When in doubt, don't do it. Electronics can be dangerous, even fatal.
-3
votes
1answer
102 views
I want to build a portable railgun and I'm a complete rookie [closed]
I'd like to enter the world of electronic hobbies by making a railgun, and so far I know that I understand the basics of the device and that I need high amounts of direct current.
However, I am ...
3
votes
3answers
137 views
How can I safely power two 3v motors from a 9v battery?
I'm making a Sumo Bot from scratch and I had purchased two 1.5-3v DC motors from Radio Shack to run with my Arduino Uno v3. I'm using a 9v battery to power my Arduino alongside an RF receiver, Quad ...
1
vote
1answer
60 views
Live-Neutral transformer fault
In this critique of an ELV PSU design, it is suggested that a "Live-Neutral" fault could result in a fault current of thousands of amps. I'm sceptical. Please could someone explain how this could be? ...
3
votes
1answer
75 views
Possible measures to make power supplies safe
I'm looking for a list of ways that mains-powered ELV power supplies with touchable terminals can be made safe in the case of transformer failure with primary and secondary coils becoming connected ...
6
votes
4answers
172 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 ...
-2
votes
1answer
99 views
Why UPS for sensitive SMD development?
My friend suggests me UPS for SMD development. I already have a a surge protector over all devices. He recommended the UPS that transmit all energy through its battery and he recommend to find some ...
3
votes
1answer
119 views
Disposal of the used acid/hydrogen peroxide etchant?
This thread repeated the question how to dispose the used acid/hydgogen peroxide etchant. So how can I dispose acid/hydrogen peroxide etchant?
Perhaps interesting thread to other readers, Disposal of ...
-5
votes
1answer
81 views
Is there any method to protect developer from lethal frequencies? [closed]
My physiological answer to "Why do 0.02A fuses not protect a person? Why no protection from shocks?" is raising new questions. So is there any method to protect developer from lethal frequencies?
1
vote
5answers
364 views
Why do 0.02A fuses not protect a person? Why no protection from shocks?
I understand the user here so that fuses do not protect people from shocks. I am planning to put put fuses such as fast-blown fuses and PPTC fuses around all kind of positions such as ...
2
votes
3answers
146 views
USB Fuse to protect USB ports?
I shorted by accident a circuit creating large voltage to my computer, luckily MBA has some sort of shorting protections -- yet this kind of thing should not happen. I would like to have a fuse ...
-6
votes
0answers
133 views
Things needed to work with super-sensitive electronics? [closed]
Super-sensitive electronics deals with small voltages in the range of 5 \$\mu V\$ and 30 mV, for example EMG or EG in the bionic development. You can measure mV voltages on locations such as hands, ...
3
votes
3answers
155 views
Building a power supply, want to stay alive
I am building a power supply for a very old laptop. The circuit uses a transformer (220 V primary to 15 V secondary, 33 VA) and that worries me a little. (Please note that I an enthusiast and so far I ...
1
vote
1answer
86 views
Electrical saftey of metal panel-mount DC jacks
Context:
I have a robotic arm with a series of servo motors, that together draw up to 3A from my bench supply (depending on the load on the servos). To make it easier to transport the robot around, ...
8
votes
1answer
17 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 ...
3
votes
2answers
27 views
Maximum Current Draw on Vin Pin
I don't want to damage the pins on my Arduino Uno, and I'm especially cautious of drawing too much current. I'm experimenting with a small servo motor (similar to this one), and have connected the ...
10
votes
3answers
43 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 ...
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?
7
votes
3answers
26 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 ...
14
votes
2answers
15 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 ...
6
votes
2answers
5 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?
17
votes
5answers
171 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?
3
votes
1answer
65 views
Redesigning TV Remote for a different User Interface
The buttons of a standard TV remote are simply conductors covered by insulators (for user protection) to be pressed in order to short circuit a node in a grid of wires.
What if we want to replace ...
2
votes
2answers
149 views
How much can I safely plug into a light socket converted to a standard outlet?
I just moved my office desk from our extra bedroom on to our stairway landing. The tricky thing was that there was no wall outlet to plug anything into. However, there was a nearby light socket, ...
0
votes
1answer
150 views
How long till Capacitors Discharge Naturally? [duplicate]
I am a super noob at this and never done anything before like this but want to try. Here is the problem I have Samsung SyncMaster 226BW that is known for bad capacitors and I think I am a victim of ...
3
votes
2answers
129 views
Why are typically fatal currents non-lethal when they pass through your body for a short time?
I've been reading up on electrical safety, and the commonly cited controversial quote "it's not the volts that kills you, it's the amps". What I have gotten out of these sources is that it is in fact ...
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 ...
-5
votes
3answers
322 views
My son got shocked by a D cell battery [closed]
My son was doing experiments at school with a D cell battery and touched each end with a paperclip. He said it shocked him hard enough to make his heart beat fast and knock him out of his chair. Is ...
3
votes
2answers
239 views
What is the recommended way to protect a circuit from non-transient overvoltage?
I'm designing a 12V battery-operated portable lighting controller, and frequently am asked about improving the run time. The simplest way is to add a second battery in parallel, but I often worry that ...
-3
votes
2answers
108 views
Electrical Fire From Batteries [closed]
I currently have an MP3 player powered by 4 "C" batteries, so does that mean I'm powering the unit off of 6 Volts?
Anyways, the specs on the sheet said 3.7 Volts, one of the comments said 3.7 to 5 ...
3
votes
3answers
276 views
Calculating current load for a switch?
This SPST switch is labelled on the box as "Rated 10A at 125VAC or 6A at 250VAC".
Is there a calculation as to the amperage it will handle at 12V DC?
(update) As JYelton points out, a naive ...
-2
votes
2answers
137 views
Is an unexposed but peeled cord safe? [closed]
So after having my iPhone for a long time, my charging cable has gotten frayed:
The rubber insulation of the cord has peeled off and the foil cross talk thing rubbed off. The cord still syncs and ...
-2
votes
1answer
62 views
How to obtain safety testing equipment? [closed]
What is the best way to obtain (buy or build) mandatory safety testing equipment? Eu standards specify a "reasonable" amount of equipment in order to sell your home made equipment (selv and other ...
-1
votes
2answers
97 views
Lithium batteries worries [closed]
For the last few days I have had this strange fear that an external short circuit would cause an explosive fire of my laptop's Li-ion battery.
Three questions:
Is it true that lithium ion ...
3
votes
1answer
402 views
Is hot glue a good insulator?
I need to mount some relays that I have soldered wires to. If I place them on a non-conductive surface and use a generous amount of standard glue from a hot glue gun, will that be relatively safe? ...
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, ...
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 ...
4
votes
2answers
142 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 ...
5
votes
3answers
441 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).
...
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 ...
2
votes
2answers
1k views
Grounding a DIY power supply
I am trying to develop a bench power supply. Now, before going on, I do realize that there are really cheap commercial ones available. I have two. I want to develop one my self.
The way I have ...
3
votes
1answer
203 views
DIY Electrical Safety
I'm quite into DIY projects and I am looking at making an electrical unit out of a Raspberry PI and a computer monitor.
I was wondering if someone could provide me any information on what I should ...
3
votes
1answer
95 views
Safely testing a DC supply with an unknown output configuration
This picture shows the connector for the DC end of a power supply I extracted from a dead HP MFD (Multi Function Device):
As you can see it consists of 4 pins in a 2x2 configuration. The sockets ...
9
votes
2answers
343 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 ...
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 ...
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 ...
3
votes
2answers
210 views
Disassembling a camera - dealing with a flash capacitor
I'm disassembling a broken old camera (an Olympus FE-110) and I've learned that I should be really careful with the capacitor inside. I wanted to follow the guide linked at the bottom of this article, ...
1
vote
2answers
141 views
Reflow oven AC cable splicing insulation and thermocouple readings
I'm building a reflow oven. I know what I'm doing, I just want to verify my plans to make sure I'm not doing anything stupid before I start.
The idea is to have an arduino (powered externally) ...
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 ...
4
votes
2answers
265 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 ...
3
votes
1answer
306 views
Safety precautions working with high voltages (Nixie Clock)
I'm building a nixie clock kit with these instructions. I'm up to the part where I have to test (page 17) the high voltage components (the power supply is 12V 250 mA) which is up to 170 volts (page ...
