*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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532 views

Multimeter into wall sockets

If you placed one of the multimeter's probes into the hot slot of the wall outlet and touched the other probe to your skin while grounded, for example to some dirt outside, would you get bitten by the ...
2
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1answer
56 views

Ground impedance monitor circuit design

I'm trying to design a ground impedance monitor. The idea is that the equipment in question needs to disallow operation if the ground wiring is disconnected or the connection is poor quality. This is ...
0
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1answer
66 views

Class II isolated power supply (wall wart) — referencing the output to mains neutral?

If you connect the - terminal of a Class II (isolated) wall-wart-type power supply to the neutral of the mains circuit feeding the wall wart, will that cause any damage or hazards that I should be ...
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6answers
1k views

How To Know If a Fuse Will Work Properly?

I want to know what kind of periodic test we use to test if a current-limiting fuse will normaly open and protect an electronic circuit (a battery charger) if a failure occur (short circuit or over ...
0
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1answer
41 views

Using a ferroresonant regulating transformer as an isolation transformer

I'm looking to use a (surplus, NOS) Sola (catalog number 22212) ferroresonant voltage regulating transformer (120V primary and secondary) as a low-power isolation transformer (4A) in case I need to ...
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4answers
108 views

Providing house wall switches with 3.3v/5V supply?

It's a bit non-technical, but I'd love to hear the opinions of the pros. I'm trying to figure out what is the best way to connect my home's wall switches (lights, etc.) to 3.3V/5V. The plan is the ...
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1answer
60 views

Safety in a capsense lamp

I'm playing around with the idea of adding a capacitive sense switch to an all-metal lamp, and have some questions around safety as I'd, obviously, prefer not to turn the whole thing live. In the ...
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1answer
60 views

Rewiring a 12V charger

I have a Windows tablet with a charger which crapped out. The old charger was 12V / 1.5A - fairly standard but it had a rare tiny pin connector. Rather than buy a new charger, I decided to cannibalise ...
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2answers
51 views

Can I use aluminum tape or naked two paralleled striped cables to connect parallel LED strips?

I need to parallel connected couple dozen cut LED strips. The total current reaching them won't exceed around 2 amps. My constraint: I can not order any more components for the job. My tools: ...
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2answers
55 views

Building a prototype rig with naked boards and wires (running 24V, 3.6 A): how to be safe?

I am building a prototype rig. It includes: 1) A "naked" 24/48 V motion control evaluation board. 2) A I=3.6 A stepper motor. 3) A power supply. I wired up the motor to the board with four wires (A-, ...
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1answer
92 views

Resistance Wire Circuit Safety Around Water

I'm working on a project that requires heating of a copper pipe with water running through it. I'm aware that this is a common issue by itself but as there will be people working around the system ...
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1answer
66 views

What is the maximum voltage of a Lithium Ion Battery

My question is about the maximum charge voltage of a Lithium-Ion cell. I have charged my battery pack with 8.4V (the maximum voltage). The pack is a Samsung ICR18650-26F. The pack has a smart ...
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1answer
60 views

Safety when charging two LiPo cells in series

NOTE: I am asking this question because I am new to this subject, and I want to be sure about what I'm doing before I go out and buy parts. I am making a really fancy watch with an OLED screen, ...
9
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2answers
321 views

I just blew a capacitor. Now what?

We worked two years on and off on this project at my friend's place. Finally we finish, I take it home. There's a power supply unit but it can't be connected directly to mains, it expects some lower ...
2
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2answers
111 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 ...
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3answers
70 views

Can I use a switch rated as 250VAC 25A to switch 50VDC 25A?

I am looking for a switch that can handle 25A continous current, the voltage will be maximum 50VDC, most often about 46VDC, and it will be used to switch on two dc-dc converters that have no load ...
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6answers
133 views

Are unearthed metal cases actually unsafe?

Take a look at this picture: It shows that if there is a fault with a device, current will flow from Live to Earth, hence you don't feel an electric shock. However, I don't completely understand ...
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0answers
58 views

IEC 60079 Explosive Atmospheres Compliance

I'm wondering whether anyone has some experience with designing electronics for compliance to IEC 60079 Explosive Atmospheres. I have designed a device to be installed in silos facilities which are ...
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1answer
43 views

Safety advice for best EMF detector and body shielding for UHF RFID reader

I've got a UHF RFID detector (860 to 960 MHz). I'm just getting into configuring the power output but I think I've been testing it at about 20dBM, I might want up to 30dBM. I'm concerned about my ...
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2answers
173 views

The safety of the capacitor

I saw this material for making capacitors (http://www.capacitorfilm.com/web/enproduct.aspx?ch=64). It said capacitor with the material is very safe, does anyone know what is the principle under which ...
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4answers
213 views

Can a current be induced in an HDMI cable that runs parallel to a 120v AC cable for 15 feet?

I just went to go unplug an HDMI cable and got shocked from the end of it! The only possible causes of this that I can think of are that the receiving or sending end of the long (50ft) HDMI cable is ...
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1answer
58 views

Is there anything besides power factor that determines the max CFL that can be used in a socket compared to the max incandescent for that socket?

When shopping for lamps recently, I've noticed that the sticker on the socket says something along the lines of "To reduce risk of fire, use maximum 60 watt incandescent or 13 watt compact ...
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1answer
84 views

Current Leakage calculations regarding shock hazard. A complete picture?

There is a quantity called current leakage which has always confused me. By reading various definitions, it seems to be the current flowing through the ground circuit of a device (whether this be an ...
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1answer
124 views

USB current limiter and under/overvoltage protection

I know recent motherboards already provide these, but lately USB ports are also available in many different gizmos (smartphone chargers, TVs, standalone players, etc.), which I am often tempted to use ...
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0answers
36 views

Needed help on earthing grid mat installation

I needed knowledge about earth mat installation for underground metro. I am not sure if a test reference electrode could be used for two earth mats. We have limited space and I want to cut off some ...
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1answer
257 views

How to measure current leakage in Macbook Pro and the long term impact of using a laptop with such a problem

I get a tingling/numbing sensation in my hand after using my new MacBook Pro for an hour (I only use the laptop when it's running on battery). The sensation sometimes travels to my arm. When I first ...
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1answer
284 views

Winding a Toroidal Transformer

I have a toroidal ferrite core which has an outer diameter of 15 cm, inner diameter of 11 cm and height of 4 cm. I want to use it to make a transformer which takes in mains voltage (240V) and outputs ...
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2answers
60 views

Actual/theoretical benefits of round or flat outlet prongs

What might be the reasoning for European connectors having rounded prongs while USA and UK connectors are primarily flat pronged? Please correct any mis-tagging.
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6answers
2k views

What makes mains voltage safe in homes?

When I started learning about electrical engineering, one of the most important safety guidelines that I learned was that voltages over 36V can be dangerous. As my circuits professor put it, 120VAC ...
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0answers
119 views

Can I determine a formula for fuse disconnection times?

This is the first time I have used this stack site so am not 100% sure this question is on topic (based on the tags I couldn't find) but thought someone may still be able to help me. For those not ...
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1answer
158 views

Unregulated AC-DC adaptor voltage response

This is my first post. I'm a long-time computer programmer but new to this field of hobby electronics. I bought a 12V 800mA AC/DC adapter to feed my circuits. Seems it's unregulated since the ...
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1answer
89 views

Manuals vs certification plates

If a device manual with a stated model reads 220-240V 50/60 Hz must the certifcation tag match? Is this different on a per country basis? (In this case Germany) For example this manual excerpt: ...
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1answer
1k views

Why is Ethernet not intrinsically safe?

I understand from a training session that ProfiBUS is considered intrinsically safe, while ProfiNET is not. Some googling indicates that ProfiNET can never be intrinsically safe, because Ethernet can ...
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1answer
139 views

Volts and frequency worldwide

If an electrical certification tag reads 220-240V 50/60 Hz can the device be used on both 220V 50 Hz and 240V 60 Hz?
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1answer
38 views

Checking my understanding of “branch in parallel current” warning

A datasheet for a power connector I was looking at tonight has this warning: Note: Do not branch in parallel current which exceeds the rated current. If branched in parallel, current ...
1
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1answer
82 views

Battery power in the home: Fire Safety

I would like to use 12v LED tape powered by an 8 x AA battery holder and switched with a motion sensor. This will be connected in my home 24/7, so I would like to know what precautions (if any) I ...
4
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2answers
131 views

Safety concerns over generic switching power supply units

I'm looking for a more stable power supply for my 3d printer. I've recently come across the following kinds of switching power supplies. They seem to come in all sorts of different sizes and ...
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2answers
71 views

How to handle / dispose of spent lithium primary cells [closed]

Disclaimer: This is a material safety question and not electrical. But it is electrical engineers who generally decide which type of battery to use when designing a system and other electrical ...
3
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3answers
193 views

Connecting a higher-current power supply to a lithium-ion charger will damage the battery. Why?

I am not asking how the battery gets damaged, because that answer is straightfoward. What I am asking is why lithium-ion chargers allow batteries to be damaged by excessive charge current in the ...
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3answers
2k views

What operation could cause the inductor or the capacitor to explode?

In really early days of electronic school, the teacher used to say something about not unplug power too quickly at an inductor or capacitor and we were used to slowly turn the voltage generator from a ...
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0answers
78 views

Does the following power supply configuration make my device a safe and legal PELV appliance?

A small disclaimer up front: I am fully aware that advice from this site is not a replacement for a safety evaluation by an expert. I merely want to check my understanding of the rules and potential ...
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1answer
287 views

current leakage in a laptop [closed]

Current leakage is apparently an issue with some aluminum Macbooks and other laptops. http://superuser.com/questions/462244/electric-shock-mild-vibrating-sensation-on-macbook-pro-when-charging Some ...
0
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1answer
202 views

Oscilloscope ground and unit under test ground issue

I am working with an instrument which has a supply of 230V AC or 400V DC. AC source is isolated at the input via 1:1 transformer and DC source is a floating supply. I have a Yokogowa DL1620 ...
15
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3answers
2k views

Are UV LEDs really dangerous?

I just bought some UV LEDs I bought them for testing banknotes and identity papers. I read the documentation and saw some warnings about UV light in which the vendor advises not to look directly at ...
2
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2answers
163 views

Measure 230V mains with 300V CAT II probe?

I need to measure harmonic distortions on a 230V 50Hz AC mains circuit. The Tektronix P2220 probes I have for my scope are rated for 300V CAT II when set to 10X impedance. Are these probes safe to use ...
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3answers
274 views

How does a “break” in the neutral wire enable it to reach the full line voltage?

The answer to Is the neutral wire considered safe? states: When everything is working correctly, it should be at most a few volts from ground. However, and this is the big gotcha, if there is a ...
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4answers
2k views

What's the advantage of 'electrical tape' over 'regular' adhesive tape?

For covering copper wire and the like (whether it is carrying current or not), what's the advantage of applying electrical tape as opposed to 'normal' consumer adhesive tape (of similar thickness? ...
0
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1answer
96 views

Faster charging of Lithium Polymer battery possible?

I am designing a system which needs to run for 3 minutes, then charge as quickly as possible, then run for 3 minutes, then charge as quickly as possible, and so on. In order to reduce the charging ...
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1answer
167 views

Why does a mains appliance give a shock after it is completely unplugged

My wife has a food processor, bought a few weeks ago, powered directly from the A.C. mains, i.e. not via a "wall wart" power supply, and, after it has been switched off at the wall and fully ...
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5answers
601 views

User safety for battery powerd device against misuse of power supply

I want to design a safety circuit for a battery powered device which measures human body impedance. It is intended to be powered only by an external battery pack (5V) via a USB cable. But I want to ...