would be elegant to use the LED itself as the diode in a half-wave rectifier, with an appropriately sized capacitor to keep it from sagging too much. Just make sure that the LED is rated to take the largest reverse voltages you're expecting.
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Oct 27, 2013 04:00
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So I'm working on a system of bicycle lights using electroluminescent wire and tape. This stuff needs to be driven with high-frequency AC, maybe 200v and 3kHz. Ideally, I'm shooting to have six different channels of lights driven by a single inverter, switching them on and off with triacs. If all the channels are disabled, though, there'll be no load connected to the inverter output and the voltage will spike, damaging it, right? That's what I have been told about these inverters anyway. I could program it to never have all the channels disabled, but I'd rather have the flexibility to do so if possible. I assume that I can solve this just by connecting a capacitor across the inverter output so that it's always got something to push against and stabilize its output. Will that work? If so, how can I calculate an appropriate value for that capacitor, and what type should I use?
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Nov 3, 2013 01:43
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Hmm. I've also had no real problems running other EL inverters with no load before, but every place I can find online suggests that it's a bad idea and these ones came stamped with a warning. So I really do want to have some sort of protection circuit in place just in case. I realized that my multimeter has a capacitance function I've never actually used! I tested a few of the lengths of the EL tape and a meter averages around 40-50nF. So at least that value's easy; 47nf should do fine. When measuring for resistance...there's no continuity between the two contacts, obviously. Measuring along the length of one wire, by probing the contacts on each end (I assume this is the core) gives me 15k resistance for the 1-meter length. The other wire (which I assume is the corona) reads 1.5 megaohms. What should I do? Just hook a 1.5M over the output and call it a day, or do something more complex?
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Nov 3, 2013 03:38
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Are there any products that are currently out on the market that you worked on? Most NDAs are okay with you saying that you worked on something after it's put on sale, as long as you aren't revealing trade secrets or whatever. Then again if you were working for a company as an outside contractor they may not want that fact publicized so I dunno. It's always hard to balance. Part of why I try to maintain an interesting side practice of my own projects, so that I always have something to talk about and show if the need arises.
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Nov 7, 2013 22:49
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Terminal Entropy posted:Any suggestions to improve the structure of this: Uh...what is it, exactly? A right-angle USB adapter?
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Nov 9, 2013 04:57
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It looks like that part has a type 3B taper, which means it's a linear potentiometer, right? If you don't know, you can check to be sure by measuring the resistance. If it's linear it will be exactly half the rated value when the dial is centered. If it is a linear pot, then electrically the arrangement of the outer wires doesn't matter -- as long as you have "IN" on one side, ground on the other and C2 connected to the middle pin, it'll work. Reversing the outer wires will reverse the direction of the dial. Sagebrush fucked around with this message at 19:00 on Nov 10, 2013 |
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Nov 10, 2013 18:56
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Eight pins? Uhm...you'll have to talk to someone else. That sounds more like a rotary encoder to me. Even a regular pot with an on-off switch shouldn't need more than five.
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Nov 10, 2013 19:41
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If the tip is oxidizing instantly, it's way too hot. Irons that don't have temperature controls will often shoot up to like 500 degrees (celsius) when you should be at more like 270-300. This is good when you're soldering big fat wires in your car or whatever but it's terrible for microelectronics. I use a Hakko 936 for 95% of the stuff I do and it's just great. They don't make those any more but the FX-888 is basically the same thing if you can take the crazy colors. For the other 5% I use a Portasol butane iron that is also excellent.
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Nov 21, 2013 20:03
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Cyril Sneer posted:What is everybody's thoughts on these two irons? I dunno, soldering irons are one of those tools where you really get what you pay for and the $100 is well worth the saved time and headache. Years ago when I was a college student I wasn't sure I wanted to spend that much (plus 25 dollars shipping!) to upgrade my iron, but the Hakko made such an enormous and immediate difference that I felt it paid for itself on the very first project. That said, Adafruit recommends this iron if you're not looking to go all the way to a station, and they won't steer you wrong: http://www.adafruit.com/products/180
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Nov 25, 2013 05:03
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When that happened to me, I started making little men and horses and things out of little bits of wire soldered together. Try it!
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Nov 25, 2013 05:19
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Well I think it depends on how far you want to go with "clone". Do you want to program it over USB? Then you'll need the bootloader, yes, but also a USB-to-serial chip. Or a 32U4 instead of the 328 but you still need the USB hardware. Do you want it to be compatible with the shields? Then you need the headers in the right places and connected to the right pins. Do you want it to have the 3.3v and 5v lines like a real Arduino? Those come from the regulator, not the board, so you'll have to add those yourself. The LED and internal resistor on pin 13? The automatic reset? What exactly do you want to do with your Arduino clone, incidentally? I used to look around at clones and bought a few cheap ones but eventually I started just using the Arduino IDE but burning the chips directly (still using an Arduino as the programmer though) and really you can't beat that combination of price and ease of use.
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Nov 25, 2013 11:05
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| # ¿ May 8, 2024 20:50 |
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Xovaan posted:What would you guys recommend for a multimeter? My shop one got stolen a while back and I've been using a $5 Harbor Freight one for the time being. This is my primary meter and I have yet to find anything wrong with it: http://www.amazon.com/Extech-EX330-Autoranging-Multimeter-Thermometer/dp/B000EX0AE4. It does pretty much everything the average electronics hobbyist would want this side of an oscilloscope. I use it in voltage or continuity test mode probably 85% of the time, and I have never used the frequency or duty cycle functions. The weird gimmick thermocouple thermometer has actually come in useful a few times, surprisingly. The best feature is the beep when testing connectivity. You have no idea how much it sucks to try to check connectivity by watching a resistance value on the screen until you've tried it the other way and had to go back for a while. Sagebrush fucked around with this message at 02:46 on Nov 27, 2013 |
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Nov 27, 2013 02:44
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