Questions tagged [safety]

*Your* health and safety while working on electrical devices, and designing devices that will not shock, set fire to, or otherwise harm the user of the device.

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ESD - Is it safe to connect yourself to an electrical outlet?

Is it safe to connect yourself to an electrical outlet? Either directly or indirectly. I would prefer to not connect myself directly to an electrical outlet, via (as I've heard) attaching a wrist ...
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DIY Beginner's DC Power Supply? [closed]

My school uses HY 3005D-3 but I want to do it myself to save on $. Before opening it, I ask for tips about: not-to-break-it, cheap DC supply and DIY-materials (not that I know them soon). So how to ...
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I think our company fields machines that can shock people. Can I try to fix it?

For more background details, you should read my original question on Workplace Stack Exchange. I am a technician at an arcade. My company is fielding machines that seem to be shocking people from the ...
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How does a “break” in the neutral wire enable it to reach the full line voltage?

The answer to Is the neutral wire considered safe? states: When everything is working correctly, it should be at most a few volts from ground. However, and this is the big gotcha, if there is a ...
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Is a stage box with an iron grid safe using this way?

See also my previous question: How should I bypass switches Where I made a circuit directly by mains, and as proposal by very useful comments to use a separate 'control' circuit at 9 or 12V. ...
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Is it safe to remove earthing from a scope? [duplicate]

I need to make some differential measurements on a device, but both nodes need to be floating from earth. I found out the hard way that the negative clip of my oscilloscope voltage probes are ...
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How much can I safely plug into a light socket converted to a standard outlet? [closed]

I just moved my office desk from our extra bedroom on to our stairway landing. The tricky thing was that there was no wall outlet to plug anything into. However, there was a nearby light socket, ...
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1answer
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How to safely use the power-socket ground for the anti static wrist strap?

I saw as practice to use the power-socket ground for the anti static wrist strap, I saw this done where there is no available specially designed ground for anti-static pads and bracelets, but this may ...
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677 views

A “fuse” that blows upon liquid exposure instead of overcurrent?

I have a board that is mounted inside a waterproof housing, but occasionally the housings develop leaks and expose the internal circuits to water. This can cause unpredictable failures as the ...
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Played with some lead solder without washing my hands for awhile, should I be concerned?

I was using some lead solder at work, and wasn't aware it was lead solder nor had anyone told me that it can be dangerous. For the most part I was just handling it. This was last week and I don't ...
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Is there a wiring design that would protect a person in bath from electrocution when a powered appliance is dropped?

Hairdryer falling into bath is a Hollywood cliche already. Jokes aside, is there a wiring design that would protect a person in this case? Overcurrent protection will trip too late, residual current ...
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What does it mean that a power supply is 'referenced to mains' and why is that dangerous?

I was watching a few different videos by BigClive on youtube. He was mentioning the danger of a particular light chain power supply because it was 'referenced to mains'. The voltage across the output ...
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412 views

How can a Live-Neutral transformer fault cause 2000 Ampere to flow?

In this critique of an ELV PSU design, it is suggested that a "Live-Neutral" fault could result in a fault current of thousands of amps. It says: Fire – (d) the plastic had a UL94-HB rating ( ...
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750 views

Circuit safety -> Preventing smoke through accidental connection of battery voltages

I'm building a circuit whereby users are able to connect their battery to the pcb which will then be sampled by a micrcontroller. Voltage divider circuitry is all good so please don't focus you ...
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What are the tradition ways to signify/advertise that a potentially dangerous long-running test is in progress? [closed]

I frequently need to run long-term tests which have some potential for damage or harm if e.g. someone disturbs the test apparatus without being aware that it's running a test. Say for example ...
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1answer
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Exceeding Relay maximum switching frequency

I read in the datasheet of the DOLD OA5611 that the maximum relay cycles/s is 10 cycles/s. Now I want to know what are the risks for the relay if I control it with a switching frequency more than 10 ...
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Explosion proof enclosure wiring

I am currently working on a device that is to be used in hostile environments. It needs to be explosion proof. Our team has decided to place our instrument in this housing shown here. http://www....
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882 views

Cheap ESD/safety Mat

I need to get some sort of ESD/safety mat (2 actually) for working at home to protect myself and equipment. I was wondering what to look for/avoid if I were to purchase a rubber mat from a rubber ...
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1answer
2k views

Clamping Inductive Kickback in AC Circuits

I want to eliminate/clamp the inductive kickback that would result from turning off a large inductor, such as a relay or a transformer. In a DC circuit, I would use a diode to flywheel the current. ...
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Charging batteries - what should I know

So I want to learn about batteries and the process of charging them. As a project, I'm going to create a solar powered charger to charge a 9v NiMh battery with 175mah capacity. I have a 15v solar ...
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1answer
350 views

DIY Electrical Safety

I'm quite into DIY projects and I am looking at making an electrical unit out of a Raspberry PI and a computer monitor. I was wondering if someone could provide me any information on what I should ...
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How can I safely power two 3v motors from a 9v battery?

I'm making a Sumo Bot from scratch and I had purchased two 1.5-3v DC motors from Radio Shack to run with my Arduino Uno v3. I'm using a 9v battery to power my Arduino alongside an RF receiver, Quad ...
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Disposal of the used acid/hydrogen peroxide etchant?

This thread repeated the question how to dispose the used acid/hydgogen peroxide etchant. So how can I dispose acid/hydrogen peroxide etchant? Perhaps interesting thread to other readers, Disposal of ...
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865 views

Does the Arduino have any specific cooling requirements?

If I were to encase my Arduino in a sealed case with no ventilation, would this be an issue? What about if I were to pot the Arduino in epoxy, would that pose a cooling issue?
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48VDC safety precautions?

I am building a bit of equipment that requires 48DVC @ 2.5A to be brought out of the metal box housing it. I intend to feed it through a piece of plastic tubing along with a sensor wire, which exits ...
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1answer
78 views

Is isolation between user accessible circuits and protective earth necessary for safety?

First let me say that I understand that this question is best answered by someone familiar with relevant standards (whatever those may be). Let me give some background. When I'm designing a board at ...
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If two objects are grounded, why do they still need to be bonded? And if they are bonded, why does each still need to be grounded? (fire safety)

When transferring a flammable liquid, both the container and the receptacle are supposed to be grounded and bonded. If they are both grounded, shouldn't the change on each be equal to ground? And if ...
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Is it healthier for a capacitor to be discharged to itself or to “ground”?

A practical-use question from a non-EE who enjoys simple repairs of home electronics. Am curious about whether "where" to discharge makes a difference to the continued health of an electrolytic ...
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7answers
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When can free-floating electrical contacts become dangerous (e.g., start a fire)?

In general, when should free-floating electrical contacts be considered potentially dangerous? Danger may be direct (e.g., due to electrical shock) or indirect (e.g., due to fire risk). In this ...
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938 views

Why do 0.02A fuses not protect a person? Why no protection from shocks?

I understand the user here so that fuses do not protect people from shocks. I am planning to put put fuses such as fast-blown fuses and PPTC fuses around all kind of positions such as computerUSB-...
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2answers
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Are touch lamps safe?

I've used "touch lamps", where you turn it on and off by touching the lamp. As I understand it, this works by putting a small electrical voltage through the human body: touching the lamp completes ...
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958 views

Static dissipative ESD footware

Are shoes like this used in professional labs or is this just a gimmick? http://www.esdshoe.com/products/Lightweight-Classic-Mid-High-ESD-Composite--Basketball-Shoe-%252d-Men%27s.html
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Mobile phone battery charger

I would like to know about the workings of mobile phone battery chargers. I know the basic principle, you take a transformer to bring it down to 9/6/3.7 volts then a bridge rectifier circuit and a ...
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Connect anti-static wrist strap to earth wire?

I have started doing some hobby electronics at home and got myself an anti-static srtist strap recently. I am unsure as to where to attach it to. Most topics I found online regarded PC building and ...
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How does power in “wall wart” power supplies work?

I'm new to electronics and am having trouble understanding how power supplies convert 120AC into a safe, manageable DC voltage. So far, I understand that there's a transformer to step the voltage down,...
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299 views

Food safe electrical cabling

I am currently developing some electronic sensors for use in monitor food quality. This type of device requires running electrical cable though piles of food products. What type of electrical cables (...
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2answers
245 views

cable jacket melts

I am new to hardware. My breadboard just arrived and I am trying to light up my LED. I used computer power supply for power (red wire for + black for -) and used strands of LAN cable for connect LED ...
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536 views

Battery pack a little bit damaged. Should I throw it out or repair?

Today my 48v 15Ah LiFePO4 ebike battery fell off from my bicycle and got a little bit of road rash on the corner: It still works. Does not seem to be heating or discharging on its own. However, ...
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895 views

Oscilloscope for troubleshooting higher voltages?

I'm working on a friends inoperative Miller 300 Amp DC inverter Tungsten Inert Gas (TIG) machine. These machines convert 240v single phase A/C to DC, then use IGBT chips to generate controlled DC ...
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Safety when using ATX power supply as benchtop supply

I found many pages where people convert an ATX power supply to a benchtop power supply to give 12, 5, 3.3V. However the current output can be very high (several amps). When using this and you NEED ...
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Can I charge a NiCd battery with a NiMH charger?

I have an old NiCd RC battery pack. It was not used for at least ten years but when I tried to charge it with the old charger I was suprised to see it still had some capacity. Now I just went and ...
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Can 12v dc circuit spark and start a fire?

I'm new to electronics and electricity. I have the following scenario: I am wiring a LED light switch and mounting it into wooden cladding. My concern is, can the wires spark unexpectedly and start ...
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Connecting a higher-current power supply to a lithium-ion charger will damage the battery. Why?

I am not asking how the battery gets damaged, because that answer is straightfoward. What I am asking is why lithium-ion chargers allow batteries to be damaged by excessive charge current in the ...
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Safety Equipment and Precautions for DC Circuit Experimentation and Development

What safety equipment and precautions should I use when learning about, experimenting with, and analyzing DC circuits? I have a power supply capable of 32V@5A and 16V@10A (which supports selectable ...
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1answer
134 views

Why is touching the live wire of a socket dangerous inside an apartment few stories up?

Let's say I touched the live wire of a power socket in my apartment that is located at the fourth floor of an apartment building. The current needs to flow through my body to ground in order for me to ...
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970 views

Does a lamp need a fuse? [closed]

I have a floor lamp in which I have installed 2 LIFX Color 1000 A19 Wi-Fi LED Smart Bulbs (http://www.lifx.com/products/color-1000) The lamp is designed to have 2 bulbs and has a two position dimmer ...
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1answer
663 views

Do they make variable isolation transformers?

As I start to set up my work bench, I've been looking at various isolation transformers, and I wondered if they have ones that use a variac as a secondary? I know variacs are autotransformers so it's ...
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1answer
168 views

Safely testing a DC supply with an unknown output configuration

This picture shows the connector for the DC end of a power supply I extracted from a dead HP MFD (Multi Function Device): As you can see it consists of 4 pins in a 2x2 configuration. The sockets ...
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Why is it safe to touch the chassis of a tube amplifier and something earth grounded simoultaneously?

I'm hoping this is not too much, originally thought it would be a simple question, but the more I thought about the matter, the more I could see this wouldn't happen. If it's too much I hope some of ...
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880 views

How to properly isolate multiple power supplies

Say you have a single 110V AC supply and need to use it for a number of devices, each requiring very different characterists. For me personally these are: a direct use of the 110V AC supply for a ...