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44

"Touch Not The Cat, Bot a Glove" DTTAH / ACNR / IANAL / YMMV * Equipment: High impedance voltmeter / oscilloscope with HV probe. High voltage low capacitance capacitors (1 10 100 1000 pF) x 2 of each. Pretest - charge capacitors to some semi known high voltage and measure with voltmeter to determine measurement ability. For purrfect results there ...


32

If you are installing a CPU in a motherboard, you don't really care about grounding - what you really want to do is to make sure that you, the CPU, and the motherboard (and any tools) are all at the same potential. If you have one of those grounding bracelets, you should connect its ground lead to the computer case or motherboard Ground - whether that is "...


28

As a bit of a riff on Spehro's, Capacitance ~ radius. You can measure your own body capacitance with your 'scope. Hook up the x10 probe, set you triggering for single shot, Scuff your feet or rub your sweater (jumper in the UK) and touch the end of the probe. You'll see your discharge through the 10 Meg Ohm of the 'scope probe. Find the 1/e point. Here'...


23

There are different bags available. Some of them are insulators (nearly, see below) and only prevent the build-up of static charge. Others are conducting (grey-metallic ones typically or black ones). I wouldn't place any powered electronics on conducting anti-static bags or mats. Even the fairly high resistance can have a big influence on the electronics (...


21

I would strongly suggest getting out of the habit of thinking of anti-static material as "safe" insulators. While that may be true enough for some materials at low voltages, all anti-static materials are conductors at higher voltages. That's what makes them anti-static. You don't know precisely what voltage below which they become safe to consider an ...


20

Interesting idea! Well I just tried it. I hooked up my trusty Keysight 34410A to the test leads and pierced what I think is dissipative foam (pink foam of an electronics shipment). The ohm reading was overload, so no measurable resistance. Which is to be expected like Bimpelrekkie suspected. Dissipative material is just too high resistance to make a usable ...


17

Most phone screens are capacitive. They work by sensing the change in capacitance due to a nearby conductive object. I can't imagine a way in which simply having some sweat on a fingertip would interfere with this mechanism. I can't reproduce the problem with my phone and a glass of salty water. However, I'll offer a guess as to what's happening: if you ...


15

A Wimshurst machine works by that process. It puts charge on plates which are close together, then moves the plates apart to generate a high voltage. When I was at school, in the '70s, a kid made one using PCB material for the disks, and gramophone needles to create the initial charge. The 'work' was done by an electric motor. Based on the length of ...


13

The process of grounding the tanker is still carried out. The first thing they do before unloading the fuel is ground the tanker to earth in order to discharge all the static charge through a safe path. This process of governed by various standards of operation. An example of the grounding setup looks like the following: Source: http://www.newson-gale.com/...


12

Problem Meowtivation and Purrpose How does one measure weight in space? Certainly not with a scale, because there's no gravity. One must use a special apparatus to deduce it indirectly - through oscillation. Similarly, you are trying to measure a value of a cat, whereby you cannot directly measure the capacitance. Luckily, there are a few things we know ...


12

Regarding the bounty quest for reliability in a cheap way: to convince yourself that this is a rather difficult task to do reliably (with laboratory precision), have a look at what it entails to measure "it" for a human, e.g. in a paper that studied it for ESD-related purposes, Numerical Calculation of Human-Body Capacitance by Surface Charge Method by Osamu ...


11

You can measure the charge on the cat using an electrocope. I built one like the one referenced, but couldn't get an MPF102. The 2N5464 worked fine instead. Build the circuit as described, enclose it in a metal box (ground the negative side of the battery to the box) and add an antenna as described in the article. If the LED lights, then you've got a ...


11

In most cars, you are isolated from the chassis when you're driving: everything is plastic, leather or textile. When you get out of your car, friction can rip off charges from the electrically neutral environment (this is called tribocharging) such that the potential difference between you and the ground increases drastically. When you set foot on the ground,...


11

I worked at a big semiconductor manufacturer last year as a software-developer and I had to handle expensive prototype chips, so I got an ESD training. The take away was, that completely destroying a chip via ESD does happen, but it happens rarely and is not much of a problem because it is easy to troubleshoot. Doesn't work? Then it's probably broken. The ...


10

Yes, the voltage increases. It seems most of us learned of this in school. My Physics professor had a setup with movable plates, and a very sensitive (actually, very high impedance) voltmeter. As the plates were pulled apart, the voltage went up. This comes from the elemental formula Q=CV. Pulling the plates apart lowers the capacitance. The charge ...


9

Can static shocks occur from grounded and ungrounded metals? Yes. A large ungrounded object still has capacitance. If there is a higher density of electrons on you than on the object, the electrons on you will feel repulsion from the other electrons on you and want to jump to the object where they will have more room to spread out. (Same goes in reverse if ...


8

I find it interesting that I didn't see any embedded solutions. You can create an RC circuit as described above where your cat is the C. Connect your cat C and a resistor R in series from ground to an IO pin on your microcontroller. Set the IO line to high output long enough to be sure you've fully charged your cat. Then switch the IO line to input and ...


8

Forget about USB for a moment, because these devices are useful in a lot more applications than just USB. First, the diodes in your first two examples would not usually be generic signal or zener diodes. They are usually purpose designed transient voltage suppressor(TVS) diodes. TVS diodes come in all different flavors, but there are three key parameters. ...


8

If you left a glass rod wrapped in a silk cloth for "some time" there would be a net transfer of charge. The difference rubbing makes is accelerates the process due to charge transfer aided by friction Look up the Triboelectric effect Materials close together on the series may not experience any charge transfer if simply touched (add friction into it ...


7

Get yourself one of these guys, and wire your ground into it. For good measure, double insulate the hot and neutral lugs inside the plug. The worst the kids will be able to do is unplug it, and they're less than $10 at most places electrical products are sold.


7

The Voltage definitely increases. Q = C * U Since you decrease C by increasing the gap but Q stays the same, U will increase. In my schooltime I did not want to believe it so my techer sent me into the experiments room with a high voltage power supply, plates, cables, isolators and a galvanometer. I've tested it and it it is true! The voltage increases as ...


7

You asked, Again, if all of this is mounted on a PCB, why might a sudden static discharge occur and where might it originate? The potential problem is ESD (Electrostatic Discharge) originating from outside the PCB, coming in from the USB connector. A user might be carrying a product across a carpet or other ESD-generator, and touch the USB connector with ...


7

To answer your specific question. Integration of pc parts into standard modular components and the ubiquity of chip-scale ESD mediation since the early 90's means that there is a higher probability that the part you are working with is less ESD-susceptible today than in the 90's. It is very common today for chip manufacturers to integrate ESD protection into ...


5

I've experienced your problem too. My hands sweat a little bit more than average, and while my phone screen is 'wet' its ability to tell my actions touch/swipe diminish. So, I just tested this on my Samsung S3 (which has a capacitive touch screen). All it took for this problem to arise was sparkling some water on its screen and trying to do any actions like ...


5

Connectivity to earth is what matters, not the size of the object. Size only matters if we are going to get nitpicky...if the wire connecting you to earth is so tiny that it vaporizes when current flows, for example. In your example, the matchbox car is useless as a grounding object, while the statue is excellent. The idea is you are looking for a way to ...


5

When you say your tools are not ESD safe, do you mean they are all metal? As in all metal tweezers? Or that they have a metal working end but have plastic handles? Like screwdrivers and pliers? I would have no qualms about all metal tools since you are wearing the ESD wrist strap when you are grabbing the tool anyways. Technically, all-metal tools aren't as ...


4

The interfacing of the cat with the measuring circuit is the biggest problem, as there are no international standards on how a measurement probe should be attached to a cat. For the purpose of circumventing the problem, we will look at the cat on a macroscopic level. Here is a simple(it's not really simple) solution. Things you need: two metal plates that ...


4

This is what you're looking for. Anti-static grounding plug Assuming the same thing is available in your local plug style, and your house grounds are correctly wired.


4

In addition to the other comments/replies, I'll add that an ESD wristband, by itself, doesn't provide much benefit if your goal is to prevent electrical overstress (EOS) due to electrostatic discharge (ESD). You also require a work surface made of engineered, static-dissipative material that is electrically bonded to the same ground as your ESD wristband. :...


3

The metal screws in the plug's wall plate are also grounded. Make sure the grounding wire has at least 1M ohm resistance between the common grounding point on the mat and the end of the wire, terminate the wire in a ring terminal, and screw the ring terminal to the screw in the wall plate. You can confirm grounding with a multimeter, but as long as the ...


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