On a sunny day (Sun, 01 Mar 2009 00:14:21 GMT) it happened James Arthur wrote in :
I am very impressed, beautiful stuff. Need to try this one day :-) And, it seems he has some RF power too in that second link.
Barf! All the senile New Yorkers move to Florida ;-)
...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 |
With all this hope and change, all you need is a dab of mayonaisse
and you\'ll have a tasty lunch on which you will choke to death.
Yes, I saw that, and I have no idea what it means.
John
On Sat, 28 Feb 2009 16:30:47 -0800, in sci.electronics.design John Larkin wrote: snip
What about this guy?
martin
--- Of course you don't...
Well, lemme see if I can jog your memory.
You may recall that I claimed that a relay armature would drop out more quickly if the coil excitation was removed quickly, resulting in greater acceleration of the common contact than if the excitation was removed slowly.
You took the opposing position and said that it wouldn't matter much whether or not the excitation was removed slowly or quickly because once the armature left the pole piece the air gap would cause the magnetic reluctance to increase rapidly with the spring quickly accelerating the armature away from the pole piece.
I then proposed an experiment to determine who was right, and you suggested using this circuit:
+V | [1K] | +------+-->TO SCOPE | | O\\ O \\ O | GNDto measure the time of flight of the common from the NC to the NO contacts of the relay.
I then built what is essentially your circuit:
+V>----+--------------+-[1K]-+---------+---[SCOPE] | | |NO NC| | | | O-> /---+-------+------+-----------+-----------+Pushed the button, released it, and after about 2 minutes captured the waveform labeled "SLOW RELEASE" on the PDF as the common left the NO contact.
Next, I modified the circuit like this:
+V>-------------------+-[1K]-+---------+---[SCOPE] | |NO NC| | | O-> /--------------+---+-----------+-----------+set the generator for about a 1s square wave and captured the waveform labeled "FAST RELEASE" as the common contact was leaving the NO contact.
In FAST RELEASE the time from the common leaving the NO and first striking the NC was about 960µs, while in SLOW RELEASE the time was about 1340µs.
Conclusion?
If the coil excitation is removed rapidly, the time of flight is less than if the excitation is removed slowly.
BTW, I was intrigued by what effect the diode might have on the flight time, so I soldered a diode across the coil and ran the tests again, both with and without the diodes, but on a different time scale so the results could be more easily compared.
The extremely interesting results are here:
news: snipped-for-privacy@4ax.com
JF
That's inaccurate. I said I didn't know if, or how much, a sustained dropout-magnitude current (ie, a slow coil current droop) would affect contact opening velocity. You seem to have found my uncertainty to be offensive somehow.
Yes, but not a huge difference.
Your scope timebase doesn't reveal when the other contact settles. If you were to add a resistor in series with one of the contacts, the three states (NC closed, NO closed, neither/in-flight) would be unambiguously resolved. And if you slow down the scope timebase, we could see the entire events.
I think I know which low-hits are which contact, but it's better to be sure.
Dual-tracing with coil voltage or better yet current would be educational, too, triggered from the drive. You seem to be internal triggering off the first contact opening.
Again, the tail end of the events are chopped off. But it looks like the last three cases are similar... can't tell for sure.
One thing I've found is that relay bounce waveforms can be a very sensitive sorta-chaotic function of coil drive current and waveform, and can vary between individual relays.
So far, there's no slam-dunk case against slow release. It looks very similar to diode clamping, at least as far as we can see so far, and your Japanese datasheet declares diode clamping to be practically mandatory.
Big question is what is the contact transition time and what is coil current decay tau? If tau > Tt, the diode case is close to the very-slow-decay case. That seems likely.
John
-- 27% is large enough to be significant and it vindicates my position, so I\'m happy with it. Plus now you\'ve got an answer to your question and you can put your uncertainties to rest.
Naaaah! It's "Weasel von Larkin" ;-)
...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 :-)
No, they spend the winter here and tell us how great NY is while they're here, driving 20 MPH below the posted speed and taking six hours to drink one cold cup of coffee while working people have to wait for an open table. Just like a lot of Canadians. A lot of college kids from Arizona and texas spend spring break in the Florida panhandle, as well.
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Except for the Canadians in Yuma during the Winter... typically around
100,000. VERY good for Yuma's economy!...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 |
I love to cook with wine Sometimes I even put it in the food
The ones who visit Florida bring a $20 bill, and generally take it back with them in the spring.
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Louisiana, too. All we had was brown mud, and the sugar-sand dunes of Destin and Pensacola were might tempting.
John
And 27% is small potatoes, and there's no real difference betweeen slow release and diode clamping, so the simple mosfet timers are fine.
I care about learning everything I can from an experiment. I think what you really care about is arguing over who is right and who is wrong. Like Sloman's AGW nonsense: really just an excuse for juvenile squabbling and crude insults.
Then there's nothing wrong with slow release, and so the simple mosfet circuits are not a threat to relay reliability. In fact, slow dropout may result in slightly less arcing time than diode clamping.
Which, I think, was the whole point.
It's easy to protect the driver and still get fast coil current dropoff. But it doesn't look like that has any real advantage as regards contact arcing, which was the original argument against slow coil current dropoff, and against several of the posted circuits.
But cheater? How's that? Who did I cheat by asking questions and learning stuff? My competitors, maybe.
Stupid name-calling insults you, not me.
John
I built a UHF TV station in Destin in the early '90s, during the off season. I got there not long after spring break ended. nasty place to work. Everything you needed was only sold to 'The trade', and no one wanted to do anything for a reasonable price. Sandestin, with all the overpriced condos was the reason. they figured that if you bought a condo you were too stupid to do anything for yourself. We had to go 100 miles just to buy some 2" Schedule 80 copper pipe, and the only way I was able to buy electrical supplies was that I had been dealing with another branch of the company in Leesburg.
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Why do you, who rarely post anything with content, call me a weasel? What I did was *question* whether slow release of a relay coil is bad for contact reliability, in response to assertions that it is indeed bad. JF's experiment indicates that it's likely no worse than conventional diode clamping and hardly a real threat to reliability. I accept his measurements to that effect.
Weaseling implies a dishonest change of position, which I have not done.
Go back to lurking, since you have nothing concrete to say. Or killfile me again... please. And quit asking me for favors privately while insulting me publicly.
John
[snip]
Do you read your own posts? You dodge around like Sugar Ray ;-)
Don't make any more blunders. I'll be watching, and noting publicly ;-)
...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 :-)
When we went to Destin, we had other activities in mind!
John
Asking questions has become blunders?
So long.
John
I wouldn't have made the trip, if they weren't paying me. By the time I was there most of the beaches were closed and you wouldn't have gone, either. The beaches were military property or closed to the public to protect the sawgrass, which was classed as endangered. Spring Breakers mostly went to Daytona by then.
The area was full of old farts, and a lot were on golf carts. In fact, the original Ft Walton Beach Rock & Roll radio station was shut down while I was there. That left a poor quality country music station, and some mixed format stations. The only TV stations could get was a low power UHF from Ft. Walton Beach, and a low band VHF station from Dothan, Alabama that still had a half hour farm report every morning. They still used christmas tree tinsel on a magnet and a rotating light to indicate rain, in the early '90s. :(
-- http://improve-usenet.org/index.html Goggle Groups, and Web TV users must request to be white listed, or I will not see your messages. If you have broadband, your ISP may have a NNTP news server included in your account: http://www.usenettools.net/ISP.htm
-- Sore loser, you are.
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