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    How much clearance is needed for DALI signal coming into mains LED driver?

    Hello,
    We have a DALI signal which comes into our non isolated offline LED driver. The DALI signal is isolated from the receiver in the LED driver by a TCLT1000 optocoupler..

    TCLT opto datasheet
    https://www.vishay.com/docs/83515/tclt1000.pdf

    The problem is , that its too long to fit on the PCB. We need to use a smaller opto…..

    Do you think we will be able to use the LTV-356 optocoupler which is 3mm shorter….
    http://www.mouser.com/ds/2/239/LTV-3...308-301539.pdf

    Will the clearance still be adequate with the LTV-356 opto? Also, if not, then can we just use a cutout in the PCB to increase clearance like that?

    •   Alt10th August 2017, 20:34

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    Re: How much clearance is needed for DALI signal coming into mains LED driver?

    Hi,

    You have to read through the safety regulations of your region.
    I doubt that the clearence is enough, even with cut.

    Klaus


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    Re: How much clearance is needed for DALI signal coming into mains LED driver?

    LTV356 is used in a unit I repaired here yesterday. You would be surprised how much chaos and damage an open circuit 43 Ohm resistor can cause when it's in the gate of a high power MOSFET bridge driver in a water treatment plant! One of the UKs biggest component suppliers hit the jackpot with the order for parts I had to place. I have greatest respect for them, they delivered all the parts ordered at 10PM Wednesday evening by 1PM Thursday afternoon (15 hours) and I'm in quite a remote area for deliveries.

    It is rated for 3.75KV so I would guess it is probably safe but you would have to be careful to route PCB traces to maximize gaps. The product I repaired was made in Canada but rated for UK use and the tracks to the opto ran directly away from the body on opposite sides.

    Brian.
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    Re: How much clearance is needed for DALI signal coming into mains LED driver?

    Thanks, in UK, Europe and USA, the required clearance between mains and isolated parts of an isolated SMPS is 6mm. So i am guessing that that is what it would be in our situation....but i am not sure.



    •   Alt11th August 2017, 06:05

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    Re: How much clearance is needed for DALI signal coming into mains LED driver?

    Hi,

    Thanks, in UK, Europe and USA, the required clearance between mains and isolated parts of an isolated SMPS is 6mm
    This is by far not true in any case.
    There are many exceptions:
    * applied input voltage
    * generated output voltage
    * dirt/dust condition
    * altitude
    * casing
    * medical and other use
    * and so on...

    Klaus



    •   Alt11th August 2017, 07:51

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    Re: How much clearance is needed for DALI signal coming into mains LED driver?

    According to the data sheet the centers of opposing pads are 6.5mm so if your PCB designer took care not to extend them too far toward each other it should meet the 6mm requirement anyway. A slot would make it even safer, I have some reservations about SMD devices in high voltage isolation because of the risk of contamination or moisture trapping under the body, DIL devices had a bigger gap but a slot would eliminate the risk.

    Brian.
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    It's better to share your questions and answers on Edaboard so we can all benefit from each others experiences.



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    Re: How much clearance is needed for DALI signal coming into mains LED driver?

    I didn't yet hear anything about the DALI interface isolation requirements. It should be specified by the DALI standard.

    In a typical DALI application, control lines and power wires are combined in a single cable. Reinforced interface insulation would be useless without double insulated cabling (separate control and power cables).

    - - - Updated - - -

    I read in a BECKHOFF application note https://download.beckhoff.com/downlo...-0810-0031.pdf

    DALI topologies can be constructed in principle using standard installation cable. A 5-core cable is recommended, since control cores (DALI+, DALI-) and supply cores (phase, neutral and PE) can be fed in one cable. The polarity can be neglected for the DALI control cores even though they are marked DALI+ and DALI-; furthermore, end resistors are not necessary. The insulation of the digital interface conforms to EN 60928 (basic insulation), thus SELV is not ensured!
    Respectively basic insulation clearance would be sufficient for DALI interface.



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    Re: How much clearance is needed for DALI signal coming into mains LED driver?

    Hi,

    Thanks, in UK, Europe and USA, the required clearance between mains and isolated parts of an isolated SMPS is 6mm
    This is by far not true in any case.
    Thankyou very much indeed Klaus, much appreciated, I meant to say “8mm” is the required creepage and 5mm is the required clearance between the isolated part of the DALI circuitry and the mains part of it.
    But this brings up a point of interest….i know these creepage and clearance values because of being around for over a decade in the industry….however, if you asked me which section of which regulation standard document I need to look at in order to prove this, -then I would be lost.
    In fact, I defy anybody to be able to quote here what is the exact sub-section, section and regulation standard document number which tells what is the safety creepage distance along the surface of an offline SMPS PCB for UK/EU/USA domestic product of power level <60W. I guarantee that nobody here will be able to do this.
    Of course, the huge Corporations can pay an internal department of “standards engineers” to keep abreast of all the standards so that their products conform to all of the multitudinous regulations. Also, they are able to, shall we say “garner the attentions” of the standards institutions so that they can be sure of acquiring the knowledge needed for conforming to the standards.
    Small start-up companies simply cannot afford to do this. These small startups not only cannot afford to buy the standards…but also, they wouldn’t actually know which particular multitude of the standards that they must conform to.
    And heaven forbid, should a small company accidentally introduce a product into the market that doesn’t conform fully to the standards, then the huge corporations would get one of their highly payed lawyers to ensure that small startup was sued for this. –Putting the startup well out of business. Destroying the competition.
    Some say that the standards are simply “common sense”. However, I beg to differ. For example, exactly why is 8mm of creepage needed on a totally enclosed offline 60W SMPS PCB for domestic use? Why wouldn’t 4mm be adequate? 4mm is well above the flashover distance of any overvoltage transient that might occur. For such a PCB placed inside a totally enclosed plastic enclosure with no vent holes, 4mm of creepage would be absolutely safe and adequate…….yet as we speak, small startups are being sued into liquidation because they simply cannot afford the activity needed to ensure total standards conformance. They are being sued because they only have for example, 4mm of creepage where the standards, quite non-sensically, say 8mm is needed. 4mm would have been perfectly safe.
    The big corporations win here…the small startups die off, and the jobs go with them.

    Has anybody tried to read the standards?...they are written in such a convoluted way that the vast majority of engineers would struggle to fully & accuratley interpret them...let alone be cognisant of exactly which of the multitudinous number of standards they actually need to conform to for any particular product.
    ..and if small companies shold make a mistake and fall foul of a standard...then the lawyers of the huge corporations are circling overhead, ready to sue them into non-existence.

    - - - Updated - - -

    Of course, the lawyers of all the big European and UK institutions are too scared to sue the Chinese…..China is big and powerful so they daren’t sue the Chinese……hence we in UK have loads of literally lethal Chinese products flooding us……such as this lethal LED lightbulb…
    https://www.youtube.com/watch?v=keaE7QTKTYE

    - - - Updated - - -

    Here's another one...
    https://www.youtube.com/watch?v=HsmTana3HnA

    - - - Updated - - -

    Here's what happens when your country imports fridges that catch fire....
    https://www.youtube.com/watch?v=-h4Eu-Ynysk
    ...all the countries own companies got closed down because they made some much lesser standards infringement, and were sued out of existence.
    Last edited by treez; 12th August 2017 at 15:32.



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    Re: How much clearance is needed for DALI signal coming into mains LED driver?

    Apparently you don't give a damn about DALI standards, or differences between basic and reinforced insulation. Discussion seems useless under this preconditions.


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    Re: How much clearance is needed for DALI signal coming into mains LED driver?

    Thankyou, I have in my possession, the following DALI standard documents.

    IEC 62386-101
    IEC 62386-102
    IEC 62386-209
    DALI manual en Tridonic

    ..None of these documents tells of the creepage distance needing to be 8mm



    •   Alt12th August 2017, 17:05

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    Re: How much clearance is needed for DALI signal coming into mains LED driver?

    As previously mentioned, the DALI application environment seems to suggest basic rather than reinforced insulation (the latter is e.g. required for SELV power supplies). Apart from the question if 6 or 8 mm or whatever clearance is required for SELV power supplies, the isolation requirements for the DALI interface would be clearly relaxed.

    I don't no how the DALI standard discusses isolation requirements. I presume it doesn't prescribe a specific clearance but should refer to isolation classes and other standard documents in this regard.


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    Re: How much clearance is needed for DALI signal coming into mains LED driver?

    Thankyou,
    Page 22, secton 4.9 of this DALI standard…

    "IEC 62386-101-2014 - DALI - Part 101 General Requirements - System components."
    States that..
    4.9 Insulation
    The minimum requirement for system components conformant to this standard shall be basic
    insulation as defined in IEC 61347-1.
    The IEC61347-1 will cost us £429...no doubt when we buy it, we will then be referred to another standard, and another, and another....more money.



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    Re: How much clearance is needed for DALI signal coming into mains LED driver?

    Hi,

    In my posts I assumed that the DALI signals have to be treated like SELV signals.

    But FvM and the regulation talk about basic isolation only.
    This makes things more relaxed in your case.

    In my eyes this means that the DALI signals have to be treated like high pot signals.

    In case you build a USB_to_DALI interface, then there you need the safety isolation...as far as I understand.

    Klaus


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