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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105 views

How is this 22 AWG cable rated 4 Amps?

I found the cable (1533576 - Actuator/Sensor-Cable, M12 Socket - Open End Connector, 2m, 4A, 250V, Phoenix Contact) here that is claimed to handle 4 A and is then written that it has a 22 AWS cross ...
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1answer
29 views

Electrostatic arc safety

I'm experimenting with early electrostatic devices, and I'm measuring spark gap length to determine voltages generated. How dangerous is it to observe these arcs with the naked eye? Should I wear ...
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1answer
33 views

Safely wiring a 120v smoke detector externally

I am building a relay box that will cut power to an outlet if an attached 120V smoke alarm detects smoke. The relay box itself will be a grounded metal electrical box hardwired to a 3 prong plug. It ...
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1answer
37 views

Calculating maximum permissible track amperage for intrinsic safe PCB

I'm reading IEC 60079-11 standard (Equipment protection by intrinsic safety "i") which discusses how to design intrinsic safe circuit boards. In section 5.6.4 it talks about permissible ...
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1answer
75 views

Can the skin / copper oxide / copper junction of an old exposed mains conductor produce a safety-significant DC component to a shock?

Copper oxide diodes are not common now but were a standard item along with selenium oxide for early power rectifiers (think old radios and those components with stacks of fins). Can the oxide layer on ...
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33 views

Is putting a board inside an anti-static enclosure enough to make it Ex ib ready?

A year ago, we made a handheld PDA based on RPi0 for a client. Now they have asked us to certificate it as Ex ib IIC T4. Here is the PDA's spec: RPi0 as processing board 4.3" capcitive LCD A ...
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1answer
79 views

Where is Pb (lead) found in an immersion heater? [closed]

Clicking "Technical data" on this page gives a pretty good overview of the composition of immersion heaters: Terminal, End Seal, Cold Pin, Alloy spiral, Sheath, and Insulation. Having ...
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1answer
45 views

Constant current driver and undervoltage protection for lipos

I'm searching for a way to drive a couple LEDs with a single-cell LiPo battery, such that the LEDs will be cut off completely when the LiPo voltage drops below, say, 3.3V. PCB space, component count ...
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91 views

Maintaining clearances in HV MOSFET footprints

I'm thinking of making a prototype PCB which would use a bridge rectified AC, which will end up with peaks around 350V in my area (+/- some smoothing). It's a through-hole design and the circuit will ...
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0answers
95 views

What is the benefit of a male output connector on a powersupply?

I saw several power supplies which use a male output connector. For example the Meanwell OWA 90E series uses a XLR 4P or ...
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2answers
69 views

When to consider Peak current/voltage vs. RMS current/voltage and vice versa

When manufacturers create power labels for AC electrical devices, what value to they use for the current and voltage? Do they use the RMS of the sine wave? Or do they use the peak of the sine wave? ...
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4answers
88 views

Does an isolation transformer make CRTs any safer to work with?

CRT tubes are often described in training materials as huge capacitors capable of delivering very high voltages, often enough to severely injure or cause death. Before working on them, they should be ...
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1answer
44 views

Saftey regulations of multiple 1mW lasers

AFAIK devices containing exposed 5mW lasers are illegal without a license, but those containing 1mW lasers are. But how about a device with ten 1mW lasers? Is it still a safe and legal device? The ...
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1answer
81 views

Is it possible to protect against ANY overvoltage?

Inspired by this question. Suppose I'm making something like a security system and I'm worried about a malicious person trying to knock it out with high voltage on some of the incoming wires. Let's ...
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1k views

Safety precautions when making a commercial electronic product

I have designed and fabricated an electronic device. High level explanation for this device is as follows: The device designed scans the environment for RFID tags and when a tag gets too close to the ...
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1answer
81 views

Safe to turn off power by removing a plug fuse indefinitely?

I'm trying to turn off the power for my dining room light and as I live in an old apartment, my fuse box only has plug fuses (and a main fuse you pull out). My plan is to cap the AC wires in the ...
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27 views

One double pole relay or two single pole relays for live and neutral?

I'm designing a PCB that will control AC 240V electric tools. For now I decided to use a single double pole relay to switch live and neutral lines. Is it also safe to use two separate single pole ...
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157 views

Will my 555 timer circuit work the way I want it to?

Essentially, I am trying to implement a safety system for another project of mine. I am running a very high current through a rather large solenoid and want to ensure that a failure in its control ...
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1answer
53 views

Right way to couple DGND to Chassis ground

So we all know certain things: DGND (and subsequently AGND) needs to be coupled to Chassis ground, or Earth at one position, at least, in a device. The Earth is otherwise considered as a hazardous ...
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5answers
2k views

How to safely power a large LED strip project

I'm making an LED matrix with a board and 4X WS2811 strips (5 m length, 150 LEDs). Each strip is 45 W, takes 12 V and is 3.75 A. I have connected them in series and injected a 12 V, 60 W/5 A adapter ...
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0answers
19 views

Standards Compliant High DC Load Safety Interlock System

I have a single AC-DC supply (42V @ 600W) which supplies three motive loads. Each motive load is physically separate and has its own cover which prevents the operator from gaining access to the moving ...
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1answer
25 views

Identifying Neutral/Active when wiring a caged SMPS

Just received a switch mode power supply from china and wanted to double check everything before applying power - The screw terminals coming from the cage have Live, Neutral, Ground marked with a ...
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1answer
79 views

High Voltage Safety Questions

I'm working on a project that uses 1700VDC provided from a 220V:1200V isolated toroidal transformer, bridge rectifier and filter cap. I have no experience with high voltages, so I'd like to ask you ...
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1answer
74 views

Handcuffs as protection?

I am not familiar with electronics at all, but as I was strolling through the stack exchange network I've noticed how it is dangerous to electrocute oneself by touching a wire with one hand and ...
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1answer
517 views

What is this electrical symbol? T with overbar in down-pointing triangle

I'd like to use an old laptop AC adapter in conjunction with an adjustable buck module as a project power supply. It works, but I'm ignorant of some safety details; for example I'm uncertain whether ...
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2answers
241 views

ESD protection during lightning storms

I'm new to electronics, and I'm currently building my electronics area. Let's say that I have an ESD bench mount drilled into my wooden workbench, and this ESD bench mount is then connected to the &...
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1answer
89 views

Are IR LEDs placed under the same category as lasers?

I am creating a device which uses IR LEDs to illuminate the human eye, while an IR camera records the pupil dilation. From my research, I see that there are two standards which are related to the ...
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1answer
63 views

Replacement of a safety capacitor

I would like to know if I can replace a safety Y2 capacitor (222m 300V - which is a 2.2nf-)with a safety X2 capacitor temporarily. I'm in a hurry and I already ordered the replacement part but while I'...
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1answer
85 views

PCB Mounting solutions in outdoor enclosure?

I've completed the design for my pool timer and now I'm down to designing how this board will actually hold itself inside an enclosure. I already have a box that I'd like to re-use. It looks like ...
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3answers
133 views

How to connect 5 kW electric heater to the weak wiring in house?

The water heater has a 5kW heater and requires 20A. Unfortunately, the wiring in our house is old and this allows us to get only 10A. Is there an easy way to reduce energy/current consumption and ...
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0answers
59 views

Heel strap vs wrist strap around ankle

I am a novice to electronics, and I am currently building a home workstation. In this question on ESD chairs, the user Sparky256 said the following in his answer: If you are wearing BOTH a wrist and ...
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2answers
263 views

ESD chair for home workstation [closed]

As mentioned here, I am a novice to electronics, and I am currently building a wooden workbench. The workbench will have an ESD bench mount and ESD matting over the entire bench. Furthermore, the ...
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2answers
73 views

How does equipment ground protects us from electrical shock?

What I have always learned is current leave the source and return back to the source, forming a closed circuit, here are the two thought experiments I had and got confused: Scenario 1: Here I have a ...
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2answers
83 views

ESD safety when working across multiple workbenches/tables

I am a novice to electronics, and I am currently building a wooden workbench. The workbench will have an ESD bench mount and ESD matting over the entire bench. I now want to have a small fold-out ...
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1answer
103 views

Is there a safe way to operate any type of a tesla coil on a functioning modern car (moving road vehicle)?

(Updated with clarifications) Could a tesla coil be safely built, installed and operated on an active road vehicle which is driving a regular city street? Let's say we want the discharges to be 20-...
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0answers
44 views

How safe are Isolation Amplifiers compared to Voltage Transformer

I was searching for a miniature transformer for my 240V AC voltage measurement circuit and a kind individual recommended me a pecular IC. The IC is a Differential Isolated Amplifier AMC1100. And it ...
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1answer
43 views

How much clearance do I need between floating ground and earth referenced ground?

I have two circuits where one side is earth reference and another floating. The floating circuit is isolated by a transformer and talk to the earth reference circuit via opto-coupler. During final ...
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1answer
63 views

Maximum amps over 24 AWG CAT5 wires [duplicate]

I have a project that runs on 5V and should draw a maximum of around 500 mA. There is an existing CAT5 cable running conveniently to this project. I'm considering powering the project by using two of ...
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1answer
53 views

Connect the oscilloscope to equipment with a common neutral and ground

I watched a video. At 3 minutes, the situation is shown when neutral and ground are joining. Why can this be dangerous? If we are talking about an oscilloscope, the crocodile must already be connected ...
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1answer
76 views

Checking if a device is safe to use

For someone with no knowledge in electrical engineering, is there a way to check if a device is "grounded" (?) and safe to use? It is not uncommon when shopping for appliances online (eg. lamps), ...
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4answers
269 views

Undervoltage protection strategy for Li-ion batteries

We are using a Li-ion battery with built-in safety PCM (Enix MGL9070), a gas gauge to monitor the battery voltage (STC3115A from ST) and a battery charger (bq24133 from TI). To protect the battery, ...
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1answer
47 views

Electric shock from cover of preamplifier

I'm using a Focusrite Scarlett as a preamplifier between my computer and amplifier. The preamp gets power only through a USB connection. Sometimes when I touch the cover of the preamp, I can hear a ...
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2answers
77 views

Feedback regarding isolation practices on a 5V/Mains PCB

I am currently designing a PCB for a project including PID-control of a heater. The heater runs on mains (220V) and is controlled using zero-crossing switching to regulate the power and minimize EMI ...
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1answer
52 views

Temperature of Power Driver ICs

I'm using TI DRV595 power driver in an application requiring several amperes of current. My observation using thermal camera has been that at 3.5 A the driver IC core reaches temperatures around 90 ...
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2answers
78 views

Overvoltage + Overcurrent protection

Our compliance agency believes that it is all too likely that a 50 V power adapter is used instead of our 5 V power adapter. Regulation wants a fuse which can protect from 50+ V, and not allow 15 W ...
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3answers
127 views

How much 12V DC current can I safely draw from an AC 230V 13A socket and why?

In my cabin I have a sollar cell and a 12V battery that I use to power my electronics. However I'm dissatisfied with the standard CL sockets used in cars (apparently I'm not the only one) and I ...
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0answers
25 views

Lithium Ion Battery - Testing & Self Discharge

It is suggested and commonly understood that if Li-ion batteries drop below a certain threshold that we consider the cell(s) unstable and untrustworthy with a loss in cell capacity and that increased ...
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3answers
136 views

What's the difference between these plugs?

I'm not an electrical engineer, but I play one on TV. Can you help me be more realistic? Our facility has three items that run on three phase 208 and plug in at a temporary building using CS (...
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1answer
49 views

UL certification and laser tag equipment

We are a 32+-year-old laser tag equipment company. We purchase parts overseas and assemble them in the US and have hundreds of installations all over the world. We have been told by 1 location that ...
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1answer
37 views

Deep cycle battery charging ventilation [closed]

I have a small boat and the main deep cycle battery is located just under a "shelf" like thing near the transom that acts as a cover for the gas tank and battery. On one side, it is completely open (...

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