RE: [APML]: 201XT electrical interface ?

[Michael Hart <mhart@netexpress.net>]

On Friday, August 29, 1997 8:36 AM, Bratislav Curcic wrote:

> 
> 
> Hi mob,
> 
> I know that this list has some very experienced guys as far as 
> Meade's 201XT which I'm contemplating to buy. I have checked the
> archives but couldn't find the answer to my question.

> Now, the question : does anyone know (or does anyone know the person
> who knows, including Meade engineers) about the layout of phone
> connector used on 201XT (I believe there will be X+, X-, Y+, Y- and
> ground/power) ? I also need to know what is the logic used (positive, i.e.
> logic 'high' activates movement or negative) ? And what that is the
> electrical side of it (TTL, CMOS, something else), and how much current
> will drivers source/sink ?

All the pinout information you need is in the latest 201XT, 208XT, 216XT,
416XT and 1616XT manual, perhaps on Meade's web site as well.
(1) +5v, (2) Ground, (3) Left, (4) Down, (5) Up, (6) Right.  If you have
high current needs I'd use an electronic relay such as the Meade 505.
As to the "logic" used, you can plug the 201XT into a Ultima 8" hand
control jack; the result is the scope moves in the same directions
as when using the hand control. 

> 
> The reason for asking is simple - as with my telescopes, my drive 
> correctors and mounts are homemede too. So I have to know how to interface
> 201XT to my drive corrector. Before anyone jumps onto me; I'm an electronics
> engineer by profession and telescope maker for more than 20 years. So I
> _do_ know what I'm doing. I just hate to void the warranty the very first
> day by opening the unit just to find out these things. If I run into 
> 'proprietary information' crap I'll just go for an used ST4.

Any manufacturer who readily gives out details of their product also risks
that those details will be used by a competitor to improve their product
without the expense of hiring electronic engineers such as yourself to do
the engineering.  In addition, a knowledgeable user can often be more dangerous
that a novice.  Recently, several hundred laptops were sent out to engineers
in a fortune 100 company fully configured.  Interestingly, all computers that
needed to be returned were from users whom classified themselves as
experts.  None were returned by novices.  Thereafter, a ban was made on
installing personal software.

Furthermore, a particular manufacturer may be selling their product abroad
where Patent enforcement is difficult, so proprietary information helps
protect them from those who would copy their design without reservations;
a painful lesson I learned too late.  Thereafter, I decided to make available
only enough information needed by a typical user of our product.

> 
> And yes, I know that ST4 is better, but I like size and power consumption
> of 201, and my guide scope is adjustable so I can always pick star bright
> enough.

The ST-4 is perhaps better in many ways, but not all.  The 201XT is very
light, compact, stand-alone and has very low power consumption
(all you need is 12 VDC, no power supply bricks or control boxes).

The 201XT at around 8 ounces is arguably the lightest autoguider available
that may well be an excellent choice for off-axis guiding due it's light weight
that minimizes off-axis guider port flexure problems.  This helps when you
use a reticle eyepiece such as the Meade 9 mm that is very close to
parfocal with the 201XT autoguider to center the selected star.  With the
light 201XT, you can remove the guiding eyepiece and insert the 201XT
that results in star coordinates indicating the star very near the center of
the 201XT CCD chip.  Heavier autoguiders designed for separate guidescopes
often cause enough flexure on off-axis guider ports that finding the star
on the chip at all can prove difficult.

> 
> Bratislav
> 
> 


-- 
Michael Hart
Husen Observatory
mhart@netexpress.net