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The point was whether slow release compromises contact life. The answer is "no." Your personality issues are irrelevant.

As the OP stated they are.

Probably not. TO-220 power fets are cheap, and can dissipate a watt or so intermittently with no problem.

I suggested measurement, I designed the experiment, you did the work. When the timebase was such as to conceal the entire shot, you repeated the measurements. Fine by me; I trust your data.

And just how was I wrong? What I did was question the claim that slow release is bad for contacts. You demonstrated that it probably isn't, certainly no worse than diode clamping.

Because I do electronics, and he doesn't. And because I'm friendly with lots of people, and he insults everybody.

Impossible. He has no "defense", just lame insults.

Amateur.

John

Reply to
John Larkin
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I'm sure they have two Lowe's and three HomeDespots, by now.

Reply to
krw 

--
The answer is "yes".

If arcing is the factor degrading the life of the contact, then slow
release will do little to minimize the problem, while fast release with
no diode will help.
Reply to
John Fields

John "Sugar Ray Weasel" Larkin has become down-right self-destructive.

...Jim Thompson

--
| James E.Thompson, P.E.                           |    mens     |
| Analog Innovations, Inc.                         |     et      |
| Analog/Mixed-Signal ASIC\'s and Discrete Systems  |    manus    |
| Phoenix, Arizona  85048    Skype: Contacts Only  |             |
| Voice:(480)460-2350  Fax: Available upon request |  Brass Rat  |
| E-mail Icon at http://www.analog-innovations.com |    1962     |
             
The first sign of senility is persistently trying to be an asshole

The second sign of senility is touting your company\'s wonderful
circuit designs as your own, while posting amateur crap on S.E.D

The third sign is acting like Polly Prissypants :-)
Reply to
Jim Thompson

Hi John, I remember from my old SxS telephony days, that they did all sorts of tricks with relays and coils, like put brass slugs on the armature end to delay operate or break, have more than one coil, so that one operated the relay, but another just held it. They did things with timing, so that 'this' would happen because relay B was still held, even though the operating current had been released, while relay A operated quickly, and the a pause in pulses on A allowed C to operate, etc.

But, yes, some contacts arced more because of slow opening and closing of the contacts, while others just eroded because they operated more.

Charlie

Reply to
Charlie E.

And all the senile Californians move to Palm Springs!

Wait, that is where I live! 8-)

Charlie

Reply to
Charlie E.

Peak fet power dissipation will be 360 mW for the equivalent of a few seconds. Not very scary. Even a TO92 can do that.

John

Reply to
John Larkin

Yep. I have in-laws living there ;-)

...Jim Thompson

--
| James E.Thompson, P.E.                           |    mens     |
| Analog Innovations, Inc.                         |     et      |
| Analog/Mixed-Signal ASIC\'s and Discrete Systems  |    manus    |
| Phoenix, Arizona  85048    Skype: Contacts Only  |             |
| Voice:(480)460-2350  Fax: Available upon request |  Brass Rat  |
| E-mail Icon at http://www.analog-innovations.com |    1962     |

         All Hail King Obama, The Resurrected Messiah :-(
Reply to
Jim Thompson

The Austin-Healey overdrive solenoid had a contact that opened when the armature was fully seated, adding some turns and resistance to the winding so it wouldn't fry. Healeys were sometimes known to vibrate.

John

Reply to
John Larkin

Cool. In some cases, rapid coil current cutoff will be significantly worse for relay contacts.

John

Reply to
John Larkin

Cool. It's servo'd.

I measured the di/dt of a solenoid whilst the armature was in flight, and extracted acceleration and dynamic inductance from that. I suppose you could deduce something about the pull-in / hold-in ratio, magnetic reluctance of the two cases, forces, yadda yadda yadda, if you had a need. Plug results into fancy model, etc.

Or you could just power the coil and yank on the armature with a scale to see how much force was keeping it pulled in... :-)

Cheers, James Arthur

Reply to
James Arthur

Vaguely recalling my mechanical engineering electives, can't you calculate all that from inductance versus armature position... Hamilton's principle?

...Jim Thompson

--
| James E.Thompson, P.E.                           |    mens     |
| Analog Innovations, Inc.                         |     et      |
| Analog/Mixed-Signal ASIC\'s and Discrete Systems  |    manus    |
| Phoenix, Arizona  85048    Skype: Contacts Only  |             |
| Voice:(480)460-2350  Fax: Available upon request |  Brass Rat  |
| E-mail Icon at http://www.analog-innovations.com |    1962     |

         All Hail King Obama, The Resurrected Messiah :-(
Reply to
Jim Thompson

For solenoids that bottom hard and go to essentially zero air gap when seated, the holding force per amp is way, way higher than the pull force.

Ac-coil relays automagically reduce their coil current as needed.

John

Reply to
John Larkin

Beats the heck outta me ... I was going to derive it from basic physics.

But then why model--probably inaccurately (or wrongly)--when you can measure? On the current waveform it was easy to see where the armature started to fly, to watch di/dt slow as the armature entered the solenoid, and flatten out abruptly once the armature slammed home.

The 'scope capture gave a great time-of-flight record too.

Cheers, James Arthur

Reply to
James Arthur

Yes, I prefer experiments myself. But I also like to understand. I didn't do much with Hamilton's principle in school, but have since used it several times when calculating the power requirements of various solenoids versus core position, AND how fast they'll move.

...Jim Thompson

--
| James E.Thompson, P.E.                           |    mens     |
| Analog Innovations, Inc.                         |     et      |
| Analog/Mixed-Signal ASIC\'s and Discrete Systems  |    manus    |
| Phoenix, Arizona  85048    Skype: Contacts Only  |             |
| Voice:(480)460-2350  Fax: Available upon request |  Brass Rat  |
| E-mail Icon at http://www.analog-innovations.com |    1962     |

"The American Republic will endure until the day Congress
discovers that it can bribe the public with the public\'s money."

                 - Alexis de Tocqueville
Reply to
Jim Thompson 

--
Yup!

   12V
    |
  [100R] COIL
    |
  [100R] FET
    |
   0V

and, yet, you were ready to plug a TO-220 in there before you were
forced to look at the numbers. 

That\'s just sloppy.

JF
Reply to
John Fields

Wrong again. You said the fet power dissipation would be a problem, and I responded that a TO220 could be used if it were.

You are really obsessed, hanging on my every word. That's sorta sick.

formatting link

Hell hath no fury...

John

Reply to
John Larkin 

--
Sorry, but no...

What I wrote was: " On top of that is the increased dissipation in the
driver, which for a larger relay and a longish time would probably
require the extra expense of a heat sink.

You must have glossed over the "larger relay" part.
Reply to
John Fields

Yeah, you've been that way since I mentioned that I'm married.

John

Reply to
John Larkin 

--
Yup; I don\'t mess around with married chicks.

JF
Reply to
John Fields

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