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Re: [EVDL] Building a controller yourself

Lee,
In your explanation below, what was typically used for the shorting bar? Was it a brush? Was it a piece of copper held tightly against the bolt heads? Or was it something else?

Thanks.

Bill Dennis

Lee Hart wrote:

>The trick is that there are intermediate contacts between positions. The
>shorting bar is wide enough to short two adjacent contacts as it moves.
>The intermediate contacts have resistors in series, to always provide a
>path for the current as the switch is moved.

>Example (view with a fixed-width font like Courier):

||
12v__________O ||---------to motor
||
__/\/\__O \movable shorting bar
|
24v_|________O

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Discussion Starter #2
Re: [EVDL] Building a controller yourself

Bill Dennis wrote:
> Lee,
> What was typically used for the shorting bar? Was it a brush?
> Was it a piece of copper held tightly against the bolt heads?
> Or was it something else?

There were several systems. The actual contacts were generally silver.
This could be silver plated copper, or a brass bolt with a silver
contact brazed onto its head.

The moving part could be built the same; if so, it would have some kind
of spring mount to allow it to shift a bit so the two contacts made good
contact. Or, the moving part could be a stack of sheet metal parts that
sweep over the contact somewhat like a squeegee on a window. Or, it
could be a carbon brush like you see for a motor controller. The
solution the designer picked depended on the power level being switched,
and how often he expected it to be moved (wear issues).
--
Ring the bells that still can ring
Forget the perfect offering
There is a crack in everything
That's how the light gets in -- Leonard Cohen
--
Lee A. Hart, 814 8th Ave N, Sartell MN 56377, leeahart_at_earthlink.net

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