(ET) "gas pedal" - or rheostat??

["Herb Crary" <jhcrary comcast net>]

There seems to be some confusion about the difference between a rheostat 
and
a potentiometer. They are different. A rheostat is a two-terminal variable
resistor. It is generally placed in series in a circuit between the power
source and the load.

 A potentiometer is a three-terminal variable resistor. It has terminals at
both ends of the fixed resistor on which the variable tap moves. The two 
end
terminals are generally placed in parallel across a power source. The
movable terminal then goes to the load. The other end  of the load is
connected to the common (to the potentiometer and source; this is often the
ground) wire. The pot(entiometer) is used to vary, or divide, the voltage
from the source. Hence the other name: voltage divider (voltage is another
name for potential).

Herb Crary
Boulder CO

----- Original Message ----- 
From: "Jim Coate" <jbc coate org>
To: "elec trak" <elec-trak cosmos phy tufts edu>
Sent: Thursday, February 26, 2004 12:10 PM
Subject: Re: (ET) "gas pedal" - or rheostat??


> It depends...
>
> The stock E20 has a pedal that uses mechanical linkages to depress a
> sequence of small switches - one switch for each speed. Making such from
> scratch for the E15 could be tricky to get it all put together. Off-hand
> I don't know where you could buy such pre-made. You could take the pedal
> unit off an E20, but the E20 has more speeds, so more switches, so a
> little wiring to figure out. And... if you have the E20 pedal you
> probably have the E20 tractor that goes with it :-)
>
> Electronic controllers often use potentiometers, which is a variable
> resistor. (A rheostat is just a bigger variable resistor). So you could
> rewire the E15 completely with one of the new AllTrax controllers and a
> matching 0-5K potentiometer.
>
> I'm looking for a source of good quality & water proof foot controls to
> use with the AllTrax controller on an E20. Either a potentiometer, or an
> inductive pickup which it can also use and which are theoretically more
> reliable. Suggestions welcome.
>
>
>
>
> Stephen & Carol Welch wrote:
>   > Whatever the appropriate electrical term (enlighten me)...  My
>   > question is this:
>   >
>   > Is it possible or practical to convert an E15 to foot speed control
>   > as is found on the E20?
>   >
>   > Or is one better off just finding a '20 if the pedal is desirable?
>   >
>   > Sorry if this has been queried before...  I'll hide behind
>   > newbieness.  :^)
>
>
>
> _________
> Jim Coate
> 1970's Elec-Trak
> 1992 Chevy S-10 BEV
> 1997 Chevy S-10 NGV
> http://www.eeevee.com
>
>
>
>
>
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