The safety tag has no wiki summary.
2
votes
3answers
64 views
Disposal of ferric chloride etchant
I've just got hold of a nice little PCB etching kit, which uses ferric chloride as the etchant. I know it's re-usable for at least a few etches (though the kit doesn't actually specify an estimated ...
7
votes
4answers
155 views
Fuses: What are the practical differences between Ceramic and Glass cartridge fuses
What are the practical differences between ceramic and glass tube cartridge fuses?
I am trying to find new fuses for a piece of consumer electronics. The original fuses are going out of production.
...
2
votes
2answers
95 views
Replacing analog scope BNC input connectors
I am wondering if it's safe to replace the BNC input connectors on my old Hitachi v-422 scope.
As long as I'm careful and stay away from the CRT etc? Or is there anything else I'm not aware of?
7
votes
3answers
191 views
Cooper Bussmann's screw-in Edison-base mini breakers aren't for inductive loads. What does “inductive” mean?
I'm thinking of buying some Edison-base screw-in miniature circuit breakers to replace some of the fuses in my house. There are some made by Connecticut Electric and some made by Cooper Bussmann.
...
4
votes
1answer
159 views
AC->DC supply, how to deal with chassis ground being connected to digital ground?
I have an external triple-output AC-DC supply with the following output pinout:
On the power supply, "ground" (pin 2) is internally connected to the ground wire of the mains plug. I'll refer to it ...
0
votes
2answers
131 views
Connecting AC wires to a PCB
I am working on a project where I am using a microcontroller to control a 5V DC relay to control a mains device (an airconditioner).
In this circuit, I would need to connect the AC wires to my PCB ...
2
votes
0answers
93 views
What's this whitish/pale-greenish substance? I found it on the bottom of a 12-year-old watch battery I found unopened in a drawer [closed]
I have here a silver-oxide button-cell SR626-size watch battery. It's still in the package. There's no well-known brand name printed on it. My dad bought the battery from the store 12 years ago, ...
4
votes
2answers
120 views
What are some cheap, reliable methods of water-proofing switches and buttons?
I'm working on a project to put together a custom bike light from some LED flashers and a battery pack. I'm looking at two different options, one which comes with a built-in switch, and another where ...
0
votes
2answers
156 views
Dual polarity power supply for project, possible choices?
For a variable power supply I require 15V to get ~0-12V, and +/-15V for an op amp as part of the project requirements, also negative rail in the future.
Two plugpacks (isolated, 15/0/-15)to me seems ...
1
vote
1answer
154 views
Putting two wall-warts in series?
I'm helping a friend make a 48 inch hot-wire foam cutter. He would like it to be as economical as possible, so I'm giving him two 15V 1.1A wall wart power supplies that I have sitting around.
I don't ...
3
votes
2answers
123 views
In i.e. a TO-220 package, why is mounting the (pin connected) tab to case safe?
All the time I hear that the tab on a TO-220 like package is electrically connected to the centre pin, for example "out" on voltage regulators.
Does mounting them to a heatsink (of which may come in ...
6
votes
2answers
148 views
How to attach (safely?) an o-scope to various sources
I've heard of course that probing mains can ruin your oscilloscope, so that is out of the picture. There are a few situations I do not quite understand however:
Is probing an i.e. 10:1 transformer ...
1
vote
2answers
132 views
Why is it safe to touch the chassis of a tube amplifier and something earth grounded simoultaneously?
I'm hoping this is not too much, originally thought it would be a simple question, but the more I thought about the matter, the more I could see this wouldn't happen. If it's too much I hope some of ...
10
votes
2answers
424 views
Electrocution in rubber swimming pool?
This doesn't immediately look so good, but if you think about it, why shouldn't it be? If the extension cord drops in, why should the electricity choose to flow through any of them, instead of just ...
8
votes
3answers
260 views
Safety Guidelines for Ultraviolet LEDs?
I'm interested in using some UV LEDs to light some projects. Specifically, painting some designs on RC aircraft with florescent paint and illuminating them with UV light for night time visibility. ...
4
votes
2answers
178 views
Why do rechargeable batteries have no short-curcuit protection?
Whenever I read a user manual to a device that runs off a rechargeable battery - like a cell phone or a power driver - the manual will always say I should store and handle the battery in such way that ...
1
vote
6answers
313 views
How to hook up a high voltage relay?
This will be my first attempt to control a 110v device (high voltage, by my standards!). Initial tests will be on a table lamp; eventual target may be a small 500W heater.
How should I wire the ...
3
votes
1answer
251 views
How can I safely charge 3 lithium 18650 batteries to use in one pack?
I'm working on a project to make my own super-bright bike taillight using an emergency flasher LED (something like this:)
The LED package requires a 12V input, but from what I've read from other ...
3
votes
2answers
241 views
Is it safe to run and charge a deep cycle battery in an enclosed space like a bedroom?
I'd like to experiment with running a small server (5.5 watts) / 85AH deep cycle battery / charged via 30 watt solar panel from my bedroom.
I generally keep the window open, but want to make sure ...
9
votes
2answers
324 views
Is it safe to disassemble an unpowered PC power supply?
Once a typical PC power is unplugged, is there any danger of receiving a shock while disassembling it? Are there typically high voltages stored that one should be aware of?
context: removing a ...
0
votes
3answers
219 views
Issues with resistor heating, for an LED?
I am direly confused on this. I've used 220 Ohm resistors in the past for all of my LEDs (at least that I can remember), however nothing on my arduino+breadboard with a few leds on the 5V breadboard ...
2
votes
3answers
130 views
Static dissipative ESD footware
Are shoes like this used in professional labs or is this just a gimmick?
http://www.esdshoe.com/products/Lightweight-Classic-Mid-High-ESD-Composite--Basketball-Shoe-%252d-Men%27s.html
2
votes
3answers
205 views
ICs with humidity or moisture sensitivity - bake recommendations
I purchased some ICs recently that included something I'd not seen before - a moisture 'sensor' on a paper strip with color indicators for a few specific levels of humidity. Once the paper reaches a ...
0
votes
3answers
246 views
Using RFID to secure and prove ownership of a stolen vehicle
Long story short: They stole my bike. This is the fourth one; apparently it doesn't matter how well you secure it, if they want it, they'll take it.
Now, the police actually caught them after a ...
1
vote
1answer
59 views
Safe operating area for different types of battery chemistry?
I'm trying to find the safe operating area for various types of batteries; in particular I need minimum and maximum termination voltages, although information on temperature / power / current is also ...
1
vote
3answers
129 views
Are solenoids/inductors dangerous to have exposed?
An inductor doubtfully will be in a position to be of harm, however a solenoid with 1A+ running through it (and of course a lot of it stored in the magnetic field) can certainly harm the circuit, if ...
2
votes
2answers
146 views
Use a lithium ion battery from a laptop, for a small project?
Now laptop batteries are very expensive, however I have a slightly beefy Dell Inspiron 1525 laptop with a half year old battery that works fine.
Other than complete depletion, of which I have heard ...
1
vote
2answers
130 views
For a nerve-teste circuit, what causes the shock at low voltage?
As a bit of a weird test for my new 555 IC, I have been thinking of stepping down a 9V PP3 battery to five or so volts and creating a square wave @ ~100Hz and shocking my finger.
I understand that a ...
1
vote
1answer
151 views
Conductivity of water, and risk of shock? (fact checking)
Through simple researching I have discovered the unit of siemens (being a reciprocal of ohms).
Now I wish to apply this to a (silly) scenario where the conductivity of tap water is 800µS/cm (from ...
5
votes
1answer
101 views
How should unidentifiable breakers and fuses be represented in arc flash studies?
When analyzing arc flash hazards in industrial power systems, I have encountered situations in which visual inspection reveals the manufacturer and the trip rating only. The breaker or fuse model ...
15
votes
13answers
773 views
Path for a child to learn electrical engineering
What are some paths for a child (7-year-old) to learn electrical engineering (in a safe way)?
I do not want to saturate (or frighten away) the child with lots of concepts, I want that my son learn ...
8
votes
7answers
2k views
How much voltage is “dangerous”?
Related:
Safe current limit for human contact?
From what I've heard:
110 V (or 220 V; household voltage pretty much) is dangerous (i.e. can kill you) I think there's consensus on this, no ...
5
votes
3answers
665 views
Decomposing Kinect Laser Projector - Is it really safe?
I am looking at Kinect Laser and couple of things that are not clear, so I thought I bring up here.
First the known facts:
- Kinect has a laser projector that works at 840nm
- Output power of the ...
3
votes
2answers
146 views
Chassis + Ground Safety
Why is it safer for ground to be connected to the chassis for an electronic system?
For example, the ground on the mains supply of an AC motor in a box fan is connected to the outer chassis of the ...
2
votes
3answers
222 views
Is there a wiring design that would protect a person in bath from electrocution when a powered appliance is dropped?
Hairdryer falling into bath is a Hollywood cliche already. Jokes aside, is there a wiring design that would protect a person in this case?
Overcurrent protection will trip too late, residual current ...
13
votes
3answers
388 views
How is using a transformer for isolation safer than just playing with it?
How is using a 1:1 transformer safer than using the mains straight off? Is it because you can limit the current coming from the transformer whereas straight from the mains its not current limited? I ...
6
votes
4answers
528 views
How does earthing work when earth is dry?
Earthing is meant to provide reliable contact of an electric appliance to earth so that if there's an insulation fault current goes into earth instead of through a person's body. This requires ...
3
votes
2answers
119 views
How to properly isolate multiple power supplies
Say you have a single 110V AC supply and need to use it for a number of devices, each requiring very different characterists. For me personally these are: a direct use of the 110V AC supply for a ...
3
votes
4answers
493 views
How do I choose a fuse?
I realise this is an extremely broad subject area but I need to know how to choose a fuse to protect a circuit.
Recently, a cheap PSU of a friend's blew up quite spectacularly (the two primary ...
4
votes
3answers
343 views
Why is power supply from electrical utility referenced to earth?
In response to the question Basic Training for working with 120V AC zebonaut had replied that "A regular wall outlet is referenced to earth" and this provides the close loop for the circuit to ...
1
vote
1answer
79 views
Are dual MOSFET devices isolated from each other? If so, to what degree?
I am using an OnSemi NTGD3148N dual MOSFET in a project. I cannot find a specification anywhere in the datasheet stating the isolation between the devices; and this holds true for most dual MOSFETs ...
7
votes
4answers
289 views
Why are some AC outlets and plugs polarized?
This will show my naivety when it comes to alternating current... but why are some plugs and sockets on AC outlets polarized (one prong is taller than the other)?
(See this question on DIY.) (Or this ...
4
votes
2answers
174 views
Microcontroler's watchdog
Can anyone explain a little more about watchdogs, specifically in the circuitry level?
If there is some kind of problem in the chip, how can I guarantee that it will be kept running? It is ...
0
votes
1answer
101 views
relationship between temperture, current, thickness, and material
I used lan cable for light LED up on my bread board
power source is PC's power supply.
without any resistor, the lan cable melt!
I reallize I have to keep OHM's law in my mind
and use proper ...
3
votes
2answers
134 views
cable jacket melts
I am new to hardware.
My breadboard just arrived and I am trying to light up my LED. I used computer power supply for power (red wire for + black for -) and used strands of LAN cable for connect LED ...
2
votes
3answers
486 views
Any problems with “floating” an oscilloscope?
I have a Chinese scope with a two-pin power cord and a plastic body, and measure megaohms between its ground terminals and the actual earth, so I believe it has an internal isolation transformer (I ...
7
votes
1answer
390 views
will a circuit breaker designed for 230VAC work for 12VDC?
Will a standard home automatic circuit breaker, designed and sold as to work on 230V AC (alternating current), and for example 16A, or 25A etc, will it work (break the circuit if it exceeds the rated ...
0
votes
2answers
261 views
Safe to open old sony remote?
I have an old sony universal remote, the rm-v15. I opened it to get to the pcb, and a strange nasty smell came out of it. Is there anything I should be worried about? Any hazards used in old remotes?
9
votes
3answers
670 views
Extra negative battery cable when charging outside car?
If you go to: http://www.battery-chargers.com/charging_instructions.htm
...Under "Operating Instructions" part "B: Charging battery outside of vehicle", it says you have to attach an extra jumper ...
10
votes
4answers
2k views
Safe current limit for human contact?
What's the point below which electrical current is generally considered safe for "casual" human contact?
Is either voltage or amperage more "dangerous" (e.g. high voltage / low amperage vs. low ...
