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From: larry@kitty.UUCP (Larry Lippman)
Newsgroups: sci.electronics,talk.bizarre
Subject: Re: "Magic Eye" tubes
Message-ID: <1871@kitty.UUCP>
Date: Thu, 23-Jul-87 23:55:48 EDT
Article-I.D.: kitty.1871
Posted: Thu Jul 23 23:55:48 1987
Date-Received: Sat, 25-Jul-87 11:31:41 EDT
References: <1495@frog.UUCP> <35ffa63b.b8ab@apollo.uucp> <6@spar.SPAR.SLB.COM> <591@inuxh.UUCP>
Organization: Recognition Research Corp., Clarence, NY
Lines: 26
Summary: More electronic component nostalgia...
Xref: mnetor sci.electronics:1045 talk.bizarre:2620

In article <591@inuxh.UUCP>, rmrin@inuxh.UUCP (D Rickert) writes:
> Yup, many years ago I did a lab project in which we used a Decatron
> for motor speed control!  The idea was for the circuit to keep the
> same little dot continuously lit if the motor speed stayed constant
> at the set point.  A wonderful mix of analog, digital, and power
> technology.  I think we may have even had a mag amp somewhere in
> the circuit (you know, solid state Neanderthal style).

	Magnetic amplifiers!  I haven't run across those gadgets for servo
control in years.  They came in half-wave, full-wave and push-pull
configurations, and were particularly handy for military applications
which involved controlling 115 volt 3-phase 400 Hz motors.
	There is something used for motor control which is even older
than magnetic amplifiers -  the amplidyne.  This gadget was a close-coupled
[AC or DC] motor driving an AC generator (often 3-phase) with a DC field
coil.  Varying the voltage/polarity of the DC field controlled the resultant
AC voltage and phase relationship.  The amplidyne generator output then
drove a servo motor (usually 3-phase).  The amplidyne was popular during
World War II for controlling search radar antennas (PPI display).  Amplidynes
were well-described in the MIT "Rad Lab" series - which was still required
reading when I got my EE during the 60's.

<>  Larry Lippman @ Recognition Research Corp., Clarence, New York
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