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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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Is it safe to use my multimeter to test UK wall outlet voltage?

From the question it should be clear I'm no expert. Just want to learn. I have a digital multimeter. If I connect the multimeter to hot+ground & hot+neutral on the 240v 50hz (max ~30A) AC wall ...
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0answers
41 views

What can cause an RLC circuit to fail? [closed]

What are some conditions that can cause an RLC circuit to fail and what are the safety considerations when making an RLC circuit?
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2answers
63 views

Why do we have “live” and “neutral” wires? [duplicate]

Our house wiring is AC. I thought that AC means we have current flowing from Wire 1 to Wire 2, after 1s/Frequency it flips and current flows from wire 2 to wire 1 and this goes on and on. I heard ...
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3answers
80 views

Do 240V AC switches only need to open the active wire?

I want to add a simple inline switch to a small, mains powered lamp (~240V AC, 10W Max). It's earthed; it has a typical 3-core cable with a 3-pin plug. I bought a bunch of switches, expecting ...
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1answer
49 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 cords". As far ...
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1answer
65 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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0answers
26 views

Is this safe? Wiring for power relay jqc-3fc(t73)dc5v

I have an ac relay jqc-3fc(t73)dc5v that I am trying to use with a atmega and drive with 5v. Is the wiring as shown in the picture a good idea? Considering that ac and DC need to be very close ...
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1answer
80 views

Can a magnet cause a microwave oven to unsafely radiate energy?

I've already successfully warped the colors on a large old CRT Television by setting unshielded speakers on top of it. If I understand correctly, this was due to the deviation of the electro-magnetic (...
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1answer
89 views

How much current does it take to injure me? [duplicate]

I'm building a 5 V and 4 A circuit that will be in contact with the body. How can I know if this amperage, in case something goes wrong, will not be a problem for my health or my life?
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0answers
34 views

Will I have issues with this circuit? [duplicate]

I have got a setup with a 500 W ATX PSU attached to a breakout board to provide a terminal output and switch to kickstart it. I want to attach the 12 V output to a galvanometer circuit I got from ...
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1answer
39 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 ...
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0answers
36 views

Why are contactor coils connected to two different safety relay outputs?

When looking through a manual for a safety relay, I began to wonder why the coils of the load contactors (K3 and K4 on pages 14-15) are always connected to two different NO contacts of the safety ...
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0answers
38 views

Wire Single E-Stop To Multiple Safety Controllers

I have an E-Stop with 2NC contacts. Can I wire each contact in parallel to the redundant inputs of two different Safety Controllers? Does this reduce the Performance level or safety category as ...
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3answers
143 views

Can 10-100mA kill a person / be deadly? [duplicate]

According to various sources something as little as 0.01A = 10mA can be painful, at 0.1A = 100mA you can expierence * "ventricular fibrillation of the heart". "an uncoordinated twitching of the walls ...
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2answers
78 views

Use of relay in a gas sensor (safety issue)

I have developed an MQ-5 based LPG gas sensor which uses a relay. Is the relay itself a fire hazard (while switching) if gas is in the vicinity ? Thanks.
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1answer
85 views

How (not) to set the house on fire? [closed]

With a recently renewed spark of interest in electronics, I’m now starting to solder stuff and build more permanent devices than before with breadboards. But with great power comes great ...
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1answer
30 views

Can you bridge off of a 240 V Breaker Box that connects to an Intermatic Timer?

I have an Intermatic T104 Timer drawing power from a Homeline Breaker Box for a home swimming pool. I'm wondering whether it would be considered safe to use the knockout in the timer enclosure to ...
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2answers
124 views

Powering two 3-LED lamps with battery/Battery pack - Multiple questions

I have seen many questions along these lines but I don't think any is an exact match (if that's incorrect, please just point me to the right match, that would be great and save everyone some time). ...
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0answers
25 views

VITA 46.0 VPX grounds isolation requirement

VITA 46.0 VPX standard demands: Rule 3-15: Plug-in modules shall provide a minimum dielectric withstanding voltage of 500VDC +/-10V and a minimum resistance of 1 megaohm between safety ground and ...
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1answer
49 views

Bad Practice - Charging Lithium Batteries while powering circuit?

I'm using a 2s BMC to charge a 2s2p lithium battery pack (7.4v, ~6Ah). The output of the charging circuit is the same as the input - they're not separate. As a result, when I want to charge the ...
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2answers
102 views

Laptop fried from spark while connected via USB to a battery system

EDIT 10/11 9:40am Central: I learned from my partner on this project I got the order of events wrong. I have edited the post accordingly. I am working on some custom electrical hardware for ...
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0answers
44 views

Does replacing Li-ion accumulator with a pair of good quality AAA NiMH makes light shoes safer?

I bought my daughter a pair of light shoes (LED). Fortunately they broke down after 2 days and she's not wearing them anymore. After buying I realised that they probably have Li-ion accu inside. So I ...
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1answer
76 views

Safely housing a power supply

I'm building a 3-d printer, which will be driven by a smoothieboard. This needs a 24V power supply. I've bought the one shown below: What I don't know is how to house this safely. I think there's ...
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0answers
34 views

Reference material for mains-interfacing circuit safety

I've designed a simple switch/timer circuit for the following environment: Residential installation for North America (technically only for Canada) Single-phase 120Vac Current of switched output ...
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1answer
114 views

100V “rated” wire on 220V supply [closed]

I am genuinely sorry for posting such a basic, basic, basic question. Moving to Thailand (220V) from Japan (100V). You cannot buy an extension cord in Thailand that is flush to the wall. Here in ...
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2answers
83 views

What is the purpose of galvanic isolation?

Is it correct to say that the primary reason to have galvanic isolation (ensuring minimum clearance and creepage distance for required voltage of power circuit between HV and LV) between the HV power ...
2
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1answer
49 views

Safety Relay Circuit

I am looking for a way to add a relay-based safety feature to my BLDC controller. In case of an emergency the user must be able to push an e-stop (probably consisting of an NC contacts) completely ...
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2answers
127 views

Protecting yourself with latex gloves

Would wearing white latex gloves(doctor gloves) protects you from getting shocked when repairing electronics? And is there a reason why you seldom see anyone wearing gloves when dealing with ...
19
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3answers
3k views

How could using an ungrounded appliance with a grounded extension cord be a fire hazard?

My local fire department, @Barrie_Fire, recently tweeted (then subsequently deleted) this: Don’t even THINK about using a 2-prong plug in a 3-hole slot! Use only the required number of slots in ...
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2answers
400 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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2answers
213 views

Safety design on mains detector

I've designed a simple mains detector which I have drawn below. The theory of operation is pretty simple. A capacitor is used to reduce the current so that my optocoupler can operate (represented by ...
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1answer
52 views

Is it appropriate to use a 300V RMS CAT I rated oscilloscope to measure 230V RMS of a power inverter?

Yesterday I decided to look at the waveform of my portable power inverter. The inverter specs are the following: Input: 12 V DC Output: 230 V RMS Rated power: 300 W I powered my inverter from a ...
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0answers
93 views

Does a lead/tin solder without rosin core release fume while soldering?

Many people address concerns regarding one possibly breathing toxic lead vapour from lead/tin solder wire by saying that the fume is from the flux in the solder wire, and not from the lead vaporising. ...
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0answers
74 views

Out of limit Touch Up current - Servicing PE

My device may not be connected to PE during normal operation, but does require 230VAC mains input. I know I have to take the touch up current of any Y-caps into consideration when developing my ...
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2answers
43 views

How Could I Implement a Fusable Safety Switch

I am looking to design a low-level safety override. This override can be represented as a three terminal device that is electrically a switch. simulate this circuit – Schematic created using ...
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4answers
653 views

Can a short circuit in the output of a transformer be dangerous?

Assume that I have a 220 to 12 volts transformer with a nominal output current of 3 A (marked "12 V 3 A"). Now what does happen if I connect the two output wires to each other or to a load with very ...
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1answer
110 views

earthing conductor

I'm studying the subject Electrical Safety in Engineering and a special term really drew my attention. When I tried to google it, no any option was suggested but Protective conductors. In the ...
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0answers
75 views

What is the definition of hull voltage?

I'm studying the subject Electrical Safety in Engineering and a special term really drew my attention. When I tried to google it, no any option was suggested but hull protection. In the presentation ...
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1answer
44 views

Safe solenoid driver: can I use a slow blow fuse?

I'm building a device that uses a microcontroller to control 15 solenoids via a preexisting multichannel DC solid state relay board. When all is working as intended, at most one solenoid will be ...
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1answer
67 views

10 Lamps setup 220v ac, would it be safe?

I am not an electrical engineering or anything, I am just a curious person trying things at my home for fun. I want to setup a lamp system for my sister's mirror where I would need to use 10 lamps ...
1
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1answer
43 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
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1answer
35 views

Long vs Short Earth Connection for Single Phase Motor vs 3 Phase Motor Frame

What is the correct way of grounding single phase motor frame if I have to choose between two options: (1) Short to earth connection: from the frame to nearest grounding rod. See below the schematic....
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1answer
623 views

What temperatures do resistors burn at?

I wanted to make a mini 12V heating element using 12 2 ohm resistors in series. What temperature will it be safe to heat it up to ? It is housed in acrylic housing which starts to melt at around 600 C
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2answers
70 views

What would be the safest method to power a laptop (IdeaPad 510 15isk) from a 14.8v battery pack?

Looking at my existing power jack and measuring it crudely with a cm ruler it looks like 3mm diameter x 1 cm length. The laptop bottom and charging adapter both say 20v @ 3.25 A max. What would be ...
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2answers
51 views

Questions about earth grounding enclosures

A text mentions about the importance of connecting the earth wire to an instrument case/enclosure as follows: Instruments with ungrounded cases can become lethal devices in the event of ...
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1answer
39 views

Wearable transceiver safety considerations

I am implementing a wearable band that will likely be fitted with a Zigbee or Bluetooth transceiver and worn on the wrist. However, I have seen many articles and datasheets specifying a distance of at ...
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1answer
51 views

ElectroVehicle batteries: safety issues

For a EV battery recycling project I am going to play with EV batteries. I will read out parameters from them (element configuration, charge, etc). I will NEVER try to recharge nor dismantle them: ...
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2answers
72 views

How can I power a device under test in a way that is safe for an oscilloscope?

Is it possible to power a circuit in such a way that makes it impossible to fry my oscilloscope with a ground loop? I've heard using a battery is a good way to prevent this. Is there a other way I ...
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2answers
101 views

Question on Use of Y2 Saftey Capacitor in AA5 Style Tube Radio

In a radio I am restoring, there is a 0.1 uF capacitor between B- and chassis, designated as C12. My thought process is that if this capacitor were to fail, I would not want B- shorted to chassis as ...
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2answers
76 views

What to look for in an isolation transformer?

What do you want from an (isolation) transformer besides it having the minimum voltage/current/power(/frequency?) specs that the to be isolated device needs? Does it matter whether the transformer is ...