72
votes
Accepted
Should I ground my body when working with 200V+?
Grounding won't protect you against shocks when touching live wires!
Quite the opposite, the better you are grounded, the higher the resulting current through your body will be.
- 10.3k
56
votes
Should I ground my body when working with 200V+?
Grounding oneself, while working on live electrical equipment, would be an open invitation to disaster.
Insulating oneself from ground would be the only way to ensure total safety.
That's why rubber ...
- 19.7k
41
votes
Can I make car starter cables out of standard appliance cables?
Current rating and voltage rating of a cable are two completely different things.
You cannot translate 240V/15A rating into 12V/300A. The 240V/15A rating is capable of 15A no matter what voltage you ...
- 5,820
38
votes
How can the contact points of jumper cables handle the hundreds of amps required to start a car?
Hint: resistance is not just a matter of cross section, but also of length.
Would you expect the jumper cables to work if they were say, 10 meters long? What about 100 meters? You got my point.
Even ...
- 16.7k
26
votes
Should I ground my body when working with 200V+?
You need to review basic electrical safety with your professor assuming you are in college. If in the workplace someone didn’t do a good job interviewing you and you need to ask for training. ...
- 369
20
votes
How to measure current up to 1000A and not go bankrupt
Use several Hall effect sensors, arranged symmetrically round the bar, so that they add for the bar field, but cancel for external fields. Much the same principle as how a Rogowski Coil rejects ...
- 185k
19
votes
How can the contact points of jumper cables handle the hundreds of amps required to start a car?
Have you noticed how the clamps get hot after a jump-start?
That means power is lost, it ends up in those clamps. You're right the connection isn't ideal so power is lost but not so much that ...
- 81.9k
19
votes
Accepted
How can the ACS712 pin handle 20 A?
Do note that this IC has been discontinued and not recommended for new designs, they recommend the ACS723 instead. It also comes on a 30A version on the exact same package.
PCB trace calculators rely ...
- 8,636
18
votes
Should I ground my body when working with 200V+?
220VAC can often cause severe permanent injury or death. Stop working with those voltage levels until you have professional training.
In an official communication, OSHA has stated that they consider ...
- 1,467
17
votes
Accepted
How do high current paths work in PCB design?
Looking closely at the calculator referred to, the trace width of 9.36 is for a trace on an internal layer and for a temperature rise of 10 degrees.
On an external layer the width is 3.60mm for the ...
- 17.5k
16
votes
Accepted
Op-amps, why do they have such low output currents
It's simple: manufacturers make what customers will buy! It's the same reason why Ferrari won't put a trailer attachment at the rear of their cars...
Price is a very important part of this, of course,...
- 88.8k
15
votes
How can the contact points of jumper cables handle the hundreds of amps required to start a car?
You seem to overestimate the effects of current on conductors. Let's take an AWG17 wire for example, which is a mere 1mm² of copper. Guess how much current it can take for 1 second before blowing up? ...
- 26.2k
15
votes
Accepted
PWM motor control, MOSFET getting very hot
The threshold Voltage of IRF3205 is between 2V-4V and the Raspberry Pi gives signal of 3.3v that will be fine
No. Gate threshold is where the MOSFET barely starts conducting. So if it varies between ...
- 58.1k
15
votes
Accepted
Are high-current (over 3 A) PWMs common?
PWM controllers are commonly used to drive transistors to switch high-current loads. That way, the controller itself only needs to provide enough current to switch the transistor (usually an N-channel ...
- 46.5k
14
votes
high current PCB traces: do we need many?
A set of parallel traces handles more current than if they are joined in a single trace. Why?
For 2A (*) we need 0.391mm but for 20A we need way more than 10X the width (9.36 mm). How this can be ...
- 16.6k
14
votes
Accepted
MOSFETs keep shorting way below rated current
tl;dr; Put the limiting resistor to drain and use a high side driver.
The answer is simpler than we all thought first. The limiting resistor is on the wrong pin of the FET. Nevertheless all previous ...
- 4,187
13
votes
Should I ground my body when working with 200V+?
Wrist Bands are to protect equipment from you(ESD) not you from from equipment.
Best you can do is to not work on live equipment and use RCD if you really have to (Also, isolation transformers are a ...
- 354
13
votes
How to measure current up to 1000A and not go bankrupt
How about field sensors? If the busbar is rectangular it shouldn't be that difficult to place the sensor.
Example 1 : ACS70310
Example 2 : two or three sensors with integrated conductor like ACS772
...
- 9,166
13
votes
Can I make car starter cables out of standard appliance cables?
@Klas-Kenny's answer is correct. The cables don't know anything about what voltage they're at until the insulation voltage is exceeded and then they start to break down. The wire is a resistor and ...
- 188k
12
votes
Can I make car starter cables out of standard appliance cables?
Aside from the cable issues, which have been amply covered in the other answers, a major concern for high current wiring is that the terminations (typically to large crocodile clips in the case of ...
- 9,234
11
votes
Accepted
Does hot melt glue damage wire insulation?
The number written on the outside of the wire is the hottest environment where the wire should be used. it is not the melting temperature of the insulation.
Hot melt glue is hotter than that, ...
- 40.6k
10
votes
2000A current sensing using STM32
The field from 2000A flowing in a conductor will be quite significant, and linear with the current. Just dangle an analogue output Hall effect IC close to the cable.
Better still, have two Hall ...
- 185k
10
votes
How to measure current up to 1000A and not go bankrupt
Use a linear Hall effect sensor attached to or close to the bus bar. They are less than two dollars. However, they measure the magnetic field, so the output will vary due to external influences, ...
- 7,775
9
votes
How can the ACS712 pin handle 20 A?
Your question applies to virtually all high current ICs and power devices. It is clear that the leads themselves are thick copper wires, and the capability goes far beyond 20A. Many power FETs can ...
- 22.3k
9
votes
How to measure current up to 1000A and not go bankrupt
Super easy. Have a conductor of known characteristics somewhere in the system. This can (and arguably, should) be any conductor that has another job and is fit for the task. Having a dedicated ammeter ...
9
votes
MOSFETs keep shorting way below rated current
The MOSFETs will be subject to extreme stress when attempting to switch off with your circuit (and switching 'on' isn't so great either).
There's only a 10kΩ resistor to drain away a couple hundred nC ...
8
votes
High current headers/ jumpers
This is how we did it when I worked for a company that made large SCR phase control units:
https://www.digikey.com/en/products/detail/nte-electronics-inc/25-B500-03/11651152
https://www.digikey.com/...
- 20k
8
votes
Are high-current (over 3 A) PWMs common?
The PWM controllers you have linked on Farnell can be used in power supplies (for example) but also can be used for motors. However, they all require that the output pin be connected to a power ...
- 503k
8
votes
MOSFETs stabilizing current in coils keeps burning, how to protect them?
What my problem is, that when I am sending larger currents (a few
amps) after some time the MOSFET responsible for current stabilization
burns.
You are using the MOSFET in a linear circuit ...
- 503k
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