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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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116 views

Is this a safe way to add extra current control for a DIY tDCs device?

I have put together the well known DIY tDCs-device Inthinkerator MK1, and wanted to add an extra safety feature, but I dont know if this is the correct way to do it. The original design is without the ...
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2answers
47 views

How Could I Implement a Fusable Safety Switch

I am looking to design a low-level safety override. This override can be represented as a three terminal device that is electrically a switch. simulate this circuit – Schematic created using ...
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2answers
59 views

Symmetrical power supply: Rail fuses useful or dangerous?

I'm designing/testing power amp stuff with symmetrical power supplies (43V-0-43V). In the next future I'm planning to control all safety/healthy stuff (like over current / over voltage / temperature ...
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1answer
68 views

Shipping & Handling Electronics & Electro-mechanical parts

What are common packaging(Shipping & Handling) guidelines (specs/stds) for Electronics & Electro-mechanical parts? Currently, working on adding onto our current generic guidelines for ...
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1answer
65 views

Is it safe to use individual conductors removed from a multi-conductor cable?

I am working on setting up a research lab at a university as a graduate research assistant. We're working on power electronics in a three-phase environment, which means we'll be using at most five ...
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1answer
178 views

Designing single fault safety into class I device

I'm trying to wrap my head around safety standards for electrical equipment. My device is medical, so for me section 8 of IEC60601-1 is what really matters to me, but it's kind of my understanding ...
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1answer
67 views

Designing a 2S Li-ion charger with 5V 2A input

I'm interested in designing a few similar charging circuits based on the specs of the title which is getting a charging for 2 cells in series(or more) from a 5V input. Now my question is: Assuming I ...
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1answer
72 views

Is there any risk in leaving a Li-ion connected to a solar panel with only step-down converter?

I have a 18V solar panel which is connected to a step-down buck converter, which drops the voltage from 18V to 3.5V. When clouds block the sun, the voltage drops to less than 3.1V. I have added a ...
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1answer
27 views

Definition of Field Wiring Terminals as in UL 499

I'm wondering if anyone can tell me where I can find the definition for "field wiring terminals" as referenced in UL 499 "Standard for Safety Electric Heating Appliances" table 27.1 "Minimum ...
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1answer
30 views

Can I simply add a 240V Neutral to SONOFF TH10 when replacing wall thermostat

So, I have purchased a SONOFF TH10 wanting to use it to replace my wall mounted thermostat. The thermostat has 2 connections: Always-Live and Switched-Live (which is activated of course by the ...
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1answer
22 views

Can a power surge have a different effect on a led driver when floating?

I have a LED driver which has 3 connections on the AC side , L,N and ground. In the event of power surge, can there be a difference in effect if the GND connection of the LED driver is floating or ...
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1answer
139 views

Is it safe to measure 220Vrms@50Hz on DSO directly?

I borrowed my friend's DSO to complete my project(Hantek DSO5072), but on scope it says CAT II/400V. So is it safe to measure 220Vrms@50Hz with it?
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1answer
35 views

Can you bridge off of a 240 V Breaker Box that connects to an Intermatic Timer?

I have an Intermatic T104 Timer drawing power from a Homeline Breaker Box for a home swimming pool. I'm wondering whether it would be considered safe to use the knockout in the timer enclosure to ...
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1answer
64 views

Safety for 48v leds in water

I'm builing a 48v DC LED system to be used inside a fountain in a public space. I'm using a 48DC 30A switching power supply. What should I do to make it safe in case any conductor gets exposed to the ...
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1answer
104 views

Oscilloscope differential measurement for battery powered circuit using single probe

I want to measure the voltage across a resistor in my circuit. The circuit is battery powered. I don't want to use the two probe method and calculate A-B to get the results. Can I use one probe to ...
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1answer
105 views

Power supplies with medical safety approval

Regarding the data sheet of this SMPS power supply. In the first page it says: 2 x MOPP Medical safety according to AAMI/ANSI ES 60601-1:2005(R) and IEC/EN 60601-1 3rd edition Then I googled to ...
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1answer
93 views

lithium coin cells, safe to completely cover? lightweight method to protect from the environment

I am trying to make equipment to measure temperature in small mammals, probably attached to a neck collar. The collar needs to be very lightweight (e.g. <3g total) so I am planning to use a ...
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1answer
107 views

Battery Disconnect Switch

I'm an Electrical Engineering student still new to power systems. I'm working on a project that uses a 24V and 200Ah battery bank made up of 4 AGM lead acid batteries. The batteries are supplying four ...
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1answer
396 views

Does a power supply GND connection need a resistor?

I am creating a power supply for my work station, and I have a input of 13.5 - 19V DC from a converter on POWER_JACK. From this input voltage I want to derive 12V, ...
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0answers
512 views

Electric fly zapper - how is this safe?

My trusty electric fly-zapper broke, so I opened it up to have a look in case it was something simple. I have to say I was a little surprised by what I found inside: the capacitor reads 473K, meaning ...
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0answers
33 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 ...
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0answers
26 views

Standard LiPo battery packs & product liability

I'm designing a high-power portable product that I would like to eventually bring to market. I need to use LiPo battery packs in order to achieve sufficient energy density, but I do not think I will ...
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0answers
59 views

Is this safe? Wiring for power relay jqc-3fc(t73)dc5v

I have an ac relay jqc-3fc(t73)dc5v that I am trying to use with a atmega and drive with 5v. Is the wiring as shown in the picture a good idea? Considering that ac and DC need to be very close ...
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0answers
45 views

Why are contactor coils connected to two different safety relay outputs?

When looking through a manual for a safety relay, I began to wonder why the coils of the load contactors (K3 and K4 on pages 14-15) are always connected to two different NO contacts of the safety ...
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0answers
89 views

What is the definition of hull voltage?

I'm studying the subject Electrical Safety in Engineering and a special term really drew my attention. When I tried to google it, no any option was suggested but hull protection. In the presentation ...
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0answers
45 views

Intrinsically Safe Li-Pol batteries to 60079 standards

I have recently been looking at SAFT batteries and they have a range of Li-Ion batteries, such as the MP-144350. One advantage quoted is "High level of safety, compatible in potentially explosive ...
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0answers
206 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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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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0answers
103 views

0.8mm PCB for a PSU circuit

I am working on a PSU that converts 230 VAC to 12Vdc (0.1 A). The board has the necessary clearance and creepage distances. Would it cause any safety issue (IEC60950) if the 0.8 mm (or 1.2 mm) thick ...
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0answers
159 views

Safety/Quality issues by modding PC PSU to be floating.

Since I don't have enough money at the moment to purchase a good bench power supply, I want to 'mod' a PSU. In the first instance not by opening the PSU, but just by making an adapter that also puts a ...
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0answers
2k 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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90 views

Safe Voltage/Amperage for Soldered Wires - aka When to Crimp Instead

I have found a lot of information that circles around what I'm looking for, but nothing that directly answers it. It is possible there is no right answer.     I am jealous of the Macbook ...
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0answers
100 views

How to line a Metal Melter secondary for higher safety

A Metal Melter is a kind of home-made low voltage (less than 40 volts, mine is 3v) welder (small-scale) made from a microwave oven transformer (MOT). I left the primary intact (the thicker wire, which ...
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39 views

Electrical safety measures in LED bulbs for the European market

Which electric safety measures are required to introduce LED bulbs on the European market? Which electric measures prevent that the plastic LED bulbs will melt down or ignite at the end of life? I ...
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0answers
15 views

Substitutability of thermal fuse

I have had this SW-104T thermal fuse blow on me. I'm not in a situation where I can obtain an the exact replacement, so I am wondering about the substitutability of thermal fuses. If I match the ...
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0answers
35 views

Reference material for mains-interfacing circuit safety

I've designed a simple switch/timer circuit for the following environment: Residential installation for North America (technically only for Canada) Single-phase 120Vac Current of switched output ...
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0answers
75 views

Out of limit Touch Up current - Servicing PE

My device may not be connected to PE during normal operation, but does require 230VAC mains input. I know I have to take the touch up current of any Y-caps into consideration when developing my ...
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0answers
100 views

Regenerative/Dynamic Brake test set up for a BLDC Motor

As all you know that BLDC motor also operates in regenerative mode during deceleratrion and in such case the current flows back to the supply. Here I am using power resistor to dissipate the extra ...
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51 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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35 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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0answers
67 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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0answers
122 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
56 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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0answers
48 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 ...
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0answers
274 views

Can anybody help me understand the monitoring function in this safety relay?

Here is a SIL3 Relay: SCS 24 V DC P2SIL3ES(made by Weidmuller). In its manual, It's written that S11,S12 and S21,S22 connections will provide a monitoring circuit for this relay. But I can't ...
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275 views

How to do insulation resistance measurement on a SMPS

Can anyone explain how to measure the insulation resistance of an isolated SMPS PCB? Is it correct to tie ACL and ACN and apply one terminal there, and the second terminal goes to the ground of the ...
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257 views

AC L+ and N- difference

Hey guys i'm on a project in which I have to use Safety Modules. I'm confused with the pin-out diagram of the safety modules. They reference L and N lines of an AC source. I'm leaving you the data-...
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41 views

Controlling 2 PSUs with an mCU

I'm finalizing my plans to make a physical control panel to interface 2 of my 3D Printers to an embedded Linux device. (Just minimal physical controls since 95% of the controlling will be done via a ...
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84 views

Is a thin power strip a safety hazard?

I have a US-style power strip that is thin enough that plugs can overhang the edge. It is easy to do this accidentally. I think that if you were to overhang a plug, and then accidentally touch the ...
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78 views

What can happen if I try to charge lead acid battery outside charger's capacity range?

I'm looking for lead acid battery charger. My battery (originally from UPS) has 12V and about 40Ah capacity. This is what I see in one charger's datasheet: Automatic charger for sealed lead acid ...