Member #666505

Member Since: March 28, 2015

Country: United States

  • Not necessarily a problem - use the relays on the board to control a power relay.

    To control DC current, use at least two relays in series. Paralleling relays is not good.

    1. Background. At the 2016 IEEE Product Safety Engineering Society symposium, the use of ‘hobby’ (arduino) processor boards, and related power-control related modules that have found their way from the home shop to the industrial/commercial setting was discussed. Should be noted that the director of OSHA’s NRTL program was present at some of these discussions, so the feds are now aware. An informal poll among a group of compliance engineers indicated some have direct experience with “more than one” incident related to use of non-compliant arduinio stuff.

    2. Your efforts to design a conforming product are commendable and very much appreciated. Compliance requirements are a morass and lie at the unholy intersection of law and physics. Few designers have successfully navigated a formal product submittal for stuff intended to be connected AC mains; most have to seek a member of the Dark Side of engineering (that would be me) to avoid being seduced by the power of hate and anger.

    3. Am not at work, so clause number and wording from standards are based on my diminishing ability to remember the multitude of garbage in the hundreds of standards and directives that taught me to embrace my anger and hate and serve well to crush my being on a daily basis.

    4. creepage requirements for 60950-1 are similar, as both are based on IEC60664-1. The seminal reference for the physics of electrical spacings is K. Stimper, ”The physical fundamentals of low-voltage insulation coordination”, VDE-Schriftenreihe, Vol. 57, Berlin, Offenbach vde-verlag

    5. . Per 60950-1, a minimum clearance (spacing through air)is 1.0mm for 120V, but this number has no margin and is intended for a widget that is enclosed in a box. Spacings for safety are based on the mains transient voltage for the intended OV category. So the absolute minimum transient rating for 120V mains would be 800V, which is used to determine the increased spacing for ‘Basic Insulation’ and to ensure that the equipment can pass the di-electric withstand test (‘hi-pot’). A more realistic transient voltage would be 1500V, which is the typical test level for Class I equipment per 60950-1.

    6. Many are in denial on the impending cruel death of national standards based on IEC60950-1, so will ignore UL62368-1 and only reference product conformity per CSA/UL60950-1.

    7. Would typically not recommend seeking a component recognition from UL, as there are other competent NRTLs that have more reasonable scheduling and rates.

    8. Subclause 1.5 and annex P1 - ratings for PCB material per UL796.

    9. subclause 3.2 and annex P1 - ratings for connectors per UL498.

    10. subclause 3.3 and annex P1 - ratings for field-wiring connectors per UL486.

    May the Light Side of The Force guide your future design efforts. And we all know that “once you start down the dark path, forever will it dominate your destiny”. So there is no hope for me…

  • Nothing written is intended as professional design advise for the purpose of compliance with various national safety regulations, standards, or directives.

    1. IEC/UL/EN60950-1 is obsolete, and should not be used for assessments of new products.

    2. Does not meet construction and/or performance requirements per CSA/UL/EN62368-1 and/or 60950-1.

    3. Could meet UL/EN61010-1 requirements where used per specific conditions of acceptability. But probably non sequitur, as the scope of this equipment is not intended for use in professional test and measurement equipment.

    4. Not recommended for switching motor power where nameplate rating for FLA or FLC exceeds 50% of relay contact rating. Not recommended for DC current interrupt.

    5. Creepage (spacing across a surface) requirements in mm, per IEC62368-1:

    120V Basic = 2.4, 240V Basic = 4.0

    120V Reinforced = 4.8, 240V reinforced = 8.0

    [these requirements for material group III, pollution degree 3]

  • The Si7012 spec sheet has this information. Anyone using these polymeric capacitive sensors should be aware of lifetime for a 95% confidence reading. My experience has been typically 6 to 22 months until replacement required, regardless of the mfr or model.

    Best long term stability is the wet/dry ‘bulb’ using thermocouples or RTDs. But these are mechanically complex and require a way to control the flow of distilled water. Have made several in previous 20 years, and all remain operable and accurate while installed in very harsh environs.

  • for both 2811 and 2812:



    Should work with all T 3.x stuff.

  • Bought book for niece off of Amazon, as she uses this silly program. Book is a bit dated and not complete.

    Do not understand why the FOSS community pushing this closed and marginal program. Should be supporting stuff like KiCad (and there are many other decent OS systems for EDA). Last year, the PCB designers at my employers reviewed several low-end and FOSS systems, because Mentor Graphics and Cadence/Allegro licenses are getting too expensive. The only low-end package they considered usable and reliable was KiCad - which is my preference for both home and work. Their analysis became important when we layed off the drafting dept, and the engineers and techs had to do our own stuff. Am most happy we did not get stuck using Eagle. FWIW, we bought Eagle’s hi-end commercial package for our evaluation, so the Mentor/Allegro comparison is valid.

  • But really wanna see a magneto-based (magnetic ?) bullet stopper. Oh, never mind - did a rough calc to determine power. Would require a huge battery pack.

    As for hating - the only thing that bothers me about the ‘LGBT community’ is the number of very smart people that will probably not reproduce. The guy sitting two cubes down is gay and it really pisses me off that such a smart and creative engineer will not be making more.

    Ok - there is your ultimate ardy product - asexual repro for humans.

  • no, note the bias V on non-inverting OA input pin. So will be referenced to approx ½ of Vcc.

  • oh holy molly… There is much more to fuses than the voltage and current ratings.

    And if you feel the need to play with the AC mains side of stuff, please consider using a variac to gradually apply power while watching input current. I do this whether testing a 5VA or 1000 kVA transformer.

  • Any response would be fraught with legal and technical liabilities. In any case, no reasonable response because intended end-use environment not defined, and installation (O/V) category not specified, and conditions of acceptability not known. But here is a minimal list to start with:

    1. reference UL60065/60950-1/62368-1 for scoped end-use requirements.
    2. reference UL796 for PCB requirements.
    3. reference UL1977 for AC mains connector requirements.
    4. reference NFPA70 (NEC) for wiring requirements.

No public wish lists :(