*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
80 views

Wiring a Key Switch to Control USB Power?

So I'm working on a project, and I'm a bit stumped on this problem I ran into. Brief explanation, I have wired a key switch into the power pin of a USB extension cable, which will allow the female end ...
1
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1answer
94 views

Will this AC-AC SSR work for a safety start / stop switch for a power tool

I'm modernising an old bench saw, and I want to replace the switch it has with a safer one, so that the tool will not start if the power is disconnected and then reconnected. The usual way to do this ...
4
votes
3answers
556 views

How can I safely use an aluminium enclosure without an earthed socket

For a mains-supplied circuit I want to use an aluminium case, so the case can act as a heat sink. However, I want it to be safe, also when there's no earth connection in the socket where the circuit ...
22
votes
2answers
4k views

Why do condors get electrocuted by power lines?

Plenty has been said about why birds are safe to land on power lines. But condors, apparently, are not. The linked article explains that condors are electrocuted often enough and endangered enough ...
6
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3answers
249 views

Add ground earth to a Chinese music player [closed]

I have this Chinese Portable Rechargeable Mp3 player. It has a two pin plug connector behind that is used to recharge it and some generic rechargeable non removable battery inside it. It has the ...
3
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1answer
102 views

Self Checking Circuit

I was reading the specs. of an electronic module used in process-safety applications & came across this note: Self-Checking (Circuitry): a circuit with the capability to electronically ...
3
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1answer
59 views

Oscilloscope Probe Noise and Safety

I have a Tektronix 531A tube oscilloscope from the late 50s. I recently bought some 20$ probes and noticed a lot of noise on the 0.005 volt/cm setting when that spring loaded hook attachment was ...
0
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2answers
76 views

Charging Li-ion batteries at a constant current for a fixed time

I just saw an Ebay Listing for some cheap Li-Ion batteries and a charger that claims to be "safe" yet doesn't seem to have any overcharging protection as such - the charger is supposed to provide a "...
0
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3answers
81 views

Aluminum sheet as an underlay for electonic equipment

I am planning to build a NAS into a (sufficiently ventilated) closet. For flame protection and heat spreading, I mean to put a 2x700x550mm aluminum sheet under the equipment. Is this a good idea? ...
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3answers
85 views

What are all the reasons that transformers are considered safer? [duplicate]

I am making a circuit for measuring AC mains voltage and current and I want to avoid using a transformer because it introduces distortions. But everyone says that the circuit will be considered unsafe ...
0
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8answers
478 views

Dangers of capacitors blowing up

I was wondering what kind of damage a 350v 6000uf (link to cap: http://goo.gl/f9iH29) electrolytic capacitor could do. will this kill me if it blew up next to me? I have never blown capacitors before, ...
0
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2answers
76 views

Is it safe to build a floatable speaker?

I'm thinking of building a floatable speaker to float along beside me in a lake or a small river while tubing. I've got some speakers and the following 12V amp: DROK Amplify Module Audio Component ...
25
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5answers
13k views

Why are Edison screws allowed to be used? [closed]

Why are the Edison screws allowed to be used? They seem unsafe. Why are they designed that way? They require a complete grounding system to ground devices for the rare situation where the hot wires ...
-1
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2answers
124 views

Using an Arduino (If Needed) to Charge 18650 Battery [closed]

I am looking for a way to charge 18650 battery with an Arduino (If needed) as simple as possible. I have seen tutorials where you have to buy 10 diffident parts. I just want the simple (But wont ...
0
votes
1answer
77 views

How dangerous are portable CRT televisions?

I want to use an old portable CRT for a project, but I don't know how dangerous the capacitors are, and if they'd be as bad as the ones inside a normal CRT. It takes in 12v dc via adapter, or 8 D ...
2
votes
2answers
59 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 ...
1
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2answers
123 views

What are design considerations for grounding an enclosed AC-to-DC converter?

Here I'm talking about a device that takes 100-240V AC in, and outputs 10-20V DC out. In terms of grounding, I'm referring to the grounding offered by a standard outlet (e.g., a NEMA-5-15R receptacle)....
8
votes
4answers
2k views

What is the identity of this shiny insulator?

fig: Shiny layer I've seen many times, on metallic objects, a kind of insulator layer is given (I've tested its resistance with multimeter and it shows infinite ohms). The layer is greenish-gold in ...
5
votes
5answers
469 views

Is there any symbol for electrical insulation?

Is there any symbol for electrical insulation? Is there any symbol for insulated wire? is there any symbol for non-insulated wire?
0
votes
2answers
70 views

What is the most efficient way to prevent reverse polarity to an opAmp?

Above is a part of a circuit which is a Schmitt trigger. As you see 24V DC Vcc and Gnd are the power rails. I will set up this circuit and some other people are going to hook up input output and ...
1
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2answers
82 views

Hot & neutral have similar voltage to ground: Finding the problem Part 2

I accepted an answer to a similar question recently, but I now have additional information and have realized that I need a more specific answer. I am nearly certain that my landlord will be unhappy ...
1
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2answers
56 views

Rule of Thumb When a Bleeder Resistor is Advisable

New to building circuits, I’m trying to develop an understanding as to when a bleeder resistor should be connected across a capacitor for safety reasons. I’ve seen several references talking about how ...
1
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1answer
61 views

Practical differences between putting circuit complexity on the ground side vs the hot side

I'm wiring some computer fans behind the fridge in my camper-van to help increase ventilation. As part of this circuit, I have a temperature controlling microcontroller plus relay and a series of SPDT ...
3
votes
4answers
81 views

Why is resistance across my arm-span so much less than across my face?

This sounds like a strange question (it is) but, from a purely biological standpoint, why is the measured resistance across my hands (I measured 120k\$\Omega\$) so much less than across my face? I ...
0
votes
1answer
45 views

Does a lamp need a fuse?

I have a floor lamp in which I have installed 2 LIFX Color 1000 A19 Wi-Fi LED Smart Bulbs (http://www.lifx.com/products/color-1000) The lamp is designed to have 2 bulbs and has a two position dimmer ...
3
votes
4answers
443 views

How does grounding the circuit provides 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 ...
0
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0answers
49 views

Table lamp CE marking / safety testing for sale to the public

I am designing a table lamp that uses the following components: An LED coin module (running at 3.15 watts, 8.4 to 9.75 volts) powered by a plug-in constant current LED driver that is CE marked I am ...
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votes
2answers
60 views

Electric shock & safety [duplicate]

An electric circuit is considered a closed circuit if there are two wires connecting to a load, namely live wire and neutral wire. Therefore someone would get electrocuted by touching live wire or ...
1
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1answer
77 views

Is This “E-Power” Machine Dangeorus?

My mother is obsessed with new-age quackery, and has rented an "E-Power" machine, a device that appears to be a waveform generator connected to a belt that you wrap around your waist. I'm concerned ...
0
votes
2answers
140 views

How safe is my soldering iron? [closed]

I'm have a low cost (<2$) soldering iron, similar to the one shown in the image, except that it has 3 plug terminals. Suddenly something got me thinking about safety, out of curiosity I cut the ...
1
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2answers
37 views

Power Transformer with two Buchholz relays

In my workplace we have a power transformer, on its conservator tank there is a device like a Buchholz relay and its named as Atmo-Seal. What is the purpose of this device?
0
votes
1answer
85 views

Arduino Bell Detector (Unsafe circuit)

I currently have a circuit that the arduino pro mini checks is the button pressed, the relay will be closed to trigger the bell alarm. And a UDP Packet will be also sent to a server to notify me. ...
1
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1answer
100 views

Safety tips for 350V @ 134kHz

I'm hooking an RFID reader up to an antenna. The reader operates at 134kHz and, due to its resonant circuit design, it can produce up to 350V (peak to peak) across the antenna terminals, with max ...
4
votes
1answer
162 views

What type of fire extinguisher do I need for lithium polymer batteries?

I plan on using reasonably cheap powerbanks (like the Aukey Mini 3600mAh) with my own circuits, and - ideally - I'd like to have an appropriate fire extinguisher on hand in case I mess up. I know ...
4
votes
2answers
140 views

How much open circuit voltage can a C.T. generate if burden is removed

The CT types I'm thinking of are those used for the general monitoring of household currents. Myth or truth, will a regular CT (in an otherwise normal and suitable current monitoring situation) ...
0
votes
1answer
73 views

How to wire the mains to a transformer for end user safety?

Because this can be deadly, and is best left to someone qualified; advice for hobbyist projects on the web are reluctant to offer advice on safely handling mains connections. The get-around is to ...
0
votes
1answer
86 views

“Dead-man” safety switch for HV bench work?

Long-haul freight trains and other systems that required an alert operator for safety would often implement a "dead-man" switch that would shut the system down if the operator couldn't actuate the ...
1
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2answers
56 views

Can we proof a scavenged transformer of unknown specification?

This step-down transformer was scavenged from a power tool battery charger. It was designed to take 120V AC current and it outputs 20V AC. I can't find any specs for it, so I'm wondering what ...
28
votes
10answers
5k views

Multimeter exploded during ACV measurment - What did I do wrong?

simulate this circuit – Schematic created using CircuitLab A DT-830B meter. I bought a new transformer, and I was trying to measure the output voltage. I plugged the probes on 'VΩmA' (not 10 ...
0
votes
1answer
55 views

would i need a fuse when experimenting with transformers?

I have a 0.7A center tapped 12v/15v transformer(i dont know details about it). However i dont know which pin is which among the output pins, so I have to jump them in many ways and measure with ...
0
votes
1answer
57 views

“Phantom” touches on appliance's capacitive buttons. A serious problem? [closed]

We have two electronic devices that operate well by themselves. Device 1 has touch (I assume capacitive) buttons. If device 1 and 2 are turned on they are fine. But if device 2's motor is engaged, ...
0
votes
1answer
73 views

Guidelines for using an unenclosed power supply?

What are the basic guidelines for safely using a "bare" unenclosed power supply (random example)? As a relative novice, my thoughts are: Definitely need a separate enclosure To avoid overheating, ...
-2
votes
1answer
91 views

Fumes from soldering [duplicate]

I breathe alot of soldering fumes and i don't have anything that is used to remove this fumes while soldering, is it really bad for my health? How it affects the brain and other organs?
1
vote
2answers
110 views

Li-ion swappable 18650 in parallel - preventing mixing charged&discharged cells

I'm designing a device that has 6 18650 elements (all parallel) in holders, made so that the end user will be able to pop out the batteries when they're discharged and plug in a set of new batteries. ...
0
votes
1answer
116 views

Are Faston tabs safe for earth grounding?

I am having a discussion with coworkers about sufficient grounding to a chassis... my opinion is that a toothed ring terminal in contact with bare metal is required, e.g. Molex 19074-0025, so that the ...
0
votes
4answers
193 views

Short circuit when probing live ATX power supply primary section with voltmeter [closed]

I was probing around an old ATX PSU to inspect voltage levels in the primary section. The first 15 minutes went smooth (bridge rectifier inputs, big caps, Power IC Vcc, etc..) but as soon as I probed ...
1
vote
1answer
156 views

active bleeder circuit for capacitor discharge

I have a circuit with a large capacitor, a solenoid and an N-channel FET fed by a 60VDC supply. When I trigger the FET the capacitor discharge activates the solenoid. This all works as expected (...
0
votes
3answers
391 views

220 AC to 220 DC Converter

I am designing a circuit that will give me an adjustable 220DC voltage. The load is approximately 2kohms, so the maximum current that will flow is 100mA.And I have design restrictions, it needs to be ...
2
votes
3answers
306 views

How can I test a wire for small holes?

I have stripped one wire, the black/hot/positive one, for a 120v appliance. I had to cut away the outer plastic that surrouneds all three wires, and now I'm afraid I may have nicked a small hole into ...
1
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3answers
400 views

Safety when using ATX power supply as benchtop supply

I found many pages where people convert an ATX power supply to a benchtop power supply to give 12, 5, 3.3V. However the current output can be very high (several amps). When using this and you NEED ...