Electrical Engineering V3 - Developers

[QUOTE=Nikita;51391173]Could somebody give me some advice/reading material on soldering? I really suck at it, and I actually need to get good with soldering, because I'm starting to deal with [i]really[/i] tiny pins at my job-slash-research place. Maybe I could get a PCB with pads of various standard sizes to practice on?[/QUOTE] Make sure you have a temperature controlled iron, you can get some pretty decent ones for under $50 if you're on a tight budget. Also invest in some good quality 60/40 or 63/37 solder, hand soldering with lead free is a massive pain in the ass so you should avoid it at all costs, get a thin solder of 0.5mm or smaller so you have better control. Use a small chisel tip of 1mm or below, avoid pencil tips since it makes heat transfer difficult. Before you solder clean the iron tip on and damp sponge and apply solder to the tip if needed until it's nice and shiny, you want to keep the tip oxide free as much as possible as it will extend the life greatly and make soldering much easier. When soldering through-hole it's a good idea to put a tiny bit of solder on the tip first to aid in heat transfer, place the tip on both the pad and component lead, allow it to heat for a second or so and feed solder on to the pad and lead from the opposite direction until there is enough solder, leave it for an extra second to ensure it's all properly heated and to burn off excess flux then remove the iron.

welp I got microwaved by my microwave engineering midterm I could sort of understand basic electromagnetics, Maxwell's equations and such, but it seems like I've reached the point where I have to just jump ship and trust the math. I'm learning all of this cool stuff but when I try to teach it to other people, it's just "oh yeah when two transmission lines get too close to each other, uh this is the equation for that". At least the math is cool though, who knew that you could abstract out incident waves on a material into a circuit and model the E and H fields just like voltage and current propagating down the circuit.

[QUOTE=halofreak472;51410090]welp I got microwaved by my microwave engineering midterm I could sort of understand basic electromagnetics, Maxwell's equations and such, but it seems like I've reached the point where I have to just jump ship and trust the math. I'm learning all of this cool stuff but when I try to teach it to other people, it's just "oh yeah when two transmission lines get too close to each other, uh this is the equation for that". At least the math is cool though, who knew that you could abstract out incident waves on a material into a circuit and model the E and H fields just like voltage and current propagating down the circuit.[/QUOTE] I felt the same way when I toke my Fields class (which I ought to relearn sometime), stub calculation and Smith Charts were always over my head until the last day or so of the semester.

[QUOTE=aydin690;51367468]Are there any power resistors that are NOT coil wound? [editline]13th November 2016[/editline] Nevermind, apparently non-inductive power resistors are a thing. [editline]13th November 2016[/editline] [B]But they are all large and expensive :why:. I guess i'm just gonna put a ton of metal oxide resistors in parallel like an idiot.[/B][/QUOTE] K, this failed. How do you deal with parasitic inductance caused by resistors (~1-5W power, 15-25KHz square wave)? :frown:

[QUOTE=aydin690;51420848]K, this failed. How do you deal with parasitic inductance caused by resistors (~1-5W power, 15-25KHz square wave)? :frown:[/QUOTE] Need more info, what resistance are you going for, what is the output impedance of the source, how much inductance can you tolerate. Surface mount power resistors are the best choice when it comes to low inductance.

[QUOTE=aydin690;51420848]K, this failed. How do you deal with parasitic inductance caused by resistors (~1-5W power, 15-25KHz square wave)? :frown:[/QUOTE] What kind of circuit are you building? It almost sounds like a converter of some kind (to which I'd recommend building a resonant converter instead)

[t]https://i.imgur.com/j3PbaR4.jpg[/t] Pretty much done. I just need to sort out the power supply since there is way too much AC ripple, I can't go above 50uF with a tube rectifier so the only real option is a [b]big[/b] inductor, although I might just replace the rectifier with semiconductors which would be a whole lot easier and cheaper that a power inductor.

A+ cable management there.

[QUOTE=LoneWolf_Recon;51421265]What kind of circuit are you building? It almost sounds like a converter of some kind (to which I'd recommend building a resonant converter instead)[/QUOTE] [QUOTE=Chryseus;51421235]Need more info, what resistance are you going for, what is the output impedance of the source, how much inductance can you tolerate. Surface mount power resistors are the best choice when it comes to low inductance.[/QUOTE] Fuck my life. I actually spent a few days on this crap. The old resistors were actually causing some inductance but not nearly enough to cause the 75degree phase lag that i was seeing. I got pretty much the same results with the metal oxide resistors. I was just looking at my input signal coupled to my output. You know what the problem actually was? It wasn't actually inductance or anything. It was just a slow as fuck opto-isolator in some small part of the circuit and i was seeing the slow as fuck rise and fall times and was assuming it's the resistors acting as some sort of shitty choke. Which again didn't make any sense because the frequency wasn't nearly high enough. :suicide: Now i have virtually no phase lag or distortions and the metal oxide resistors have pretty much no inductance. Now i just have a ton of overshoot and ringing. Time to order some diodes and caps... [editline]24th November 2016[/editline] Not a converter btw. It's some sort of weird driver for a MEMS actuator.

Hey guys, I need some form of electronic switch for my project which would allow current to flow freely in either way, much like how a regular switch would operate. Single transistors or FET's only really allow current to flow reliably in one way which is not ideal for my intended application. The closest contraption I could think of which would perform what I have in mind is pictured below. I'm unsure why I put the diodes in there, they may not be of actual use, but oh well. [thumb]http://i.imgur.com/vjXyLdM.png[/thumb] Theoretically, when "GATE" is high, the whole thing acts as a closed switch, allowing current to pass between terminals X and x freely, forwards or backwards. In practice this doesn't work so well, as I've noticed through a circuit simulator by using a sine wave generator. Anyway, is there any electronic part/circuit that can act as a switch that can be closed off/on? Something inexpensive or part of an IC would be great.

[QUOTE=supervoltage;51427842]Hey guys, I need some form of electronic switch for my project which would allow current to flow freely in either way, much like how a regular switch would operate. Single transistors or FET's only really allow current to flow reliably in one way which is not ideal for my intended application. The closest contraption I could think of which would perform what I have in mind is pictured below. I'm unsure why I put the diodes in there, they may not be of actual use, but oh well. [thumb]http://i.imgur.com/vjXyLdM.png[/thumb] Theoretically, when "GATE" is high, the whole thing acts as a closed switch, allowing current to pass between terminals X and x freely, forwards or backwards. In practice this doesn't work so well, as I've noticed through a circuit simulator by using a sine wave generator. Anyway, is there any electronic part/circuit that can act as a switch that can be closed off/on? Something inexpensive or part of an IC would be great.[/QUOTE] What you're looking for is called a TRIAC, it allows AC to pass between the two terminals (MT1, MT2) when triggered with the gate terminal, when the trigger signal is removed it remains latched on until the AC zero crossing similar to a thyristor. If you plan on using it with mains voltage the gate must be isolated, you can buy opto-TRIACs which include an optoisolator. Alternatively you may be interested in a solid state relay which is basically the same.

Thank you very much for your reply! The suggestion is fantastic, however I should have probably mentioned that I'm looking for parts on a logic level - in essence, voltages not exceeding 5V and currents not exceeding 40 mA. Is there a logic equivalent for a triac or thyristor?

[QUOTE=supervoltage;51427957]Thank you very much for your reply! The suggestion is fantastic, however I should have probably mentioned that I'm looking for parts on a logic level - in essence, voltages not exceeding 5V and currents not exceeding 40 mA. Is there a logic equivalent for a triac or thyristor?[/QUOTE] Yes you can get them for logic level such as the BTA06, MAC97A8, BT131, etc.

Thank you very much, MAC97A8 seems to be what I need for my project! I will report back with updates when I'm finished (if I finish, I tend not to follow through on promises unfortunately)

[IMG]http://i.imgur.com/dOS9Rhc.jpg[/IMG] So I'm doing some studying on switchmode power supplys. I came across this diagram and I'm a bit confused about the graph in the upper right corner. I'm probably wrong, but I feel like they've drawn it incorrectly. The square wave is being generated by comparing Verror to the Clock Ramp, so shouldn't it look like this: [IMG]http://i.imgur.com/Qsy58KL.png[/IMG] The pulse widths are different and its inverted.

[QUOTE=No_Excuses;51429509][IMG]http://i.imgur.com/dOS9Rhc.jpg[/IMG] So I'm doing some studying on switchmode power supplys. I came across this diagram and I'm a bit confused about the graph in the upper right corner. I'm probably wrong, but I feel like they've drawn it incorrectly. The square wave is being generated by comparing Verror to the Clock Ramp, so shouldn't it look like this: [IMG]http://i.imgur.com/Qsy58KL.png[/IMG] The pulse widths are different and its inverted.[/QUOTE] No, have a look at the operation of pulsewidth comparators e.g. [url]http://www.ti.com/lit/ug/slau508/slau508.pdf[/url] page 4

[QUOTE=metallics;51429769]No, have a look at the operation of pulsewidth comparators e.g. [url]http://www.ti.com/lit/ug/slau508/slau508.pdf[/url] page 4[/QUOTE] Oh thanks, so it inverts the signal. I have to look at it in more detail, but I'm right about the pulse widths still? As in, it should look like: [IMG]http://i.imgur.com/mJjkgqe.png[/IMG]

I've got a cool project for my mechatronics class that I'm going to show you all in about 2 weeks. Related: can you charge an android phone with just 5v into the USB? Does it need support hardware?

[QUOTE=chimitos;51437770]Related: can you charge an android phone with just 5v into the USB? Does it need support hardware?[/QUOTE] Most chargers just provide 5V and leave the data lines disconnected.

[QUOTE=Chryseus;51437827]Most chargers just provide 5V and leave the data lines disconnected.[/QUOTE] My android phone requires them to be shorted to ground

[QUOTE=Chryseus;51437827]Most chargers just provide 5V and leave the data lines disconnected.[/QUOTE] It'll only charge with 500 mAh, but that's the 'default' charging behavior. [URL="https://en.wikipedia.org/wiki/USB#USB_Battery_Charging"]If wikipedia isn't lying, then you'd need to short the two data lines by connecting them together.[/URL] [QUOTE]USB Battery Charging defines a new port type, the charging port, as opposed to the standard downstream port (SDP) of the base specification. Charging ports are divided into 2 further types: the charging downstream port (CDP), [B]which has data signals, and the dedicated charging port (DCP), which does not. Dedicated charging ports can be found on USB power adapters that convert utility power or another power source (e.g., a car's electrical system) to run attached devices and battery packs[/B]. On a host (such as a laptop computer) with both standard and charging USB ports, the charging ports should be labeled as such.[95] The charging device identifies the type of port through non-data signalling on the D+ and D− signals immediately after attach.[B] A DCP simply has to place a resistance not exceeding 200 Ω across the D+ and D− signals[/B][/QUOTE]

[QUOTE=Van-man;51439365]It'll only charge with 500 mAh, but that's the 'default' charging behavior. [URL="https://en.wikipedia.org/wiki/USB#USB_Battery_Charging"]If wikipedia isn't lying, then you'd need to short the two data lines by connecting them together.[/URL][/QUOTE] Yeah. I've read that before. You also have to be careful with certain cheap cables that were only for charging dumb devices and have no data lines - as your phone will only slow charge.

Our dorm's old elevator got decomissioned, and we grabbed the control unit. It's 100% relay-controlled, absolute madness! [t]https://my.mixtape.moe/omawqm.jpg[/t] [media]https://www.youtube.com/watch?v=f9cVee5gyRg[/media] We also got the original plans, which we will scan later.

[QUOTE=Van-man;51439365]It'll only charge with 500 mAh, but that's the 'default' charging behavior. [URL="https://en.wikipedia.org/wiki/USB#USB_Battery_Charging"]If wikipedia isn't lying, then you'd need to short the two data lines by connecting them together.[/URL][/QUOTE] Default USB behavior is 100mA without negotiation, 500mA maximum afterwards, tie data lines together to indicate you're a wall charger. (Obviously no negotiation happens with a wall charger, you step the current up until the voltage starts sagging, and then you go back down a bit)

I've been reading about semiconductor manufacturing and Im convinced its effectively black magic now. Like, I had no idea that cpu manufacturers are running into issues with the conductivity of traces not being high enough - causing issues with time delay between transistors. Holy shit. This was prompted by Newegg saying my 6700k is coming today. I'm going from 32nm to 14nm, yay. What I don't understand, though, is why the TDP of lower lithography processors is always lower? My 1070 has quadruple the CUDA cores of my 570 but the TDP is 20w lower iirc. The 6700k has a 5w lower TDP. This doesn't intuitively make sense - how does the manufacturing process affect TDP?

[QUOTE=paindoc;51445743]I've been reading about semiconductor manufacturing and Im convinced its effectively black magic now. Like, I had no idea that cpu manufacturers are running into issues with the conductivity of traces not being high enough - causing issues with time delay between transistors. Holy shit. This was prompted by Newegg saying my 6700k is coming today. I'm going from 32nm to 14nm, yay. What I don't understand, though, is why the TDP of lower lithography processors is always lower? My 1070 has quadruple the CUDA cores of my 570 but the TDP is 20w lower iirc. The 6700k has a 5w lower TDP. This doesn't intuitively make sense - how does the manufacturing process affect TDP?[/QUOTE] Effectively, the smaller the transistors, the less current they are switching and thus the less wasted power being generated. Also the operating voltage of transistors scales with their lithography at 14nm they'll operate at 0.8V, 90nm operates at ~1.8V, 350nm operates at ~3.3V, and ~600nm operates at 5V. (As their gate oxides can only handle these voltages max without rupturing).

[QUOTE=LoneWolf_Recon;51445819]Effectively, the smaller the transistors, the less current they are switching and thus the less wasted power being generated. Also the operating voltage of transistors scales with their lithography at 14nm they'll operate at 0.8V, 90nm operates at ~1.8V, 350nm operates at ~3.3V, and ~600nm operates at 5V. (As their gate oxides can only handle these voltages max without rupturing).[/QUOTE] Oh, okay. I posted a similar question to /r/askscience too, which I imagine will result in me being buried in info thats way too dense for me to actually understand. Now this is something I imagine you know about, then. Does this lower scale leave transistors more vulnerable to radiation damage? I can already see lower lithography processors being much more vulnerable to adverse space weather, since geomagnetic storms alone can induce high amperage loads on a spacecraft

[QUOTE=paindoc;51445931]Oh, okay. I posted a similar question to /r/askscience too, which I imagine will result in me being buried in info thats way too dense for me to actually understand. Now this is something I imagine you know about, then. Does this lower scale leave transistors more vulnerable to radiation damage? I can already see lower lithography processors being much more vulnerable to adverse space weather, since geomagnetic storms alone can induce high amperage loads on a spacecraft[/QUOTE] They don't get used on anything that needs to be "rad hard" there is a whole subset of VLSI design dedicated to this. How you package up your chips makes a lot of difference too, it is possible to adequately shield higher scale devices.

[QUOTE=paindoc;51445931]Oh, okay. I posted a similar question to /r/askscience too, which I imagine will result in me being buried in info thats way too dense for me to actually understand. Now this is something I imagine you know about, then. Does this lower scale leave transistors more vulnerable to radiation damage? I can already see lower lithography processors being much more vulnerable to adverse space weather, since geomagnetic storms alone can induce high amperage loads on a spacecraft[/QUOTE] Yup, which is the main reason most rad-hard stuff is using late 90s/early 2000s lithographies such as 250nm or 130nm (The latest processor such as the RAD750 used on Curiosity is at ~150nm). Its alot easier for a single beta or gamma ray to flip a bit when the charge difference to turn a gate on/off is tiny due to lower gate capacitance, making bit flips alot more likely. The more dangerous damage comes from lattice displacement or gate rupture which the later instantly kills that transistor (Shorts the gate to source since the gate oxide is now damaged). Thus larger lithographies are inherently stronger against gate ruptures, et. al. I know you're fairly familiar with the TID metric which basically measures the level of lattice displacement until whatever performance tolerance (say the processing speed, transistor delay or current consumption gets past a point). Rad-hard processes protect more from latch-up by creating the IC on sapphire or heavily oxidized silicon instead of normal bulk silicon as this prevents charges from migrating and affecting other nearby transistors. Gate rupture and lattice displacement are still some of the most challenging problems with rad-hard design, which can sometimes be alleviated from thermal annealing. /crashcourse

Okay, thanks for both of those responses. I imagined SEM incidence would increase due to the ease of flipping bits on smaller transistors. Lattice displacement and gate rupture are terms I'm familiar with, but I didn't know the mechanism was the gate shorting to the source. Makes sense that's sort-of a bitch, lol. I didn't know that changing the wafer material from bulk silicon to other materials was a thing that happened though, although it does make sense. That's due to the greatly increased resistivity, I'm guessing? Dielectric constant doesn't seem that different.