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Controlling defrost fans

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recapen(at)earthlink.net
Guest

Posted: Thu Jan 17, 2008 6:39 am Post subject: Controlling defrost fans

I have a pair of 1.5"x1.5" fans (Radio Shack 273-240) mounted forward of the instrument panel on my 6A slider - think about the intersection of the support bulkhead parallel and forward of the instrument panel and the ribs that point aft that support the top of the instrument panel in three places.



I am wondering if a straight on-off switch is sufficient or should I put in a rheostat to control the fan speed?  KISS would dictate that a simple on-off switch would work - but has anyone out there wished for a half-speed?



Here on the DelMarVa peninsula - I'm certain that I'll need it on a regular basis



Thanks,

Ralph

ronlee(at)pcisys.net
Guest

Posted: Thu Jan 17, 2008 7:10 am Post subject: Controlling defrost fans

A rheostat probably has the same numbers of wires but you can turn it.

Hardly seems harder and it does offer flexibility.



Ron Lee



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Dale Ensing

Joined: 11 Jan 2006
Posts: 571
Location: Aero Plantation Weddington NC

Posted: Thu Jan 17, 2008 7:17 am Post subject: Controlling defrost fans

Ralph, I have a pair of 4" fans mounted in the top skin forward of the 

instrument panel to blow on W/S of my 6A slider. No need for speed control. 

Maybe the larger fans turn lower RPM. They are similar to cooling fans in a 

computer tower.

BTW I use them in the summer to pull hot air from behind the panel and help 

cool the avionics.

Dale



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_________________
Dale Ensing
RV-6A
Aero Plantation
Weddington NC

n616tb(at)btsapps.com
Guest

Posted: Thu Jan 17, 2008 7:22 am Post subject: Controlling defrost fans

I doubt that anything more than an on off switch would be needed.  I

installed a fan in mine but have not needed it.  Enough heat develops under

the panel that just having the opening in there has been sufficient.  I park

in a hangar however so if you need to seriously defrost, than a simple on/

off switch would be all you would need.

My opinion of course.

Tim



[quote] --

Ted French

Joined: 09 Jan 2006
Posts: 54
Location: Kelowna BC Canada

Posted: Thu Jan 17, 2008 7:23 am Post subject: Controlling defrost fans

I have the same fans, but I just let them run all the time. No switch...



Do Not Archive



Ted French C-FXCS 

RV-10  Flying

--

_________________
Ted French
RV-10 fuselage

DOUGPFLYRV(at)aol.com
Guest

Posted: Thu Jan 17, 2008 8:36 am Post subject: Controlling defrost fans

RALPH, WE HAVE HAD FANS IN THE LAST 3 RV'S WITH JUST THE ON/OFF SWITCH. U  SURE WOULDN'T BE ABLE TO HEAR THEM.

 DOUG PRESTON

 N372RV



Start the year off right.  Easy ways to stay in shape in the new year. 

  [quote][b]

Knicholas2(at)aol.com
Guest

Posted: Thu Jan 17, 2008 9:26 am Post subject: Controlling defrost fans

I have several computer cooling fans in my RV9A on the wind screen.  I  only have on/off,  they are very quiet and also serve as a window  defroster.  I see no need for a rheostat.

  

 Kim Nicholas

  

  In a message dated 1/17/2008 6:40:48 A.M. Pacific Standard Time,  recapen(at)earthlink.net writes:

  	  Quote: 	
		  I am    wondering if a straight on-off switch is sufficient or should I put in a    rheostat to control the fan speed?  KISS would dictate that a simple    on-off switch would work - but has anyone out there wished for a    half-speed?

	




Start the year off right.  Easy ways to stay in shape in the new year. 

  [quote][b]

n212pj(at)gmail.com
Guest

Posted: Thu Jan 17, 2008 10:33 am Post subject: Controlling defrost fans

Wouldn't the variable  speed or rheostat be a good source for noise problems in the old headset?   Best just use an on/off switch.  Those fans are so quiet, who cares if they  run full tilt, but they should be able to be turned off in case amps need to be  shed, small amount of amps, though.  

  

 John Jessen

  

 do not  archive



   From: owner-rv-list-server(at)matronics.com  [mailto:owner-rv-list-server(at)matronics.com] On Behalf Of  Knicholas2(at)aol.com

Sent: Thursday, January 17, 2008 9:24  AM

To: rv-list(at)matronics.com

Subject: Re: RV-List:  Controlling defrost fans

 

 I have several computer cooling fans in my RV9A on the wind screen.  I  only have on/off,  they are very quiet and also serve as a window  defroster.  I see no need for a rheostat.

  

 Kim Nicholas

  

  In a message dated 1/17/2008 6:40:48 A.M. Pacific Standard Time,  recapen(at)earthlink.net writes:

  	  Quote: 	
		  I am wondering if a straight    on-off switch is sufficient or should I put in a rheostat to control the fan    speed?  KISS would dictate that a simple on-off switch would work - but    has anyone out there wished for a  half-speed?

	




   Start the year off right. Easy ways to stay in shape in the new year. 

[quote]



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href="http://forums.matronics.com">http://forums.matronics.com

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[b]

Carl

Joined: 04 May 2007
Posts: 44
Location: Aiken, SC

Posted: Thu Jan 17, 2008 3:20 pm Post subject: Controlling defrost fans

Is there any chance of getting a picture?  What a great idea.



--

_________________
Carl Bell
Building N947CB
RV 7A

Dale Ensing

Joined: 11 Jan 2006
Posts: 571
Location: Aero Plantation Weddington NC

Posted: Thu Jan 17, 2008 4:52 pm Post subject: Controlling defrost fans

I'll try to take a couple of  good pictures tomorrow and send.

Dale

do not archive



---

_________________
Dale Ensing
RV-6A
Aero Plantation
Weddington NC

gmcjetpilot

Joined: 04 Nov 2006
Posts: 170

Posted: Fri Jan 18, 2008 11:16 am Post subject: Controlling defrost fans

I think ON/OFF is fine, but if you want to control it try a 

PWM (pulse width modulation) control "rheostat".

  

http://solorb.com/elect/pwm/pwm1/

  

There are hobby kit's you can buy with all the parts 

and board, as well (google it). George

   

   

  >From: "Ralph E. Capen" <recapen(at)earthlink.net (recapen(at)earthlink.net)>

 	  Quote: 	
		  Subject: Controlling defrost fans

  >I am wondering if a straight on-off switch is sufficient or should 
	


 	  Quote: 	
		  I put in a rheostat to control the fan speed?  KISS would dictate 

that a simple on-off switch would work - but has anyone out 

there wished for a half-speed? Thanks, Ralph

  
	


 



   [quote][b]

mikerv6a(at)ao.com
Guest

Posted: Mon Jan 21, 2008 7:50 pm Post subject: Controlling defrost fans

Here is a simple two-speed fan control using an spdt switch. I'm using a

fan from DigiKey, cat no. 603-1055-ND that's 80mm square and 25.4mm

thick, about 3.15" x 1". It has ball bearings and relatively high airflow

for its size. Rated power at 12V for this fan is 6 watts. I measured fan

current at about 0.52A at 12.0 volts. The relationship between voltage and

current was close to linear down to 6V, and the fan continues to run at

still lower voltage. I chose 8V as a target votlage for "slow" speed, and I

found fan current to be about 0.33A at this voltage. Speed of these fans is

easily controlled either by providing variable voltage or by inserting a

resistor in series with the fan circuit. I used a 15-ohm 10-watt resistor

having an aluminum housing which includes tabs for mounting on a couple of

screws. This results in about 8.5 volts on the fan with 13.5V power bus

voltage. Power dissipation in this resistor is calculated to be about 1.7

watts. The reason for my "oversizing" the power rating of the resistor

I selected is that the built-in mounting provision for the 10W resistor is

very convenient. The resistor is DigiKey catalog no. 810F15RE-ND.

        (Low Speed)             Resistor

                 O--------------/\/\/\/------

                /                            |

  -------------/    O (OFF)                  |

 spdt switch                                 |

 w/ center-off   O---------------------------

                  \

                   ------------------------------- FAN--------

        (Full Speed)

Mike Linse

RV-6A (canopy...)

Corvallis, OR

Carl

Joined: 04 May 2007
Posts: 44
Location: Aiken, SC

Posted: Mon Feb 04, 2008 5:39 pm Post subject: Controlling defrost fans

Mike,



Did you get a chance to make a couple of pictures, I bought the fans and

would love to see your installation.  Thx C



Carl W Bell

New Venture Consulting

Mobile:  803.640.2760

www.newventureconsulting.com

carlbell(at)gforcecable.com

--

_________________
Carl Bell
Building N947CB
RV 7A

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