New answers tagged safety
1
From the cold heat website:
We do not recommend the ColdHeat Cordless Soldering Pen for soldering temperature-sensitive or very small electronic components, because the temperature variation of the tip can be dramatic and quick, too quick even for your incredible reflexes. Similarly, it will not work handsomely on large joints that require long, continuous ...
3
I've built many RC aircraft and on average my "small" planes (considered "micro" in RC world) can use 20A of current. By comparison 2A starts going into the "ultra-micro" realm (most ultra-micros I own actually use around 10A, building 2A planes is possible but very difficult and require specialized building skills). Most normal ...
4
Skin acts like a VBO, not a resistor.
You're expecting human skin to be ohmic: follow V=IR. Nope.
Human skin works more like a VBO (Voltage Breakover) device. It doesn't flow current until a certain voltage, and then, it does.
That voltage varies wildly by conditions (generally, wetness). But 12V is a very safe number; the only time someone was killed by ...
1
It might differ outside of Europe, but the following could be used as some basic overview of how to evaluate and select the standards needed, before comercializing a power supply.
Before starting with the design process you should define the following:
Customer / Field (e.g. medical, industrial, etc)
Location to be used (e.g. country)
Standards
Depending ...
3
In olden days when testing systems which were necessarily live, the standard approach was to stick tape over the contacts you didn't want to touch. Most people would get a few unpleasant reminders of where to put the tape until they knew the layout they were testing well enough to do it in advance.
You'd not be wanting to wear a metal watch or other ...
28
"How do people prototype circuits without getting shocked?" They switch off the power before soldering it up. This is not for fear of shock but for fear of damaging the components. The soldering iron tip is usually grounded for the same reason.
Only experienced engineers should ever try soldering a live circuit. They know how to avoid harming the ...
6
The amount of amps \$I\$ you get depends on the combination of resistance \$ R\$ and voltage \$V\$ you have, this relationship is called ohms law
\$\frac{V}{R}=I\$
Your drone has a low resistance in it's circuit, so you get 3 amps circulating in it.
\$\frac{5V}{R}=3A\$
\$R=\frac{5V}{3A}=1.6\Omega\ \$
Thats a pretty low resistance.
On the other hand, your ...
22
Human skin has a pretty high electrical resistance at low voltage (you can measure it with an ohmmeter, just grab the probes). If you stick your finger on low voltage like below 24V you won't feel anything. Some current will pass in your finger but it will be microamps. Last time I punctured a finger with the pointy end of a wire that had about 12V on it, I ...
62
It’s a common misconception with beginners that a 2A power supply will force 2A through anything that touches it. This isn’t the case. Most power supplies are (more or less) constant voltage, so the resistance of the load determines what current flows. The human body has a relatively high resistance and so low voltage circuits can be handled with only ...
12
If it's got two points of contact with the rest of the circuit, then the current vs. voltage relation is fixed. You can give it a fixed voltage and get a fixed current, or a fixed current and get a fixed voltage -- you can't independently control voltage and current.
If you make two points of contact with a voltage source, you're the "it" from ...
1
On the London Underground, the fourth rail is certainly not just a "return current" rail, and is nowhere connected to ground.
It is maintained at -210V, which combined with the +420V on the 3rd rail, gives the required 630V.
See the following section in Wikipedia:
On the London Underground, a top-contact third rail is beside the track, energized at ...
1
Yes, if the return rail is 210 volts off earth, it is energized and dangerous to touch unless known to be de-energized under London Underground safety procedures.
It being a "return rail" in name does not overrule the fact that there's a potential difference of 210 volts from it to ground, which you will be subjected to if you step onto it while ...
0
The last time I asked this, the answer was that the inverter tries to change the frequency and the grid is so large in comparison that the grid frequency does not move so the inverter senses a difference.
When the grid has disappeared then the frequency is easily changed which means the inverter stops output to prevent issues like islanding.
1
5V, as said, is safe by all means (less than 60V, by IEC, CENELEC ad UL standards, ad less than 50 V, OSHA).
John D mentioned correctly the problem of burns, if you wear a metal ring.
Then you have to consider the way you interrupt the 42A and if there is a connector that should bring that current and may be extracted with current on. Usually I put several ...
0
IEC and UL norms states that you can touch with your finger, without health risks, the following 2 types of voltages with respect to the ground of the circuit AND with respect to EARTH:
DC voltages: max 60 VDC
Non DC voltages: max 42 Vpp (peak to peak)
Those are considered safe voltages that we all human beings can safely touch.
If your power supply is ...
0
First you'd draw a schematic and ensure the 0V between the Uno and the L298 board is connected. You'd then be able to post the schematic where others could look at it.
As for the 'tingle' - how is this powered? By a switchmode supply from the mains?
Assuming you have a valid schematic, you'd then visually check your wiring. Then if there is doubt, use the ...
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