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## RE: [TowerTalk] (another)Problem That Needs Ideas,

 To: "Tower Talk List - Postings" RE: [TowerTalk] (another)Problem That Needs Ideas, "Tom Scott" tomrscott@sterlink.net Wed, 8 Dec 2004 13:24:36 -0800
 ```Chuck, Any time you have to drive a control voltage at significant current down a long line the resistance of the line forms a voltage divider with the load and drops your voltage. What you really want in this case (long lines feeding a resistive/inductive load, motors, relays, etc.) is a constant current source. That way you don't care how long the line is. There is a real simple circuit configuration to do that on the data sheet of several versions of a three pin adjustable voltage regulator (LM317, LM338, and some others). It only requires the regulator and one low ohm resistor. If you need a weird value resistor you can tweak it by paralelling several if you have trouble getting just the right value. You really don't need an engineering degree to do this. Three pins on one part, and two on the other. You can get the LM338 in a 5amp version with a TO-3 package (needs a heat sink for full power though). If memory serves me (please verify with the data sheet before trying this) you put the resistor in series with the regulator's output pin and connect the adjustment pin to the other side of the resistor along with the load. I think the resistor value in ohms was equal to the current desired in amps. You start with a power supply of enough voltage to handle the drop, and the constant current will insure that you get enough current for starting and yet prevent over heating. This is REAL simple and works great. The circuit is toward the back pages of the data sheet on several of these regulators from different vendors. You can figure out the current you needed if you don?t have a spec for your motor or relay by running it through an amps meter with short leads and the voltage it is specified for. Then set up a current source for that much current and supply the current source with a higher voltage. I drove a 3V screwdriver motor through 1000' of wire using a 24V supply and it worked perfectly, never overheated or stalled. ? Tom Scott §§§§§§§§§§§§§§§§§§§§§§§§§§§§§§§§§§§§§§§§§§§§§§§§§§§§§§§§§§§§ 27005 NE Neill Road Newberg, Oregon 97132-9446 503-538-5839 Home 503-330-6867 Cell 503-554-9468 Fax KD7DMH -----Original Message----- From: towertalk-bounces@contesting.com [mailto:towertalk-bounces@contesting.com] On Behalf Of Chuck Dietz Sent: Wednesday, December 08, 2004 12:37 PM To: towertalk@contesting.com Subject: RE: [TowerTalk] (another)Problem That Needs Ideas I have been using 24 volts on 12 volt coil relays for years and I have never had a failure. Occasionally I have left a switch on with a relay energized for as long as a week. The higher voltage also compensates for resistance in the lines to the relay too. Chuck W5PR -----Original Message----- From: towertalk-bounces@contesting.com [mailto:towertalk-bounces@contesting.com] On Behalf Of w9ge Sent: Wednesday, December 08, 2004 1:52 PM To: towertalk@contesting.com Subject: Re: [TowerTalk] (another)Problem That Needs Ideas I have a two port six pack that I have relegated to the back bench because of relays not always pulling in. It is tough on amplifier tubes to be running into an open! My rotator has no brake, so cannot try that method. A very light touch on the offending relay always makes em pull in however. 73 bob de w9ge ----- Original Message ----- From: To: Sent: Wednesday, December 08, 2004 8:06 AM Subject: Re: [TowerTalk] (another)Problem That Needs Ideas > Don't have an RCS8V, but it reminds me of a problem I occasionally > have with a sixpack switch... One or two of the ports on one side are > intermittent unless I click the brake of my ham rotor 50 feet above > it. > > If I don't hear anything when I turn things on, I can click the brake > a couple of times, then the relay engages. I think it's the 10M port. > > Odd, but I just have lived with it. Dirty contacts? > > 73, > Blake N4GI > > ----- Original Message ----- > From: Bill Jackson > Date: Tuesday, December 7, 2004 8:21 pm > Subject: Re: [TowerTalk] Problem That Needs Ideas > >> Pat, >> >> I have an Ameritron RCS-8V which has been in service for almost 20 >> years.Shortly after I purchased it new, I started having intermittant >> problems similar to yours, especially in cold weather. This was the >> case until I discovered the relay arms were touching the inside of >> the plastic cover and would only partially actuate. The cure was to >> place a couple of flat washers between the plastic case the and the >> chassis in all four corners,increasing the clearance between the case >> and the relays. It has operated >> flawlessly ever since. >> >> I would try operating the switch with the cover off to see how the >> relaysactuate. >> >> 73 de Bill >> >> >> _______________________________________________ >> >> See: http://www.mscomputer.com for "Self Supporting Towers", >> "Wireless Weather Stations", and lot's more. Call Toll Free, 1- >> 800-333-9041 with any questions and ask for Sherman, W2FLA. >> >> _______________________________________________ >> TowerTalk mailing list >> TowerTalk@contesting.com >> http://lists.contesting.com/mailman/listinfo/towertalk >> > > _______________________________________________ > > See: http://www.mscomputer.com for "Self Supporting Towers", > "Wireless Weather Stations", and lot's more. Call Toll Free, > 1-800-333-9041 with any questions and ask for Sherman, W2FLA. > > _______________________________________________ > TowerTalk mailing list > TowerTalk@contesting.com > http://lists.contesting.com/mailman/listinfo/towertalk > _______________________________________________ See: http://www.mscomputer.com for "Self Supporting Towers", "Wireless Weather Stations", and lot's more. Call Toll Free, 1-800-333-9041 with any questions and ask for Sherman, W2FLA. _______________________________________________ TowerTalk mailing list TowerTalk@contesting.com http://lists.contesting.com/mailman/listinfo/towertalk _______________________________________________ See: http://www.mscomputer.com for "Self Supporting Towers", "Wireless Weather Stations", and lot's more. Call Toll Free, 1-800-333-9041 with any questions and ask for Sherman, W2FLA. _______________________________________________ TowerTalk mailing list TowerTalk@contesting.com http://lists.contesting.com/mailman/listinfo/towertalk _______________________________________________ See: http://www.mscomputer.com for "Self Supporting Towers", "Wireless Weather Stations", and lot's more. Call Toll Free, 1-800-333-9041 with any questions and ask for Sherman, W2FLA. _______________________________________________ TowerTalk mailing list TowerTalk@contesting.com http://lists.contesting.com/mailman/listinfo/towertalk ```
 Current Thread Re: [TowerTalk] (another)Problem That Needs Ideas, n4gi Re: [TowerTalk] (another)Problem That Needs Ideas, w9ge RE: [TowerTalk] (another)Problem That Needs Ideas, Chuck Dietz RE: [TowerTalk] (another)Problem That Needs Ideas,, Tom Scott <= Re: [TowerTalk] (another)Problem That Needs Ideas, Stephen Reichlyn Re: [TowerTalk] (another)Problem That Needs Ideas, VR2BrettGraham