When in doubt, don't do it. Electronics can be dangerous, even fatal.
24
votes
1answer
353 views
What is / how can I get a student-safe power supply for electronics projects?
What is / how can I get a student-safe power supply for electronics projects?
I'm looking for a student-safe power supply for solder less breadboard. I'm developing a course to teach electrical ...
17
votes
5answers
169 views
Is an Arduino capable of running 24/7?
I'm curious as to the durability of the Arduino Uno. Does anybody have any experience in "killing" one due to excessive use? If so, how long did it take for the board to fail?
16
votes
13answers
1k 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 ...
14
votes
2answers
13 views
How to water-protect my Arduino?
I am building a watering system with an Arduino. Basically it runs on a track with a hose that drips water down on plants a couple of times every day. Its outside, and water might sometimes get from ...
13
votes
3answers
3k 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 ...
12
votes
2answers
833 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 ...
11
votes
9answers
828 views
Safety of making PCBs
I've been making a few hobbyist PCBs at home and note that the photoresist developer and ferric chloride etch solutions are both pretty nasty chemicals that come with all kinds of warnings.
So I've ...
11
votes
4answers
3k 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 ...
10
votes
7answers
16k 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 ...
10
votes
2answers
1k 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 ...
10
votes
3answers
1k 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
3answers
36 views
How much current can I draw from the Arduino's pins?
What's the maximum amount of current which I can draw from each of the Arduino's pins without tripping any of the internal fuses? Is there a limit per pin as well as an overall limit for the whole ...
10
votes
1answer
210 views
Is this LED fixture safe for use with its current fabrication?
My father is currently interested in investing into a Ukrainian LED fixture manufacturer, and after he bought home a sample, I'm scared. There are 94 LEDs paired up with diodes, all in series, ...
9
votes
7answers
840 views
What if I overload a cheap AC adaptor?
I'm experimenting with PIC microcontrollers and various related circuits both on plugboards and simple homemade PCBS.
I'd like to use various old AC power adaptors I have lying around to power my ...
9
votes
4answers
582 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 ...
9
votes
5answers
3k 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.
...
9
votes
2answers
342 views
What is this strange long wire for in a single induction cooking unit?
Tonight I dismantled one of those single induction hobs:
Inside there were two PCBs. The incoming mains was wired to the top left PCB, while the other contained all the low voltage components, plus ...
9
votes
4answers
2k views
What does it mean when there is a voltage difference between ground and neutral?
Between ground and hot there's approximately 120V as expected.
I had expected the voltage difference between ground and neutral to be 0v, but instead it's 0.4V. Why would this not be the case? Is ...
9
votes
2answers
216 views
How to ensure my device is safe for every day use?
I have put together a simple wake up light. It has an external powersupply, at the moment rated 7V and 600mA. Inside it has Arduino and bunch of LEDs controlled by a MOSFET.
It works fine at the ...
9
votes
3answers
2k 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. ...
8
votes
4answers
1k 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 ...
8
votes
4answers
2k views
Moving PIR sensor (or IR camera), aka Predator like alien scanner
To avoid public transport and the car, I decided to go to work on foot everyday but I have to pass a small, but dark (in the evening) and scaring wood.
Even if I use flashlights, I'd like to have a ...
7
votes
3answers
655 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.
...
7
votes
3answers
1k 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 ...
7
votes
1answer
614 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 ...
7
votes
2answers
776 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 ...
7
votes
1answer
12 views
Can Arduino operate under water?
I have an idea for an automated small toyish submarine. Can I use the Arduino for this? Does it behave well under the ocean surface? I think I'll need some kind of casing with silicone around it, and ...
7
votes
3answers
19 views
How can I safely connect both Arduino and a 120V 10A circuit?
I'm building a thermostat, and the idea is to have it fire one of two 120V 10A circuits (one to heat, one to cool). I have two of these modules for the relay and I ...
6
votes
8answers
742 views
Basic Training for working with 120V AC
I'm planning to build a digitally-controlled light dimmer circuit. I'm not trained in electrical engineering, and I don't want to do something that an electrician would immediately recognize as ...
6
votes
7answers
940 views
Is it safe to use a DC power adapter that isn't UL Listed or CSA certified?
I picked up a 9V switching DC adapter from SparkFun a while back, but I've been hesitant to use it because it doesn't have any of the usual "safety" approvals that you normally see on power adapters ...
6
votes
3answers
252 views
Conductive Lubricant for Connectors?
I'm making a safety disconnect for an experimental RC craft. It will be tethered to the ground, and if it goes out of control the tether will pull a plug disconnecting the power. I will make the ...
6
votes
2answers
211 views
Designing electronics and their enclosures for the outdoors
I think the title captures it, but to expand upon this further. What are some of the best practices that you use to place electronics outdoors? Include what you do for the cases and mention issues ...
6
votes
2answers
4 views
Check the quality of not original Arduino boards?
There are several reproduction Arduino boards available. How can I check that the board is wired correctly and that the ATmega chip and the other parts are comparable to the official design?
6
votes
4answers
166 views
Detect “real” overcurrent/short-circuits vs. current peaks
We have a MOSFET that drives a load. The load has a sense resistor in its current path and its voltage is used to trigger a circuit that can disconnect the load if we detect an over current ...
6
votes
1answer
307 views
Very small scale electronic goods manufacturing regulations
I would like to make a 12v rechargeable battery operated robotic toy, for sale as a kit. This would be more of a hobby for me, selling say 5 units a month with a very small turnover. It would just ...
6
votes
1answer
119 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 ...
5
votes
4answers
3k views
DIY Beginner's DC Power Supply?
My school uses HY 3005D-3 but I want to do it myself to save on $. Before opening it, I ask for tips about: not-to-break-it, cheap DC supply and DIY-materials (not that I know them soon). So how to ...
5
votes
3answers
434 views
Which of these approaches for a watchdog timer?
I recently learned about watchdog timers, and am trying to implement one for my circuit for the purpose of resetting my (AVR) microcontroller if it hangs (i.e., doesn't respond to the watchdog).
...
5
votes
3answers
145 views
Running router out of its case
I'm currently building a robot, and as part of its spec it must connect to a wifi network. I have a Belkin wireless router, which I have taken out of its case to expose the PCB.
My question is:
Is ...
4
votes
4answers
1k views
At what current and voltage Typical Resistors explode?
I don't have an explosion chamber so I cannot test critical values.
If you explode resistors with too high current-voltage combination, does it damage your equipment, such as multimeter and ...
4
votes
4answers
3k 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
2answers
555 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 ...
4
votes
2answers
270 views
Microcontroller'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 ...
4
votes
3answers
790 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 ...
4
votes
2answers
224 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 ...
4
votes
2answers
263 views
Circuit safety -> Preventing smoke through accidental connection of battery voltages
I'm building a circuit whereby users are able to connect their battery to the pcb which will then be sampled by a micrcontroller. Voltage divider circuitry is all good so please don't focus you ...
4
votes
3answers
684 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 ...
4
votes
1answer
2k 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 ...
4
votes
2answers
138 views
grounding connection?
What's the easiest way to connect a ring terminal to the ground terminal of an AC outlet? Are there plugs you can buy that make this easy?
I don't need (or want) the line and neutral wires ...
4
votes
1answer
21 views
Does the Arduino have any specific cooling requirements?
If I were to encase my Arduino in a sealed case with no ventilation, would this be an issue? What about if I were to pot the Arduino in epoxy, would that pose a cooling issue?
