Return-Path: Received: from mail1.teleport.com ([192.108.254.26]) by truman.olsusa.com (Post.Office MTA v3.5.1 release 219 ID# 0-52269U2500L250S0V35) with SMTP id com for ; Fri, 23 Jul 1999 18:49:01 -0400 Received: (qmail 2884 invoked from network); 23 Jul 1999 22:52:18 -0000 Received: from i48-10-36.pdx.du.teleport.com (HELO fat-albert) (216.26.4.100) by mail1.teleport.com with SMTP; 23 Jul 1999 22:52:18 -0000 Message-ID: <007501bed55c$d18340a0$2a00a8c0@fat-albert> From: "Pat Weston" To: "LML" Subject: Re: Master relay Date: Fri, 23 Jul 1999 15:42:26 -0700 X-Mailing-List: lancair.list@olsusa.com Mime-Version: 1.0 <<<<<<<<<<<<<<<<--->>>>>>>>>>>>>>>> << Lancair Builders' Mail List >> <<<<<<<<<<<<<<<<--->>>>>>>>>>>>>>>> >> Sean wrote "I dissagree" That is your prerogative. Sean wrote "You mean to say that the pull in current is never more than the holdin current. My understanding of a coil, solenoid or contactor is that pull-inin current is greater and the hold-in current less due to the increasedinductance due to the magnetic circuit being closed. Also it is apositivedesign feature as as the pull-in forse is greater than the holdinforse. acontiuous cycle of opening and closing would give an overall aversgeincreased power consumption. Increased power consumption = increasedpowerthat needs to be dissipated." No, I never meant to say that at all. You are perfectly correct in what you said above. However, the minimum pull in current is exactly that, minimum. This is a specified parameter that tells one at what current the contacts will close. The minimum hold in current is exactly that too, minimum. This is also a specified parameter that tells one at what current the contacts will remain closed. Now, in the system that we're discussing, simple application of relays to conventional, albeit experimental, aircraft systems the current through the coil in the stable on state will be significantly greater than either the pull in and hold in specified values. There is an example below of an Omron relay which is typical of most electro mechanical relays... Omron G8J-1C6T-F-DC12 Operating voltage 12VDC Coil resistance 78 Ohms Pull in current 115mA Hold current 15mA Nominal current 154mA Contact rating (resistive) 35 Amp for the normally open pair and 20 Amp for the normally closed. As you mentioned the pull in current is indeed much greater than the hold in current, but as you can also see that the nominal current at 12VDC is greater than both.. So if one had to design a more complex system that took advantages of these differences then you would be right in that a greater power would be dissipated with frequent activation and de activation of the relay. But this is not the case in the simple set up we normally put in airplanes. KISS. Sean wrote "May be I have miss understood something. Yourcomments contradict what have learnt in college, experienced inpractice andinformation researched in ctalogue from Allen Bradley to Sprecher andShuh." I think perhaps you had misunderstood something. My previous comments never addressed the hold in and pull in currents as this was moot in the particular system under discussion. I hope this clears it up. Keep the shiny side up and right rudder (perhaps left rudder down under?)! Pat Weston VP of Engineering Diamond Multimedia Systems Communication Division 360 604 1538 >>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>> LML homepage: http://www.olsusa.com/Users/Mkaye/maillist.html