Détails technique sur le système PEC

Technical details about this PEC system

 

Description des circuits électriques actuels: (electrical scheme)

 Le système est composé d'un câble partant du port parallèle, connecté directement à la prise RJ12 (6 contacts) du panneau avant du LX50 (Autoguider). De plus, un petit circuit avec deux opto-coupleurs permet de piloter les deux mouvements de correction AD+ et AD- (commutation à la masse). Un piquage par domino a été créé sur le fil retour du codeur et entre par la broche 13 du port parallèle (Sub D 25 points). Ainsi, la position de la vis est connue à chaque instant par le micro-ordinateur. Ceci permet d'enregistrer et de commander ensuite la correction nécessaire pour chaque position de la vis. (Une correction par tour moteur).

The system is composed by a cable between parallele PC port and RJ12 (6 pins) in front of the LX50 (Autoguider). Moreover, a small circuit with 2 opto-couple devices allow to pilot the two correction movements RA+ and RA- (mass commutation). A connection on the return information of moteur encodeur is linked to the pin 13 of the parallele port (Sub D 25). Like this, the screw position is allays known by the computer. This way is used to record and following play the needed correction for each screw position. (One correction by motor turn).

 

 Voir aussi les plans du LX50 - LX50 scheme 

Notes about design : The opto-couplers used here are TIL111 (a bad and old component). Therefore, these units are suffisant to command LX-50 inputs autoguider. All others opto-couplers can be used. I think they are necessary to command the LX-50 by the computer // port. In fact, RA+ and RA- input's autoguider must be put to 0Volts to achieve a LX50 motor correction (a button will be just suffisant in manual mode).

In an other way, if LX50 inputs are kept to the 5V output // port when we don't want to command correction, I think this can push 5V computer in the 5V LX50 (Not sure => opto-coupler security!!!).

See also notes about programmation.

In order to connect opto-couplers :

Anode :

to // output port (pin 3, 4, 5, 6 DB25)

Cathode :

to 0 V // output port (pin 1 DB25)

Emitter :

to 0V meade (pin 2, RJ12)

Collector :

to autoguider input (DEC+, DEC-, RA+, RA-)

Base :

Not Connected

You can use any opto-coupler (like T4N36, TIL111...).

The pin 13 of the DB25 is connected to the encoder ouput of the LX50:

There is two methods to do that,

- 1) insert a connector on the white wire in the LX50 main box between the white connector of the main board and the ouput of the photo-diode. Like this, you can pick in // the encoder information (+5V).

- 2) fix a strap on the LX50 main board between pin 1 of the RJ12 autoguider connector and the pin 2 of JP5. Notes that the pin 1 is not used by Meade!

 

After, you have to found a RJ12 connector (6 contacts) with a 6 wires cable (see an electronic retailer, and ask him to "plug" the wires in the RJ12).

I prefered the second solution : it's lighter.

For the gear, it's a bit more complicated : it's necessary to connect a wire between pin 3 of the UDN2993B and the pin 12 of the DB25.

 

Programme sur le PC: (PC program)

Vous pouvez obtenir les fichiers sources et exécutables zippé. Pour cela, cliquer sur "Télécharger" (15 Ko).

 

For the program signification : I'm not sure! It's work, but Meade microcontroller achieve some corrections backlash after mine correction.

Notes about programmation : This sofware is developped under Turbo Pascal 6.0 on DOS plateform.

This schematic is for recording errors and play them back with the PC and software. Details : the RA corrections are introduced by pressing the "w" and "x" buttons of the computer. In this way, the sofware gives signals to the autoguider port of the LX50 in recording first and in reading second.

For the moment, this program provide only 1 cyle shaft : just to try.

Vous pouvez obtenir un pack de développement zippé. Pour cela, cliquer sur "Télécharger" (583 Ko).

 

 

Electrical PEC diagram (project):

 

 This diagram is used in the sofware above.

Future platine électronique ? :

 

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