Hi,
i would like to clarify what the project openDrive is all about.
It's:
- a universal telescope mount control
- open source and open hardware (GPL) community project enabling amateur astronomers to program their own ideas and to learn how things work. (maybe establishing some kind of standard, so folks can build up upon the work of others in the field of electronics, programming and astronomy and don't need to invent the wheel again and again)
- a DIY project with free schematics and open source firmware
- modular and extensible with various robust PCBs serving different tasks connected through a bus with power, SPI and I2C etc. (80mm x 100mm PCBs linked with a stackable 64 pin connector)
- powerful enough to drive bigger mounts/motors accurate and fast
What openDrive is NOT:
- a faked DIY project with no building plans or kits available
- running proprietary firmware with no way to fix bugs or add extensions to it yourself
- commercial (anybody could of course sell PCBs and part kits or even assembled boards)
So far the following features are planned or have already been implemented (Take a look at this video:
http://www.youtube.com/watch?v=PWyo-2PWCHA):
Stepper motor driving board:
- 64 micro step resolution
- up to 30V operation
- high current (2.5A_eff/coil = 5A_max/motor)
- fast slew (more than 20rps with a Escap P530 motor at 24V)
- build in sequencer with internal calculation of acceleration ramps etc. (pictures: https://github.com/selste/openDrive/wiki/Hardware)
MCU board:
- based on the ethersex project: www.ethersex.de or https://github.com/ethersex/ethersex
- AVR ATmega1284P mcu with 128kB flash and 16kB ram
- Ethernet:
- with an internal webserver for configuration of mount parameters etc.
- control of the mount through LX200, INDI or ASCOM (youtube)
- bootloader for firmware upgrades via network
- small object catalog on dataflash
- RTC with battery backup
- 2 and 3 star alignment
- input for low cost GPS receivers for accurate time sync and location info (like the MediaTek MT3329, http://shop.trenz-electronic.de/cata...roducts_id=759)
- synced to radio time signals (f.ex. DCF77 in Europe)
- PPEC - permanent periodic error correction - with hall or opto sensor at the worm
- ST4 guiding input
- focuser stepper motor connected through I2C (TMC222 based)
- multiple 1-wire temperature sensors (DS18B20)
You could of course build your cpu boards hw & sw based on Arduino
(The ethersex sw will also run on Arduino hw, as long as the mcu is equivalent).
Or use some completely different mcu like pic, arm, etc.
I didn't choose Arduino because:
- the (original) mcu boards are to expensive for what they offer
- very limited memory in the affordable hw versions
- did not find any complex software projects using it
- many many very useful things are already implemented in the ethersex sw. http://old.ethersex.de/index.php/Feature_Liste (in German; an English wiki is on it's way: www.ethersex.de)
Handbox:
I/O-board:
- various I/Os for example for a dew heater (PCA 9532 based)
Power-board:
- switching converter from the input voltage to the internal 5V supply
- fuse
- battery deep discharge protection
- (initially there were plans for a internal (12V->30V) 150W power converter ;-), but these were abandoned because of the availability of low cost notebook power converters (12V->24V) on the market)
There are plans for a linux add on board (probably based on raspberrypi),
[as a second stage but only if enough folks participate in the first]:
- webcam (usb) based auto guiding
- (automated) pointing model generation for stationary observatories
- large object catalogs
- camera control
How to get started?:
I hope to find participants for this development in the very active Australian DIY community. (I'd like to visit you guys at the other side of the planet some day...)
Michael
P.S.
It's totally o.k. to hear critical comments about this concept but I'm also aware that some people will try to badmouth it because they like to sell their own stuff...
