• DC relay latching voltage

    From Pimpom@21:1/5 to All on Fri Aug 23 16:07:38 2024
    A quick question:
    Is it reasonable to assume that most small general-purpose DC relays
    will not engage at 50% or the rated coil voltage? If not, how about 40%?
    (This is *not* about the release voltage).

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  • From Arie de Muijnck@21:1/5 to Pimpom on Fri Aug 23 13:09:17 2024
    On 2024-08-23 12:37, Pimpom wrote:
    A quick question:
    Is it reasonable to assume that most small general-purpose DC relays will not engage at 50% or the rated coil voltage? If not, how about 40%?
    (This is *not* about the release voltage).

    Not safe. If an external magnetic field is present (e.g. from nearby relays) or a mechanical shock occurs it can activate and hold.
    Been there, had that.

    Arie

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  • From Pimpom@21:1/5 to Arie de Muijnck on Fri Aug 23 17:17:55 2024
    On 23-08-2024 04:39 pm, Arie de Muijnck wrote:
    On 2024-08-23 12:37, Pimpom wrote:
    A quick question:
    Is it reasonable to assume that most small general-purpose DC relays
    will not engage at 50% or the rated coil voltage? If not, how about 40%?
    (This is *not* about the release voltage).

    Not safe. If an external magnetic field is present (e.g. from nearby
    relays) or a mechanical shock occurs it can activate and hold.
    Been there, had that.

    Arie

    Thanks. The immediate application I have in mind is highly unlikely to
    be subjected to such external factors. and it won't have disastrous consequences if it did happen. But it's good to know for future
    consideration.

    The application *is* likely to cause 20-25% of the nominal coil voltage
    to appear across the terminals for some 50 milliseconds though.

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  • From piglet@21:1/5 to Pimpom on Fri Aug 23 11:16:40 2024
    Pimpom <Pimpom@invalid.invalid> wrote:
    A quick question:
    Is it reasonable to assume that most small general-purpose DC relays
    will not engage at 50% or the rated coil voltage? If not, how about 40%? (This is *not* about the release voltage).


    That roughly fits my observations but I don’t think it can be trusted , aging, vibration or temperatures outside room temp could make it pull in earlier. You might need to characterise the relays you have in mind.

    --
    piglet

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  • From Pimpom@21:1/5 to piglet on Fri Aug 23 17:29:05 2024
    On 23-08-2024 04:46 pm, piglet wrote:
    Pimpom <Pimpom@invalid.invalid> wrote:
    A quick question:
    Is it reasonable to assume that most small general-purpose DC relays
    will not engage at 50% or the rated coil voltage? If not, how about 40%?
    (This is *not* about the release voltage).


    That roughly fits my observations but I don’t think it can be trusted , aging, vibration or temperatures outside room temp could make it pull in earlier. You might need to characterise the relays you have in mind.


    Thanks for the reply. Actually, my calculations indicate that less than
    25% of the nominal voltage will appear across the coil for some tens of milliseconds when it should be disengaged. This is caused by a decaying
    supply voltage, not an inductive spike.

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  • From John Robertson@21:1/5 to All on Fri Aug 23 07:36:58 2024
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  • From john larkin @21:1/5 to All on Fri Aug 23 08:09:48 2024
    On Fri, 23 Aug 2024 16:07:38 +0530, Pimpom <Pimpom@invalid.invalid>
    wrote:

    A quick question:
    Is it reasonable to assume that most small general-purpose DC relays
    will not engage at 50% or the rated coil voltage? If not, how about 40%? >(This is *not* about the release voltage).

    Most data sheets have a must-operate voltage and a must-release
    voltage, but typicals are well, typically, very different.

    Test a few! I'd expect that it would be very unlikely for an em relay
    to operate at 40%.

    We test parts and document whatever we learn.



    FTR-B3 relay non-latch 12 volts JL June 2015

    Coil measures 1.0K

    Typical pickup = 7.7 volts spec is 9
    dropout = 2.1 spec is 1.2

    The 5 volt version pulls in at about 2.5 and drops at 1.4.

    One non-energized relay measured 47 and 44 mohms on its NC contacts,
    measured at both 1.3 amps and 100 mA.

    JL Jan 2024

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  • From Pimpom@21:1/5 to John Robertson on Fri Aug 23 23:11:45 2024
    On 23-08-2024 08:06 pm, John Robertson wrote:
    On 2024-08-23 4:59 a.m., Pimpom wrote:
    On 23-08-2024 04:46 pm, piglet wrote:
    Pimpom <Pimpom@invalid.invalid> wrote:
    A quick question:
    Is it reasonable to assume that most small general-purpose DC relays
    will not engage at 50% or the rated coil voltage? If not, how about
    40%?
    (This is *not* about the release voltage).


    That roughly fits my observations but I don’t think it can be trusted , >>> aging, vibration or temperatures outside room temp could make it pull in >>> earlier. You might need to characterise the relays you have in mind.


    Thanks for the reply. Actually, my calculations indicate that less
    than 25% of the nominal voltage will appear across the coil for  some
    tens of milliseconds when it should be disengaged. This is caused by a
    decaying supply voltage, not an inductive spike.

    I'd suggest using a power supply at the maximum decay voltage you expect
    then bang the relay a bit to see if it will engage. I assume you have
    the normal back diode across the coil for clamping the ringing voltage.
    You could use the NO contacts in the relay to keep it energized (Hold)
    if it momentarily closes during testing.

    John :-#)#

    That would give a good indication but wouldn't guarantee the same result
    with another sample.

    I can't give too much detail but this is broadly what the circuit has to do: The relay and associated circuits are to be a part of a multi-section
    project. The relay switches another section on at power-up and then
    quickly disengage that section soon after power is switched off.

    Normal power supply decay will not release the relay quickly enough. So
    I've added a section that turns the 12V relay off when the decaying PS
    drops below 7.5V. Works fine in simulation.

    However, due to interaction with other sections, the gate voltage of the transistor driving the relay rises again briefly to about 2.5V before
    the shutdown process is complete. But by this time, the 12V supply has
    dropped to less than 3V.

    I don't think any normal 12V relay will re-engage at 3V, but I wanted to
    be sure. When I cited 50% and 40% of the rated coil voltage, I was being conservative and night have misled readers. Sorry about that.

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  • From Don Y@21:1/5 to John Robertson on Fri Aug 23 12:43:48 2024
    On 8/23/2024 7:36 AM, John Robertson wrote:
    I assume you have the normal
    back diode across the coil for clamping the ringing voltage.
    If you care about the life of the relay (and how well it "opens"),
    a better approach is to add a zener rated at the coil voltage in
    series with that diode. The diode, by itself, delays opening of
    the contacts and leads to more opportunities for arcing. The
    zener speeds up this transition.

    --- SoupGate-Win32 v1.05
    * Origin: fsxNet Usenet Gateway (21:1/5)
  • From John Robertson@21:1/5 to All on Fri Aug 23 22:05:27 2024
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  • From Don Y@21:1/5 to John Robertson on Fri Aug 23 23:29:48 2024
    On 8/23/2024 10:05 PM, John Robertson wrote:
    On 2024-08-23 12:43 p.m., Don Y wrote:
    On 8/23/2024 7:36 AM, John Robertson wrote:
    I assume you have the normal back diode across the coil for clamping the >>> ringing voltage.
    If you care about the life of the relay (and how well it "opens"),
    a better approach is to add a zener rated at the coil voltage in
    series with that diode.  The diode, by itself, delays opening of
    the contacts and leads to more opportunities for arcing.  The
    zener speeds up this transition.

    Don't you mean that one could use a zener diode in place of the back-EMF diode
    - or parallel with it?

    In series. It speeds up the decay of the magnetic field (and, thus, the opening of the armature) by allowing a higher potential to exist across
    the coil while it is "opening". The ideal condition is with NO catch diode (but that tends to fry solid state switches! :> ) You're making a
    snubber, of sorts.

    We've been using 1N400X (and 3A in some cases)diodes since the 70s for protecting pinball driver transistors - not too worried about the decay time so
    haven't really looked deeper into it before.

    It really only matters if you are really concerned over the actual opening
    time (delay) of the relay and/or how long you want the relay (contacts) to last. (many of my designs have to have service lives of decades or more.)

    <https://www.te.com/commerce/DocumentDelivery/DDEController?Action=srchrtrv&DocNm=13C3264_AppNote&DocType=CS&DocLang=EN>
    will give you a quick overview.
    I have better notes from (relay) application engineers but I'm busy baking, tonight, so can only take quick pokes at my mail, etc.

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  • From Liz Tuddenham@21:1/5 to Pimpom on Sat Aug 24 11:11:19 2024
    Pimpom <Pimpom@invalid.invalid> wrote:
    [...]
    Normal power supply decay will not release the relay quickly enough. So
    I've added a section that turns the 12V relay off when the decaying PS
    drops below 7.5V. Works fine in simulation.

    However, due to interaction with other sections, the gate voltage of the transistor driving the relay rises again briefly to about 2.5V before
    the shutdown process is complete. But by this time, the 12V supply has dropped to less than 3V.

    Add a few diode drops in the supply to the Base of the transistor and a pull-down resistor from Base to Earth. You could even use a 7.5v Zener
    so the transistor switched directly off the PS and no other active
    components were needed.


    --
    ~ Liz Tuddenham ~
    (Remove the ".invalid"s and add ".co.uk" to reply)
    www.poppyrecords.co.uk

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  • From Lasse Langwadt@21:1/5 to Don Y on Sat Aug 24 14:32:06 2024
    On 8/23/24 21:43, Don Y wrote:
    On 8/23/2024 7:36 AM, John Robertson wrote:
    I assume you have the normal back diode across the coil for clamping
    the ringing voltage.
    If you care about the life of the relay (and how well it "opens"),
    a better approach is to add a zener rated at the coil voltage in
    series with that diode.  The diode, by itself, delays opening of
    the contacts and leads to more opportunities for arcing.  The
    zener speeds up this transition.


    or use a fet that is avalanche rated or has build in clamping

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  • From Pimpom@21:1/5 to Liz Tuddenham on Sat Aug 24 20:28:45 2024
    On 24-08-2024 03:41 pm, Liz Tuddenham wrote:
    Pimpom <Pimpom@invalid.invalid> wrote:
    [...]
    Normal power supply decay will not release the relay quickly enough. So
    I've added a section that turns the 12V relay off when the decaying PS
    drops below 7.5V. Works fine in simulation.

    However, due to interaction with other sections, the gate voltage of the
    transistor driving the relay rises again briefly to about 2.5V before
    the shutdown process is complete. But by this time, the 12V supply has
    dropped to less than 3V.

    Add a few diode drops in the supply to the Base of the transistor and a pull-down resistor from Base to Earth. You could even use a 7.5v Zener
    so the transistor switched directly off the PS and no other active
    components were needed.


    Now that sounds like a good idea. Thanks. I'll check it out to see if it
    suits my purpose. For one thing, switching the transistor will not be a
    snap action, but that shouldn't matter as long as the relay contacts
    snap open. The relay is likely to be a 12V 400Ω model so that the slow
    turn off wouldn't unduly stress the transistor.

    No offense, but this is one of those "Why didn't I think of that"
    moments.But then no one else seems to have done so either. :-)

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  • From john larkin @21:1/5 to Liz Tuddenham on Sat Aug 24 09:44:08 2024
    On Sat, 24 Aug 2024 11:11:19 +0100, liz@poppyrecords.invalid.invalid
    (Liz Tuddenham) wrote:

    Pimpom <Pimpom@invalid.invalid> wrote:
    [...]
    Normal power supply decay will not release the relay quickly enough. So
    I've added a section that turns the 12V relay off when the decaying PS
    drops below 7.5V. Works fine in simulation.

    However, due to interaction with other sections, the gate voltage of the
    transistor driving the relay rises again briefly to about 2.5V before
    the shutdown process is complete. But by this time, the 12V supply has
    dropped to less than 3V.

    Add a few diode drops in the supply to the Base of the transistor and a >pull-down resistor from Base to Earth. You could even use a 7.5v Zener
    so the transistor switched directly off the PS and no other active
    components were needed.

    A 2-resistor voltage divider can reduce mosfet gate swing.

    Or an R-C in his case of a transient gate drive spike.

    Or both.

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  • From piglet@21:1/5 to All on Sat Aug 24 22:10:49 2024
    john larkin <jlarkin_highland_tech> wrote:
    On Sat, 24 Aug 2024 11:11:19 +0100, liz@poppyrecords.invalid.invalid
    (Liz Tuddenham) wrote:

    Pimpom <Pimpom@invalid.invalid> wrote:
    [...]
    Normal power supply decay will not release the relay quickly enough. So
    I've added a section that turns the 12V relay off when the decaying PS
    drops below 7.5V. Works fine in simulation.

    However, due to interaction with other sections, the gate voltage of the >>> transistor driving the relay rises again briefly to about 2.5V before
    the shutdown process is complete. But by this time, the 12V supply has
    dropped to less than 3V.

    Add a few diode drops in the supply to the Base of the transistor and a
    pull-down resistor from Base to Earth. You could even use a 7.5v Zener
    so the transistor switched directly off the PS and no other active
    components were needed.

    A 2-resistor voltage divider can reduce mosfet gate swing.

    Or an R-C in his case of a transient gate drive spike.

    Or both.



    If the C is gate to drain (or base to collector) then the miller effect
    slows rate of flux collapse enough to remove need for any additional
    components across the coil.


    --
    piglet

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    * Origin: fsxNet Usenet Gateway (21:1/5)
  • From John Robertson@21:1/5 to All on Sat Aug 24 22:03:07 2024
    T24gMjAyNC0wOC0yMyAxMToyOSBwLm0uLCBEb24gWSB3cm90ZToNCj4gT24gOC8yMy8yMDI0 IDEwOjA1IFBNLCBKb2huIFJvYmVydHNvbiB3cm90ZToNCj4+IE9uIDIwMjQtMDgtMjMgMTI6 NDMgcC5tLiwgRG9uIFkgd3JvdGU6DQo+Pj4gT24gOC8yMy8yMDI0IDc6MzYgQU0sIEpvaG4g Um9iZXJ0c29uIHdyb3RlOg0KPj4+PiBJIGFzc3VtZSB5b3UgaGF2ZSB0aGUgbm9ybWFsIGJh Y2sgZGlvZGUgYWNyb3NzIHRoZSBjb2lsIGZvciBjbGFtcGluZyANCj4+Pj4gdGhlIHJpbmdp bmcgdm9sdGFnZS4NCj4+PiBJZiB5b3UgY2FyZSBhYm91dCB0aGUgbGlmZSBvZiB0aGUgcmVs YXkgKGFuZCBob3cgd2VsbCBpdCAib3BlbnMiKSwNCj4+PiBhIGJldHRlciBhcHByb2FjaCBp cyB0byBhZGQgYSB6ZW5lciByYXRlZCBhdCB0aGUgY29pbCB2b2x0YWdlIGluDQo+Pj4gc2Vy aWVzIHdpdGggdGhhdCBkaW9kZS7CoCBUaGUgZGlvZGUsIGJ5IGl0c2VsZiwgZGVsYXlzIG9w ZW5pbmcgb2YNCj4+PiB0aGUgY29udGFjdHMgYW5kIGxlYWRzIHRvIG1vcmUgb3Bwb3J0dW5p dGllcyBmb3IgYXJjaW5nLsKgIFRoZQ0KPj4+IHplbmVyIHNwZWVkcyB1cCB0aGlzIHRyYW5z aXRpb24uDQo+Pg0KPj4gRG9uJ3QgeW91IG1lYW4gdGhhdCBvbmUgY291bGQgdXNlIGEgemVu ZXIgZGlvZGUgaW4gcGxhY2Ugb2YgdGhlIGJhY2stIA0KPj4gRU1GIGRpb2RlIC0gb3IgcGFy YWxsZWwgd2l0aCBpdD8NCj4gDQo+IEluIHNlcmllcy7CoCBJdCBzcGVlZHMgdXAgdGhlIGRl Y2F5IG9mIHRoZSBtYWduZXRpYyBmaWVsZCAoYW5kLCB0aHVzLCB0aGUNCj4gb3BlbmluZyBv ZiB0aGUgYXJtYXR1cmUpIGJ5IGFsbG93aW5nIGEgaGlnaGVyIHBvdGVudGlhbCB0byBleGlz dCBhY3Jvc3MNCj4gdGhlIGNvaWwgd2hpbGUgaXQgaXMgIm9wZW5pbmciLsKgIFRoZSBpZGVh bCBjb25kaXRpb24gaXMgd2l0aCBOTyBjYXRjaCBkaW9kZQ0KPiAoYnV0IHRoYXQgdGVuZHMg dG8gZnJ5IHNvbGlkIHN0YXRlIHN3aXRjaGVzIcKgIDo+ICnCoCBZb3UncmUgbWFraW5nIGEN Cj4gc251YmJlciwgb2Ygc29ydHMuDQo+IA0KPj4gV2UndmUgYmVlbiB1c2luZyAxTjQwMFgg KGFuZCAzQSBpbiBzb21lIGNhc2VzKWRpb2RlcyBzaW5jZSB0aGUgNzBzIGZvciANCj4+IHBy b3RlY3RpbmcgcGluYmFsbCBkcml2ZXIgdHJhbnNpc3RvcnMgLSBub3QgdG9vIHdvcnJpZWQg YWJvdXQgdGhlIA0KPj4gZGVjYXkgdGltZSBzbyBoYXZlbid0IHJlYWxseSBsb29rZWQgZGVl cGVyIGludG8gaXQgYmVmb3JlLg0KPiANCj4gSXQgcmVhbGx5IG9ubHkgbWF0dGVycyBpZiB5 b3UgYXJlIHJlYWxseSBjb25jZXJuZWQgb3ZlciB0aGUgYWN0dWFsIG9wZW5pbmcNCj4gdGlt ZSAoZGVsYXkpIG9mIHRoZSByZWxheSBhbmQvb3IgaG93IGxvbmcgeW91IHdhbnQgdGhlIHJl bGF5IChjb250YWN0cykgdG8NCj4gbGFzdC7CoCAobWFueSBvZiBteSBkZXNpZ25zIGhhdmUg dG8gaGF2ZSBzZXJ2aWNlIGxpdmVzIG9mIGRlY2FkZXMgb3IgbW9yZS4pDQo+IA0KPiA8aHR0 cHM6Ly93d3cudGUuY29tL2NvbW1lcmNlL0RvY3VtZW50RGVsaXZlcnkvRERFQ29udHJvbGxl cj8gDQo+IEFjdGlvbj1zcmNocnRydiZEb2NObT0xM0MzMjY0X0FwcE5vdGUmRG9jVHlwZT1D UyZEb2NMYW5nPUVOPiB3aWxsIGdpdmUgDQo+IHlvdSBhIHF1aWNrIG92ZXJ2aWV3Lg0KPiBJ IGhhdmUgYmV0dGVyIG5vdGVzIGZyb20gKHJlbGF5KSBhcHBsaWNhdGlvbiBlbmdpbmVlcnMg YnV0IEknbSBidXN5IGJha2luZywNCj4gdG9uaWdodCwgc28gY2FuIG9ubHkgdGFrZSBxdWlj ayBwb2tlcyBhdCBteSBtYWlsLCBldGMuDQo+IA0KDQpHb29kIHJlYWRpbmchIEl0IGFwcGVh cnMgY291bnRlcmludHVpdGl2ZSwgYnV0IGlmIEkgd2FycCAoISkgbXkgaGVhZCANCmFyb3Vu ZCBpdCBJIHNob3VsZCBiZSBhYmxlIHRvIHNvcnQgaXQgb3V0Lg0KDQpUaGFua3MsIHRoYXQg aXMgdmVyeSBoZWxwZnVsLg0KDQpKb2huIDotIykjDQoNCi0tIA0KKFBsZWFzZSBwb3N0IGZv bGxvd3VwcyBvciB0ZWNoIGlucXVpcmllcyB0byB0aGUgVVNFTkVUIG5ld3Nncm91cCkNCiAg ICAgICAgICAgICAgICAgICAgICBKb2huJ3MgSnVrZXMgTHRkLg0KICAgICAgICAjNyAtIDM5 NzkgTWFyaW5lIFdheSwgQnVybmFieSwgQkMsIENhbmFkYSBWNUogNUUzDQogICAgICAgICAg KDYwNCk4NzItNTc1NyAoUGluYmFsbHMsIEp1a2VzLCBWaWRlbyBHYW1lcykNCiAgICAgICAg ICAgICAgICAgICAgICB3d3cuZmxpcHBlcnMuY29tDQogICAgICAgICJPbGQgcGluYmFsbGVy cyBuZXZlciBkaWUsIHRoZXkganVzdCBmbGlwIG91dC4iDQo=

    --- SoupGate-Win32 v1.05
    * Origin: fsxNet Usenet Gateway (21:1/5)
  • From Don Y@21:1/5 to John Robertson on Sat Aug 24 23:21:03 2024
    On 8/24/2024 10:03 PM, John Robertson wrote:
    Good reading! It appears counterintuitive, but if I warp (!) my head around it
    I should be able to sort it out.

    Think about the extremes:

    - with NO diode or snuber, there is nothing to keep the magnetic
    field intact when the switch opens. So, the spring force is the
    sole actor in play, pulling the contacts open
    - with a diode, some current continues to "recirculate" in the coil
    thus keeping the magnetic field active -- so it is trying to hold
    the relay closed while the spring is trying to open it. *When*
    the recirculating current falls, the field collapses and the relay
    can open.

    The zener lets the circuit look more like the "no diode" case.

    --- SoupGate-Win32 v1.05
    * Origin: fsxNet Usenet Gateway (21:1/5)
  • From Don Y@21:1/5 to Don Y on Sat Aug 24 23:22:01 2024
    On 8/24/2024 11:21 PM, Don Y wrote:
    On 8/24/2024 10:03 PM, John Robertson wrote:
    Good reading! It appears counterintuitive, but if I warp (!) my head around >> it I should be able to sort it out.

    Think about the extremes:

    - with NO diode  or snuber, there is nothing to keep the magnetic
      field intact when the switch opens.  So, the spring force is the
      sole actor in play, pulling the contacts open
    - with a diode, some current continues to "recirculate" in the coil
      thus keeping the magnetic field active -- so it is trying to hold
      the relay closed while the spring is trying to open it.  *When*
      the recirculating current falls, the field collapses and the relay
      can open.

    The zener lets the circuit look more like the "no diode" case.

    i.e., imagine that case as having an infinite voltage zener (open
    circuit) in series with the diode -- NO diode!

    --- SoupGate-Win32 v1.05
    * Origin: fsxNet Usenet Gateway (21:1/5)
  • From piglet@21:1/5 to John Robertson on Sun Aug 25 07:40:49 2024
    John Robertson <jrr@flippers.com> wrote:
    On 2024-08-23 11:29 p.m., Don Y wrote:
    On 8/23/2024 10:05 PM, John Robertson wrote:
    On 2024-08-23 12:43 p.m., Don Y wrote:
    On 8/23/2024 7:36 AM, John Robertson wrote:
    I assume you have the normal back diode across the coil for clamping >>>>> the ringing voltage.
    If you care about the life of the relay (and how well it "opens"),
    a better approach is to add a zener rated at the coil voltage in
    series with that diode.  The diode, by itself, delays opening of
    the contacts and leads to more opportunities for arcing.  The
    zener speeds up this transition.

    Don't you mean that one could use a zener diode in place of the back-
    EMF diode - or parallel with it?

    In series.  It speeds up the decay of the magnetic field (and, thus, the
    opening of the armature) by allowing a higher potential to exist across
    the coil while it is "opening".  The ideal condition is with NO catch diode >> (but that tends to fry solid state switches!  :> )  You're making a
    snubber, of sorts.

    We've been using 1N400X (and 3A in some cases)diodes since the 70s for
    protecting pinball driver transistors - not too worried about the
    decay time so haven't really looked deeper into it before.

    It really only matters if you are really concerned over the actual opening >> time (delay) of the relay and/or how long you want the relay (contacts) to >> last.  (many of my designs have to have service lives of decades or more.) >>
    <https://www.te.com/commerce/DocumentDelivery/DDEController?
    Action=srchrtrv&DocNm=13C3264_AppNote&DocType=CS&DocLang=EN> will give
    you a quick overview.
    I have better notes from (relay) application engineers but I'm busy baking, >> tonight, so can only take quick pokes at my mail, etc.


    Good reading! It appears counterintuitive, but if I warp (!) my head
    around it I should be able to sort it out.

    Thanks, that is very helpful.

    John :-#)#


    An even simpler coil catcher is a resistor. Many times the extra power consumption is not an issue and resistors are even cheaper and more
    reliable than zener + diode.

    --
    piglet

    --- SoupGate-Win32 v1.05
    * Origin: fsxNet Usenet Gateway (21:1/5)
  • From Don Y@21:1/5 to piglet on Sun Aug 25 02:03:55 2024
    On 8/25/2024 12:40 AM, piglet wrote:
    An even simpler coil catcher is a resistor. Many times the extra power consumption is not an issue and resistors are even cheaper and more
    reliable than zener + diode.

    A lot depends on the relay's (coil) duty cycle.

    To limit the peak transient (to approximately the supply voltage) when
    the coil opens, R needs to be on the order of the coil resistance.
    If the this halves the load resistance that must be driven when the
    coil is active.

    Of course, if the duty cycle is low and 2X the driving current is
    within the capabilities of the device you had already planned on
    using for the switch, then this has minimal impact.

    OTOH, if the coil current is higher, already taxing the capabilities
    of the switch or the duty cycle has the coil energized more often
    than not, then this can be a significant factor.

    And, as R approaches the coil's resistance, the opening time/delay of
    the relay *increases*. I.e., you want R to approach infinity to get the
    best opening transition but this also gives the highest switching
    transient voltage -- often many times the supply voltage!

    --- SoupGate-Win32 v1.05
    * Origin: fsxNet Usenet Gateway (21:1/5)
  • From Don Y@21:1/5 to Don Y on Sun Aug 25 02:07:27 2024
    On 8/25/2024 2:03 AM, Don Y wrote:
    On 8/25/2024 12:40 AM, piglet wrote:
    An even simpler coil catcher is a resistor. Many times the extra power
    consumption is not an issue and resistors are even cheaper and more
    reliable than zener + diode.

    A lot depends on the relay's (coil) duty cycle.

    To limit the peak transient (to approximately the supply voltage) when
    the coil opens, R needs to be on the order of the coil resistance.
    If the this halves the load resistance that must be driven when the
    coil is active.

    Of course, if the duty cycle is low and 2X the driving current is
    within the capabilities of the device you had already planned on
    using for the switch, then this has minimal impact.

    OTOH, if the coil current is higher, already taxing the capabilities
    of the switch or the duty cycle has the coil energized more often
    than not, then this can be a significant factor.

    And, as R approaches the coil's resistance, the opening time/delay of
    the relay *increases*.  I.e., you want R to approach infinity to get the best opening transition but this also gives the highest switching
    transient voltage -- often many times the supply voltage!

    <https://www.te.com/commerce/DocumentDelivery/DDEController?Action=srchrtrv&DocNm=13C3311_AppNote&DocType=CS&DocLang=EN>

    --- SoupGate-Win32 v1.05
    * Origin: fsxNet Usenet Gateway (21:1/5)
  • From Liz Tuddenham@21:1/5 to Pimpom on Sun Aug 25 09:48:14 2024
    Pimpom <Pimpom@invalid.invalid> wrote:

    ...The relay is likely to be a 12V 400Ω model so that the slow
    turn off wouldn't unduly stress the transistor.

    At half-voltage and half-current, the most stressful condition, the
    dissipation of the transistor would be 90 mW.


    --
    ~ Liz Tuddenham ~
    (Remove the ".invalid"s and add ".co.uk" to reply)
    www.poppyrecords.co.uk

    --- SoupGate-Win32 v1.05
    * Origin: fsxNet Usenet Gateway (21:1/5)
  • From john larkin @21:1/5 to All on Sun Aug 25 08:09:21 2024
    On Fri, 23 Aug 2024 22:05:27 -0700, John Robertson <jrr@flippers.com>
    wrote:

    On 2024-08-23 12:43 p.m., Don Y wrote:
    On 8/23/2024 7:36 AM, John Robertson wrote:
    I assume you have the normal back diode across the coil for clamping
    the ringing voltage.
    If you care about the life of the relay (and how well it "opens"),
    a better approach is to add a zener rated at the coil voltage in
    series with that diode.  The diode, by itself, delays opening of
    the contacts and leads to more opportunities for arcing.  The
    zener speeds up this transition.


    Hi Don,

    Don't you mean that one could use a zener diode in place of the back-EMF >diode - or parallel with it?

    We've been using 1N400X (and 3A in some cases)diodes since the 70s for >protecting pinball driver transistors - not too worried about the decay
    time so haven't really looked deeper into it before.

    Thanks,

    John :-#)#

    Is there a community of pinball machine people?

    At my new office, the next-door neighbor's husband has pinball
    machines, and I invited him over if he needs help with electronics.

    The downside is that he plays drums too. I don't understand why anyone
    would do that. Lotta noise, both cases.

    --- SoupGate-Win32 v1.05
    * Origin: fsxNet Usenet Gateway (21:1/5)
  • From john larkin @21:1/5 to blockedofcourse@foo.invalid on Sun Aug 25 08:19:04 2024
    On Fri, 23 Aug 2024 23:29:48 -0700, Don Y
    <blockedofcourse@foo.invalid> wrote:

    On 8/23/2024 10:05 PM, John Robertson wrote:
    On 2024-08-23 12:43 p.m., Don Y wrote:
    On 8/23/2024 7:36 AM, John Robertson wrote:
    I assume you have the normal back diode across the coil for clamping the >>>> ringing voltage.
    If you care about the life of the relay (and how well it "opens"),
    a better approach is to add a zener rated at the coil voltage in
    series with that diode.  The diode, by itself, delays opening of
    the contacts and leads to more opportunities for arcing.  The
    zener speeds up this transition.

    Don't you mean that one could use a zener diode in place of the back-EMF diode
    - or parallel with it?

    In series. It speeds up the decay of the magnetic field (and, thus, the >opening of the armature) by allowing a higher potential to exist across
    the coil while it is "opening". The ideal condition is with NO catch diode >(but that tends to fry solid state switches! :> ) You're making a
    snubber, of sorts.

    Essentially all modern discrete mosfets avalanche safely at ballpark
    120% of rated abs max drain voltage. Try it.

    The damage limit becomes average power dissipated, which would be low
    in most cases of driving a small relay.

    I recently designed a board brickwalled with about 130 power relays.
    Each has a sot-23 logic-level mosfet on the bottom of the board,
    snuggled between the thru-hole relay pins. No catch diodes.

    https://www.dropbox.com/scl/fi/fiy73ou127rd5hi23jkw9/P948_A6.jpg?rlkey=symijy4b0veq1s5ho982r0sa0&raw=1


    We've been using 1N400X (and 3A in some cases)diodes since the 70s for
    protecting pinball driver transistors - not too worried about the decay time so
    haven't really looked deeper into it before.

    It really only matters if you are really concerned over the actual opening >time (delay) of the relay and/or how long you want the relay (contacts) to >last. (many of my designs have to have service lives of decades or more.)

    <https://www.te.com/commerce/DocumentDelivery/DDEController?Action=srchrtrv&DocNm=13C3264_AppNote&DocType=CS&DocLang=EN>
    will give you a quick overview.
    I have better notes from (relay) application engineers but I'm busy baking, >tonight, so can only take quick pokes at my mail, etc.

    Baking what? I'm getting whining that we are out of both biscuits and
    bread pudding, so I won't get much electronics done today.

    --- SoupGate-Win32 v1.05
    * Origin: fsxNet Usenet Gateway (21:1/5)
  • From John Robertson@21:1/5 to All on Sun Aug 25 08:30:25 2024
    T24gMjAyNC0wOC0yNSAyOjA3IGEubS4sIERvbiBZIHdyb3RlOg0KPiBPbiA4LzI1LzIwMjQg MjowMyBBTSwgRG9uIFkgd3JvdGU6DQo+PiBPbiA4LzI1LzIwMjQgMTI6NDAgQU0sIHBpZ2xl dCB3cm90ZToNCj4+PiBBbiBldmVuIHNpbXBsZXIgY29pbCBjYXRjaGVyIGlzIGEgcmVzaXN0 b3IuIE1hbnkgdGltZXMgdGhlIGV4dHJhIHBvd2VyDQo+Pj4gY29uc3VtcHRpb24gaXMgbm90 IGFuIGlzc3VlIGFuZCByZXNpc3RvcnMgYXJlIGV2ZW4gY2hlYXBlciBhbmQgbW9yZQ0KPj4+ IHJlbGlhYmxlIHRoYW4gemVuZXIgKyBkaW9kZS4NCj4+DQo+PiBBIGxvdCBkZXBlbmRzIG9u IHRoZSByZWxheSdzIChjb2lsKSBkdXR5IGN5Y2xlLg0KPj4NCj4+IFRvIGxpbWl0IHRoZSBw ZWFrIHRyYW5zaWVudCAodG8gYXBwcm94aW1hdGVseSB0aGUgc3VwcGx5IHZvbHRhZ2UpIHdo ZW4NCj4+IHRoZSBjb2lsIG9wZW5zLCBSIG5lZWRzIHRvIGJlIG9uIHRoZSBvcmRlciBvZiB0 aGUgY29pbCByZXNpc3RhbmNlLg0KPj4gSWYgdGhlIHRoaXMgaGFsdmVzIHRoZSBsb2FkIHJl c2lzdGFuY2UgdGhhdCBtdXN0IGJlIGRyaXZlbiB3aGVuIHRoZQ0KPj4gY29pbCBpcyBhY3Rp dmUuDQo+Pg0KPj4gT2YgY291cnNlLCBpZiB0aGUgZHV0eSBjeWNsZSBpcyBsb3cgYW5kIDJY IHRoZSBkcml2aW5nIGN1cnJlbnQgaXMNCj4+IHdpdGhpbiB0aGUgY2FwYWJpbGl0aWVzIG9m IHRoZSBkZXZpY2UgeW91IGhhZCBhbHJlYWR5IHBsYW5uZWQgb24NCj4+IHVzaW5nIGZvciB0 aGUgc3dpdGNoLCB0aGVuIHRoaXMgaGFzIG1pbmltYWwgaW1wYWN0Lg0KPj4NCj4+IE9UT0gs IGlmIHRoZSBjb2lsIGN1cnJlbnQgaXMgaGlnaGVyLCBhbHJlYWR5IHRheGluZyB0aGUgY2Fw YWJpbGl0aWVzDQo+PiBvZiB0aGUgc3dpdGNoIG9yIHRoZSBkdXR5IGN5Y2xlIGhhcyB0aGUg Y29pbCBlbmVyZ2l6ZWQgbW9yZSBvZnRlbg0KPj4gdGhhbiBub3QsIHRoZW4gdGhpcyBjYW4g YmUgYSBzaWduaWZpY2FudCBmYWN0b3IuDQo+Pg0KPj4gQW5kLCBhcyBSIGFwcHJvYWNoZXMg dGhlIGNvaWwncyByZXNpc3RhbmNlLCB0aGUgb3BlbmluZyB0aW1lL2RlbGF5IG9mDQo+PiB0 aGUgcmVsYXkgKmluY3JlYXNlcyouwqAgSS5lLiwgeW91IHdhbnQgUiB0byBhcHByb2FjaCBp bmZpbml0eSB0byBnZXQgdGhlDQo+PiBiZXN0IG9wZW5pbmcgdHJhbnNpdGlvbiBidXQgdGhp cyBhbHNvIGdpdmVzIHRoZSBoaWdoZXN0IHN3aXRjaGluZw0KPj4gdHJhbnNpZW50IHZvbHRh Z2UgLS0gb2Z0ZW4gbWFueSB0aW1lcyB0aGUgc3VwcGx5IHZvbHRhZ2UhDQo+IA0KPiA8aHR0 cHM6Ly93d3cudGUuY29tL2NvbW1lcmNlL0RvY3VtZW50RGVsaXZlcnkvRERFQ29udHJvbGxl cj8gDQo+IEFjdGlvbj1zcmNocnRydiZEb2NObT0xM0MzMzExX0FwcE5vdGUmRG9jVHlwZT1D UyZEb2NMYW5nPUVOPg0KPiANCj4gDQoNCklzIHRoZXJlIGFuIGluZGV4IHRvIHRoZXNlIHVz ZWZ1bCBBcHBsaWNhdGlvbiBOb3Rlcz8NCkkgb25seSBmb3VuZCB0aGlzIHdoZW4gSSBzZWFy Y2hlZCBmb3IgImFwcGxpY2F0aW9uIG5vdGVzIjoNCg0KaHR0cHM6Ly93d3cudGUuY29tL2Vu L3Byb2R1Y3RzL3JlbGF5cy1hbmQtY29udGFjdG9ycy9yZWxheXMvaW50ZXJzZWN0aW9uL2Fw cGxpY2F0aW9uLW5vdGVzLmh0bWwNCg0KQW5kIGRpZCB5b3UgaGFwcGVuIHRvIHdyaXRlIHNv bWUgb2YgdGhlbSBieSBjaGFuY2U/DQoNCkpvaG4gOi0jKSMNCg0KLS0gDQooUGxlYXNlIHBv c3QgZm9sbG93dXBzIG9yIHRlY2ggaW5xdWlyaWVzIHRvIHRoZSBVU0VORVQgbmV3c2dyb3Vw KQ0KICAgICAgICAgICAgICAgICAgICAgIEpvaG4ncyBKdWtlcyBMdGQuDQogICAgICAgICM3 IC0gMzk3OSBNYXJpbmUgV2F5LCBCdXJuYWJ5LCBCQywgQ2FuYWRhIFY1SiA1RTMNCiAgICAg ICAgICAoNjA0KTg3Mi01NzU3IChQaW5iYWxscywgSnVrZXMsIFZpZGVvIEdhbWVzKQ0KICAg ICAgICAgICAgICAgICAgICAgIHd3dy5mbGlwcGVycy5jb20NCiAgICAgICAgIk9sZCBwaW5i YWxsZXJzIG5ldmVyIGRpZSwgdGhleSBqdXN0IGZsaXAgb3V0LiINCg==

    --- SoupGate-Win32 v1.05
    * Origin: fsxNet Usenet Gateway (21:1/5)
  • From John Robertson@21:1/5 to All on Sun Aug 25 08:37:31 2024
    T24gMjAyNC0wOC0yNSA4OjA5IGEubS4sIGpvaG4gbGFya2luIHdyb3RlOg0KPiBPbiBGcmks IDIzIEF1ZyAyMDI0IDIyOjA1OjI3IC0wNzAwLCBKb2huIFJvYmVydHNvbiA8anJyQGZsaXBw ZXJzLmNvbT4NCj4gd3JvdGU6DQo+IA0KPj4gT24gMjAyNC0wOC0yMyAxMjo0MyBwLm0uLCBE b24gWSB3cm90ZToNCj4+PiBPbiA4LzIzLzIwMjQgNzozNiBBTSwgSm9obiBSb2JlcnRzb24g d3JvdGU6DQo+Pj4+IEkgYXNzdW1lIHlvdSBoYXZlIHRoZSBub3JtYWwgYmFjayBkaW9kZSBh Y3Jvc3MgdGhlIGNvaWwgZm9yIGNsYW1waW5nDQo+Pj4+IHRoZSByaW5naW5nIHZvbHRhZ2Uu DQo+Pj4gSWYgeW91IGNhcmUgYWJvdXQgdGhlIGxpZmUgb2YgdGhlIHJlbGF5IChhbmQgaG93 IHdlbGwgaXQgIm9wZW5zIiksDQo+Pj4gYSBiZXR0ZXIgYXBwcm9hY2ggaXMgdG8gYWRkIGEg emVuZXIgcmF0ZWQgYXQgdGhlIGNvaWwgdm9sdGFnZSBpbg0KPj4+IHNlcmllcyB3aXRoIHRo YXQgZGlvZGUuwqAgVGhlIGRpb2RlLCBieSBpdHNlbGYsIGRlbGF5cyBvcGVuaW5nIG9mDQo+ Pj4gdGhlIGNvbnRhY3RzIGFuZCBsZWFkcyB0byBtb3JlIG9wcG9ydHVuaXRpZXMgZm9yIGFy Y2luZy7CoCBUaGUNCj4+PiB6ZW5lciBzcGVlZHMgdXAgdGhpcyB0cmFuc2l0aW9uLg0KPj4+ DQo+Pg0KPj4gSGkgRG9uLA0KPj4NCj4+IERvbid0IHlvdSBtZWFuIHRoYXQgb25lIGNvdWxk IHVzZSBhIHplbmVyIGRpb2RlIGluIHBsYWNlIG9mIHRoZSBiYWNrLUVNRg0KPj4gZGlvZGUg LSBvciBwYXJhbGxlbCB3aXRoIGl0Pw0KPj4NCj4+IFdlJ3ZlIGJlZW4gdXNpbmcgMU40MDBY IChhbmQgM0EgaW4gc29tZSBjYXNlcylkaW9kZXMgc2luY2UgdGhlIDcwcyBmb3INCj4+IHBy b3RlY3RpbmcgcGluYmFsbCBkcml2ZXIgdHJhbnNpc3RvcnMgLSBub3QgdG9vIHdvcnJpZWQg YWJvdXQgdGhlIGRlY2F5DQo+PiB0aW1lIHNvIGhhdmVuJ3QgcmVhbGx5IGxvb2tlZCBkZWVw ZXIgaW50byBpdCBiZWZvcmUuDQo+Pg0KPj4gVGhhbmtzLA0KPj4NCj4+IEpvaG4gOi0jKSMN Cj4gDQo+IElzIHRoZXJlIGEgY29tbXVuaXR5IG9mIHBpbmJhbGwgbWFjaGluZSBwZW9wbGU/ DQoNCnJlYy5nYW1lcy5waW5iYWxsIC0gYnV0IGl0IGhhcyBwcmV0dHkgbXVjaCBkaWVkLiBX aGVuIGdvb2dsZSBzdG9wcGVkIA0KcmVndWxhdGluZyBwb3N0cyBhIGZldyB5ZWFycyBiYWNr IGl0IHdhcyBvdmVyd2hlbG1lZCBieSBjcmFwIGFuZCB3YXMgDQphYmFuZG9uZWQgYnkgdGhl IHJlbWFpbmluZyByZWd1bGFycyBleGNlcHQgZm9yIGEgZmV3IGRpZWhhcmRzLg0KDQpOb3dh ZGF5cyBpdCBpcyB0aGUgb25saW5lIGZvcnVtcyB0aGF0IHNvYWsgdGhlIG5hdHRlcmVycy4N Cg0KPiANCj4gQXQgbXkgbmV3IG9mZmljZSwgdGhlIG5leHQtZG9vciBuZWlnaGJvcidzIGh1 c2JhbmQgaGFzIHBpbmJhbGwNCj4gbWFjaGluZXMsIGFuZCBJIGludml0ZWQgaGltIG92ZXIg aWYgaGUgbmVlZHMgaGVscCB3aXRoIGVsZWN0cm9uaWNzLg0KDQpJZiB5b3UgbmVlZCBtYW51 YWxzL3NjaGVtYXRpY3MgSSBoYXZlIGh1bmRyZWRzIHNjYW5uZWQgYW5kIGEgY291cGxlIG9m IA0KdGhvdXNhbmQgd2FpdGluZyBzY2FubmluZy4gQW5kIHRoZXJlIGlzIGEgZ3JlYXQgcmVz b3VyY2Ugc2l0ZSAtIA0KaHR0cHM6L2lwZGIub3JnIGZvciBwaW5iYWxsIHBob3Rvcywgc2Vy dmljZSBpbmZvLCBhbmQgcGhvdG9zDQoNCj4gDQo+IFRoZSBkb3duc2lkZSBpcyB0aGF0IGhl IHBsYXlzIGRydW1zIHRvby4gSSBkb24ndCB1bmRlcnN0YW5kIHdoeSBhbnlvbmUNCj4gd291 bGQgZG8gdGhhdC4gTG90dGEgbm9pc2UsIGJvdGggY2FzZXMuDQoNCkhvcGUgaGUgd2VhcnMg ZWFycGx1Z3MhIEFuZCBzb2xpZCBzdGF0ZSBwaW5iYWxsIGdhbWVzIGhhdmUgdm9sdW1lIGNv bnRyb2xzLg0KDQpKb2huIDotIykjDQoNCg0KLS0gDQooUGxlYXNlIHBvc3QgZm9sbG93dXBz IG9yIHRlY2ggaW5xdWlyaWVzIHRvIHRoZSBVU0VORVQgbmV3c2dyb3VwKQ0KICAgICAgICAg ICAgICAgICAgICAgIEpvaG4ncyBKdWtlcyBMdGQuDQogICAgICAgICM3IC0gMzk3OSBNYXJp bmUgV2F5LCBCdXJuYWJ5LCBCQywgQ2FuYWRhIFY1SiA1RTMNCiAgICAgICAgICAoNjA0KTg3 Mi01NzU3IChQaW5iYWxscywgSnVrZXMsIFZpZGVvIEdhbWVzKQ0KICAgICAgICAgICAgICAg ICAgICAgIHd3dy5mbGlwcGVycy5jb20NCiAgICAgICAgIk9sZCBwaW5iYWxsZXJzIG5ldmVy IGRpZSwgdGhleSBqdXN0IGZsaXAgb3V0LiINCg==

    --- SoupGate-Win32 v1.05
    * Origin: fsxNet Usenet Gateway (21:1/5)
  • From Don Y@21:1/5 to John Robertson on Sun Aug 25 11:52:11 2024
    On 8/25/2024 8:30 AM, John Robertson wrote:
    <https://www.te.com/commerce/DocumentDelivery/DDEController?
    Action=srchrtrv&DocNm=13C3311_AppNote&DocType=CS&DocLang=EN>

    Is there an index to these useful Application Notes?

    No idea. I'm just leaning on lessons learned decades ago and searching for documents that would likely confirm those issues.

    I only found this when I searched for "application notes":

    https://www.te.com/en/products/relays-and-contactors/relays/intersection/application-notes.html

    And did you happen to write some of them by chance?

    No. I don't publish anything "for general consumption"; only specific
    issues for specific audiences. Not enough time in the day to do the
    things I *want* to do while considering "optional" efforts.

    Don't kill yourself worrying about this sort of thing for a pin table.
    You're likely not as concerned with durability. The board's already
    (likely) designed. And, it's already got an established (tolerable?)
    level of EMI.

    Rather, it should be seen as a counter to the "old saw" that you *just* use
    a recirculating diode without considering the consequences. Just like considering how to *drive* the coil based on how it will be used.

    [Remember the "pull in" coils and "end of stroke" switches on flipper solenoids?]

    --- SoupGate-Win32 v1.05
    * Origin: fsxNet Usenet Gateway (21:1/5)
  • From john larkin @21:1/5 to blockedofcourse@foo.invalid on Sun Aug 25 20:03:16 2024
    On Sat, 24 Aug 2024 23:22:01 -0700, Don Y
    <blockedofcourse@foo.invalid> wrote:

    On 8/24/2024 11:21 PM, Don Y wrote:
    On 8/24/2024 10:03 PM, John Robertson wrote:
    Good reading! It appears counterintuitive, but if I warp (!) my head around >>> it I should be able to sort it out.

    Think about the extremes:

    - with NO diode  or snuber, there is nothing to keep the magnetic
      field intact when the switch opens.  So, the spring force is the
      sole actor in play, pulling the contacts open
    - with a diode, some current continues to "recirculate" in the coil
      thus keeping the magnetic field active -- so it is trying to hold
      the relay closed while the spring is trying to open it.  *When*
      the recirculating current falls, the field collapses and the relay
      can open.

    The zener lets the circuit look more like the "no diode" case.

    i.e., imagine that case as having an infinite voltage zener (open
    circuit) in series with the diode -- NO diode!


    The losses in a real relay will limit the peak voltage, which will
    actually be a damped ringing thing.

    L changes substantially as the parts move around, decreasing as the
    magnetic loop goes from closed/seated to open/air gap. Envision some
    weird waveforms.

    That's the reason that AC-coil relays are prefered over DC relays in
    industrial control systems.

    --- SoupGate-Win32 v1.05
    * Origin: fsxNet Usenet Gateway (21:1/5)
  • From John Robertson@21:1/5 to All on Sun Aug 25 22:01:50 2024
    T24gMjAyNC0wOC0yNSAxMTo1MiBhLm0uLCBEb24gWSB3cm90ZToNCj4gT24gOC8yNS8yMDI0 IDg6MzAgQU0sIEpvaG4gUm9iZXJ0c29uIHdyb3RlOg0KPj4+IDxodHRwczovL3d3dy50ZS5j b20vY29tbWVyY2UvRG9jdW1lbnREZWxpdmVyeS9EREVDb250cm9sbGVyPyANCj4+PiBBY3Rp b249c3JjaHJ0cnYmRG9jTm09MTNDMzMxMV9BcHBOb3RlJkRvY1R5cGU9Q1MmRG9jTGFuZz1F Tj4NCj4+DQo+PiBJcyB0aGVyZSBhbiBpbmRleCB0byB0aGVzZSB1c2VmdWwgQXBwbGljYXRp b24gTm90ZXM/DQo+IA0KPiBObyBpZGVhLsKgIEknbSBqdXN0IGxlYW5pbmcgb24gbGVzc29u cyBsZWFybmVkIGRlY2FkZXMgYWdvIGFuZCBzZWFyY2hpbmcgZm9yDQo+IGRvY3VtZW50cyB0 aGF0IHdvdWxkIGxpa2VseSBjb25maXJtIHRob3NlIGlzc3Vlcy4NCj4gDQo+PiBJIG9ubHkg Zm91bmQgdGhpcyB3aGVuIEkgc2VhcmNoZWQgZm9yICJhcHBsaWNhdGlvbiBub3RlcyI6DQo+ Pg0KPj4gaHR0cHM6Ly93d3cudGUuY29tL2VuL3Byb2R1Y3RzL3JlbGF5cy1hbmQtY29udGFj dG9ycy9yZWxheXMvIA0KPj4gaW50ZXJzZWN0aW9uL2FwcGxpY2F0aW9uLW5vdGVzLmh0bWwN Cj4+DQo+PiBBbmQgZGlkIHlvdSBoYXBwZW4gdG8gd3JpdGUgc29tZSBvZiB0aGVtIGJ5IGNo YW5jZT8NCj4gDQo+IE5vLsKgIEkgZG9uJ3QgcHVibGlzaCBhbnl0aGluZyAiZm9yIGdlbmVy YWwgY29uc3VtcHRpb24iOyBvbmx5IHNwZWNpZmljDQo+IGlzc3VlcyBmb3Igc3BlY2lmaWMg YXVkaWVuY2VzLsKgIE5vdCBlbm91Z2ggdGltZSBpbiB0aGUgZGF5IHRvIGRvIHRoZQ0KPiB0 aGluZ3MgSSAqd2FudCogdG8gZG8gd2hpbGUgY29uc2lkZXJpbmcgIm9wdGlvbmFsIiBlZmZv cnRzLg0KPiANCj4gRG9uJ3Qga2lsbCB5b3Vyc2VsZiB3b3JyeWluZyBhYm91dCB0aGlzIHNv cnQgb2YgdGhpbmcgZm9yIGEgcGluIHRhYmxlLg0KPiBZb3UncmUgbGlrZWx5IG5vdCBhcyBj b25jZXJuZWQgd2l0aCBkdXJhYmlsaXR5LsKgIFRoZSBib2FyZCdzIGFscmVhZHkNCj4gKGxp a2VseSkgZGVzaWduZWQuwqAgQW5kLCBpdCdzIGFscmVhZHkgZ290IGFuIGVzdGFibGlzaGVk ICh0b2xlcmFibGU/KQ0KPiBsZXZlbCBvZiBFTUkuDQoNCkFjdHVhbGx5IHRoZSAybmQgbGlu ayB5b3UgcHJvdmlkZWQgdGhhdCBzcGVha3Mgb2YgQ29pbCBTdXBwcmVzc2lvbiB3aXRoIA0K REMgcmVsYXlzIHBvaW50ZWQgb3V0IHRoYXQgdGhlIHplbmVyIGFuZCByZWd1bGFyIGRpb2Rl IGluIHNlcmllcyBoYWQgYSANCmRyb3AgLW91dCB0aW1lIG9mIGFsbW9zdCB0aGUgc2FtZSBh cyBhbiB1bnByb3RlY3RlZCBjb2lsLCBidXQgdGhlIEVNSSANCndhcyBsaW1pdGVkIHRvIHRo ZSB6ZW5lcidzIHJhdGluZyBhbG9uZyB3aXRoIHRoZSBkaW9kZSB2b2x0YWdlIGRyb3AuIA0K V2hhdCBpcyBpbnRlcmVzdGluZyBpcyBpZiB5b3UgaGF2ZSBhIHJlZ3VsYXIgZGlvZGUgYWNy b3NzIHRoZSBjb2lsIGl0IA0KdGFrZXMgYXJvdW5kIDUgdGltZXMgYXMgbG9uZyB0byBkZWNh eS4gVGhhdCBtYXkgYWN0dWFsbHkgbWF0dGVyIGluIA0KcGluYmFsbCBnYW1lcyAtIG9uZSBj b3VsZCBnZXQgc25hcHBpZXIgY29pbCBhY3Rpb24gd2l0aCB0aGUgemVuZXIvZGlvZGUgDQpj b21iaW5hdGlvbiAob3IgemVuZXIgYWNyb3NzIHRoZSBkcml2ZXIgdHJhbnNpc3RvciAtIHNr aXBwaW5nIHRoZSANCnJlZ3VsYXIgZGlvZGUgYXMgbWVudGlvbmVkIGluIHRoZSBub3RlKSBh bmQgZm9sa3MgbWF5IGJlIGFibGUgdG8gbm90aWNlIA0KdGhhdC4gSG1tLCAxLjltcyB2cyA5 LjhtcyAtIGNhbiBodW1hbnMgZGV0ZWN0IHRoYXQgd2hlbiBwbGF5aW5nIA0KY29uc2lkZXJp bmcgdGhhdCBmb3IgdGhlIG1vc3QgcGFydCAxMDBtcyBpcyBjb25zaWRlcmVkICdpbnN0YW50 YW5lb3VzJz8gDQpJIG1heSBoYXZlIHRvIHNldCB1cCBhIGdhbWUgYW5kIHNlZS4uLg0KDQoi TWFueSBlbmdpbmVlcnMgdXNlIGEgcmVjdGlmaWVyIGRpb2RlIGFsb25lIHRvIHByb3ZpZGUg dGhlIHRyYW5zaWVudCANCnN1cHByZXNzaW9uIGZvciByZWxheSBjb2lscy4gV2hpbGUgdGhp cyBpcyBjb3N0IGVmZmVjdGl2ZSBhbmQgZnVsbHkgDQplbGltaW5hdGVzIHRoZSB0cmFuc2ll bnQgdm9sdGFnZSwgaXRzIGltcGFjdCBvbiByZWxheSBwZXJmb3JtYW5jZSBjYW4gYmUgDQpk ZXZhc3RhdGluZy4gUHJvYmxlbXMgb2YgdW5leHBsYWluZWQsIHJhbmRvbSAidGFjayB3ZWxk aW5nIiBmcmVxdWVudGx5IA0Kb2NjdXIgaW4gdGhlc2Ugc3lzdGVtcy4iDQoNCg0KPiANCj4g UmF0aGVyLCBpdCBzaG91bGQgYmUgc2VlbiBhcyBhIGNvdW50ZXIgdG8gdGhlICJvbGQgc2F3 IiB0aGF0IHlvdSAqanVzdCogdXNlDQo+IGEgcmVjaXJjdWxhdGluZyBkaW9kZSB3aXRob3V0 IGNvbnNpZGVyaW5nIHRoZSBjb25zZXF1ZW5jZXMuwqAgSnVzdCBsaWtlDQo+IGNvbnNpZGVy aW5nIGhvdyB0byAqZHJpdmUqIHRoZSBjb2lsIGJhc2VkIG9uIGhvdyBpdCB3aWxsIGJlIHVz ZWQuDQo+IA0KPiBbUmVtZW1iZXIgdGhlICJwdWxsIGluIiBjb2lscyBhbmQgImVuZCBvZiBz dHJva2UiIChFT1MpIHN3aXRjaGVzIG9uIGZsaXBwZXINCj4gc29sZW5vaWRzP10NCg0KT2gs IHllcywgd2UgY29uc3RhbnRseSBkZWFsIHdpdGggdGhlbSwgYW5kIHBpdHRlZCBjb250YWN0 cyBvbiB0aGUgRU9TIA0Kc3dpdGNoZXMgaW4gb3VyIHNob3AuIFdvdWxkIHplbmVyIGRpb2Rl cyBhY3Jvc3MgdGhlIGNvbnRhY3RzIGhlbHAgcmVkdWNlIA0KcGl0dGluZz8NCg0KSm9obiA6 LSMpIw0KDQotLSANCihQbGVhc2UgcG9zdCBmb2xsb3d1cHMgb3IgdGVjaCBpbnF1aXJpZXMg dG8gdGhlIFVTRU5FVCBuZXdzZ3JvdXApDQogICAgICAgICAgICAgICAgICAgICAgSm9obidz IEp1a2VzIEx0ZC4NCiAgICAgICAgIzcgLSAzOTc5IE1hcmluZSBXYXksIEJ1cm5hYnksIEJD LCBDYW5hZGEgVjVKIDVFMw0KICAgICAgICAgICg2MDQpODcyLTU3NTcgKFBpbmJhbGxzLCBK dWtlcywgVmlkZW8gR2FtZXMpDQogICAgICAgICAgICAgICAgICAgICAgd3d3LmZsaXBwZXJz LmNvbQ0KICAgICAgICAiT2xkIHBpbmJhbGxlcnMgbmV2ZXIgZGllLCB0aGV5IGp1c3QgZmxp cCBvdXQuIg0K

    --- SoupGate-Win32 v1.05
    * Origin: fsxNet Usenet Gateway (21:1/5)
  • From Don Y@21:1/5 to John Robertson on Sun Aug 25 23:27:23 2024
    On 8/25/2024 10:01 PM, John Robertson wrote:
    Don't kill yourself worrying about this sort of thing for a pin table.
    You're likely not as concerned with durability.  The board's already
    (likely) designed.  And, it's already got an established (tolerable?)
    level of EMI.

    Actually the 2nd link you provided that speaks of Coil Suppression with DC relays pointed out that the zener and regular diode in series had a drop -out time of almost the same as an unprotected coil,

    Yes. What that implies is the contacts don't "linger" in close proximity/partial contact. The opening action is more "snappy",
    as intended by the choice of armature spring.

    but the EMI was limited to the
    zener's rating along with the diode voltage drop.

    Yes. You also have to remember that you are going to see a larger voltage spike than the simple diode (that would have clamped it to the supply rail).
    If the semiconductor switch can't handle this...

    What is interesting is if you
    have a regular diode across the coil it takes around 5 times as long to decay.

    That's the point; the relay is operating in a mode that wasn't intended
    (i.e., shit or get off the pot!)

    That may actually matter in pinball games - one could get snappier coil action
    with the zener/diode combination (or zener across the driver transistor - skipping the regular diode as mentioned in the note) and folks may be able to

    It depends on what you are talking about. In an old electromechanical game where the relays implemented the logic, the effects would largely be unnoticed. Driving a pop bumper or flipper solenoid could see some improvement in the "liveliness" of the action.

    But, in the case of kicking targets, remember that the setting of the
    sense contacts probably has a bigger impact on the feel of the game;
    if the target reacts too soon or too late, the kinematics change as
    the ball is in a different place with respect to the design of the
    kicker.

    notice that. Hmm, 1.9ms vs 9.8ms - can humans detect that when playing considering that for the most part 100ms is considered 'instantaneous'? I may have to set up a game and see...

    An easier way to do it would be to have a little piece of code that allows
    you to vary the delay between contact sense and solenoid actuation. Remember, most kicking targets do their work on the "activation stroke"; thereafter, they are just "recovering".

    "Many engineers use a rectifier diode alone to provide the transient suppression for relay coils. While this is cost effective and fully eliminates
    the transient voltage, its impact on relay performance can be devastating. Problems of unexplained, random "tack welding" frequently occur in these systems."

    On an old machine, such a failure would be pretty obvious. I don't know if newer (electronic) machines take any action to determine if their hammer drivers are failed or coils faulty.

    [I spent a shitload of time designing the interface to the irrigation
    valves (solenoids) in my irrigation controller to avoid these sorts
    of failures -- as well as detecting "forced" failures (e.g., user wired
    the valves -- ir god knows what else! -- to the controller incorrectly).
    But, the cost of a repair, there, far exceeds that of hauling a pin
    table into the back room!]

    Rather, it should be seen as a counter to the "old saw" that you *just* use >> a recirculating diode without considering the consequences.  Just like
    considering how to *drive* the coil based on how it will be used.

    [Remember the "pull in" coils and "end of stroke" (EOS) switches on flipper >> solenoids?]

    Oh, yes, we constantly deal with them, and pitted contacts on the EOS switches
    in our shop.

    But, you have the advantage of being able to pull the machine off the floor, and burnish and regap the contacts. And, you get some idea of how likely
    the need base on how many plays it sees.

    If the device in question is on a mountain in tibet... (yes! <frown>)

    Would zener diodes across the contacts help reduce pitting?

    An RC snubber might work better.

    But, *maintaining* a pin table is half the fun! (unless, of course, you
    are in a business to make money from them!)

    --- SoupGate-Win32 v1.05
    * Origin: fsxNet Usenet Gateway (21:1/5)
  • From John Robertson@21:1/5 to All on Mon Aug 26 10:00:30 2024
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    --- SoupGate-Win32 v1.05
    * Origin: fsxNet Usenet Gateway (21:1/5)
  • From Don Y@21:1/5 to John Robertson on Mon Aug 26 13:49:05 2024
    On 8/26/2024 10:00 AM, John Robertson wrote:
    Rather, it should be seen as a counter to the "old saw" that you *just* use
    a recirculating diode without considering the consequences.  Just like >>>> considering how to *drive* the coil based on how it will be used.

    [Remember the "pull in" coils and "end of stroke" (EOS) switches on flipper
    solenoids?]

    Oh, yes, we constantly deal with them, and pitted contacts on the EOS
    switches in our shop.

    But, you have the advantage of being able to pull the machine off the floor, >> and burnish and regap the contacts.  And, you get some idea of how likely >> the need base on how many plays it sees.

    Pinball games are more service trouble than most operators want to deal with. Anything we can do to make them more reliable is part of our business model.

    And I hate repeat service calls.

    Of course! My father-in-law (and HIS father-in-law) ran a route. So,
    unlike an arcade -- where there IS a "back room" -- problems meant a
    trip to <someplace>, often during THEIR working hours. (So, it's
    neither convenient for you or them!)

    If the device in question is on a mountain in tibet...  (yes!  <frown>)

    Would zener diodes across the contacts help reduce pitting?

    An RC snubber might work better.

    But, *maintaining* a pin table is half the fun!  (unless, of course, you
    are in a business to make money from them!)

    Ah, but you see that is the point of doing repairs that are better than (improve upon) the original design.

    Yes, John. My tongue was so firmly in my cheek that I looked like a chipmunk! Pin tables -- even solid state -- are perpetual maintenance problems. Whether its a broken rubber, solenoid, jammed coin mech, blown general illumination, misadjusted targets, etc. SOMETHING *always* needs attention.

    Or, is giving you clues that something WILL need attention.

    I always prefered older tables to the electronic ones. So, that much *more* maintenance. "Hmmm... the hundreds reel only advanced by 400 instead of 500. Something needs to be regapped (and lets pray it's not a mechanism issue!)"

    But, I think that was part of the appeal -- keeping such a machine in top working condition was a point of pride.

    [Until you run out of hours in a day/week/month/year to keep up with it!]

    Back in the 80s I figured out why one
    manufacturer's games were blowing up their driver transistors randomly and published the answer in the trade journals of the day. It was a ground issue, where the commons were done through Molex pins and as the pins aged the ground
    connections generated resistance, which led to transistors not fully biasing off and burning out. The fix was to beef up the ground connections and all subsequent games we serviced never blew the driver transistors any more and customers were happy!

    Need I mention the factory never acknowledged the error and did NOT implement my recommendations.

    (sigh) Don't get me started on that! I had a piss-poor opinion of many of the (hardware) "practitioners" in that era. I used to say that, as cavemen, they rode around in cars with square wheels (think the Flintstone's car). And, after a while, the corners of the wheels would wear off, leaving them ROUNDed.

    At which point, they would promptly REPLACE them with nice, new SQUARE wheels!

    <frown>

    Of course, it's hard to know how to apportion blame. There was a lot of emphasis on reuse -- not just designs but actual *assemblies*. If you're
    only making a few thousand of an item -- and, that item is REALLY REALLY
    REALLY similar to the last item you made! -- there is a strong incentive to reuse "what worked" (even if it didn't work all that well!)

    Software folks were always pleading for common-sense changes to designs
    ("Why do I have to serialize a bit-stream to drive the CVSD? That
    sorely limits the types of sounds -- speech! -- that can be generated
    and consumes 100% of the CPU! Why can't you put a frigging shit register there, instead??? Even if *I* have to clock it, at least I won't
    ALSO have to shift the data in the accumulator!") But, a lot of
    pressure on cost (I wonder how much of a price increase the market
    could have tolerated to improve the quality/appeal of the product and
    reduce time to market?)

    Larry & Eugene would have "wet themselves" for something as trivial as
    a 2MHz design...

    By the 80s they gained a reputation for unreliability that plagued them until they finally closed shop in the mid-90s. Oddly enough the same company was considered the Rolls-Royce of pinball up to the Solid State machines. Their solid state games looked and played great until the ground issues started randomly occurring (fried coils and driver transistors) and then operators would get rid of that manufacturer's games and buy other brand's machines.

    To be fair, you are also competing against the garage shops that want
    to sell conversion kits (much cheaper than new games -- at least for video)
    at the expense of the "original designs".

    There are two cases I deal with - commercial and home clients. Both would rather see less of my shop then they have to and I am happy to oblige them because I hate fixing simple things that could be made more durable. Also we've
    gained a bit of a reputation of machines lasting longer after being serviced by
    us and I wish to improve that score.

    Of course. I gave away all of my arcade pieces. But, always to someone who *could* maintain them (technicians, etc.). I knew that, otherwise, the
    games would quickly be unplayable and just collect dust in someone's basement.

    [I've toyed with getting -- or making -- a Robotron (something along the
    lines of a DINING ROOM TABLE, instead of a cocktail, so it would hide in
    plain sight. A full upright would be like storing a refrigerator in the
    living room! :<) But, suspect I would find too many excuses to play it instead of doing "productive" work. And, SWMBO would quickly tire of the hearing that deep bass "thumping" all day! (plus the next wave fanfares!)]

    SWMBO is the only exception to the "could maintain it" rule -- but, then again, she's got *me*! :-/

    So, reducing contact arcing is very important to me and my customers!

    We only get more business the better we fix the games!!

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