Shock Sensor Question

[Carter Shore]

On Mon, 10 Dec 2001 17:42 Steve Flanagan wrote:

> 
> Anyone have a brainstorm of an inexpensive shock
> sensor.
>
1) You could use a threaded rod, running inside a
plastic tube. Two optosensors pairs attached to the
tube, arranged with the light axis perpendicular to
the axis of the rod. The beam is arranged so that a
thread just obscures, and the root of the thread lets
light pass. So as the rod moves, the opto's create a
square wave signal. The two sensors are arranged so
that the phase of the two square waves is offset, to
allow quadrature detection of the direction that the
rod is traveling. By knowing the TPI of the rod, you
can count the pulses to get the displacement. The
output of the quadrature detector tells which
direction, to add or subract each pulse. 

2) Use a simple linkage from the suspension to an arm
connected to a pot mounted on the chassis. As the
suspension moves, the arm rotates the pot. Size the
arm go get 120 degrees of rotation from full droop to
full compress on the suspension. The voltage vs
displacement curve is non-linear, but can be easily
calibrated. For a good example of a cheap effective
adjustable linkage, check out the float adjustment rod
attachment system on one of those toilet bowl
replacement valves (I'm serious, dammit, just look!).
A flat piece of steel engaging the float is bent into
a U shape. Spring tension keeps it firmly anchored to
the rod, you just pinch the ends to loosen, and slide
it to the desired position. Lightweight, cheap,
simple, effective, easy to use, an elegant piece IMHO.

3) Get one of the new low cost DRO units that attach
to lathes and milling machines. Calaero sells a 0-6"
one with 0.001" accuracy for about $60. It has a bus
output that can connect to a central controller. Would
it stand up to the environment? Dunno, but the
machining environment is not very friendly, so maybe
so.

4) Get a carbon rod, or a piece of conductive plastic.
Attach electrodes to the end, fabricate a metal
slider, and voila! giant linear potentiometer.

Is four ideas enough for tonight? I'm getting tired
(maybe the drugs are kicking in)

Carter Shore

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