*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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2answers
60 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
40 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
47 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
49 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
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4answers
71 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
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1answer
41 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
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4answers
425 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
42 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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2answers
52 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
72 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
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2answers
124 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
35 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?
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1answer
82 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
97 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
122 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
128 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
72 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
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1answer
79 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
53 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
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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' ...
0
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1answer
51 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
54 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
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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
82 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
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2answers
81 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
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1answer
99 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
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4answers
149 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
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1answer
116 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
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3answers
297 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
298 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
283 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 ...
0
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3answers
188 views

Recommended capacitor rating for this mains zero-crossing detector

I found this zero-crossing detecting circuit here I want to recreate it, using the parts that I have on hand (or can get cheapest), but I'm not sure how to choose the correct 0.1uF capacitors. ...
3
votes
2answers
153 views

Isolation transformer and AC potential between grounds

Wisely (I think) after connecting my DUT (Tektronix 2710 Spectrum Analyzer) to an isolation transformer, I measured AC voltage between the DUT chassis ground and my scope (Tektronix 2440) ground lead. ...
2
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3answers
138 views

Why is it safer to place a switch on the positive side of a voltage source?

According to the research I've done, it is safer to place a switch on the positive side of a voltage source: http://www.allaboutcircuits.com/textbook/direct-current/chpt-3/safe-practices/ This ...
7
votes
1answer
198 views

Is it possible to test a lithium ion battery for safety? How?

There have been stories in the news recently about fires that are believed to be caused by the lithium-ion batteries inside hoverboards. If you had one of these devices and didn't mind taking the ...
1
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3answers
109 views

Contradictions in conductivity

I mostly know how electricity flows but cannot understand some aspects, and have three examples that I cannot fathom: The pilot lighting electrode wire on my house central heating water heater ...
1
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2answers
120 views

Should Class I electric devices be connected to unearthed sockets?

I rent an old house and most of the power sockets do not have earth/ground. I need to connect Class I devices (such as laptop chargers, full PC towers, soldering irons) which require an earth to ...
2
votes
0answers
15 views

Is C-SAM test needed for new baking oven for IC?

I bought a conventional oven for baking ICs. Do i need to perform C-SAM test on the units after baking? I think units will not be affected if you will use the required baking temperature and time ...
1
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2answers
70 views

Quick safety question probing 120VAC

I did read several questions about safely probing high AC voltages with an oscilloscope. I had been taught to isolate the scope, which I see now is dangerous. So I think what I should do is then ...
0
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3answers
122 views

Christmas lights - how many strands can I connect? [closed]

I am putting lights around my house this season, and am finding myself concerned about safety and what the company who makes the bulbs says is safe. I think they are being way over-cautious, because ...
4
votes
1answer
245 views

Clamping Inductive Kickback in AC Circuits

I want to eliminate/clamp the inductive kickback that would result from turning off a large inductor, such as a relay or a transformer. In a DC circuit, I would use a diode to flywheel the current. ...
-3
votes
1answer
88 views

How to make a 240v ac to 12v 2amp dc transformerless step down circuit [closed]

I want to make a 100-240vac to 12vdc 2amp transformerless stepdown circuit any safe reliable circuit digram is accepted
-4
votes
2answers
96 views

Is it safe to connect a USB port to a transistor to a power strip, so I can control Christmas lights with a USB port? [closed]

Okay, so a usb port has 4 pins, a ground, two I/O pins, and a (may or may not be switchable) 5V pin. I had an idea to to connect one of the pins to the base of a transistor. Then I would rip the ...
1
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2answers
100 views

Nixie Tube Voltage Safety

I have seen clock designs like this one: where the nixie tube leads are not fully inclosed. There is likely 145-170V on these lines. I am just wondering if it's safe to allow the leads to be ...
1
vote
2answers
66 views

Things to consider before baking components

I will be using my own baking oven for components/ICs. What I only know is the baking conditions of MSL devices as per Jedec or as per required baking conditions as per MSL label of the part. For ...
1
vote
1answer
102 views

Automotive or solid state relay as main switch for 3D printer?

I have 47A 12V server power supply for my 3D printer project. The idea is to add a relay before printer hardware (RAMPS, Arduino Mega clone, steppers, bed heater etc). The normally open relay is then ...
3
votes
1answer
190 views

Exceeding Relay maximum switching frequency

I read in the datasheet of the DOLD OA5611 that the maximum relay cycles/s is 10 cycles/s. Now I want to know what are the risks for the relay if I control it with a switching frequency more than 10 ...
0
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2answers
119 views

If I drive an LED whose forward voltage is 2V with a source that's 3.3V limited to 20ma, will I harm the LED?

Background: I built a 10x20 LED matrix for use inside a jack-o-lantern. The matrix is driven by 74HC595 shift registers that are connected to an Arduino. I've attached the Vcc of the shift registers ...
0
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2answers
144 views

Can touching connections between each WS2812B-LED result in a shock [duplicate]

WS2812B LED-strips are ran at 5V, and can consume up to 60mA per LED. This can quickly add up to a few amperes. Would I receive a chock if I'd touch the ...
2
votes
3answers
125 views

How can I quickly and safely make defunct electronics safe and free of charged capacitors?

I am planning a movie set which will contain old circuit boards from TVs, VCR's and other old electronics. The plan is to go to several Goodwill stores and buy up all of the TV's and such that they ...