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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66
votes
9answers
375k views

How much voltage/current is “dangerous”?

Related: Safe current/voltage limit for human contact? From what I've heard: 110 V (or 220 V; household voltage pretty much) is dangerous (i.e. can kill you) I think there's consensus on this, ...
0
votes
1answer
51 views

AC power supply safety

I am planning on building a vintage tube radio from schematics. Part of the radio will include its (multi-voltage output) power supply, with an AC power cord, AC switch, and transformers. Are they ...
3
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2answers
761 views

Is a capacitive touch screen safe to use?

I was reading about capacitive touch screens. I understood that your hand picks some current flowing on screen. That sounds alarming. Is it safe to use a capacitive touch screen, since it picks small ...
1
vote
1answer
2k views

Proper Chassis Grounding

I'm starting to design things that run off mains voltage and I want to be sure that I have a proper connection from my chassis to earth ground. I've been reading a bit about proper grounding and have ...
2
votes
3answers
737 views

Is a separate safety earth connection necessary when using an earthed power entry module?

Testing the Schaffner FN1394-10-05-11 power entry module with a multimeter shows continuity between the ground pin and the body of the module. Consequently, when the module is fitted into an aluminum ...
1
vote
1answer
112 views

Are there more (mains) electrical safety incidents in the United States compared to the UK? [closed]

Forgive me if this question isn't exactly "on topic" for this site -- it's a bit meta. I am an academic in the UK, and I occasionally design electrical devices that plug into "the mains" in one ...
0
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1answer
57 views

How to measure laser class of LIDAR

I just bought a LIDAR with the intention of building an indoors robot that uses it to navigate rooms in my apartment. The manufacturer website states: Low power infrared transmitter conforms to ...
6
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3answers
6k views

Maximum Current Draw on Vin Pin

I don't want to damage the pins on my Arduino Uno, and I'm especially cautious of drawing too much current. I'm experimenting with a small servo motor (similar to this one), and have connected the ...
0
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3answers
67 views

Electrical Standards - Earth Wire at Low Voltages?

I got a question about safety standards: I'm designing a consumer device and I'm not sure whether I need an earth wire. I have an AC-DC converter plug that outputs 5 V and up-to a maximum of 1 A ...
0
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1answer
75 views

How to power up a project with 3 devices, between 0 and 12 volts

I'm working on a project which involves a DC heating element, a computer fan and an Arduino/ESP8266. I'd like to use one power supply for those devices..... The requirements: The heater needs a ...
1
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1answer
239 views

Designing a 2S Li-ion charger with 5V 2A input

I'm interested in designing a few similar charging circuits based on the specs of the title which is getting a charging for 2 cells in series(or more) from a 5V input. Now my question is: Assuming I ...
0
votes
1answer
870 views

Using a residual current device when there is an isolation transformer

In a system, currently there is no circuit breaker and RCD, but there is an isolation transformer as in the diagram below: simulate this circuit – Schematic created using CircuitLab As you see ...
1
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0answers
93 views

How to know what is the safety standard to apply to a PCB design?

I want to design a PCB with some points at some KV during certain times, less than 10KV and no more than 30mA of current. After dealing with concepts and getting the main idea about my circuit needs, ...
0
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3answers
124 views

What connectors should I use with 5V DC current?

In a personal project, I need to power several 5V appliances which, together, use up to 12A. I want to use a 60 inch cable between a case to which those appliances are connected, and the transformer ...
0
votes
2answers
268 views

Is it safe to measure 220Vrms@50Hz on DSO directly?

I borrowed my friend's DSO to complete my project(Hantek DSO5072), but on scope it says CAT II/400V. So is it safe to measure 220Vrms@50Hz with it?
2
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2answers
88 views

Earth continuity of slot together aluminium enclosure

If I were to use a slot together aluminum enclosure for a mains powered device, and I earthed one panel of the enclosure by fitting a stud, how could I ensure continuity of the earth to the whole ...
5
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3answers
2k views

Safety of Aluminium for enclosure earthing

To earth an Aluminium enclosure, is it safe to use a welded Aluminium stud and then use a nut and washer to attach a hook-ended earthing wire to the stud? Aluminium oxidises to develop a thin ...
0
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0answers
44 views

Does the Machinery Directive (EN60204) require separate mechanical Start and Stop switches?

I have a prototype machine with mechanical moving parts (all contained inside a transparent interlocked enclosure) to review. Single-phase AC power enters at the rear via a fused IEC 60320 C14 inlet, ...
17
votes
8answers
72k views

Why is it dangerous use a coiled extension cord

What aspect using a coiled extension cord makes it more dangerous than using an unrolled power cord. Many fire safety websites reference that an extension cord should not be used while coiled. Is ...
0
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0answers
108 views

Calculate electric field from wire with AC current through

Here an experiment picture The wire(with some resistance) connected to 220 V 60 Hz AC voltage source. The peak current through wire is 0,3 A How to calculate mean, or at least peak electric field ...
2
votes
3answers
356 views

Computer Power Supply Testing Safety

I have a 750 watt ATX power supply that I will be testing with a multimeter to make sure the right voltages are present. How can I make sure that I do this safely? Is there anything that's threatening ...
1
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3answers
115 views

Testing and safety requirements for selling homemade electricals

I am currently researching and designing electrical audio equipment, example devices: Tube and solid state guitar amplifiers Guitar effects pedals Mixing / filtering units Synthesizers Some of these ...
1
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4answers
1k views

How does grounding the circuit provide safety?

I don't understand the concept of grounding a circuit for safety reasons, in this circuit that I simulated, imagine my hand touching the circuit as the closed switch. I am creating a closed loop ...
8
votes
3answers
6k views

How can I safely connect both Arduino and a 120V 10A circuit?

I'm building a thermostat, and the idea is to have it fire one of two 120V 10A circuits (one to heat, one to cool). I have two of these modules for the relay and I ...
-1
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2answers
489 views

Can a stripped USB charging cable electrify you and how dangerous would it be? [closed]

I have a USB type C charging cable that I charge my cellphone with. Couple of days ago I found out that it got frayed on some parts of its plastic cover. I always charge my cellphone in bed and before ...
1
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3answers
2k views

How to run 5v relay on 9v?

I have a 5v(coil) dpdt relay. Running it with 9v is safe or not? How can i reduce the voltage from 9v to 5v ? How much resistor i need ?(i do no want to use voltage regulator pls)
0
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2answers
168 views

Is there a risk of 18650 li-ion battery explosion in a low current application?

I have several used 18650 batteries from my old laptop battery. They all look OK, I have charged them and discharged. The capacity is around 1700 mAh, nominal capacity was 2500 mAh when new. I'm ...
5
votes
3answers
2k views

Do low voltage “Nixie tubes” exist?

I want to make a small clock using Nixie tubes (for the cool/retro/steampunk look of them), I have some basic knowledge of electronics, but I have never done anything with more than 12V DC and ~10A. I ...
1
vote
2answers
114 views

How damaging can a leaky microwave oven be?

This question is mainly about EMC and disruptive RF emissions. I have noticed recently that each time we use our microwave oven the WiFi network becomes unusably slow (it is still working if you get ...
0
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3answers
73 views

Can a desolder pump aerosolize lead particulates?

I have been reading up on the dangers of leaded solder. I understand the risk of actually soldering with it are minimal but my question is specifically its removal via "solder suckers." Does this ...
1
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2answers
1k views

Power tool safety: Grounding v/s Double insulation

OSHA regulation 29 CFR 1926.404(f)(7)(iv) states that electric power tools must be grounded except when they are double insulated. I quote from the Black & Decker rotary drill manual: "Do not use ...
7
votes
1answer
725 views

Electric fly zapper - how is this safe?

My trusty electric fly-zapper broke, so I opened it up to have a look in case it was something simple. I have to say I was a little surprised by what I found inside: the capacitor reads 473K, meaning ...
1
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0answers
44 views

Electrical Safety Guideline for LVD Compliance

We are making a product -a warning light- with 220V rated voltage. The product has a non isolated offline buck regulator. The 220V part can be accessed without the use of a special tool (there is a "...
16
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3answers
4k views

Is this resistor leaking? If so, is it a concern?

I found this resistor on the control board of an old Whirpool washing machine: Is that fluid leaking from the resistor? (Why would that happen?) Could it be something like stray epoxy or a chemical ...
20
votes
3answers
15k views

Is it OK to solder a power cord?

A few people have advised me to never solder a power cord directly to a PCB, but they couldn't explain why not. Why can/can't I solder it directly?
2
votes
1answer
85 views

EL Wire safety? [closed]

Electroluminscent wire is often used on party-shirts or to decorate other wearables. They come with little "EL Inverters" that run on 3-12V DC power. I measured the output voltage that's output into ...
0
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2answers
76 views

Connect charger to device first or to power first? [closed]

What reduces the chances of frying a device? Connecting the charger to the power plug first or to the device first?
19
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11answers
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 ...
2
votes
3answers
443 views

Lead Contamination when Soldering [duplicate]

I bought a soldering station a while back and was practicing on a kit and had the website on assembly up while I was soldering using 60/40 tin-lead solder. Should I worry about splatter on the ...
1
vote
0answers
31 views

Standard LiPo battery packs & product liability

I'm designing a high-power portable product that I would like to eventually bring to market. I need to use LiPo battery packs in order to achieve sufficient energy density, but I do not think I will ...
18
votes
3answers
3k views

Health risks of exposed contact to a capacitive sensor

I want to make a wearable metal trinket with the ATtiny85 chip acting as a capacitive sensor (with the same technique that this Arduino library uses), so it can detect when it's being worn. Are there ...
1
vote
3answers
763 views

Maximum safe amperage for LED Strips

A lot of online resources never question the use of high amperage power supplies for powering LED Strips. As an example, 5 meters of low density (30 LEDs per m) WS2812B strips already use ...
0
votes
1answer
49 views

Clearance distance and resin filler

I'm designing a circuit to detect presence of AC line voltage. It's actually a very simple device with AC side made up of a 200Kohm 1W resistor and an optocoupler and a protection diode. There will be ...
0
votes
2answers
3k views

Microwave starts working when door opens - how dangerous is it?

I've just rented a house that came with an equipped kitchen, and I've found that the microwave has a rather weird behavior - opening the doors seems to trigger it to start working, which the owners ...
0
votes
2answers
73 views

Earth line safety [closed]

I am working with a conductive appliance that a user will be in constant contact with over extended periods of time and the appliance is constantly earthed. These two facts cannot change, other than ...
2
votes
3answers
494 views

Intrinsically safe circuits

Is there a power threshold below which a circuit is considered to be intrinsically safe? For example, if one were to power a tiny Arduino circuit at 5vdc / 30mA = .15W could such a device be ...
9
votes
8answers
7k views

Is it safe to use a DC power adapter that isn't UL Listed or CSA certified?

I picked up a 9V switching DC adapter from SparkFun a while back, but I've been hesitant to use it because it doesn't have any of the usual "safety" approvals that you normally see on power adapters (...
2
votes
2answers
198 views

Why is 100 volts or less generally “low voltage” and “safe”? [closed]

In the United States in many state jurisdictions, wiring that operates either exactly at or below 100 volts is not required to be installed by a licensed electrician, and no site plan, building permit,...
0
votes
2answers
108 views

Optocoupler isolation necessary?

The circuit diagram below shows two possible options for a circuit: simulate this circuit – Schematic created using CircuitLab The difference between both circuits is the use of the ...
4
votes
1answer
202 views

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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