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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How to protect power supplies and pulser in DC bias + high voltage pulser combined circuit?

I am building an electric circuit in which a DC bias power supply and a high voltage pulser are mixed. I need to save each one from the other with proper safety measures. I have researched several ...
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5 views

Need advice on how to detect an object in the way of a closing door [migrated]

I have a system design with a 149oz-in stepper motor for opening/closing a drawer style door. My cross sectional dimensions of the door opening are 20" width by 15" height. The motor ...
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3answers
65 views

Explanation of structure and function of a safety relay

I am reading a safety guide from Pilz. This guide contain a chapter about safety relays. A circuit given in this guide is given below: I know the purpose of all switches and buttons defined in it. ...
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49 views

Is this design feasible? Door-open warning light circuit with safety interlock switch and general SPDT relay on wall voltage (120VAC)

I am trying to design a very simple system for my workplace that turns on a warning beacon light when a swinging door is opened. My current thinking is to use a non-contact magnetic safety interlock ...
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3answers
67 views

Why am I getting 239 VAC between GND and line when the device is turned off?

I noticed a weird thing that I don't understand. I'm working on an electronics project which has inside of it a 230 VAC (I'm in Europe) to 12 VDC transformer. For the convenience, the project is ...
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1answer
38 views

Measuring current on 25W incandescent lamp - loud bang/spark from DMM probes?

I was trying to do a power calibration on a Tasmota smart switch, using this procedure: https://tasmota.github.io/docs/Power-Monitoring-Calibration/ I had an 25W incandescent globe (resistive load), ...
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5answers
2k views

Placement of fuse on neutral wire. Why?

I have come across several occasions on this website where a circuit is shown with a fuse on the neutral wire rather than the line wire of mains power. For example from this question. I can think of ...
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3answers
142 views

Is this DC instalation a dangerous situation?

At an industrial plant, we have three electrolytic cells supplied with a 6 V Rectifier (max current 10 kA). Each of the three cells is currently absorbing ~1000 A at 6 V through 8 240 mm² copper ...
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22 views

Low voltage beak away/tension release connectors for building to building overhead cables

Are there low voltage breakway or tesion release connectors that should be used for overhead, building to building applications? The background is we are running a single pair of speaker cable, and a ...
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4answers
119 views

Keeping a cheap, DIY transformer safe

I want to design a cheap but safe, low-wattage, always-on heater to keep a small space above freezing. (A small underground tunnel that the water pipe for an automatic horse waterer goes through.) I'...
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3answers
868 views

Sophisticated order to connect the poles for a jump start of the car battery [closed]

How to connect or jump start a car battery. So in what order to connect the poles and why? I read so much (different) explanations and I would like to have a final generally accepted/recognized answer ...
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1answer
70 views

Possible capacitive coupling on soldering iron

I have bought a cheap soldering iron. It seems to work fine. Out of curiosity I tested the metal enclosure (and thus also the tip) with an electric tester and it lit up. Then I tested it with a multi-...
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1answer
50 views

What options do I have for a DC disconnect switch ~72VDC ~7A

I'm would like to implement a disconnect switch between my power supply and my system. Both the power supply and my system are fused, but I'd like the ability to safely disconnect the system for ...
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1answer
59 views

audio jack ground to main earth ground, safe or not?

My audio amplifier got some unclear noise from ground. amplifier ground is connected to player, and use some decent RCA cables, also tried to add ground loop isolatior to RCA cables. None of them ...
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1answer
49 views

Turning a circuit off using a 240v signal

I have a home-built controller for a HERMS brewing system (Heat Exchanging Recirculating Mash System). The purpose of this controller is to drive liquid (wort) from a large mashing vessel (a cooler ...
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2answers
47 views

How to find out how much voltage and current a soldering agent can handle

Is there any way to find out the maximum voltage and current that a soldering agent can handle based on the material and/or the information that I find on the package? For example, I have this ...
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1answer
71 views

Securing a very, very old 220V switch

We recently acquired a very old saw that accepts either 220V or 120V. It came with a suicide (male-male) cord, in turn going to a female-socket cable: which in turn goes to a DPST switch: in turn ...
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1answer
51 views

Do E-Stop switches/buttons normally operate relay switches?

I have a high-power system requiring an e-stop button, but a browse on Farnell suggests that no buttons are really designed to do the job of circuit breaking directly, based on their current/voltage ...
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57 views

How do I safely power 2m 144 LED/m WS2812B strip with 5v and 10a?

I am using a 2 meter strip with 144 led/m on a WS2812B led strip. By doing the maths on how much current would be required to power this we get 60mA * 288 = 17.28 amps. However, I am not planning on ...
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1answer
30 views

How to verify whether an electrical appliance is properly grounded?

I read that an electrical appliance/equipment that is not properly grounded can kill people, especially if it uses mains socket where the current drawn can be high. In fact, even a simple microphone ...
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2answers
52 views

Safety Considerations for Wired Bathroom Cleaning Electric Brush [closed]

I've this Hurricane Spin Scrubber basically a battery operated surface cleaning brush. I love its convenience and effectiveness however I'm getting sick of the battery power limitation though, minutes ...
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3answers
256 views

What are the correct procedures when someone accidentally touches high voltage live cable and is getting electrocuted?

Suppose a family member accidentally touches high voltage live cable and is getting electrocuted in the toilet while he is installing lights. The problem with electricity is risk of conduction and ...
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1answer
29 views

Gas discharge tube and IEC class II device

I'm looking at a design for a IEC class II device, and can see that there is a Gas Discharge Tube being used for suppressing high voltage transients/surges. Since the device doesn't have an earth ...
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0answers
55 views

Supervisory watchdog to assure UV LEDs are off and stay off during non-use

I'm designing a circuit consisting of 3 pairs of LEDs. Each pair has one UV-LED and a white LED. The pairs will be turned on consecutively and for about 1 second each. Between each use there will be ...
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0answers
33 views

Will these gloves comply with electrical arc flash safety?

I am beseeching any OSHA, CalOSHA or electrical safety experts out there on this one for a little help. I know this is not strictly electrical engineering but this is the closest Stack to the topic. ...
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1answer
99 views

How to use FG ground on a meanwell buck DC\DC power supply

I would like to know how to safely connect a 48V 200A battery to a step-down converter. The step-down converter is this. SO the step-down converter is to be used inside a forklift to drop the 48V DC ...
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1answer
62 views

Are capacitor vents safe to touch?

I couldn't find this information anywhere. Every tutorial on how to safely handle a capacitor tells you to absolutely avoid touching the capacitors leads, and to grab a capacitor by its insulated ...
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1answer
50 views

How do I safely measure secondary transformer voltages (Or ratio to primary)?

Let me begin by saying that I am a hobbyist, and I've been stupid with transformers before and I'm fed up with that. This question doesn't have to do with design so much as just not killing myself, ...
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4answers
3k views

Is ground connection in home electrical system really necessary?

I know that the answer to my question is "Yes, it is!". The ground connection is needed to avoid a person touching a metallic part of faulty equipment to be electrically shocked. So the ...
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2answers
123 views

Safety rules for DIY projects involving 220V

I'm planning to add some home automation to my home, using a 5V relay and most likely an ESP8266. This will be used, for instance, to control the lights or the heaters, certainly through Home ...
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4answers
174 views

How to dim one of these cheap 5mW laser modules?

I used to have an old 3x LR44 lithium cell laser pointer for presentations. With the batteries slowly dying, the outputted beam also went dimmer. Recently I bought one of these cheap 650nm laser ...
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4answers
118 views

Can measuring back EMF spikes damage the oscilloscope?

I want to measure the voltage across an inductor as soon as I disconnect one of its terminals to visualize how back EMF changes with and without a fly-back diode. From videos on Youtube: https://www....
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2answers
211 views

How 3mG can be dangerous if the Earth's magnetic field is 500mG? [closed]

All the things I have read says that magnetic fields above 3milligauss is dangerous for people. How this can be true if the Earth has a magnetic field of 500mG? Do smartphones and gaussmeters measure ...
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1answer
117 views

Is printing a PLA box for electronic components safe?

not sure I'm in the good place. I'm working on a small project, building a connected light dimmer for my home. I'm using a raspberry pi zero and an AC dimmer (this one : Universal AC MAINS Dimmer - ...
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3answers
124 views

How is this 22 AWG cable rated 4 Amps?

I found the cable (1533576 - Actuator/Sensor-Cable, M12 Socket - Open End Connector, 2m, 4A, 250V, Phoenix Contact) here that is claimed to handle 4 A and is then written that it has a 22 AWS cross ...
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1answer
30 views

Electrostatic arc safety

I'm experimenting with early electrostatic devices, and I'm measuring spark gap length to determine voltages generated. How dangerous is it to observe these arcs with the naked eye? Should I wear ...
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1answer
36 views

Safely wiring a 120v smoke detector externally

I am building a relay box that will cut power to an outlet if an attached 120V smoke alarm detects smoke. The relay box itself will be a grounded metal electrical box hardwired to a 3 prong plug. It ...
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1answer
40 views

Calculating maximum permissible track amperage for intrinsic safe PCB

I'm reading IEC 60079-11 standard (Equipment protection by intrinsic safety "i") which discusses how to design intrinsic safe circuit boards. In section 5.6.4 it talks about permissible ...
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1answer
76 views

Can the skin / copper oxide / copper junction of an old exposed mains conductor produce a safety-significant DC component to a shock?

Copper oxide diodes are not common now but were a standard item along with selenium oxide for early power rectifiers (think old radios and those components with stacks of fins). Can the oxide layer on ...
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0answers
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Is putting a board inside an anti-static enclosure enough to make it Ex ib ready?

A year ago, we made a handheld PDA based on RPi0 for a client. Now they have asked us to certificate it as Ex ib IIC T4. Here is the PDA's spec: RPi0 as processing board 4.3" capcitive LCD A ...
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1answer
81 views

Where is Pb (lead) found in an immersion heater? [closed]

Clicking "Technical data" on this page gives a pretty good overview of the composition of immersion heaters: Terminal, End Seal, Cold Pin, Alloy spiral, Sheath, and Insulation. Having ...
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1answer
52 views

Constant current driver and undervoltage protection for lipos

I'm searching for a way to drive a couple LEDs with a single-cell LiPo battery, such that the LEDs will be cut off completely when the LiPo voltage drops below, say, 3.3V. PCB space, component count ...
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2answers
116 views

Maintaining clearances in HV MOSFET footprints

I'm thinking of making a prototype PCB which would use a bridge rectified AC, which will end up with peaks around 350V in my area (+/- some smoothing). It's a through-hole design and the circuit will ...
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0answers
96 views

What is the benefit of a male output connector on a powersupply?

I saw several power supplies which use a male output connector. For example the Meanwell OWA 90E series uses a XLR 4P or ...
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2answers
79 views

When to consider Peak current/voltage vs. RMS current/voltage and vice versa

When manufacturers create power labels for AC electrical devices, what value to they use for the current and voltage? Do they use the RMS of the sine wave? Or do they use the peak of the sine wave? ...
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4answers
114 views

Does an isolation transformer make CRTs any safer to work with?

CRT tubes are often described in training materials as huge capacitors capable of delivering very high voltages, often enough to severely injure or cause death. Before working on them, they should be ...
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1answer
44 views

Saftey regulations of multiple 1mW lasers

AFAIK devices containing exposed 5mW lasers are illegal without a license, but those containing 1mW lasers are. But how about a device with ten 1mW lasers? Is it still a safe and legal device? The ...
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1answer
88 views

Is it possible to protect against ANY overvoltage?

Inspired by this question. Suppose I'm making something like a security system and I'm worried about a malicious person trying to knock it out with high voltage on some of the incoming wires. Let's ...
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6answers
1k views

Safety precautions when making a commercial electronic product

I have designed and fabricated an electronic device. High level explanation for this device is as follows: The device designed scans the environment for RFID tags and when a tag gets too close to the ...
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1answer
90 views

Safe to turn off power by removing a plug fuse indefinitely?

I'm trying to turn off the power for my dining room light and as I live in an old apartment, my fuse box only has plug fuses (and a main fuse you pull out). My plan is to cap the AC wires in the ...

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