13

The 3-dot sets between some of the closer pads is a fairly routine fix for when wave soldering can create a short (it acts in a similar way to the solder resist mask). When I worked in contract manufacturing, we often used this trick to deal with cases where the PCB wasn't really designed for wave solder manufacture. The majority of these dot groups will be ...


12

That is glue used to stick components on the lower side of the board during pick&place manufacturing, so that they don't fall off the board before the board completes its course through the reflow soldering oven, i.e. until all the components are held in place by the solder joints. See, for example, this NASA document about the placement of glue dots (...


9

The salt (NaCL) water solution is an electrolyte solution which is, essentially, a conductive solution. The conductivity of the salt water is due to the presence of both positively and negatively charged ions. These ions in solution are free to accelerate in the presence of an electric field and thus, like the free electrons in a metal conductor, are able ...


7

Most materials do not change when a current flows through the material. The material somehow allows charge (in most cases electrons) to pass through the material without affecting the material. Metals are very good at this because some of the electrons in a metal are very loosely bound to the atoms. Pure water consist mostly of H20 molecules. They offer ...


6

You have a good chance of dying in a real world situation. You have a moderately good chance of dying in a theoretical situation that properly reflects what you'd see in reality in your example. You have misunderstood the units. If the units were ohms/cm you would expect the resistance to rise as cm increased. As siemens are the inverse of ohm then it ...


6

Yes, many of us have had problems with conductivity of no-clean flux. It's not just anecdotal, a quick search will yield solid studies- which in part seem to blame the process conditions, but as a user, "whatever" it still can create invisible terrible problems, and if they're intermittent because of whatever the contract assembler is doing, that's actually ...


6

While flux may be pristine before it's used, its job is to clean the surfaces of the metals the solder is supposed to join, physically and electrically. So where does all the junk the flux dissolves go? Into the flux, of course, and if there's enough of it and it's the right kind of junk, it could well provide a conductive path through the cooled flux which ...


5

Don't do that. The kapton tape you linked to has adhesive on one side, which will interfere with whatever you try to do with it. Kapton is available in much more suitable forms, for example these 24 x 24 inch sheets. Kapton is one of the most common materials used as a substrate for flexible printed circuits. You can simply call your favorite flexible ...


4

What's wrong with this: - What you see above are three things: - Some cables being bound together by... A cable tie-wrap which loops thru a... Self Adhesive, (or screw fixing) Cable Tie Mount Here's a link I'm think a paper stapler wouldn't have the strength to pierce a metal sheet plus you can't really control it from breaking the insulation and ...


4

Capacitive touchscreens are designed to react to the capacitance of a human body, which is about 100 pF according to Wikipedia. So when a regular user touches it with their finger, the equivalent schematic might look something like this: simulate this circuit – Schematic created using CircuitLab Now, when you made your tweak to your head stick, you ...


4

First, is your pen well-shaken, so the ink is silver-laden? If not, the ink may be barely conductive. The ink will settle out to form a silver clot inside the pen, and the your circuit-lines are mostly the solvent, not the silver. These pens contain weighted beads to stir up the silver and distribute it in the ink. (Like the metal beads inside an aerosol ...


3

As anti-static foam isn't reusable, if the laptop has no exposed electrical connections, and the threat you're guarding against is ESD damage to the laptop, and the cost of the foam is small compared to that of the laptop, then use the most conductive foam you can find, namely cushion grade conductive foam. (I feel faintly embarrassed posting this. You ...


3

100 mA into a strip of heavy duty kitchen aluminum foil, width a few millimeters, driven by a AA battery will be just fine. If some part of the foil is too thin and generates too much heat because you're drawing amps' worth of current, the foil will act like a fuse and burn off. I would just use a good coat of acrylic conformal coat to insulate it, rather ...


3

Two common products used in the power industry include NO-OX-ID and Noalox. These products primarily improve conduction by preventing oxidation. The NO-OX-ID page specifically mentions its use in battery terminal applications. You can also try DeoxIT which I found using the search term "electrical grease".


2

Just to add, since none of the other answers have pointed it out, but electricity CAN jump through air. Or even rubber or other insulators, with the right voltage and current. Ever see a spark? A air gap between two wires can be bridged, and it happens accidentally (spark when you plug something into an outlet, when you connect jumper cables to a car, static ...


2

eBay is not the right resource for materials like this, and neither are little shops. This is a highly specialized material, which is rare and probably very expensive. If it weren't you would find it in every motor or generator. I would contact the manufacturer for information on distributors (if any) and availability. Note: If it conducts only 40 times ...


2

Earthing mats do look like silicone rubber, but are made of, or coated with, some flexible conductive material. Therefore appearance alone is insufficient to assume it is not earthed. If you have one of the screwdriver type mains testers, it is easy to verify earthing: (source) Grab the metal clip at the back of the tester firmly using the mat as a ...


2

Short answer: Yes. Long answer: Yes, but... I have used all manner of thing to attach wires to things: stables, tacks, hot glue, tape, even gum once in an emergency. But just because you can doesn't mean you should. Even if you are careful there is a risk you will piece the wire or nick the insulation. This will cause a short, and could cause all kinds ...


2

Boy, this seems like an HP7475-style plotter hacked to take a pen with conductive ink would be the way to go. These were plotters that moved pens in x and z, while y was handled by a paper-mover. I don't know if there's anything like it out there today. They were pricey in the late '80s. Poking around a bit, I can find a ref to them being used for PCB ...


2

You're using the Arduino to measure a resistor (call it R1) that is in series with the contact resistance of the magnet snap (call it R2). Because they are connected in series, the Arduino can only measure the series combination R1+R2. I assume you also have a DMM (Digital Multi-Meter), pretty much a required tool for any serious electronics work. The ...


2

If you put the thread across the terminals of a meter measuring resistance, no matter where you touch the thread there should be a small change in resistance but, unfortunately, that resistance change would be the same throughout the length of the thread - this on its own prevents you from achieving what I believe you want. However, if you have two threads ...


2

I have had trouble with conductive ink not that being all the conductive. It may have been old stuff but it never really worked that well for me. I ended up using very thin and narrow copper tape. Once applied it can be rubbed until it sits flat on irregular surfaces. It is like flat wire that sticks to stuff.


2

As an addition to other answers: There is no problem to use staples (or other metal things like nails), but there is always a risk you will destroy insulation of the conductor, which may eventually lead to a short-circuit. A staple (or a nail, a screw etc.) uses force to keep the wire stick and this force can deform the insulation. It is also necessary you ...


2

It is likely using parasitic capacitance. In the case of the Touch Board it is using a dedicated (Proximity Capacitive Touch Sensor Controller) chip called the MPR121 by NXP (which was Freescale (which was Motorola)). Using a dedicated chip will likely result in more dependable operation then using the built in touch switch features of some embedded micro ...


2

This is a good shop for FPC boards . They all the design info you need. This is what they use for car mirror defrost heaters but NOT room heaters. There we use Nichrome or Tungsten wire for cost reasons. https://www.protoexpress.com/flex-pcb


2

I doubt you'll have much luck with resistive sensing - the chitin shell and legs of an insect will have a very high resistance. Any voltage high enough to give reasonable current is likely to cook the little buggers. Not that that's a bad thing, of course. By the same token, I'm dubious about the capacitance, as well. I'd suggest a different approach, such ...


1

Touch IC | Freescale MPR121 source


1

The EM wave travels in the midspace and arround two conductors. EM wave is a pure energy transfer, while the current in the wires is a pure loss. Actualy you can imagine two conductors like train bins that guide that EM wave. If the frequency is higher you can observe a phenomena skin effect due to eddy currents in the conductor, so the majority of current ...


1

You would get a number but I'm not sure it would be a good one, due to possible potentials and polarization. I think you'd be better to use mains or low-audio frequency AC with a series resistor and measure the AC voltage across the electrode vs. the total voltage, then you can easily calculate the AC resistance of the electrode. simulate this circuit &...


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