Actually, giving it another thought, the cheapest and easiest,would
probably be to use the innards of an old mouse. Wrap a spring-loaded
string (waxed?) several turns around the shaft of one of those small
wheels in the mouse. Remember the frequency indicators on real old radios?
(In this case it will be the string moving the axle, not the axle moving
the string). Hook up a scope to the mouse: pin 5 is ground. Pin 2
or 3 is output, and one of the other pins supply the power. Examine the
output. Your circuit will have to be designed to remember the last
position before power-down, or you can simply move the manifold to an
end-stop and reset the position counter. Finn Finn Lassen
wrote:
Hi
Ed,
This is off-the-wall, but what is used in the $20 electronic
dial calibers? Maybe it's possible to pick up the signals to the LCD
segements... I told you it was off the wall.
Now, you can make
your own:
Need a strip of binary tape: one strip is black 1/2 the
length white the rest, the second stripe is black-white-black-white, the
third twice as many black-whites, etc. down to the resolution you want.
Then a number of led/photo-transistors pickups that can read the
stripes.
The easier way is of course just one stripe and your
circuit just counts the changes as the stripe passes through the
led/photo-transistors reader - but requires the circuit remembers the
current position. Also some way to determine direction.
Take
apart an old mouse and see how that works.
There must be 10's of
ways to do this.
Finn
Ed Anderson wrote:
Hi Guys,
I am finishing up the
design and fabrication of my variable length EDDIE intake and need
some assistance. I want to use a voltmeter (or LEDs) to indicate
the postion of the manifold. The simplist approach would appear
to have a linear resistor attached such that its arm is moved as the
manifold moves thereby changing the resistance indicating
distance.
I've done a lot of Web surfing and found
a number of linear postion potentiometers. The problem is they
cost more than I have invested in the manifold. Regular audio
linear potentiometers do not have the mechanical range I need. I
need a position indictor that has at least 5 1/2 - 6" of travel.
Anyone have any ideal where something reasonably priced might be
found.
If you know of a retail catalog
that have such things I'd appreciate a pointer. I can find
plenty of Linear Postion Potentiometers - but they cost in the
hunderds of $$. Need something much cheaper.
I know I could devise a 3:1 lever ratio
or some such thing and use one of the cheap (but mechanically range
restricted) linear potentiometers for audio circuits, but would rather
not.
Thanks
Ed Anderson
RV-6A N494BW Rotary
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