OnStep powered Go-To Star Tracker

thingiverse

GoTo Star Tracker Mount - Powered by OnStep ==================================== By GuitsBoy at (Gmail, CloudyNights, OnStep) CAUTION: This is still in heavy BETA mode. Continue at your own peril. Please tether your camera and/or anything you dont want to smash on the ground if something breaks, delaminates, slips, moves, twists, disintegrates, or exhibits any other unexpected behavior. The documentation and assembly instructions are very poor. If you've managed to figure out how to 3D print in general, then you should have no trouble assembling this thing after looking at a couple pictures. Alt-Azimuth Adjustable Base can be found here: https://www.thingiverse.com/thing:5411792 **What is Still Under Development** - Cover for Electronics Most materials / components can be found on amazon, though they will be more expensive than ebay or AliExpress. **Bill of Materials** - WeMos ESP32 board - CNCv3 Shield - (2) NEMA 17 Stepper Motor, 1.8 degree - LV8729 Stepper Driver, TMC2209 under testing - (2) 5mm x 90mm shafts - (4) 6804zz Bearings, 20x32x7 - (4) 605zz Bearings 5x14x5 - (2) 18mm OD x 10mm ID x 300mm long aluminum tube - 12.7mm aluminum rod - (2) GT2 Belt - 158mm - (2) GT2 Belt - 400mm **Optional Materials** - 15T or 16T Alloy GT2 Pulley - 60T Alloy GT2 Pulley - Metal Vixen Dovetail Clamp - Gates GT2 timing belts (158 and 400 mm) - ABEC5+ Bearings **Misc Hardware:** - M3 Socket Cap Screw Assortment M3x8, M3x12, M3x16 - M2-M6 Grub Screw Assortment - 1/4-20 Threaded Insert - Counterweight (1/2" bore) or adapter - Misc M4, M5, M6 socket cap screws for saddle clamp **Design Notes** I tried to keep the price point down to around $100 USD, not counting filament or a tripod. That probably requires printing your own 15/16T and 60T GT2 pulleys, and a vixen dovetail mount. But for higher precision, I suggest going with the metal upgrades. I wanted to keep both the RA and Dec housed in the same body, so we wouldnt need a bunch of wires. And I went with a "sidewall and bearing block" layout to keep things modular. That way, if I or someone else decides to re-design a component, we only have to replace the single component, not reprint the entire body. I originally intended to use 20mm axis shafts, however they are slightly larger than the ID of the bearing. Rather than turn them down, I incorporated shims into the shaft collars to allow the 18mm shaft to ride on the 20mm bearings. One more important note. I did not add threads. Anywhere. All plastic holes are merely slightly undersized, and the screws cut their own thread. I havent found 3D printing such small threads to be reliable, and actually find having the screw cut it's own threads to work better. Ive used this method for a few years without any trouble. But just wanted to give you the heads up again it. **Choosing What to Print** Youll always need these: - Side Plate - Side Plate (Mirrored) - CW Block - (2) NEMA17 Bracket - (2) Axis Block - (2) Axis Shaft Collar - (2) Axis Shaft Shim Youll also need to choose which large pulleys to print. You can calculate your spacing here: https://www.technobotsonline.com/timing-pulley-distance-between-centres-calculator.html 91 to 92 mm spacing is nice, as long as your stepper motor wires/connector is not squished against the NEMA17 block. If you lave an obtrusive connector or wires, you might want to increase pulley spacing to 95 or 96mm. My first iteration used 15T and 168T pulleys for 96mm spacing, but I have since moved to 15T to 174T at 91mm spacing. I'd start with something in this area. Really, anything in the 15-16T x 164-176 range should work well with a 400mm belt. Let your stepper motor wire/connector determine how much space you need. Choose the right size for your application, and print two of them. They are the same piece for each axis. Youll also need to print either the "Dovetail Clamp" part, which is a vixen style dovetail clamp, or youll need to print the "Saddle_Block" part which is simply a provision for you to mount your own alloy dovetail clamp. I highly recommend buying metal 12T, 15T or 16T small GT2 pulleys. And to a slightly lesser extent, the 60T as well. I believe the larger axis pulleys can be printed without much added periodic error. But if youre really trying to cut costs, you can print the 15T and 60T pulleys included. Youll need to add a spacer on top of the output shaft coming out of the NEMA17 bracket (gearbox). The spacer is needed to get the small pulley to teh same height as the big pulley. You may ned to tweak this a bit taller by stretching it in your slicer. Its a very quick print. Lastly, youll need a way to connect your tripod and hold the RA shaft, which supports the entire tracker. I printed a simple 45º wedge that will hold the RA shaft. The shorter sides have a ~10mm hole, which I used to add a 1/4-20 metal insert. This allows for the relatively short threads of my tripod to grab into the metal insert rather than directly into soft plastic. Eventually I hope to design a proper adjustable Altitude-Azimuth base to replace this part. **Printing Notes:** Creality Ender 3 v2 Material: PETG Nozzle Temp: 250º Bed Temp: 75º Bearing blocks were printed at 30% infill, 4 layer walls, top, and bottom. Sidewalls and Pulleys were printed at 50% infill, 5 layer walls, top and bottom. The one sidewall needs to be mirrored in your slicer to get the opposing side. The 5x8 spacer can be stretched vertically in your slicer as needed **Assembly** It should be pretty easy to figure out how this thing goes together simply looking at the pictures. I'll try to sum up the steps anyway. *(2) Gear Box Assemblies* - Two 605zz bearings go into each NEMA17 block - Stepper motor goes into the cutout. Loosely screw it in place. - Attach 15T pulley on the stepper motor shaft. - Insert 5mm x 90mm shaft through both bearings. - Attach 60T to the driven side of the shaft - Attach 15T pulley to the NDS side of the shaft - Put belt between the 15T and 60T, tension belt by sliding motor and snug into place. - Do the above a second time. *(2) Axis Block Assemblies* - Stuff a 6804zz bearing into each end of the Axis Block - You may want to cut your DEC axis shaft to 150mm length. I left my RA shaft full length. - Fasten the Axis Shaft Collar (larger diameter) flush against the bottom of the axis shaft. - Insert the axis shaft through the bearings in the block. - Slide the Axis Shaft Shim down the shaft and into the bearing. - Large puley goes down onto the shaft. Snug everthing up so there's no play. *Counterweight shaft* - Pretty simple, just stuff the CW shaft into the CW block. - One side of the block is slightly shortened, to allow clearance for your RA stepper motor wire between the Axis block and the CW block. - For permanent install, use eight m5 grub screws from the all sides. - For quicker disconnect, use M5 grub screws from the narrow sides only. These will be accessible through the side plate windows. *Side plates* - Dec Axis Block gets attached to the sidewall plate corner (narrow side) with the collar pointing inward, and large pulley facing outward. - RA axis block gets attached to the middle of the long side of the side plate, shaft collar side facing inward, and large pulley facing outward. - Both gearbox assemblies are mounted on the slots. Leave them loose so y ou can adjust main belt tension. - Counterweight shaft block gets attached to the side plate where the two small windows are. - Run stepper motor wires up to the area for the control boards. - Repeat with the other side plate. - Place belts between output shaft of the gearbox assembly and the large axis pulley. Tension belts by moving the gearbox assembly in the slots, then snug down. *Tripod and Saddle* - Fasten saddle block to the Dec Axis shaft - Slide RA Axis shaft through the wedge piece and tighten grub screws. **Electronics / Control** This part gets kicked over to the OnStep project. If youre unfamiliar, the main wiki should get you started. https://onstep.groups.io/g/main/wiki This mount was designed to use the WeMos R32 / CNCv3 boards with OnStep. You can find more detailed information here: https://onstep.groups.io/g/main/wiki/19670 But to sum up, its mostly just snapping the two boards together, setting the microstep jumpers as needed, dropping the stepper drivers into the sockets, and connecting the stepper motor wires. Youll need to figure out how to get 12v to both boards. I typically solder some wire from the bottom of the wemos board, and insert into t he +/- terminals on the CNCv3 board. Or you can run 12v into them both individually. You can also power the WeMos via USB, however I try to use the USB socket as little as possible, since its delicate and prone to break off. For this reason, I prefer ASCOM over bluetooth. Youll need to download the Onstep code, edit the config, and flash it to the WeMos. There's plenty of documentation available in the OnStep wiki, or on their users board. When flashing the config, dont forget to enable bluetooth if you plan to use a BT connection from your phone or laptop. The included pulleys were created from Parametric pulley - lots of tooth profiles by droftarts January 28, 2012. It can be found here: https://www.thingiverse.com/thing:16627 Some basic settings are as folows: Teeth 172 Profile 12 shaft 18.3 m3 dia 3.6 hex 4 flats 6 depth 0 retainer 1 ht 1 idler 1 ht 1 pulley t ht 7 pulley b ht 10 pulley b dia 40 nuts 4 angle 90 distance 0 OK, That's about it. Feel free to ask any questions, or give me any feedback/suggestions you might have. Thanks and clear skies!