Re: Re: Brushless Servo

Hi List.
Re Tape drive motors.
The unhelpful answer is BOTH steppers and motors are used, and it VARIES.

Reel drives are usually DC motors but not always, sometimes AC mtors are used.
These (AC & DC) are usually fairly low power often 24/28 volt.

The capstan motors which actually drive the tape when reading or writing,
are either DC or stepper motors, and the DC ones at least will usually have
some kind of encoder attached, but usually only giving a speed output, ie no
quadrature output.

To an old HiFi buff the concept of a stepper driving the tape was a total
contradiction in the world of electronics - but this is digital not analogue.

Jim Gregg

At 06:48 10/10/99 +1300, you wrote:

>From: "Raynor Johnston" <rhj-rbj@...>
>
>Yes Jon... absolutely right with closer inspection it's dca is 2.1 amps so I
>guess not a lot of use for too much.
>
>On this list i think people have mentioned that the older large central
>computer processors are a source of quality motors suitable for axis drives.
>The suggestion was that the tape drives..the sort that drive those big tape
>reels on the vertical face of the processor...so beloved in 'Hollywoods
>James Bond mad prof control rooms ilk' are quality servos or steppers. Can
>anyone expand on that are there any names that have those ie. IBM
>models......etc. so I can take a look about here and are they steppers or
>servos?
>thanks all
>Raynor Johnston (NZ)
> -----Original Message-----
>>From Jon
>>Well, the info is confusing. Is that REALLY 21 Amps? Seems VERY excessive
>>for a photocopier. Anyway, 30 V x 21 A = 630 Watts in, should be able to
>>produce 600 Watts out, at least. So, either the 21 Amps has lost a decimal
>>point or this motor has an enormous peak current rating, with a dismal
>>continuous rating (39 W). I don't know what sort of XYZ robot you are
>>planning, but this might be able to operate a gripper or something, but not
>>too good a prospect for an axis drive. What is the DC resistance of one
>>of the windings?
>>
>>Jon
>
>>Welcome to CAD_CAM_EDM_DRO@...,an unmoderated list for the

discussion of shop built systems in the above catagories.

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