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[tg_quigley]

I recently acquired a practically new ETX90-M from a bid on shopgoodwill.com. When I received it and inspected it, I was surprised to discover that the optics appeared to be like new for a 1998 (as I determined) ETX. Yes, it’s got all the plastic, but when I compared it side-by-side with my 3.5 1959 Questar (with 10 year-old broad-band optics) the image quality is indistinguishable.

So, I decided to make it just a bit better. I took the entire scope apart, and I determined it might work with encoders. Let’s walk through the process and the re-engineering.

PARTS LIST:
2 - CUI-3132-1FT Cable w/ 5 Pin Connector, 5 Individual Discrete 22 AWG Wires
1 - ESP32S CP2102 2.4GHz WiFi Bluetooth Development Board
2 - SameSky (CUI) AMT102-v incremental encoders
1 - Bi-Directional Logic Level Converter 5V to 3.3V
4 - #4-40 x 1/2 machine screw
1 - #6-32 x 1 aluminum standoff
1 – ¼ x 1 nylon spacer
1 - #8-32 x 1 aluminum standoff (retap to 8-24)
1 - #8-24 x1/2 socket set screw
1 - #6-32 x 1 hanger bolt
1 - #6-32 nut & washer
1 – 3” knockout pipe test cap
Many F-F Dupont Connectors

REFERENCE SITES:
I copied the code from AstroStuff.wixsite.com and referred to the text in https://www.cloudyni...oders/?hl=magic

Follow the reference sites as to loading the Arduino environment, code compilation and uploading the ESPl32 dev board. Test all the connections and WIFI before proceeding. When using any encoder that has 5V input, you must use a logic level converter to connect the encoder inputs to the ESP32. I tried to just run the system on just 3.3V and the CUI encoders didn’t seem to work properly.

TESTING BEFORE ASSEMBLY
You will be wise to pre-assemble the encoders, level converter and ESP32. If you are using a breadboard to the testing be aware that it may not fit into the base. Since I chose to leave the original drive motor and circuit board, I ended up using the Dupont connectors to make all the connections.

ENGINEERING THE AXIS ATTACHMENTS:
The AZ axis on the ETX was a lag bolt! I used the 6-32 hanger bolt and epoxied the nut to the bolt. The 6-32 standoff was fitted with the white CUI sleeve, then tightened against the nut.

The ALT axis was easier although it required re-tapping the 8-32 standoff to 8-24, and then screwing in the #8-24 x1/2 socket set screw to the standoff. This unit will be attached to the existing ALT hub. The standoff was fitted with the blue CUI sleeve. The sleeve was flush with the end of the standoff. The encoder base was attached to the arm using the 4-40 screws.

WIRING THE ALT AXIS
The ALT axis 5pin connector cable wires lead from the encoder through the arm underneath the metal plate that the arms attach to and through a hole drilled on the side of the center hub of the upper half of the base. The cable is NOT connected yet, as it needs to run through the hole drilled in the bottom half of the drive base.

WIRING THE AZ AXIS
The AZ axis 5pin connector will connect to the encoder after the drive base is assembled.

INSTALLING THE ENCODERS
The arm assembly will have the ALT encoder wires threaded through the center hub hole. Use the modified ALT axis and mount the encoder to the axis hub, connect the 5 pin connector to the encoder. Using the new AZ axis hub/attach bolt reconnect the top and bottom halves of the drive base, and tighten the assembly down, not too tight, try to make it spin smoothly without play.

The AZ axis encoder will need to have two 6MM high spacers made using the nylon spacer to raise the encoder up from the hub. Attach the encoder to the axis and plug in the 5 pin encoder wires.

FINAL ASSEMBLY

Attach all Dupont F-F connectors from the encoders to the logic leveler, and from the logic leveler to the ESP32. Without a breadboard, I had to do a lot of soldering of connectors to access the 5V and ground pins on the ESP32.
I would recommend ditching the motor and board and making a nicer set of connections.

OPERATION
Follow the other write ups on connecting to SKYSAFARI.

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