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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61 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 ...
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2answers
187 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?
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2answers
46 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 ...
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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 ...
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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, ...
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2answers
127 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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8answers
55k 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 ...
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35 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 ...
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3answers
304 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 ...
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1answer
130 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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gfci versus circuit breaker [migrated]

This is, I am sure, an extremely naive question. I hope that's okay (and I hope it can be answered at a level I'll understand). The background: My swimming pool has underwater light fixtures, on ...
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1answer
119 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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101 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 ...
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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 ...
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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 ...
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2answers
120 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 ...
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2answers
6k views

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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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)
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1answer
51 views

Fuel Level Sensor Safety

I'm looking up fuel level sensor manufacturers (Omnicomm, Technoton etc) and noticed that a lot of them offer capacitive fuel sensors for all types of fuel. However, based on my understanding, ...
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6answers
4k views

Why aren't starter circuits protected?

In most cars and trucks, a thick cable connects the battery directly to the starter (solenoid). Why don't these circuits have have any kind of overcurrent protection? It is an accepted practice ...
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2answers
86 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 ...
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3answers
1k 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 ...
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2answers
99 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 ...
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3answers
57 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 ...
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2answers
219 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 ...
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1answer
595 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 ...
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27 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 "...
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2answers
841 views

How to rinse container used for ferric chloride etching?

From what I have gathered online, after etching one stores the "used" ferric chloride (more specifically FeCl2 and CuCl) in some container which can then be taken to a waste disposal facility. What ...
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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 ...
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3answers
12k 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?
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1answer
80 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 ...
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2answers
47 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?
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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 ...
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3answers
213 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 ...
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0answers
109 views

Safe Voltage/Amperage for Soldered Wires - aka When to Crimp Instead

I have found a lot of information that circles around what I'm looking for, but nothing that directly answers it. It is possible there is no right answer.     I am jealous of the Macbook ...
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0answers
27 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 ...
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3answers
2k 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 ...
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3answers
79 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 ...
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1answer
41 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 ...
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2answers
165 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 ...
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2answers
58 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
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3answers
390 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 ...
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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 (...
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2answers
87 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,...
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2answers
65 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 ...
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1answer
92 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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0answers
39 views

How to wire an entire room / kitchen with LED light strips? [closed]

As the question suggests, I'm looking into adding LED light strips throughout the kitchen (over cabinet, under cabinet, and kick -- I think under the countertop would be neat, but harder to hide). ...
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3answers
190 views

12v nichrome wire water heater. Is it safe?

I want to heat the contents (water) of a two liter thermos flask using a low power (50-100 watt) 12 volt DC heater. Rather than buying a tiny little immersion heater, I've got some nichrome wire ...
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4answers
44k views

Safe current limit for human contact?

What's the point below which electrical current is generally considered safe for "casual" human contact? Is either voltage or amperage more "dangerous" (e.g. high voltage / low amperage vs. low ...
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2answers
883 views

safety relays and PLCS

I am having trouble trying to get my head around using safety relays in PLC controlled machinery. I want to install a PLC into a machine that needs upgrading, it is straight forward enough, well i ...