Around six months ago, I did some light solder work in my room.  I was pretty reckless with the lead solder, and even ate while soldering on several occasions.  Should I be worried about the lead exposure?  Since soldering in my room, I have vacuumed and wiped down my desk several times.  Could small pieces of lead still be present?
120956
I was reading about tin alloys for electronics soldering and found it it has about 40% of lead in composition. Lead, everyone knows, it's very dangerous to breathe due to being a heavy metal. Also, I found some recommendations using the combination of an exhauster and a respirator when working with soldering. Is there any international regularization of which respirator type should I use? If not, which type do you recommend? Beyond this, is there any additional safety equipment recommended?  For economics reasons and for better soldering resistance, I've already discarded Pb free solder reflow.
30475
I'm trying to measure the resistance of a surgical screw that seems to have a low resistance, around maybe one ohm. I use a 1908P multimeter and wires having for resistance around 0.005 ohm.  Since the screw resistance is a small value, I've tried the 4 points measurement method. I get something around 0.3 ohm, but the value changes very easily depending on the orientation of the wires (see below). It goes from 0.3 to 70 ohms.     I'm wondering if it's either my circuit that is wired wrong, the screw because of its properties or if its the lack of precision of the multimeter( it a 5.5 digits) that causes that fluctuation.  Any idea of how I can improve this measurement?
76423
My cast iron pan has started to give off tiny black flakes after 3 months of use.  Are these dangerous in any way?  Are we ingesting iron?  There are patches on the skillet that are now a little lighter than their surrounding areas.
88983
How does the tester screwdriver work? If I put the tester screwdriver inside the "hot wire" of an electrical socket, it lits up if I press my finger against the metal cap on top of the screwdriver. This happens also if I stand on a surface of isolating material, such as wood. I read elsewhere that this happens due to stray capacitance formed by the "hot wire", the human body, and the ground. One has  $$ Z = R + \dfrac{1}{j \omega C}  $$  for the impedance, so if C  is high enough, the impedance should be close to r , the "effective resistance" of the formed circuit. Here I get lost; why r  is small enough to cause a current in the range of mA  even if I stand on an isolating surface?  So really what I am asking is how one may represent the system hot wire - screwdriver - human body - wooden floor - building - ground as an electrical circuit, and which parts of the physical system contribute to the resistance, capacitance (and inductance?) and in which proportion, even very approximately.
53033
This may be a stupid question, but I have searched online for a little bit and can't seem to find my answer. I am working on a circuit board that uses buttons that i've never seen before. These buttons just have a metal lead around them and an LED in the middle (for lighting up the button I'd assume) but how does a button like this even work? I've attached some pictures to show you what i mean.    this is the back of the push buttons from the device
60680
When you look at the board, there is a weird part of the PCB right of the top left mounting hole. There is also another one above the top right mounting hole.    ****                            ↓ Here's one                                            **   This image is directly copied from .    What are these? Is this just created when this is manufactured (to grip to to move the board or to grip during solder mask creation), or does it serve a purpose (something to hook a multimeter to)?
8850
I'm a total beginner when it comes to soldering, and recently I've been trying (and failing) to solder together a simple circuit I put together for a Raspberry Pi sensor.    Although it works fine on the breadboard, when I solder it onto one of my , the sensor no longer turns on.    Here is a topdown view of my soldered circuit:    Here is a view of the connections (the red block is just covering up old connections from past attempts):    More pictures of the connections.  What might I be doing wrong?
121541
We've all played with different transformers and power supplies that have an LED indicator that dims before going out entirely when the power supply is unplugged.  I'm working on designing an accent light which would involve a translucent crystal light source (probably made of resin or glass if I can find a cheap supplier) containing LEDs and certain electronics, and a base which would supply electrical current. For gamers, it might appear somewhat like a Welkynd Stone. My question is what is the simplest way to cause the LEDs to dim slowly (say over 2-10 seconds) when the crystal is removed from the base? Similar to the unplugged transformer, but with an intentional and controlled dimming.  I just purchased some LEDs and plan to build a test system over the next month or two. These LEDs are in a 5 meter strip divided into 3 LED series run in parallel and rated at 12v. I do not know the amp rating of the LEDs, but I'm guessing in the 20ma range (what I've read is average for bright white). I will probably use 4 series totaling 12 LEDs in the test build.   If I have the transformer from AC power built into the base, I was guessing I could use a number of capacitors in parallel with a resistor to store electricity and slowly discharge it into the LEDs. But I'm a self-taught enthusiast so I honestly don't know if this would actually work. Nor do I know the number and ratings of capacitors and resitor that I would need.  If I have the transformer built into the crystal, the transformer and rectifier would retain a small amount of electricity, but I don't think it would be nearly enough to provide the effect I'm looking for, so something else would have to be added to make it last for several seconds.  A nicad battery with control electronics is literally my last resort for achieving this effect, and I'll probably give up on the idea before I go programming my own circuit board.  That's my main question. If anyone wants to toss in some thoughts on how to connect the crystal to the base, I'm open to suggestions. My original plan was to simply have a direct copper to copper connection with the base. But I've recently been considering an EM charging system (akin to a powermat or  my dad has). The concern with the wireless is providing consistent power to the LEDs, though it is safer. I've also learned quite a bit already about constructing the power supply from perusing this SE site, but if anyone has any suggestions for that, too, I'm all ears. For the test build I'll probably hook it up to a computer power supply, or a laptop power supply if I can find a 12v one at Goodwill or the local electronics parts store.  If I get the test model to work, I plan on building possibly a dozen of these for accent lighting around my home.
15576
Answers to other questions here (e.g. ) show capacitors used to drop AC voltages to levels suitable for a LED. I've seen much simpler circuits such as the one below         &ndash; Schematic created using   Assuming it's in a suitable enclosure, are there significant drawbacks or dangers to this circuit compared to others?
30761
For example, say I submerged a computer mouse entirely. Assuming that I ensured that all traces of the water were gone, would the device suffer any issues?  It is my understanding currently that provided that there is no power being supplied to a device, and assuming that non-electronic damage like rust etc. hasn't taken place, then once the device is completely dry, it can be used without issue. Is this correct?
16491
In low-cost mass-produced items I often run into black blobs of what looks like resin applied directly on top of something on the PCB. What are these things exactly? I suspect this is some kind of custom IC that is layed out directly on the PCB to save on the plastic  housing/connector pins. Is this correct? If so, what is this technique called?    This is a photograph of the inside of a cheap digital multimeter. The black blob is the only non-basic piece of circuitry present, along with an op-amp (top) and a single bipolar junction transistor.
109390
In the poor student or youth worker days it was popular to have never ending soup; a large pot on the stove that was topped up with new and leftover ingredients when available.  Normally the pot was stored in the fridge overnight.  Food items added were sometimes plate leftovers from fellow flat (share house) mates, who would in turn be eating the soup, too.  Most days other ingredients would be fresh(ish) vegetables, beans, grains, and fresh meat products sourced from the local butcher as money allowed.  Brussels sprouts where banned, and so were strong spices (you added those to your bowl before serving).  Also, for irony, a large (cleaned) stone is always left in the pot.  Fresh bread was sometimes baked in the oven while cracked bones were browning, but the oven was often an electrical and environmental death trap.  The pot kept going till the summer holidays, and no one got food poisoning in my time, or from any student stories I have ever heard.  This sort of activity is recorded in history as being a popular resource-saving idea.  Are there any real food safety implications with this method of cooking? And have any actual studies of this technique ever been published?  I still recommend this money-saving idea to current students, not keen on bad practices being continued though.
8908
I want to repair my computer mouse cable which has become disconnected from the PCB. The wire is insulated with enamel and I have to remove it before soldering it back onto the board.  How should I remove the enamel?
114810
I'm putting on my desktop computer on steel rack as usual. A while ago, when I touch the steel rack for seconds, practically I feel a tingling sensation, sort of electrical shock in my finders. After that I measured how voltage the steel rack has, the multi-tester meter indicated almost 50V by AC mode. Is this safe to touch or keep the PC on the position, or I should get away the PC somewhere electricity-safe? I'm not sure this site is suit for asking this kind of question, but I'm very worrying whether this is safe or not since this experience is my very first time. Thank you.
75588
I'm currently reading an article () and the author compares two devices (hard disks) of the same model one manufactured by Company A and the other manufactured by Company B. One of the things he compares is how solder looks like on the boards.  Company A device board has soldered parts looking like this:    and this is claimed to be "low quality tin-coating". What I see is that solder spots are not shiny and the solder layer is thinner near the spot edges and thicker far from the edges (a bit concave).  Company B device has soldered parts looking like this (that's exactly the same area of the board as on the Company A device):    and this is claimed to be "high quality tin-coating". What I see is that solder spots look shiny and the solder layer looks having uniform thickness across each spot.  So to me the first board just looks neater. From what I know about soldering once the surfaces have been properly degreased with soldering flux and the solder was melted properly the connection will be just fine regardless of how shiny and neat looking it is.  However the author claims that the Company B device is of higher quality and should be preferred because of (among other factors) the "better quality" of tin-coating. How reasonable is such claim? Can device reliability be judged based on such tin-coating analysis?
91194
Just bought my first bike and it was put together by the store. I was wondering if this little cable/wire is okay, it's hitting my pedal every time I’m riding. It doesn’t really bother me, but I don’t want it to end up messing something up really bad. Help please new bike owner
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Everybody has had the time where water gets all over their electronics, and the whole thing gets ruined, like cell phones.  At that low of a voltage (3-5&nbsp;volts), I don't understand why it is such a short-term harm (long term makes sense - corrosion, etc.)  If an LED was in parallel with water, maybe a bit more current would be drawn, but it doesn't seem to be enough at all to short out the system, and the LED would still shine.  So what is it that permanently damages some electronics and what is the cause?