Re: RE: Deep electronic question..

From: jon@dakota-truck.net
Date: Sun Jun 20 2004 - 16:40:24 EDT


Don <y2kota@y2kota.us> wrote:

: I trying to find a way to turn off the ele. fan at speeds above 40mph
: and turn on when below 40mph.

   I have heard of people accomplishing this in the past by hanging
"something" in the airstream - where exactly, depends on the particular
vehicle - perhaps next to the radiator, perhaps somewhere in the air
dam area, etc. Anyway, the "something" is basically a flat piece of
metal, plastic, etc. whatever you might happen to have handy. You set
it up such that as it is blown back, it triggers a microswitch (which
is used as the input to a relay to interrupt the fan circuit). You
just need to play with the size of the flap until you get it to the
point where it is triggering the microswitch at 40mph. (Picture
something, perhaps the size of a playing card, hanging under the
truck, with a hinge at the top, and a microswitch positioned behind it
such that it will trigger it when it is blown back far enough.) I
don't recall now where I saw this, but as I recall, it was quite
effective.

  It might also be possible to use something similar to a Hall type
air speed indicator (popular on ultralights due to their light weight
and low cost) Basically, its a vertical tube, with a ball in it,
and at the bottom, a pitot tube facing into the wind. As you go
faster, the air pressure pushes up on the ball, and raises it in the
tube. The tube then has marks on the side showing what speed
you are at when the ball is at that point. (An actual air speed
indicator would normally use a flat disk which rides on a pin,
but if you are going the DIY route, a ball would probably be
simpler.) In your case, you wouldn't need the graduations, just
a microswitch at the level which corresponds to 40mph.

  The slickest solution would be the one already offered by other
DMLers - use electronics to count the pulses from the VSS or an ABS
sensor. However, if you aren't handy with electronics, one of the
above methods might be a way to get it done.

-- 
                                          -Jon-

.-- Jon Steiger ---- jon@dakota-truck.net or jon@jonsteiger.com --. | 1970 Barracuda - 1990 Dakota 'vert - 1992 Ram 4x4 - 1996 Dakota | | 1996 Intruder 1400 - 1996 Kolb FireFly - 2001 Ram QC 3500 CTD | `------------------------------------ http://www.jonsteiger.com --'



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