Threads posted for mains circuits

Discussion in 'Feedback and Suggestions' started by MaxHeadRoom, Jun 24, 2018.

  1. MaxHeadRoom

    Thread Starter Expert

    Jul 18, 2013
    15,694
    4,571
    I am fully aware of the forum rules and conditions but I find it it a little ironic when this thread is closed
    https://forum.allaboutcircuits.com/...o-240v-wall-light-switch.149902/#post-1281935
    And almost every day there is a thread on mains derived circuits using an SCR or Triac's etc including working on non-isolated Treadmill controllers where none are closed.
    The only way to completely guarantee complete safety and conform to the rules is to limit all questions that do not include any voltage over the recognized value of 50v. ! :rolleyes:
    Max.
     
  2. strantor

    AAC Fanatic!

    Oct 3, 2010
    4,986
    2,987
    Wait, are we back to a ban on mains circuits? Or was it never lifted? I thought everything including automotive was on the table since the acquisition. Shows how well I keep up. I guess my "30kVA/480V/3phase Supply From Residential Power" project will not be welcome in the "Completed Projects" corner of this site.
     
    MaxHeadRoom and wayneh like this.
  3. wayneh

    Expert

    Sep 9, 2010
    14,707
    5,226
    Dang. I just got this running and was hoping for some help with the grid tie. :p

    upload_2018-6-24_19-39-11.jpeg
     
    shortbus, JoeJester, xox and 4 others like this.
  4. DickCappels

    Moderator

    Aug 21, 2008
    4,864
    1,471
    I just had a look. The topic of the thread is in the very touchy LEDs to mains realm. This is currently prohibited as shown in the moderators closing post. As I understand it, the concern is over inexperienced users playing with the mains resulting in something very grim happening.

    Contrary to the perceptions of some, circuitry that connects to the mains is not prohibited and as far as I can remember it never was, it is jut the application of LEDs to mains and power supplies that are not isolated from the mains (I personally add: in situation in which there is a potential safety issue, such as a benchtop power supply.)

    The owners and administrators have been asked to modify those provisions in the User Agreement, the thinking among some is that it is far better to give good advice and some supervision than to cast off those who would take on such projects to do it on their own. So far, the change has not been made.

    If the LED wasn't that post, the thread would still be open.
     
    jpanhalt likes this.
  5. Danko

    Member

    Nov 22, 2017
    469
    169
    I think it can be LED, but without mains.
    For example:
    Switch.PNG
     
    Last edited: Jun 25, 2018
  6. xox

    Member

    Sep 8, 2017
    299
    63
    It's really quite silly if you think about it. An unconnected capacitor can kill a person and conversely there are many cicuits which can be safely connected directly to the mains (trust me, I figured that out myself from careful experimentation after a thread on the subject was closed on this forum).

    Anyone messing with electrical circuits should already be well versed in the risks and plan accordingly. We don't need archaic forum rules put in place to protect people from themselves any more than we need "DO NOT EAT" labels on desiccant packages. Censorship is not the answer.
     
  7. ElectricSpidey

    Member

    Dec 2, 2017
    443
    95
    It's called "Taboo" they rarely make any sense outside of a very narrow context...like eating ham, after germs were discovered.

    When I stared to explain the disadvantages of such a policy, I got my ass handed to me.
     
  8. BR-549

    AAC Fanatic!

    Sep 22, 2013
    3,922
    1,013
    The problem is we don't have experienced or studied people here asking those questions. Someone reads a web LED article and decides to use AC powered LEDs. ON THE CHEAP.

    I used to disagree with this policy........but people that are not studied......will refuse to realize the danger. And even argue with you about it because of what they have heard.

    I've seen it several times. This site loses nothing with this ban. There are other sources.
     
    JoeJester likes this.
  9. JoeJester

    AAC Fanatic!

    Apr 26, 2005
    3,898
    1,725
    My personal feelings is always to err on the side of safety. Voltages as low as 30 Volts can be dangerous. Yes, that is correct. Granted not many in the general population would be exposed to the conditions where 30 Volts could cause irreparable harm. There are many sources of electrical safety. The 30 V figure I use was based on the U.S. Naval services documentation.

    Electrical Safety Study Guide

    Module 1 Chapter 3 of the Navy Electricity and Electronics Training Series, NEETS, also covers electrical safety. NEETS is linked below.

    Finally, very few people know anything about a first time poster. They must discern their knowledge and experience by how they pose their questions. Then of course, this is the internet and no one can not quote some code from every country in the world. They can only know their own countries and the Generally Accepted Practices. There could be a chasm between those two with respect to electrical safety.

    In the end, one could message a poster and carry on whatever conversation they wish to in private, if they feel the rules are too strict.

    I just don't answer some questions. I hold no expectations from others, other than following the rules.
     
  10. Hymie

    Member

    Mar 30, 2018
    462
    95
    This thread should have been banned – but had it not been permitted, I doubt the TS would have managed to fix the ice-maker without the assistance from this site; there are many other such examples.

    https://forum.allaboutcircuits.com/...cation-process-stalled-icemaker-board.149315/

    Perhaps what is needed is a standard worded warning added to posts involving circuits operating above say 60Vdc (40Vac) – mitigating any potential claims that those operating this site are encouraging persons un-skilled to engage in unsafe practices.
     
  11. bertus

    Administrator

    Apr 5, 2008
    18,352
    3,516
  12. Xavier Pacheco Paulino

    Active Member

    Oct 21, 2015
    542
    45
    I have posted some threads on non-isolated circuits from mains. However, I'm aware of electric safety. I have 2 years of technical repair experience and had to deal with many of these cases. As said above by @BR-549, some people just start dealing with mains and it can be dangerous at some point. So I clearly understand these kind of prohibitions in the forum.
     
  13. WBahn

    Moderator

    Mar 31, 2012
    22,865
    6,828
    The adding of the automotive forum was completely independent of the acquisition. Unrelated to that we discussed adding some new forums and were able to get the owners to agree to modify the ToS/UA so that we could include the automotive forum as part of that.

    We have had a few discussions with the keeper of the ToS/UA about how to loosen or even eliminate the restrictions on mains-connected low-voltage circuitry (making it case-by-case) and a couple of times I thought that the ToS/UA was going to be modified, but it didn't happen either time. But keep in mind that modifying the ToS/UA (for something like that) is very close to the bottom of a pretty long priority list. In the meantime, the mod staff is bound by the ToS/UA as it currently exists and we can only do the best we can.
     
    strantor likes this.
  14. WBahn

    Moderator

    Mar 31, 2012
    22,865
    6,828
    The intent of the policy, as I understand it, is NOT about not permitting mains-powered circuits. It's far more about having mains-powered low-voltage circuits. When someone, even a very inexperienced person, is working on house wiring or a big motor or something similar, they know that they are working with a high-voltage circuit that requires due care. But many inexperienced people start with low-voltage circuits and develop habits that reflect what you can do with low-voltage circuits and when they see a circuit that lets them power it directly from the mains using a capacitive voltage divider or get an accurate clock signal by just tying an input pin to the mains with a large resistor, they still see the circuit as a low-voltage circuit that they can poke around in just like they are used to. But now those habits become very dangerous. And the isolation is only part of the issue. If you use an isolation transformer to power such a circuit you still leave yourself very vulnerable to getting tangled up with mains-level voltages that can push lethal currents while you are dinking around with what you think is a 5 V or 15 V circuit. Even without anything failing.

    We have been trying to get the owners to change the ToS/UA to allow discussions that are currently prohibited precisely so that these dangers and issues can be discussed and the member educated, and also with the understanding that the mod-staff can shut down a discussion (about this or anything) if it appears that the TS (or whoever) is not learning or willing to abide by the recommended safety practices.

    But until the ToS/UA is actually changed, we have no choice but to abide by the existing version.
     
    Kjeldgaard and xox like this.
  15. Hymie

    Member

    Mar 30, 2018
    462
    95
    I work within the area of electrical product safety, and have often wondered why such an important topic is not on the syllabus of electrical engineering courses.

    I can still recall the lecture I attended on linear transformers covering all sorts of parameters from efficiency, magnetic coupling, parasitic effects etc. But never once was it mentioned that the transformer was providing the very important function of isolating the low voltage circuit from the mains – and the separation requirements thereof.

    Prior to being involved in electrical product safety, it never occurred to me that the material used for plastic enclosures are made using flame retardants, or that Y1 safety capacitors (providing reinforced insulation) existed; and of course many, many other product safety requirements.

    But the optic is extremely complex, and I suspect that this is one of the main reasons it is not covered in college courses.

    As an example, in WBahn’s post above he advises against obtaining an accurate clock signal by just tying an input pin to the mains with a large resistor (good advice). However such a construction would be perfectly acceptable (according to the product safety standard IEC/EN 60950-1), with the proviso that the resistor meets the required component approval, and limits the current to within specified values, and has the required separation (between Primary and Secondary circuits) at the component terminals.
     
Loading...