Hot answers tagged

53

If your ground strap has a proper current limiting resistor, then you would be perfectly fine connecting it directly to ground. If your ground strap does not have a resistor, then it greatly increases your chances of dying if you connect it directly to ground. If you don't have a resistor in your ground strap, and you touch a live wire while wearing your ...


46

Your problem is the gate drive voltage. If you look at the datasheet for the STP16NF06, you'll see that the 0.08 Ω Rdson only applies for Vgs = 10 V, and you're driving it with only (a bit under) 5 V, so the resistance is much higher. Specifically, we can look at Figure 6 (Transfer Characteristics), which shows the behavior as Vgs varies. At Vgs = 4.75 V ...


32

Components are damaged by two or more of their pins being at a large enough potential difference. If the component has a conductive case, or pad, then that counts as a 'pin' too. It's possible to break them by trying to charge them up to a new potential through one sensitive pin, while the voltage of the other pins is held more or less constant through ...


31

Hopefully your parts are packaged in an ESD-dissipative tray or bag. Then when you set them down on your ESD mat in your lab, any charge that's built up on them can drain away through the packaging and the mat. They won't discharge quickly enough to damage the components because both the bag and the mat have substantial resistance (1 megohm to ground is ...


31

The best way is to use an ESD strap, that is connected to earth via a 1MOhm resistor. This slowly but continuously discharges you without creating high currents. This way it does not hurt or damage anything. But I also want to mention one "trick", when you dont want to use special equipment like an ESD strap. Discharging at the earth connection of mains ...


30

My go to method is my ghetto ESD-gun (a cheap electronic lighter) ala - Long neck lighter Split it open, strip the wires and zap away :) It should produce a few kilo volts.


28

Is static electricity really so dangerous? Yes. The conductive paths inside an IC are really small, so it doesn't take much energy through them to vaporize them.¹ There are millions of such paths inside the ICs of an Arduino, and it only takes damage to one of them to break the device. It is possible that you could get lucky and break some feature that ...


26

You (and the some of the other answers) focus too much on the actual value of the resistance to ground; the fact is that the actual value is irrelevant regarding ESD. The ESD charge just needs a path. If that path is high-ohmic (few mega-ohms) it will only take slightly longer for the charge to find its way to ground. But it will still be a fraction of a ...


21

Best Practice Firstly (as a bit of a cop out) personally, in designs I always ground through a 0R resistor so that the decision can be changed. This goes for pretty much any shield (Ethernet, USB etc) The main problem that can arise is when the shield is grounded at either end, and the two ends don't agree on what 0V is. This can cause damage to either end,...


17

The 1meg resistor is needed to safeguard the user from faults from other equipment connected to mains earth. Keep in mind that the wrist strap is a permanent connection to the electric system of the building. If another piece of equipment experiences a fault, there could be a big fault current through the mains earth wiring system. That means that, in ...


16

You are forgetting that these voltage sources are "ideal". So if your input is 20V directly from a supply, it will always be 20V. Throw a series resistor in there and you can see how it works. I used LTspice to model the circuit. R1 is the input resistance for some IC pin. I did a DC sweep from -10V to 10V with 1V increments. As you see, as I start to ...


16

It makes no difference where you connect the anti-static strap to your body. The reason is that your body is much lower resistance between any two points than the strap is. Also, most of the resistance between any two points on your skin is getting thru the skin at each point. You're just a bag of saltwater (electrically, anyway). The bag has a ...


16

The point about the gate voltage is valid, but if the MOSFET is not heating up, I'm not sure that is the actual culprit here. 16 meters of 12 V LED strip driven at several amps is going to have a significant inductance at typical PWM frequencies. This causes voltage spikes at the drain every time the MOSFET turns off. These spikes are short in duration, but ...


16

You can use a ESD mat, which is directly connected to the electrical ground. Just place it under your electronics and wear the connected bracelet when you are working with them. Touching the mat when you arrive at your desk would also discharge the static charge without affecting your PC. Image source


15

This is like asking, if I pour a cup of water off a skyscraper, why can't that drive a turbine to produce some meaningful electricity? It's got the gravitational potential, so what's the problem? After all, hydroelectric dams not as tall as a skyscrapers generate many megawatts. Static electricity can have the capacity to kill. This occurs in nature and is ...


15

I like being graphical. Your hair, when charged electrostatically, acts like small capacitors charged to high voltages. The energy stored in those little capacitors is finite and small, and so it can do little harm to you. On the other hand, a 220 Vrms outlet has a much lower voltage, but it is an unlimited source of energy. Even acting upon the same load ...


14

This is an awesome question because it touches on two things that 'beginners' (if I may) often don't have a good feeling for: How important electrical protection and conditioning is Where to put electrical protection Here is what you should do: You should protect any outgoing and incoming electrical signals that a user will touch Any I/O lines that exit ...


14

should the alligator clip of the wrap always be grounded to the mains earth in a way? Yes, the alligator clip should be earthed. As should the work surface beneath the work piece. Is this type of wearing antistatic wrist strap aiming to protect the human from ESD shock or sensitive electronic circuits in general? It's meant to protect the electronics, ...


13

Grounding yourself is only part of mitigating ESD. You can still cause damaging discharges while properly grounded when the device you're working on is itself charged, when the tools you use (like a multimeter or screwdriver) are carrying a charge or when your workbench/parts bin is charged. Ideally you'd ground everything that can come into contact with ...


12

Don't get hung up about connecting things 'to ground', that is, that brown stuff outside the door. What is important for you, your worktop, your tools, your components, is that they are all at the same voltage, before anything touches anything else. That's all you have to achieve, it doesn't matter how you achieve it. People who say it must be done this ...


12

My understanding is that ESD safety things are designed to bring everything that can touch a component to the same electrical potential energy That's when you're right. ground. And here's when you're wrong. There is no such thing as "universal ground". Not even Earth is. You just pick a point of a circuit and say "Hereby, by the power vested in me by ...


11

These bags are pink for identification purposes. These bags prevent static build up, but do not protect their contents much from external sources of static. There are also silver bags that protect from those external sources and blue bags that are almost the same as the pink ones but work at a greater humidity range.


11

The circuit protects against overvoltage and ESD subject to certain conditions. The main assumption is that Vd is "stiff" compared to the energy source on Vpin. This is usually true for Vd = power supply of say 1 A + capabilty amd Vpin is a typical signal source. If Vpin is eg a car battery all bets may be off as to how long it is before D3 is destroyed. . ...


11

Even if I doesn't take such precaution, chips behave as expected. Is that normal? Yes, ESD is an unpredictable event, and you can't see it (most of the time, sometimes you can see damage on IC's). Sometimes it only damages a trace partially and it could take months or years for a chip to fail, sometimes the effect is immediate and the circuit ceases to ...


11

Yes, mosfets drains are sensitive to ESD. If you look at the Vds spec in the datasheet, it cannot be exceeded (for the IRF530, it's 100V), even for short amounts of time. ESD over-voltage conditions can reach thousands of volts. To prevent failure of the mosfet, install ESD protection. One way to do this would be to use a TVS diode that limits the voltage ...


10

IPC-A-610: Acceptability of Electronic Assemblies Section 3.1.2 mentions compressed air as a possible source of electrostatic discharge. This forum post which claims to lay out the "Truths, myths, and flat out lies" about ESD notes that compressed air is a source of ESD due to the air rubbing against the air. But it claims that most of the charge is ...


10

You'll indeed risk building up high static voltages. Blowing air can do this easily. Think of thunderstorms when a cold front slides under the warmer air pushing it high upwards: the air-against-air movement can build up millions of volts. In the case of the compressor your "lightning strikes" will be restricted to a few cm maximum, with energies of a few ...


10

ESD precautions: I would like to get an anti-static mat for my bench top Buy the cheapest one in the size you need. Suitable materials for ESD desktop sheets: Any somewhat conductive sheet of material that is grounded via a 1 to 10 megohm resistor will work as an anti electrostatic work surface. (Sheets with very low resistance per square risk ...


10

Electrically, it doesn't matter where it makes contact, with contact being the key word! I find however that it doesn't suit my workflow round either wrist or ankle. If worn on my wrist, the trailing wire interferes with stuff on my bench. If worn on my ankle, it's a long way down to attach and detach, and being out of sight, it's easy to be working for a ...


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