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Brekelefuw posted:etches I was trying this weekend were just on scrap brass, bronze and nickel silver. The nickel silver is the only metal that has a great looking etch. The rest etch quickly and then the amps go to 0. I think it's forming an oxide layer or something, which is preventing conductivity. Change up your electrolyte. Put a little bit of acid in there, start with acetic or citric (vinegar/lemon juice) then move up to muriatic. I'm not entirely sure what the peroxide is for; it's typically not considered an ionic electrolyte species. Note that alumimum very very quickly forms an oxide layer. Get a stainless steel scrubby and then wrap your cloth around that.
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Sep 6, 2017 01:08
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Zero VGS posted:Yeah, I just googled a high-end 12v inverter and it has the cutoff range 10v up to 15v, so that might work OK with 3 in series, it'd cut off once the voltage sags below 3.33 per cell which is about where they're dead anyway. I did a few tests and gave up on the inverter as not really worth it (I'll just use it in the car; the only thing i was really going to use it with is my laptop anyway), instead I wired up some LED strips to a boost converter and am going to use the 18650's to power those so I have a nice bright room-filling light in addition to my flashlights and smaller lantern. I will probably pick up one of those power banks you listed though for later, that does seem real useful, thanks!
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Sep 6, 2017 05:26
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babyeatingpsychopath posted:Change up your electrolyte. Put a little bit of acid in there, start with acetic or citric (vinegar/lemon juice) then move up to muriatic. I'm not entirely sure what the peroxide is for; it's typically not considered an ionic electrolyte species. Note that alumimum very very quickly forms an oxide layer. Get a stainless steel scrubby and then wrap your cloth around that. I had read somewhere that adding hydrogen peroxide helps make it more effective because of the extra hydrogen in the water.
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Sep 6, 2017 14:35
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I was looking for a transistor/MOSFET to go with my Arduino/LED strip project, oh my there are a lot of them. Will most normal ones handle my 12V and 2-3A requirements? This seems pretty low demand considering electronics in general, and ploughing through all the data sheets strikes me as being a sedative
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Sep 6, 2017 16:59
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Fat Turkey posted:I was looking for a transistor/MOSFET to go with my Arduino/LED strip project, oh my there are a lot of them. Will most normal ones handle my 12V and 2-3A requirements? This seems pretty low demand considering electronics in general, and ploughing through all the data sheets strikes me as being a sedative I buy nothing but IRLB8721's now. They're fairly cheap, work with 3.3V logic, and they're comical overkill for most applications. Adafruit, Amazon, eBay from China.
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Sep 6, 2017 17:14
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Fat Turkey posted:I was looking for a transistor/MOSFET to go with my Arduino/LED strip project, oh my there are a lot of them. Will most normal ones handle my 12V and 2-3A requirements? This seems pretty low demand considering electronics in general, and ploughing through all the data sheets strikes me as being a sedative Go to https://octopart.com/ and you can basically specify the ranges of things you want in a MOSFET and it will find them for you, without having to read datasheets (or at least not read that many datasheets) Also seconding the IRLB8721 recommendation if you don't feel like that either
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Sep 6, 2017 17:39
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Thanks for the quick posts, want to play with the Arduino / LED strips tonight so I'll use the database to check I'm getting something compatible and pick it up tonight, but in the long run will order some N and some P to cover future projects.
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Sep 6, 2017 17:49
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Brekelefuw posted:I had read somewhere that adding hydrogen peroxide helps make it more effective because of the extra hydrogen in the water. "Extra hydrogen in water" means a lower pH, which means an acid. If you want more hydrogens, add acid. The peroxide may act as an oxidizing (or reducing?!) agent for metal ions, but that's probably not important for etching.
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Sep 6, 2017 22:54
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babyeatingpsychopath posted:"Extra hydrogen in water" means a lower pH, which means an acid. If you want more hydrogens, add acid. The peroxide may act as an oxidizing (or reducing?!) agent for metal ions, but that's probably not important for etching. Just did some reading. The hydrogen peroxide helps oxidation of copper molecules which allows the creation of copper chloride, which is the starter for making a copper etchant. I guess I will remove that and try adding acetic acid or maybe something stronger. I do have a jug of ferric chloride, but I want to try to stay as clean as possible.
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Sep 7, 2017 00:07
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Brekelefuw posted:Just did some reading. Hydrogen peroxide works very well for speeding up ferric chloride for etching copper circuit boards. The downside is drugstore the hydrogen peroxide you can easily buy is very diluted, so you need to add a bunch, which also dilutes the etchant. I prefer using an aquarium bubbler for etching boards though. That way you don't end up making more and more dilute etchant. The highest convenient hydrogen peroxide concentrations are only 30%, which is still a lot of water to be adding. On top of the fact that the hydrogen peroxide breaks down into oxygen and yet more water. babyeatingpsychopath posted:"Extra hydrogen in water" means a lower pH, which means an acid. If you want more hydrogens, add acid. The peroxide may act as an oxidizing (or reducing?!) agent for metal ions, but that's probably not important for etching. Depends on the metal. Some metals need to be oxidized before they can be effectively dissolved (etched). Take the famous example of gold and aqua regia. Neither sulfuric acid or nitric acid acid can effectively dissolve gold alone, but the combination can. Nitric acid doesn't react with gold, it's not a strong enough oxidizer. Sulfuric acid is, but gold sulfate doesn't dissolve, and the reaction itself isn't particularly favored. In aqua regia the sulfuric acid created a sufficiently oxidizing atmosphere for the nitric acid to actually react with the gold, forming gold nitrate which dissolves. Brekelefuw posted:PS. With 15-24V at lets say 1A, will I die? With dry hands you can touch it all day long even if it had hundreds of amps (or more!) going though it. Unless the part was getting hot from all that current, then you'd get a regular burn. What matters here is your skin's resistance, not the current going though the part. If you get your hands wet your resistance could easily drop to the point where that voltage range could give you a serious injury.
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Sep 7, 2017 04:51
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Aurium posted:Depends on the metal. Some metals need to be oxidized before they can be effectively dissolved (etched). Take the famous example of gold and aqua regia. Yeah, acid based semiconductor/metal etching recipes often have peroxide in them. The "etching theory" I have been taught is that the peroxide helps create oxides and that the acid more effectively etches the oxide.
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Sep 7, 2017 14:52
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Stabby McDamage posted:I buy nothing but IRLB8721's now. They're fairly cheap, work with 3.3V logic, and they're comical overkill for most applications. There is a link to them showing up on the ebay page you posted. The IRLB8721 is rated for 30v and 62 amps. The IRLZ44 is rated for 55v and 47 amps. I'm too lazy to do all the math to pick a transistor correctly. :| The learning experience I had with using the wrong mosfet is that if they are not getting enough gate voltage to turn on all the way, then they will allow the expected voltage through, but only a tiny, tiny amount of current. Like, 1/10th if a milliamp. Or less. If you measure the voltage from them it looks normal, but nothing connected to that voltage works???... If you measure the current through them, you see it is only a minuscule amount....
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Sep 7, 2017 20:18
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edmund745 posted:I usually buy IRLZ44's. I think they need 4 volts to turn on tho, so maybe not good for CMOS... I mainly do 5v logic things. It depends on how much gate voltage you give it. Sometimes that happens, other times it's just enough to turn on most of the way but still behave like a resistor and dump half the energy in your circuit into its probably-inadequate heatsink 
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Sep 7, 2017 21:05
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edmund745 posted:I usually buy IRLZ44's. I think they need 4 volts to turn on tho, so maybe not good for CMOS... I mainly do 5v logic things. When they're barely on, they act like a large resistor. If you stick a resistor on a battery and then measure across the battery + resistor you'll measure the full voltage of the battery, it's only when you draw current that the voltage will sag. (Perportional to the current drawn, and the resistance, aka ohms law.) Assuming that you're using a 5v supply, and that your load is a negligible resistance, you're turning on the mosfet well enough for it to be somewhere in the neighborhood of 50k ohms. This is one of the reasons you can't really see if a battery is good just by putting a voltmeter across it, as one of the things that causes a battery to be bad is its internal resistance goes up.
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Sep 7, 2017 21:28
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Aurium posted:Hydrogen peroxide works very well for speeding up ferric chloride for etching copper circuit boards. >30% is getting towards the concentrations where mixtures with organic stuff will spontaneously ignite or explode, so there's a pretty good reason why drugstores don't sell it.
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Sep 8, 2017 06:06
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Speaking of ferric chloride, anyone have any tips for getting stains off everything it touches I made the mistake of cleaning off etched boards in my sink, and now my sink has a brown tinge of a stain on it
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Sep 8, 2017 16:07
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ate all the Oreos posted:Speaking of ferric chloride, anyone have any tips for getting stains off everything it touches Most acids can take care of ferric chloride stains, including weak organic acids if you're patient, or if the thing is delicate. I'd skip straight to CLR though. Chemistry discussion here:
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Sep 8, 2017 16:31
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Has anyone tried driving a HUB75 interface LED module with an ESP8266/32? It seems like it should be possible to at least to some degree, and I'd be ok with just pure RGB without PWM if it meant not messing with FPGAs. edmund745 posted:I usually buy IRLZ44's. I think they need 4 volts to turn on tho, so maybe not good for CMOS... I mainly do 5v logic things.
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Sep 9, 2017 16:44
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mobby_6kl posted:Has anyone tried driving a HUB75 interface LED module with an ESP8266/32? It seems like it should be possible to at least to some degree, and I'd be ok with just pure RGB without PWM if it meant not messing with FPGAs. Definitely possible. People have driven HUB75s with arudinos, and the 8266 is much more powerful. mobby_6kl posted:I got a bunch of FQP30N06s from ebay, lower threshold voltage was a must for working with the ESP. One of the uses is PWM for an RGB led strip, and even though by my calculations they should be able to handle it without any issues, they do actually get uncomfortably hot. Probably not dangerously so, but still. Ether the calculations were wrong, or they're not fully on and there's still some resistance. Hmmm. Threshold voltage is not the voltage they're should be at working at, it's the minimum voltage they can turn on at. Lets take the FQP30N06. If you look at the datasheet, and it says Vgs(th) is 2-4 volts, so it will start turning on in that region. It also says Rds(on) is .04ohms max, but under test conditions for this test, it says Vgs = 10v. That means they're telling you the on resistance when they're applying 10v to the gate. The on resistance when you're applying 3.3v to the gate will easily be an order of magnitude higher, probably worse still. They don't even really give you the graphs required to see if it's a good fit, the closest is figure 2 (Transfer Characteristics) which shows how fast current falls off as you approach the threshold voltage. (which is pretty fast) Another way of looking at it is that at the root of that curve, passed current is 0, so the resistance must be very high, and the root of that curve is ~ 4ish volts (at 25c) Next up, the IRLB8721PbF (also on this page) Vgs(th) = 1.3-2.5, Rds(on) is again specified at 10v and is .008ohms. Whats the resistance where you're actually using it? Who knows! The good news is that if you look at Fig 3 (Typical Transfer Characteristics) you'll see that instead of being at the base of the curve at 3.3v you're up much higher on it, because you're still a few volts above the threshold voltage. This makes this a much better choice for low voltage work. Finally the IRLZ44 Vgs(th) 1-2v. Rds(on) .028 @ 5v. What's this? They're specifying the on resistance at a low voltage? Yep, some actually do put their low voltage performance front and center. In short, this is also a good choice for logic level stuff. Oh, and the IRLB8721PbF is also actually does have a specified resistance at 4.5v, it's in the table, just not on the front page. It's actually .016 max which means it's actually a slightly better choice than the irlz44 here. I just wanted to show that seeing a low Rds(on) or seeing a threshold voltage in the region of where you're working does not tell you enough.
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Sep 9, 2017 21:32
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I'm making some halloween props. I bought a small prop that gives off some sounds like lights when you flip a switch on the front. It's a plastic switch and the way it operates is that is pushes two small pieces of flexible metal tougher to make contact. When off they just spring back away from each other. The prop runs off 3 AAA batteries I want to wire this so it can also control some lights running off 120v. What's the best way to accomplish this? I'm assuming I can't wire that switch with 120v EDIT: I need a relay, of course 
FCKGW fucked around with this message at 22:57 on Sep 9, 2017 |
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Sep 9, 2017 22:22
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I'm looking to control some automated velux skylights and while I'm not giving up on the gateway/protocol angle, it's a tough nut to crack. In the meanwhile I'm investigating options for building a small robotty thing to prod at the touchscreen control with some capacitive prodder(s). What would be the simplest thing that would work to achieve this? Jury-rigged xy plotter with one prodder? An array of individual prodders individually actuated via electromagnets? From looking at the interface I don't think I'd need to drag at any point, just lots of arbitrary touching (like a good second date).
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Sep 10, 2017 13:38
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Aurium posted:Definitely possible. People have driven HUB75s with arudinos, and the 8266 is much more powerful.
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Sep 10, 2017 13:56
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So the USB connector on my phone partially broke and now it only slow charges when any cable is held at certain angles. After looking up how much it would be to send in for warranty service, it would be about the same price if I finally take the plunge into SMD, get a proper hot air station and do it myself. I've done tons of iron work and a few light SMD fixes with one. What all do I need to know? Who makes good rework stations? I understand the solder paste just to hold the tiny stuff in place. What about Kapton tape for protecting nearby stuff on boards? That stuff seems gimmicky to me.
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Sep 11, 2017 18:31
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This perhaps depends on the phone, but mine uses a connector like this: I'm pretty certain these can be done with just some wick and a regular iron with a well tip. Even if the pin pitch is a bit smaller, it should be doable with the same principle: https://www.youtube.com/watch?v=hoLf8gvvXXU&t=436s
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Sep 11, 2017 19:05
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I've been looking at the Sparkfun hot air station for $114, if you really want to buy a tool. It seems to get recommended a lot, and the only complaint I've seen is that the air pressure can't be dialed down low enough for really small pieces.
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Sep 11, 2017 21:16
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kid sinister posted:What about Kapton tape for protecting nearby stuff on boards? That stuff seems gimmicky to me.
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Sep 12, 2017 02:05
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Acid Reflux posted:It actually does a pretty admirable job of protecting the surrounding components from stray solder bits and excessive direct heat, as long as you don't just mash the iron into it or point the air nozzle at it for long periods. It's also great for preventing the inevitable "oops" when you slip and smack your hot iron tip into an unidentifiable (and now missing) 0201 resistor or something. Airplane nerd: It also conducts electricity when you burn it so, ya know, dont burn it.
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Sep 12, 2017 17:55
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CarForumPoster posted:Airplane nerd: It also conducts electricity when you burn it so, ya know, dont burn it.
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Sep 12, 2017 21:20
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eddiewalker posted:I've been looking at the Sparkfun hot air station for $114, if you really want to buy a tool. That seems a bit much, I got this no-name chineese one: https://www.amazon.com/Kohree-Digital-Rework-Station-Solder/dp/B00ITMPQS2/ref=sr_1_3?ie=UTF8&qid=1505255355&sr=8-3&keywords=hot+air+station I've been using it about a year and so far have no complaints at all, it's made desoldering or reworking so much easier i have no idea how I ever got along without one.
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Sep 12, 2017 23:30
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mobby_6kl posted:This perhaps depends on the phone, but mine uses a connector like this: The Nexus 6 is a little different in that it uses a bottom mount connector. I managed to find a couple on Mouser that should work, along with a set of tiny Torx screwdrivers. Those were expensive... Whatever size my phone's screws are, it's smaller than T5, and there's confusion online whether it takes T3 or T4. I'll try it with wick first.
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Sep 13, 2017 00:18
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Jaded Burnout posted:I'm looking to control some automated velux skylights and while I'm not giving up on the gateway/protocol angle, it's a tough nut to crack. If it's just a handful of locations, individual styluses would be the easiest way of going about it. It gets pretty inconvenient when you have a bunch of locations, or when you have things that are close enough to interfere with each other.
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Sep 13, 2017 01:39
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eddiewalker posted:I've been looking at the Sparkfun hot air station for $114, if you really want to buy a tool. For whatever it's worth, I've been pleased with the hot air station Adafruit sells.
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Sep 13, 2017 03:44
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Is the nRF51822 a good choice for a noob to make something with BTLE? I want it to mostly sleep and sample i2c and analog sensor data occasionally and send it to ESP32 (which I don't have yet either). My "supplier" has only that and TI CC2541.kid sinister posted:The Nexus 6 is a little different in that it uses a bottom mount connector. I managed to find a couple on Mouser that should work, along with a set of tiny Torx screwdrivers. Those were expensive... Whatever size my phone's screws are, it's smaller than T5, and there's confusion online whether it takes T3 or T4.
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Sep 13, 2017 10:55
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mobby_6kl posted:Good luck! It might definitely be more challenging if the connectors are bottom mounted. Oh it's on the same side of the board as the rest of the components, yet is still a reverse connector. To me that says "OK I just finished designing this board! ...oh poo poo, I reversed the pins... Quick, get reversed connectors!" I'm worried because what I've seen of teardowns, there's a resistor or cap right next to the pins of this connector. I might need that luck.
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Sep 13, 2017 21:31
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I am having a problem with a stepper motor that overheats and loses steps. There's lots of people online that report this (usually with 3D printers) but there doesn't seem to be any clear consensus as to if just overheating the motor can cause it to lose steps. This machine has two nema-34 stepper motors on it, basically running as an X-Y tube-winding configuration. Both motors spin continuously in one direction in use; they don't have to stop or change direction at all. The stepper motor that overheats is spinning at a speed range of about 12 to 48 RPMs. The motor is a 965 oz, the physical load on it is fairly light, and it never appear to bog down at all. It's being driven in 4X mode (1600 steps per turn). It works perfect for a few minutes but as it overheats more and more, it loses more and more steps. After about 10 minutes it is visibly losing steps and is hot, and after 20 minutes or so it's too hot to touch for more than a few seconds. I dunno what the exact temperature is. Of course, with no other motors to swap these out for, I don't really KNOW that it's the hot motor that is acting wrong. It could be either one.... I'm just assuming it is the over-heating motor, since the other motor stays perfectly cool to the touch and doesn't even get warm at all. The other motor is a bigger size (1232 oz) that is turning a heavier load at higher speeds, and in 6400x mode: it is basically turning at 4X the RPMs of the first motor, and probably at least 2x or 3X the physical load. Both motors use the same brand + model of driver (that is--there is a separate driver for each motor). Neither motor driver appears (or feels) to be overheating at all. Both drivers have cooling fans. Both motor drivers are sold for nema-34 size motors, and are set to their lowest current setting, which is 2.0 amps. Both drivers are also set to use 50% holding torque, but that should not be engaging at all while they are in use. I have a nema-23-sized driver on hand but it only goes down to 1 amp current. I haven't tried that yet, as I have ordered a couple nema-17 drivers that go from .4 amps up to 3 amps or so. Some stepper drivers have warnings about the maximum motor size to use them with, but I dunno if that applies to the minimum load as much as it does to the maximum loads....? Because of the mount for the current motor and what it has to drive, it's not very practical to remove the nema-34 motor and put a smaller motor size in. The easiest way is to just drive a nema-34 motor with a much smaller driver, but the power requirement apparently isn't that big. The question I can't find answered online is this: if the motor is getting too much current, then can the overheating alone cause it to lose steps? I've not found anything that really says this either way.
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Sep 13, 2017 22:21
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edmund745 posted:The question I can't find answered online is this: if the motor is getting too much current, then can the overheating alone cause it to lose steps? Yes. Once the windings are hot enough, their resistance rises to above what the driver can provide, and steps are lost. Check all your connections and terminations. Unplug the motor and driver and see if you can measure any resistance along that wiring path. Also check the resistance of each coil of your motor (when cool, and when hot). They should both agree to within 5% or so. If both coils are 8ohms cold, but one is 200ohm hot and the other is 12ohms, then you know your motor is dying. Otherwise, it's probably the driver. If they're really identical drivers, swap them and see if the problem switches over to the other motor.
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Sep 13, 2017 22:26
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babyeatingpsychopath posted:Yes. Once the windings are hot enough, their resistance rises to above what the driver can provide, and steps are lost. I'd just add that current regulation is typically the job of the driver. If it's like the cheaper hobby drivers I've seen, there will be a potentiometer on it to set the current limit. So the solution may be as simple as turning a knob or screw. Maybe yours is fancier/different.
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Sep 13, 2017 22:50
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Stabby McDamage posted:I'd just add that current regulation is typically the job of the driver. If it's like the cheaper hobby drivers I've seen, there will be a potentiometer on it to set the current limit. So the solution may be as simple as turning a knob or screw. Maybe yours is fancier/different. I've seen motors begin to fail that develop high resistance. When they're just connected straight to voltage, this isn't a problem, as they just turn slower. However, steppers have constant-current (or max-current) supplies. If your coil had 1ohm before, and you're running 3A max, that's 3W. If the thing has overheated and the resistance of the coil goes up to (say) 10ohm, that's now 30W, and the thing gets hot fast. If it's partially open and partially shorted, then you could have 200-300ohm through a coil, and then it's the driver thermally cutting (and missing steps) as it overheats, but still trying to run that hundred-watt heater attached to the motor shaft.
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Sep 14, 2017 00:24
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The motor + driver is the ones here: http://www.ebay.com/itm/NEW-ARRIVAL-Nema34-Stepper-Motor-965oz-In-34HS9456-Driver-DM860A-CNC-Router-/192210208269 The motors are basically new/unused. It'd be a bummer if it had a shorted turn in it already. I have the stuff to check for that but I'm not going to bother until the small driver arrives.
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Sep 14, 2017 00:55
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I never really learned about passive components in school so I'm building a USB condom to further my edumacation. I get how voltage dividers work and how to pick resistor values to get desired voltages on D+ and D-, but how should I select the power rating for the resistors? Ideally I would need to know how much current would be expected to be sunk through D+ and D- and use the voltage on each pin to calculate the power and choose a resistor with a power rating greater than or equal to that, correct?
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Sep 14, 2017 01:54
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