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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1answer
69 views

How to use FG ground on a meanwell buck DC\DC power supply

I would like to know how to safely connect a 48V 200A battery to a step-down converter. The step-down converter is this. SO the step-down converter is to be used inside a forklift to drop the 48V DC ...
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0answers
21 views

Will these gloves comply with electrical arc flash safety?

I am beseeching any OSHA, CalOSHA or electrical safety experts out there on this one for a little help. I know this is not strictly electrical engineering but this is the closest Stack to the topic. ...
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1answer
43 views

Are capacitor vents safe to touch?

I couldn't find this information anywhere. Every tutorial on how to safely handle a capacitor tells you to absolutely avoid touching the capacitors leads, and to grab a capacitor by its insulated ...
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9answers
72k views

Is soldering wires directly on a NiMh battery safe?

I'd like to know if soldering two wires directly on a NiMh battery is considered as safe or not. My fear is that battery would explode (right in my face) because ...
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3answers
129 views

What are the safety and device risks associated with not connecting the grounding prong on a 120V AC device?

For example, imagine a device that comes with a 3-prong (grounded) AC plug. What are the risks associated with, for example, plugging this device into a 2-prong extension cord which effectively ...
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5answers
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Are hand held AC power testers (the ones that looks like a screwdriver) completely safe? Why/why not?

What are chances that the carbon resistor gets shorted and we experience lot of current and die? Cause of doubt arisal: https://www.youtube.com/watch?v=wLAJ-keFmpk
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1answer
40 views

How do I safely measure secondary transformer voltages (Or ratio to primary)?

Let me begin by saying that I am a hobbyist, and I've been stupid with transformers before and I'm fed up with that. This question doesn't have to do with design so much as just not killing myself, ...
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2answers
9k views

Dangerous to store jump-starter power bank in car when outside temperatures peak at ~105°F?

I'm looking to buy a portable jump-starter power bank that's rated for up to 140°F. I'm wondering how dangerous it would be to store it in the car (trunk or globebox) if I know outside temperatures ...
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4answers
3k views

Is ground connection in home electrical system really necessary?

I know that the answer to my question is "Yes, it is!". The ground connection is needed to avoid a person touching a metallic part of faulty equipment to be electrically shocked. So the ...
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2answers
115 views

Safety rules for DIY projects involving 220V

I'm planning to add some home automation to my home, using a 5V relay and most likely an ESP8266. This will be used, for instance, to control the lights or the heaters, certainly through Home ...
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4answers
134 views

How to dim one of these cheap 5mW laser modules?

I used to have an old 3x LR44 lithium cell laser pointer for presentations. With the batteries slowly dying, the outputted beam also went dimmer. Recently I bought one of these cheap 650nm laser ...
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1answer
175 views

Battery Disconnect Switch

I'm an Electrical Engineering student still new to power systems. I'm working on a project that uses a 24V and 200Ah battery bank made up of 4 AGM lead acid batteries. The batteries are supplying four ...
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1answer
470 views

Designing single fault safety into class I device

I'm trying to wrap my head around safety standards for electrical equipment. My device is medical, so for me section 8 of IEC60601-1 is what really matters to me, but it's kind of my understanding ...
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5k views

How to safely discharge oneself

At work I have the problem that I seem to collect a lot of static charge as soon as I leave my desk and return. I am not quite sure why this happens. Strangely enough the effect is stronger the ...
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1answer
167 views

Normally Closed Negative Output, Positive Input Relay

I'm attempting to wire up my remote start in my manual transmission vehicle to ONLY start when the vehicle is in neutral. The way that the transmission works is like this: When in neutral, resistance ...
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4answers
111 views

Can measuring back EMF spikes damage the oscilloscope?

I want to measure the voltage across an inductor as soon as I disconnect one of its terminals to visualize how back EMF changes with and without a fly-back diode. From videos on Youtube: https://www....
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2answers
199 views

How 3mG can be dangerous if the Earth's magnetic field is 500mG? [closed]

All the things I have read says that magnetic fields above 3milligauss is dangerous for people. How this can be true if the Earth has a magnetic field of 500mG? Do smartphones and gaussmeters measure ...
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2answers
210 views

Is this a safe way to add extra current control for a DIY tDCs device?

I have put together the well known DIY tDCs-device Inthinkerator MK1, and wanted to add an extra safety feature, but I dont know if this is the correct way to do it. The original design is without the ...
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1answer
74 views

Is printing a PLA box for electronic components safe?

not sure I'm in the good place. I'm working on a small project, building a connected light dimmer for my home. I'm using a raspberry pi zero and an AC dimmer (this one : Universal AC MAINS Dimmer - ...
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1answer
237 views

Power supplies with medical safety approval

Regarding the data sheet of this SMPS power supply. In the first page it says: 2 x MOPP Medical safety according to AAMI/ANSI ES 60601-1:2005(R) and IEC/EN 60601-1 3rd edition Then I googled to ...
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1answer
76 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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3answers
113 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
71 views

Safety Rule: Sum of wire lengths over two phases may not exceed X. What is this for?

Everybody knows various flavors of the rule "don't connect too long electrical lines to an outlet / generator / whatever". They sometimes come in the form of "don't chain your extension ...
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1answer
34 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
38 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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0answers
34 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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8answers
39k views

Is hot glue a good insulator?

I need to mount some relays that I have soldered wires to. If I place them on a non-conductive surface and use a generous amount of standard glue from a hot glue gun, will that be relatively safe? I'...
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2answers
125 views

Symmetrical power supply: Rail fuses useful or dangerous?

I'm designing/testing power amp stuff with symmetrical power supplies (43V-0-43V). In the next future I'm planning to control all safety/healthy stuff (like over current / over voltage / temperature ...
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2answers
6k views

I just blew a capacitor. Now what?

We worked two years on and off on this project at my friend's place. Finally we finish, I take it home. There's a power supply unit but it can't be connected directly to mains, it expects some lower ...
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2answers
1k views

Definition of Field Wiring Terminals as in UL 499

I'm wondering if anyone can tell me where I can find the definition for "field wiring terminals" as referenced in UL 499 "Standard for Safety Electric Heating Appliances" table 27.1 "Minimum ...
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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
201 views

Can I simply add a 240V Neutral to SONOFF TH10 when replacing wall thermostat

So, I have purchased a SONOFF TH10 wanting to use it to replace my wall mounted thermostat. The thermostat has 2 connections: Always-Live and Switched-Live (which is activated of course by the ...
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1answer
46 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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2answers
98 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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1answer
125 views

Does this circcuit pose a safety risk that could be avoided?

I was looking over the circuit design for OpenEVSE. I was specifically interested in the GFCI portion of the circuit: This circuit measures the current difference between Line and Neutral on a 120/...
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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
436 views

Ws2812b circuit safety with 5V 12A

i am making a arduino project using 5v ws2812b 300leds/meter. Its going to be a motion activated led strip that runs along the side of the stairs. I will be using 3.5m of the led strip so 210leds at ...
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2answers
73 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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1answer
138 views

ATEX: PCB design for intrinsically safe, output capacitor

We're looking into restricted breathing or encapsulation concept because PCB has a complex circuit that makes it impossible to achieve SMD clearance under 'ic' or increased safety concept. I have a ...
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4answers
95 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
83 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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1answer
58 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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6answers
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
84 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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0answers
159 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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0answers
30 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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1answer
179 views

lithium coin cells, safe to completely cover? lightweight method to protect from the environment

I am trying to make equipment to measure temperature in small mammals, probably attached to a neck collar. The collar needs to be very lightweight (e.g. <3g total) so I am planning to use a ...
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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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