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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0answers
262 views

Earth leakage from isolated power supply

I have recently put together a DIY bench power supply using a DPS5015 from Rui Deng and an old laptop power supply. Everything seems to be working fine except for a small amount of current leaking to ...
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3answers
379 views

grounding a moving robot

I'm am designing an external battery pack for a robot, Pepper, a robot by Softbank (I'm am not making the battery itself but the circuit connecting two batteries). I am going to connect a 25V (LiFe-...
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2answers
309 views

Safety: Mains step down transformer vs SMPS for bench power supply?

Between a mains step down transformer and a SMPS, which would be safer for a bench power supply? I cannot look inside the transformer in either case to judge the insulation quality. But, if the ...
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1answer
207 views

Piezo element microcontroller connection

I have a "noname" piezoelement from Aliexpress: I'd like to control it via microcontroller. Now I use this circuit to drive the piezo element: Microcontroller ports produce PWM signals. Everything ...
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2answers
533 views

Connect two lab bench power supplies in series safely

Lets assume in European Union, that I have two power supplies, that each have 3 terminals. One marked +, second - and third GND. I assume that GND is connected to the protective earth of AC power cord ...
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1answer
48 views

low-voltage wet locations and EGC

Underwriters Lab allows DC voltages of up to 30vdc in wet locations, per UL 1838 As best I can tell, this spec does not address the issue of grounding, specifically the relationship of the 30vdc to ...
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2answers
2k views

How do I determine eye safety limits for IR LEDs?

IR LEDs typically report wavelength and radiant intensity (mW/sr). There are many warnings abound on the internet and from other local engineers to be careful of eye damage, but I find it difficult to ...
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0answers
66 views

Does iphone shock transfer AC or DC current to body? [closed]

Suppose an iphone gave a little jolt when pressing the power button. Is that AC or DC current? The phone was connected to a laptop which was connected to a power outlet.
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2answers
74 views

Safest way to store a laptop that's rarely used? Plugged in or not? [closed]

I have a laptop (mid-2009 MacBook Pro: aluminum, non-user-serviceable battery) that I almost never use, but might need in the future. The original battery was replaced by Apple a few years ago (The ...
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2answers
1k views

Safe and stable discharge rate for Li-Ion battery packs

I have found a battery pack with 74Wh capacity and it supports Qualcomm Quick Charge 3.0 on its output (up to 18W). I wonder is there anything like a safety limit of battery discharge? Is it even ...
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1answer
91 views

Safety Standards for Low Voltage Systems

I am looking for safety standards which could be applied to the piece of equipment desribed below. Basically the piece of equipment is a housing which inherits a 24V 100Wh Battery (2x SBS60) and a ...
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1answer
158 views

Piezoelectric component connection circuit

I have a question about piezoelectric component and microcontroller connection circuit. I use 7BB-20-6L0 Murata piezo. Here is the datasheet - Link Here is my current variant: Is this schematic ...
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3answers
584 views

How to control High Voltage Power Supply (HVPS) voltage output?

I am trying to explore good options that allow me to control the voltage output of an HVPS from 1KV to 10KV DC voltage. I have very little experience dealing with voltage range above 1KV. I understand ...
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0answers
53 views

Dismantling 110v DC LiFePo4 Battery Pack

I've inherited a 110v battery pack that used to be used for a solar array made of 34 each 100 amp hour LiFePo4 3.2v for a nominal voltage of 108.8v all together. I'm getting about 90v total from the ...
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1answer
77 views

looking for a device or tester to know if car is electrified [closed]

I'm new here and definitely not an electrical expert - so please forgive any lack of clarity and errors in my terminology or tags. We live in a rural area and drive a plug-in hybrid electric vehicle ...
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1answer
64 views

Warming up metal plate safely [closed]

I want to design a riddle: 1. 12 metal plates on the wall 2. 8 plates at room temperature. 3. 4 plates at 40-45 Celcius(104-113 Fahrenheit), it is important the plate doesn't exceed the temperature ...
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7answers
1k views

When can free-floating electrical contacts become dangerous (e.g., start a fire)?

In general, when should free-floating electrical contacts be considered potentially dangerous? Danger may be direct (e.g., due to electrical shock) or indirect (e.g., due to fire risk). In this ...
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4answers
105 views

Should circuit breaker be installed before hand switch?

I am a student of mechanical engineering so I am not very familiar with electronics. Recently I started working on a project where I am researching a control system for a motor which does some work. ...
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4answers
127 views

How is it possible to have high voltage that is safe?

I am aware that current is very dangerous and only 0.2 amps is enough to stop a heart. However I always see that high voltage is dangerous. Tasers produce a high voltage but since there is low current ...
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0answers
38 views

Scope Probe Voltage Ratings

I am wondering what the voltage ratings on passive scope probes really mean. Suppose there is an inductive spike that exceeds the rating. Will this damage the probe? Will it damage the scope? Is ...
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2answers
90 views

Electrical safety: Cracks on wiring

Today I installed a couple of light bulbs with my friend. The two wires coming from the ceiling we connected to the lamps using connection strips. On close examination we noticed that one of the ...
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3answers
4k views

What is the difference between “medical” grade and ordinary AC-DC power supplies?

Background My wife and I are expecting a baby soon and a family member has given us their previously-used, thoroughly cleaned electric breast pump. The pump came from the vendor with a "medical grade"...
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2answers
13k views

Can I use a 25 meter LED stripe with a single power adapter?

I have 5 stripes of 5m length and 300 RGB LEDs (type 5050) each. One LED consumes about 20 mA at 12 V. Therefore, my whole 25m setup would use about 30 A. Is it safe to connect the 5 stripes series ...
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1answer
180 views

What happened to my plug adapter? [closed]

I use a travel adapter to plug my microwave (UK plug) into an Austrian, European outlet. The other day, whilst the microwave was switched on but not cooking anything (ie the magnetron was not powered),...
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1answer
101 views

Can a ceramic power resistor catch fire? [closed]

If I go over the max wattage of a ceramic power resistor by a few watts, can it catch fire/produce a flame?
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1answer
113 views

CE mark for art works. Necessary? [duplicate]

Im making lamps which are hand built, and each one is sold as a signed one out of a series of a predetermined number. The lamps are made of plexiglas, they use an LED strip which is connected to a ...
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1answer
344 views

Dangers of ESD wrist wrap / mat / ground Plug Adapter in an Apartment building?

I would like to know if there are any dangers when we are using a wrist wrap connected to an ESD mat that is connected to ground on the wall socket in an apartment building. Lets imagine that in your ...
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0answers
77 views

Help with Laser MPE calculation

I am building a laser room and I'm basically trying to calculate the maximum time of laser radiation to they eye before causing any harm. I found that to be 7 seconds but I would very much appreciate ...
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1answer
1k views

What is a safe level of electromagnetic radiation measured in terms of received signal strength indicator (RSSI) e.g. -26 dBm?

We know that the laws of our countries set the regulatory limits of EM radiated power based on the EIRP transmit power of the antennas of devices. However, the received incident power is more ...
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0answers
128 views

Creepage and clearance of through hole resistor

Recently I found a resistor broken on a PCB. It is a MOF type 1/2W through hole resistor. I found that the resistor is directly placing (touching) on a PCB Live trace and I know that the potential ...
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0answers
57 views

Using a larger fuse in my multimeter

I am trying to replace the burned out fuse in my multimeter. It is very small with dimensions of 3.6mm X 10.25mm and has a rating of 600mA @ 250V. I can't seem to find this fuse. I can find one with ...
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4answers
3k views

At what level of complexity should I consider UL listing my widget?

I am interested in making a widget to sell, but it will probably have a small market and small volume. At what level of complexity should I consider UL listing (or otherwise certifying) my widget? I ...
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1answer
64 views

'Simple 220V' relay with a 36W LED Par light

I have the relay below, it has 3-7 input voltage needed for the control signal, I'm using a STM32F103C8T6 which is 3.3V and it is able to control the relay successfully. For testing: - The top left ...
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0answers
2k views

Calculate RC snubber for 240v ac coil relay

In a project I use several 12v dc coil electromechanical relays. I use diodes in parallel to the coil protect them from flyback. I also have one relay with an 240v ac coil. I have learned that I ...
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2answers
810 views

Connecting `signal ground` to `earth`: should I?

We usually have 3 wires in the outlet: L (line), N (neutral) and PE (protection earth). It is pretty common that the N is tight to PE in the distribution board or power plant. If the device have ...
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2answers
160 views

Is the maximum audible noise from power supplies regulated in Europe?

Power supplies make sometimes a lot noise in the range of kHz. Is there a regulation for the maximum allowed noise emission for consumer electronics on the European market? Is there a regulation ...
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4answers
273 views

Food safe electrical cabling

I am currently developing some electronic sensors for use in monitor food quality. This type of device requires running electrical cable though piles of food products. What type of electrical cables (...
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1answer
317 views

Wrong target voltage in Li-Po charger

What would be the consequences of using a charger that targets 4.3V to charge a 4.2V Li-Po battery? Will the battery be damaged? In what way?
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2answers
256 views

Led strip turning on dimly when touched

I have a 12V led strip connected to a (cheap) 12V 5A switching mode supply. The supply is connected to a remote control switch. The supply does not have earth connection (only neutral and live) The ...
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1answer
114 views

Designing dimmer circuit for main

I saw a dimmer on instructables and try to create circuit and pcb for it. However the it looks nice and probably will work but I'm not confident the reliability on long run. So my question would be if ...
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3answers
613 views

Is a stage box with an iron grid safe using this way?

See also my previous question: How should I bypass switches Where I made a circuit directly by mains, and as proposal by very useful comments to use a separate 'control' circuit at 9 or 12V. ...
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1answer
90 views

is this li-ion battery still safe to use?

While replacing my phone's screen I seem to have scratched and maybe damaged the battery. I don't know much about li-ion batteries so I'm wondering if it's still safe to use, or if I should look for a ...
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3answers
182 views

Why is this switch sparking?

I have a Vega 650 power supply which does not have a power switch. So I wired a switch into the power cord. When I flip the switch, there is about a 1 second delay, then the power supply fan turns ...
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4answers
742 views

How can I connect more than device on the same Isolation transformer?

Why isolating transformer should be used to protect only one item of equipment at a time? I tried to search and I found this answer, but I could not understand it. This is why, ideally, an ...
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3answers
1k views

Wire gauge for low voltage, high current DC application

For the past few weeks I've been shopping for a remote controlled car for my son, along with some batteries and a charger that will work with them and his other RC toys. To make a very long story ...
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1answer
505 views

Is it electrically safe to use an ATX PSU's PCI output for SATA/MOLEX instead of graphics cards?

My question here is about electrical safety of a proposed PSU cable hack. The situation is a single rail 1600W PSU (to avoid partitioning of the current) that has to power some 20-24 HDDs. I've ...
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1answer
334 views

What Caused Hoverboard Lithium Ion Fires? [closed]

Purpose of this question: In the interest of making my own BMS circuit designs safe and robust, i seek to understand causes of BMS failures in known systems. I'm not seeking consumer advice or ...
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5answers
1k views

Is hand held tester(The one looking like screwdriver!) completely safe why/why not?

What are chances that the HIGH CARBON RESISTOR gets shorted and we experience lot of current and die? Cause of doubt arisal: https://www.youtube.com/watch?v=wLAJ-keFmpk
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2answers
174 views

ESD and equalizing static charge of sensitive ICs before handling and soldering

When I'm handling an IC that is sensitive to ESD that comes packaged in an antistatic bag, do I nullify my ESD protection procedures if I peel back the cut-tape and dump out the IC into a plastic cup ...
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0answers
49 views

GCM circuit design redux

I'm coming back to this design again after some time away from it. Previously I was trying to design the circuit to be completely passive, but that hasn't wound up being very reliable, so now I'm ...