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Potentiometers question

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nuckollsr(at)cox.net
Guest

Posted: Wed Aug 23, 2006 6:24 am Post subject: Potentiometers question

At 02:26 PM 8/22/2006 -0400, you wrote:



Bob,



I am building a RV10 and am using your wiring diagram, dual Alt dual bus. I 

am also installing a blower motor to use as a source to blow heated air on 

to the windscreen. I have sourced a blower, via west marine that is 12 

volts 6amp and will work I think quite nice. I would like to have a 

variable switch/potentiometer to control the unit, to turn it on as well as 

control the fan speed. I have been to DIGIKEY and Mouser to find a POT that 

would work, the problem is that I don't know what values to use 5K 10K 15K 

25K etc&..for this application.



Can you provide any guidance&.Your help is appreciated

   You're going to need something heftier than a panel-mounted,

   stand-alone potentiometer. Potentiometers are limited to

   currents on the order of a few milliamperes. Rheostats (really

   BIG potentiometers) are available to handle much larger

   currents on the order of amps . . . but they get so hot

   and are so large that mounting them on the panel (or anywhere

   else in the airplane) is not practical.



   You need a variable duty cycle motor controller. A number of

   folks here on the List have been modifying a kit offered by

   Marlin P Jones at:



http://www.mpja.com/productview.asp?product=4057+MD



   This product is advertised as capable of handling 10A

   of motor current. As you can see, it's CONTROLLED by

   a relatively small potentiometer (milliamps) but the

   motor current is carried by a transistor on a heatsink

   (amps).  I know nothing about this kit and it has some

   obvious packaging issues for aircraft. The electronics

   board needs to be mounted in some kind of box and the

   potentiometer brought out on leads to be mounted on the

   panel.



   Suggest you join the AeroElectric List and talk with

   folks who have used this kit. They can probably offer

   a variety of options for utilizing this kit in your

   project.



        Bob . . .

      ---------------------------------------------------------

      < What is so wonderful about scientific truth...is that >

      < the authority which determines whether there can be   >

      < debate or not does not reside in some fraternity of   >

      < scientists; nor is it divine. The authority rests     >

      < with experiment.                                      >

      <                            --Lawrence M. Krauss       >

      ---------------------------------------------------------

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klehman(at)albedo.net
Guest

Posted: Wed Aug 23, 2006 10:09 am Post subject: Potentiometers question

sorry I've lost the original post but that is a huge fan for defrost. If 

you really think you need it you could also look at an automotive fan 

speed control arrangement.



For just blowing air up through the instrument glareshield I found that 

a little axial fan as seen in computer power supplies seems to work fine 

for me. No speed control required.



Ken



Robert L. Nuckolls, III wrote:



 	  Quote: 	
		   

 <nuckollsr(at)cox.net>



 At 02:26 PM 8/22/2006 -0400, you wrote:



 Bob,



 I am building a RV10 and am using your wiring diagram, dual Alt dual 

 bus. I am also installing a blower motor to use as a source to blow 

 heated air on to the windscreen. I have sourced a blower, via west 

 marine that is 12 volts 6amp and will work I think quite nice. I would 

 like to have a variable switch/potentiometer to control the unit, to 

 turn it on as well as control the fan speed. I have been to DIGIKEY 

 and Mouser to find a POT that would work, the problem is that I don't 

 know what values to use 5K 10K 15K 25K etc&..for this application.



 Can you provide any guidance&.Your help is appreciated

   You're going to need something heftier than a panel-mounted,

   stand-alone potentiometer. Potentiometers are limited to

   currents on the order of a few milliamperes. Rheostats (really

   BIG potentiometers) are available to handle much larger

   currents on the order of amps . . . but they get so hot

   and are so large that mounting them on the panel (or anywhere

   else in the airplane) is not practical.



   You need a variable duty cycle motor controller. A number of

   folks here on the List have been modifying a kit offered by

   Marlin P Jones at:



 http://www.mpja.com/productview.asp?product=4057+MD



   This product is advertised as capable of handling 10A

   of motor current. As you can see, it's CONTROLLED by

   a relatively small potentiometer (milliamps) but the

   motor current is carried by a transistor on a heatsink

   (amps).  I know nothing about this kit and it has some

   obvious packaging issues for aircraft. The electronics

   board needs to be mounted in some kind of box and the

   potentiometer brought out on leads to be mounted on the

   panel.



   Suggest you join the AeroElectric List and talk with

   folks who have used this kit. They can probably offer

   a variety of options for utilizing this kit in your

   project.



        Bob . . .

- The Matronics AeroElectric-List Email Forum -

Use the List Feature Navigator to browse the many List utilities available such as the Email Subscriptions page, Archive Search & Download, 7-Day Browse, Chat, FAQ, Photoshare, and much more:

http://www.matronics.com/Navigator?AeroElectric-List

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