RE: RE[2]: ATM I just recieved a new Byers gear

["Antonio de Ugarte Postigo" <ugarte@mad.servicom.es>]

Dwight,

    Yes I have 220V 50Hz, that is why I would like to build my own circuits.
I don't understand when you say that the motor would get hot when running at
a slower rate, why is this?
    I am going to have a look through the archives to see what I can find.
    Thanks for your message,

                    Antonio de Ugarte Postigo
-----Mensaje original-----
De: Dwight Elvey <elvey@hal.com>
Para: ugarte@mad.servicom.es <ugarte@mad.servicom.es>
Fecha: jueves 17 de diciembre de 1998 19:21
Asunto: RE[2]: ATM I just recieved a new Byers gear


>"Antonio de Ugarte Postigo" <ugarte@mad.servicom.es> wrote:
>>
>> I think it is a Syncronous motor, it is 115V and 60Hz.
>> Out of it come 4 wires: Two of them must be joined together, and you
apply
>> the voltage between these and one of the others (which are conected
through
>> a big capacitor, deppending the way in which you want the motor to turn.
See
>> the drawing:
>
>Hi Antonio
> This would work with one of the inverter designs mentioned in
>the archives someplace. For guiding, you want to be able
>to change the speed to 150% and 50%. The motor you have
>would be OK at 150% but might get hot running at 50% for
>too long. Some use 0% and 200% for guiding as well. The
>problem is that at 200%, the motor might not have enough torque.
> What you have is a capacitor phased motor. The capacitor
>causes a phase shift on one of the windings that causes
>the armature see a rotating field. The speed of the rotation
>is caused by the frequency of the voltage applied.
>Many of the circuits use a 555 as a frequency reference.
>These are analog parts and suffer a little from temperature
>variations but things like periodic error in the telescope
>mounts often dominated guiding anyway. One could use a
>crystal controlled frequency reference but there is
>little to be gained by this.
> One of the power inverters, such as Orion sells would work.
>They have a 140 watt unit for $59. One can get better
>prices if one shopped around. I've seen this size unit for
>as little as $19. The problem with these is that the
>frquency is usually also controlled by a 555 type circuit
>but it is not user adjustable. These circuits are often
>floating on the output voltage and can be quite dangerous
>to play with. I have modified a similar unit for use
>on an old Celestron mount I have but without a good
>understanding of the specific circuit, it would be difficult to
>do in the general case. Buying one of these inverters
>would be much more economical than building your own
>but if you need guiding, it might make sense to build
>one.
> Is your local power 115 Volt 60 Hz or are you one of the
>50 Hz areas?
>Dwight
>
>