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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What can I do to reduce risk with buying DC converters online [closed]

I'm finding myself moving into obscurity when it comes to stuff I want to do with computers that involves electronics but don't have a background in electronics. Recently, I've wanted do deploy ...
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4 answers
92 views

Can I run resistor at a power higher than rated if I have external cooling?

Say I have a 1 ohm 100 W resistor that can work properly in still air. I now want to run it at 150 W, but I am also using a strong fan to cool it down to its usual temperature. Is this okay?
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What is a safe amount of resistance required for a 9V battery?

I am new to electrical circuits and created the following circuit using falstad: With a 9V battery, what is the least resistance (instead of the 220k resistor) required to: Complete the circuit Not ...
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1 vote
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Should a 5V wall adapter output 150V pk-pk AC relative to earth?

I've recently bought a wall adapter off amazon which claims to be able to output 5V @ 2A. I tested this adapter by connecting a probe to the +5V output, and WOW! My scope shows a 150V Pk-pk 60 Hz... ...
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3 answers
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Interrupt rating of all fuses in branches of same circuit

I am redesigning my boat's DC electric circuit, and when looking at the main battery fuse to determine its correct interrupt rating (i.e. the current the fuse will be able to fully interrupt without ...
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Metal fork creating scorch marks and sparks in microwave oven [closed]

I had a metal fork in a bowl in a microwave oven. I turned it on, the turning plate rotated, and the end of the fork struck the back wall of the microwave. There were sparks, and a black arc ...
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Does this AC to DC + breadboard setup have the ability to kill/severely hurt me?

I'm currently building a PC peripheral that uses an AC to DC converter to power a set of DC fans. I'm not a trained EE or electrician, so I want to make sure I'm not putting myself a risk with this ...
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TP4056 - high temperature

The TP4056 (1A) gets very hot (around 80-100*C) when charging the cell, so much so that it is impossible to hold it for more than a few seconds. Is it safe to use this circuit without any cooling?
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IR LED Safety: Subtend Angle and Retinal Exposure Limit

The relevant formulas from OSRAM AN090 "Eye safety of IREDs used in lamp applications" with slight modifications : $$ Z = (l + w)/2 $$ $$ \alpha = Z/d $$ $$ L_{ir} \approx \frac{I_e R(\...
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2 votes
2 answers
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Power camping lantern with 12v AGM battery

I have a 3 AA battery powered LED camping light/lantern. It draws (measured with a multimeter in series) about 18 mA when ON and 0 mA when OFF (ON/OFF controlled by a switch button). It’s ON all night ...
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7 votes
2 answers
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Do neon signs emit x-rays?

I'm interested about whether or not a conventional neon sign such as this one could emit x-ray that could be harmful. The sign that you can see in the picture is just below my office window so I'm ...
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What prevents old (low current) USB cables from catching fire if used to Quick Charge modern devices (at high-current)?

Let's say I have A very old Micro-USB cable. It's USB 2.0 and rated for a max current of 5V, 0.5A (2.5W). A modern, power-thirsty, quick-charging tablet that charges over micro-USB at a max of 100W. ...
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5 answers
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Help designing a safety indicator for a high current transformer

I'm working with a neon sign transformer and want an indicator (preferably a light) on the high/output side to give me a visual cue when there is current coming out of the transformer. I'm not 100% ...
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3 votes
3 answers
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How can failure of Class Y capacitors lead to electric shock?

This article mentions "Due to the fact that equipment cases are usually grounded, Y caps require higher safety to avoid risks of electrical shocks to users" How can an equipment with ...
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How to safely protect input sensing AC Line Voltage

I'd like to detect the presence of AC line-level voltages in my PCB project, and I'd like to follow best-practice for doing this. I'm a controls engineer so I'm happy with dealing with mains with ...
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What conditions are required for a Lithium Polymer battery to ignite?

If a Lithium Polymer battery cell sustains a small amount of damage that only effects the pouch (eg a small puncture or tear in an area where no contact is made to the electrolyte / anode / cathode ...
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2 answers
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Use of multiple earthings for single installation

For a home electrical wiring, is it acceptable to have to multiple earth rods on different (reasonably apart from each other) locations? In good practice, to keep earth resistance low, we use multiple ...
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1 answer
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Button contact ratings

Inside an enclosure, a device is powered by an SMPS as follows: The device operates under 12 VDC and sinks 6 A from the SMPS. The SMPS is wired to AC by an IEC inlet. Now I want to install an ...
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1 vote
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Safety transformer second fault

I understand the working principles of these types of transformers as there is no connection to earth on the secondary but still can’t get my head around the safety aspect if there was a second Fault ...
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2 answers
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Simple e-stop circuit

I have a motor controller that has an electronic stop function where if I put 5v on a pin the motor runs. Once that 5v gets interrupted (goes to ground) the motor stops immediately. On my device I ...
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1 answer
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Have I been poisoned by lead dust from my blown fuse

just wondering if I've poisoned myself. I was doing something silly and the 10A fuse exploded in my multimeter with the glass cylinder and alloy dust shattering and splattering making a mess on the ...
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Load testing using a resistor bank

I have a bespoke 48V down converter that I'm looking to test which should be able to provide a maximum of 500W of power. I'm looking to test the device under various loads - from 50W to 500W. I'm ...
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24V DC Industrial equipment - which IEC standards to comply with

I'm trying to design a commercial industrial product/PCB for the first time. In order to do it "right", I would like to be aware about the most common IEC / IPC standards to comply with. ...
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2 votes
1 answer
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Why does Japan use 100V AC as opposed to 120 or 230V, and why are many of their plugs ungrounded?

I don't live in Japan but I have noticed this interesting phenomenon when it comes to their electronics. I'm buying a PC-9800 and because it remained isolated in Japan its power supply is only rated ...
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1 answer
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Singular 15kW VFD - Arc Flash Risk

In our research lab we are setting up a VFD to run an experiment. The power comes into the building through a 45 kVA, 240 V, three-phase transformer and the project will be powered from a 240 V three-...
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How to protect home from the main connection line short circuit?

I am living in a village and we often face issues with main connection input neutral getting shorted and having good amount of current/voltage. The transformer often gets issues, disrupting supply and ...
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2 answers
138 views

How unsafe is 220V over NEMA 5-15 really?

I'm from the Philippines but the U.S. had a very large influence on our electrical standards. It is especially evident on our electrical sockets. While all of the sockets in a typical Filipino home ...
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1 vote
0 answers
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What is this electric heater thermostat component for?

I am trying to fix an old electric heater that does not turn on. After opening the casing, I identified the part in the picture to be probably a bimetallic thermostat. When I push the part with red ...
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0 votes
1 answer
106 views

Can solder sucker tools release lead particles?

I have been desoldering a lot in my work. I use those manual spring solder suckers. I noticed that the opposite side of the nozzle ( the plunger, where the thumb goes) is impregnated with solder ...
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-1 votes
2 answers
47 views

LED Bulbs are not shutting off correctly

I just bought a house with LED lights in the dimmable ceiling fan that never shut off. I thought the fan was defective. But I put new dimmable LED bulbs in, and everything worked fine. I found that ...
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Is there any standard or norm for this situation?

Considering a metallic enclosure(which has PSU and electronics in it) with an IEC mains socket, an example shown below: And it uses an IEC power socket such as: For this kind of enclosure is there ...
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2 answers
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Electronics take-apart student activity

We're planning a (6th-8th grade) student take-apart day, with small non-functioning items like hair dryers, clock radios, coffee makers, etc. (no microwaves, TVs, monitors.) Even though items have not ...
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Can an extender with USB ports be wired direct to the mains?

I have an extension lead that has been wired directly into the mains (there is no space behind a cupboard to plug it into the wall socket that was there). I think this is the same situation as adding ...
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Is earthing pointless without a residual-current device?

I don't quite understand what the situation is with the safety ground. In theory, it evens out the voltage to zero but only if the resistance is exactly zero. Even if the ground has only a resistance ...
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-4 votes
1 answer
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Mosquito SOS - Bangalore

We have mosquito rackets at home, i think it is too harsh a way to deal with things living. Is there a way to down the effect of the shock from them? I'm in India, Bangalore.
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6 votes
1 answer
266 views

What are the drawbacks of connecting circuit GND and Chassis via multiple mounting screws (for EMC and Safety)?

Although there are various suggestions around for how to connect circuit GND to the earthed chassis (say, the chassis has a point-to-point resistance of around 1 mΩ) in devices, there seem to be two ...
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6 votes
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Is lead color a safety issue?

BNC to alligator clip connectors were made for a function generator in our lab. Whoever made them decided that the ground connector wire should be red and the signal connector wire should be white. ...
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1 vote
3 answers
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Why are Fuses on space heaters necessary?

Why does a space heater (electric fan heater for home use) have a fuse? Isn't the house itself connected via a circuit breaker? Wouldn't that stop potential safety issues? PS: First post on here :)
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Can I charge my laptop with powerbank? [closed]

I have a Lenovo laptop with a L16L2PB3 lithium-ion battery. It has 4610mAh capacity which is enough for 3-4 hours of power. I want to have an ability to charge it when no sockets are around and for ...
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-3 votes
1 answer
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"Our auto cradles operate on DC power, So there is no chance of electricity shock. It's 100% safe for babies as well as for parents." Is true? [closed]

I am not electrical engineer but I have a doubt that DC power can give shock to human or not. I am trying to buy an electronic product which i have to plug with power. This will be for a baby so i ...
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0 votes
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Using components (in a modular synthesizer) that contain vactrols -- safe for the end user?

I am looking to purchase a MakeNoise modular synthesizer whose modules use vactrols (I've been told). I was told that the "Optomix" module, which is discontinued, uses them, but other ...
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Is this type of polyethylene mat ESD safe?

I have a few metal keyboards which have a slight risk - if there is too great a charge, it will go through the case and potentially short the PCB inside. Ideally the case is designed well enough to ...
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0 votes
2 answers
55 views

New lithium ion battery cells stored in small cardboard boxes, potential fire risks? [closed]

I have some new lithium ion battery cells stored in individual small cardboard boxes at room temperature with low humidity. Are there possible fire risks storing the battery cells like this? I'm ...
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1 vote
3 answers
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How to guarantee clearance/creepage on mains side of an optocoupler used for 230VAC zero-crossing detection?

Update: Added a diode to protect optocoupler LED As stated in several safety standards (UL 60950 or UL 60750 for example,) we have to guarantee a minimum clearance/creepage between signals of opposite ...
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Are there water heating elements that literally explode when turned on dry?

When I grew up these things were pretty commonplace: In case you've never seen one, it's a very primitive water heater that you simply place inside a pot of water (or a jar, or even a cup of tea-to-...
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Making a variable transformer "safe"

I have a US mains voltage variable transformer that I am using as a variable DC power supply for some robotics experiments I am doing. I have built the below circuit in a metal box that is grounded. ...
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3 answers
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Detecting enclosure voltage for batteries

I have made an enclosure out of metal that is used to enclose my battery pack. I have stacked this enclosure with 18650 lithium batteries to build up a battery pack (24V). Every time an error is ...
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Is the SWER (single-wire earth-return) system dangerous? If not, why not?

When a live/hot wire touches the Earth ground, it creates step voltage and so it's dangerous to walk on ground during this fault. But in a single-wire earth-return system, we use earth/soil as ...
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How to specifiy my USB cable so there is no risk of fire?

I am making a USB powered device that draws very little power. It is powered by a USB 2.0 cable, with the power wires soldered to contacts on the PCB. The cable has to be about 3 meter (10 foot) long. ...
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-1 votes
2 answers
180 views

Can I use this US extension cord in Europe? [closed]

Long story short: I need an extension cord to charge my EV when the standard charger does not reach the socket. I spent hours researching what options I have and most review websites I found were US-...
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