Re: Need speed switch for DIY funicular/hillside elevator

[Marc_F_Hult <MFHult@xxxxxxxxxxxxxxxxxxxxx>]

On 28 Oct 2006 11:44:25 -0700, astutesolutions@xxxxxxxxxxxxx wrote in message
<1162061065.466027.213040@xxxxxxxxxxxxxxxxxxxxxxxxxxxx>:

>I am thinking of having some way of measuring the outfeed speed of the

On 28 Oct 2006 12:42:24 -0700, astutesolutions@xxxxxxxxxxxxx wrote in message
<1162064544.727178.267460@xxxxxxxxxxxxxxxxxxxxxxxxxxxx>:

>The trick is, how to determine when it is going fast.  I almost need
>some kind of centrigal device on the cart or at the spool

On 28 Oct 2006 13:55:15 -0700, astutesolutions@xxxxxxxxxxxxx wrote in message
<1162068915.042171.16460@xxxxxxxxxxxxxxxxxxxxxxxxxxx>:

>I'm still at a loss though as to how to easily trigger it on the speed,
>although obviously a simple solution may be out of my reach.

As far as I can tell, you didn't get an answer to the question you raised
above despite all the posts ....

It would be straight-forward to make a sensor that would determine the
rotational speed of the cable capstan(s) and provide a safe/not-safe (go/
no-go) signal.

One way would be with one or more small magnets attached to the rim of the
capstan, a hall-effect sensor that would sense the magnet and produce a pulse
every time a magnet passed by, a frequency-to-voltage converter which might
be a single IC like http://cache.national.com/ds/LM/LM2907.pdf or a charge
pump made from a cheap op amp http://cache.national.com/ds/LM/LM324.pdf  and
a capacitor-resistor network , and a simple comparator
http://cache.national.com/ds/LM/LM339.pdf (or an op-amp used as a comparator)
to compare the measured voltage with a threshold set with a potentiometer or
resistance divider. This c/would cost less than $10 to make with parts from
Radio Shack. Sounds more complicated than it is.

What you do with the go/no-go signal would be a 'nuther matter.

HTH ... Marc
Marc_F_Hult
www.ECOntrol.org