OnStep for Seben EQ3 mount

Adapting SEBEN EQ3 telescope mount or similar types to OnStep goto controller, by Howard Dutton project.

How to this working? See my video: https://youtu.be/mOXqw7EN8YE

• My OnStep Controller Box on base STM32 Blue Pill
• Alternative OnStep Cotroller Box on base MiniPCB2 and Teensy3.2
• Old OnStep Controller Box for on Arduino Mega2560 board
• FreeCAD sources on Github

Version 1.0 - 3D printed gears 54:16

• 1x RA motor is 17HS15-1684S-PG5 with Gear Rate 3.7:1 (1+46/17) :1
• 1x DEC motor is 17HS15-1684S-PG5 with Gear Rate 3.7:1 (1+46/17) :1

OnStep config.XXX.h for A4988 stepper drivers with 16 micro steps

• RA primary worm screw transver raito is 138:1
• DEC primary worm screw transver raito is 88:1

// Axis1 is for RA/Az // calculated as : stepper_steps* micro_steps* gear_reduction1* worm_reduction / 360 // : 200* 16* 54 / 16* (1+46/17)* 138 / 360 = 15342.35294 #define StepsPerDegreeAxis1 15342.35294

// Axis2 is for Dec/Alt // calculated as : stepper_steps* micro_steps* gear_reduction1* worm_reduction/ 360 // : 200* 16* 54 / 16* (1+46/17)* 88 / 360 = 9783.529412 #define StepsPerDegreeAxis2 9783.529412

// PEC, number of steps for a complete worm rotation (in RA) // calculated as : (StepsPerDegreeAxis1360)/worm_reduction. //: (15342.35294360)/138 = 40024 #define StepsPerWormRotationAxis1 40024L

Version 2.0 - metal parts and belt GT2 reduction 60:25

• 2x GT2 Timing Pulley with 60 Teeth and Bore 5mm for 6mm belt
• 2x GT2 Timing Pulley with 25 Teeth and Bore 8mm for 6mm belt
• 2x GT2 Timing Belt 6mm wide 2mm pitch 180mm-2GT 90 teeth
• 1x RA motor is 17HS15-1684S-PG5 with Gear Rate 3.7:1 (1+46/17) :1
• 1x DEC motor is 17HS4413AG5.18-X with Gear Rate 5.18:1 (1+46/11):1

OnStep config.XXX.h for TMC2130 stepper drivers with 32 micro steps

• RA primary worm screw transver raito is 138:1
• DEC primary worm screw transver raito is 88:1

// Axis1 is for RA/Az // calculated as : stepper_steps* micro_steps* gear_reduction1* worm_reduction / 360 // : 200* 32* 60 / 25* (1+46/17)* 138 / 360 = 21820.23529 #define StepsPerDegreeAxis1 21820.23529

// Axis2 is for Dec/Alt // calculated as : stepper_steps* micro_steps* gear_reduction1* worm_reduction/ 360 // : 200* 32* 60 / 25* (1+46/11)* 88 / 360 = 19456.00000 #define StepsPerDegreeAxis2 19456.00000

// PEC, number of steps for a complete worm rotation (in RA) // calculated as : (StepsPerDegreeAxis1360)/worm_reduction. // :(21820.23529360)/138 = 56922 #define StepsPerWormRotationAxis1 56922L

Auxiliary PCBs for this version:

• RA PBC design is on EasyEDA* DEC PBC design is on EasyEDA
• OnStep SHC (Smart Hand Controller)
• OnStep ST4 Handheld controller
• 3D printed - Small Travel EQ telescope mount
• OnStep for Sky-Watcher EQ5 mount
• My DIY Telescope
• Wood tripod upgrade for telescope with Eyepiece plate

Category: DIY