Alcor - A Microcontroller-Based Control Circuit for Conventional AC Telescope DrivesMany telescopes still use 50- or 60-Hz AC motors controlled by variable-frequency AC power sources. This paper describes a programmed microcontroller that can be used as the oscillating element in such drive controllers, providing efficient two-phase drive, smooth frequency changes, and precise sidereal and lunar rates.
NOTE ADDED 2011: This project is over 10 years old and the microcontroller needed for it may be hard to get.
Use the PIC16LF84A chip and the '84A versions of the .HEX files.
The .HEX files have been zipped because some browsers would not download the original versions properly.
Please note that the published paper is a reference design intended to inspire other designs, not "plans" to be built by people who do not understand the circuit. If you do not understand the circuit and are not equipped to troubleshoot it, please get help locally from someone more experienced. Many ALCORs have been built and used successfully, but this is not a commercial product and is not supported by anyone.
If you cannot program PICs yourself, ask for help locally and on the Internet. Vendors that sell chips are often able, for a fee, to program them. Dontronics no longer does this, but you may be able to find others that do, or buy your own programmer.
NOTE ADDED 2005: The PIC16F84 and PIC16F84A are not interchangeable. The assembly-language program must be assembled for the right one. Be sure you download the version that corresponds to the processor you are using.
The PIC16LF84A is a complete substitute for the PIC16F84A and is what I am now using for new Alcor circuits. It uses the same .ASM and .HEX files.
- Paper in PDF as published in Journal of the B.A.A.
- Original manuscript (same paper) in PDF
- PIC16F84 code (in assembly language) (OBSOLETE CHIP)
- PIC16F84 code (in .hex format) (OBSOLETE CHIP)
- PIC16F84A code (in assembly language) (USE THIS VERSION)
- PIC16F84A code (in .hex format) (USE THIS VERSION)
- Fast-slewing version of Alcor (60 Hz only) for '84A (in assembly language)
- Fast-slewing version of Alcor (60 Hz only) for '84A (in .hex format)
- LX3 version for PIC16F84 (in assembly language) (OBSOLETE CHIP)
- LX3 version for PIC16F84 (in .hex format) (OBSOLETE CHIP)
- Alcor circuit with dec. motor relays, as built for the Atlanta Astronomy Club
- Schematic circuit diagram of Meade LX3 telescope base
- Programmed chips are NO LONGER available from Dontronics in Australia, but other vendors can still do this.
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