Finally got around to ordering some better motors. Arrived this morning: 3 NEMA 23 type Steppers. 1.8deg per step 0.4A but more important is the power – 34N/cm. thats about 200 times stronger than the last lot and they feel it, very hard to stop.
So wired them with connectors and plugged into the Driver pcb. Tweaked the software and uploaded it. Made up some quick brackets to hold the motors to the mounts. Ran the tests. Absolutely perfect!
Movement is quite quick and accurate. Driver runs at 200 steps per second with a 1.8 deg motor and 50:1 gearing I get 10,000 steps to 360 degrees or 0.036 deg accuracy. Full 360 deg turn in 50 seconds.
Youtube video for visual show:
Cold, rainy and cloudy outside so no practical testing, still happy with the result though.
All I need to do now is tidy it up and weatherproof it a bit more.
Future changes will be to remake the whole mount out of metal (aluminium) instead of wood. Wood made it easy to chop and change but now it’s pretty set metal will give it more solid movement and better life (and look better 😉 )
Also intend on adding a Bluetooth module to remove the controller wire and to improve the MCU board. I have an NXP Arm proto board here I’d like to use. Gives me the ability to make it more responsive and featured.
Thats all for today.
Long time no see? 🙂 …
After a long delay due to high workload over xmas sales and having to move house (again), the telescope goto mount progresses.
The man-cave is now mostly setup as a workshop and various projects begin once again.
*A-hem* back to the project 🙂 …
Programming the PIC Micro goes into gear with the motors now controlled by an interrupt service routine. The timer is on about a 5ms tick. each tick it tests the speed setting of each of the 3 motors. If the motor is within 10 degrees of the aim the speed is set to slow by the main routine else it’s fast. The ISR will either tick the motor over every interrupt on fast, or every 4 ticks on slow.
Perhaps a tad rough but its a start and it works 🙂 (well after much debugging and swearing as usual ).
With only 5ms per tick I needed to keep the ISR code as simple as possible, my first attempt had it too slow and there wasn’t enough time for the LCD code in the main routine to work!!!
Also I found the motors turn much smoother and stable with the ISR control. Though I’m not convinced the steppers I chose will be strong enough for the end design but at least they are easy to swap over.
For those of you who may be interested in the code just let me know in the comments, if needed I’ll clean it up and post it.
So onward to sleep 🙂 back again soon I hope!
As the above YouTube video shows, circuit now has 3 stepper motors under individual control. Serial IO commands can be sent to set each of the 3 motor positions independently.
Motors will be used for Altitude, Azimuth and focus.
Yes this progress took many modifications both hardware and software as well as much swearing and coffee.
Now I am happy to end another day. Next aim is to put the motors on a timer control so I can control their speed. Then its on to mounting them on the actual mount itself.
Until then, enjoy!
Greetings, work on my DIY Telescope GOTO mount continues again.
ET-Base40 Proto board with PIC16C877 cpu, 2-line LCD Display, Stepper motor and driver board. Wired up for first test.
After several attempts re-learning ‘C’ to program the pic, I have the motor on a swing with the rotation on the LCD display.
Unfortunately due to working on it late at night a couple night ago, I managed to fry one driver chip and destroy a motor. Oh well, progress is not without some costs. (about $7, not really a concern)
Here’s a youtube shot of the action: http://www.youtube.com/watch?v=MIUbCfqXFwA
Time to get back into it, more work to be done!
Damn it was cold this morning, had to get a jug of water to wash the ICE off the windscreen of the car so I could go to work 😕
The Dashboard display read 2 Deg C as I left for work… sure is winter!