Build your own custom R/C system!

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The MicroStar 2000 is an 8 channel Radio Controlled Transmitter design that you can build and use to upgrade your favorite old transmitter. The transmitter shown is a Proline Custom Competition radio that I have upgraded. This design consists of two major components, the Encoder, and the RF Deck.

 

 


The Encoder

The Encoder is responsible for reading all of the switches, buttons, and stick positions and developing the modulation signal that is sent to the RF deck. This is a computer radio and the Encoder uses the MicroChip PIC18F8722 mircocontroller. This is a wonderful part and contains 70 digital IO lines and 16 10 bit ADC inputs. This allows the MicroStar 2000 to be a 1024 system! Most of the features are similar to the ACE MP8000, but this is a new design. I have written all of the software, in assembly language, the firmware takes about 34K of memory. The PIC18F8722 contains the entire RAM and EPROM used for operation of the system. The flash program memory is also used to save the aircraft setup data. The features of this system are listed below:

  • 1024 resolution
  • Shift programmable
  • 2 line 16 character per line display
  • Auto ID
  • Warning buzzer
  • 8 channels (programmable number of channels up to 8)
  • 3 mixer switches, 4 mixer functions per switch
  • Dual aileron, Flaperon, and Vtail mixing
  • Throttle preset
  • Auto trim
  • 6 Alternate aircraft
  • Right and Left snap roll buttons
  • Frequency selection built into encoder, when using my RF Deck
  • 3 dual rate switches; Aileron Elevator, and Rudder
  • PC computer interface built into encoder
  • Master/Student function
  • 96 model memory
  • Tach, using optional detector
  • Countdown timer with alarm
  • Voltmeter, TX and RX
  • Throttle Hold function
  • Idle Up function
  • 3.9" x 1.8" board size
  • Sub trims
  • Encoder software can be upgraded with no special hardware, only using the serial interface
  • All parts through hole, except the microcontroller, to support easy assembly

The mixing functions are more advanced than the ACE MP8000. You have the normal functions you see in the MP8000 but you can also do the following:

  • Indirect mixing; Mix two channels using a third channel to determine the mixing level.
  • Table lookup; This function allows you to define a 10 point lookup table to define any non linear function you like. Eight global lookup tables are provided as well as 2 tables specific to each aircraft.

The two-line display allows the name of your model to be placed on the second line. I also have a feature I call Auto ID. This uses the second line of the display to tell you what switch you just pressed. For example, when you switch the elevator dual rate switch to low the second line of the display will read "ELE D/R LOW". This way you do not need to label the switches and buttons. The second line is also used for the tach display.

Revision history:

The original Encoder was based on the PIC17C766. This included revisions 1 through 3 of the hardware and software versions 1.0 through 1.1. This version is no longer in productions and the 18F8722 version of the encoder, revision 4.0, is now available. This hardware revision used software version 2.0. The new encoder is hardware compatible with the revision 3.0 encoder. The same connectors are used on the encoder with the same connector names. The pin one orientation of the connectors is not the same so be careful if you are updating encoders.

Why did I develop a major update to the Encoder? There are several reasons that I have listed below:

  • The old PIC (17C766) is reaching end of life and is an expensive part. This PIC requires a EPROM eraser to clear its memory before you can reprogram and special hardware to reprogram. The new PIC uses FLASH memory and can be reprogrammed without any special equipment and the user can update the application in the field.
  • The new Encoder is significantly smaller than the old design. This allows installation in smaller transmitters. This has been a significant problems for a number of transmitter upgrade projects.
  • The old PIC's program memory was full and I could not add any new functions, this was a major factor in the redesign decisions. The new PIC is using less than half its available memory thus allowing addition of a number of new features. Here is a list of functions I intend to add in the near future:
    • Digital trims, this will allow any combination of analog and digital trims
    • Transmitter configuration upgrades to simplify programming
    • Advanced mixing features
    • Helicopter mixing, CCPM
    • 4 line display options
    • Graphics display options

Upgrading the revision 3.0 encoder:

If you have a revision 3.0 encoder and would like to upgrade to the 18F8722 version with all the new features you can install an adapter in a revision 3.0 encoder. To do this you need to remove the old PIC socket and install the adapter PC board with the 18F8722 in place of the socket. This is not a trivial job! Full details are available here Adapter installation instructions. I will do this install and checkout free of charge including the shipping costs and I will keep the old PIC and socket as payment for the install effort. Please check the products page for the price of the adapter board, the adapter comes fully assembled and programmed.

Building a revision 4.0 encoder:

If you would like to build a revision 4.0 Encoder there are several options:

1.) I sell blank PC boards, the details are on my products page. To build this you will need to solder in the PIC and its a 0.025" lead pitch part, so if you don't have experience with surface mount don't try it! The PIC is the only surface mount part on the Encoder.

2.) I sell PC boards with the PIC installed and programmed, again on my products page. The remaining parts are all through hole so its pretty easy to build. The documentation and parts list are on my downloads page.

3.) This is the best option, buy a full kit (includes everything you need, PC board with the PIC installed and programmed, display etc) for only $55! You can't beat this deal! You can get these kits by contacting Kees at This email address is being protected from spambots. You need JavaScript enabled to view it. . Kees also has other options so please contact him for details and visit his web site at http://www.qsl.net/k5bcq/MS2K/MS2K.html.

4.) Danny Miller (This email address is being protected from spambots. You need JavaScript enabled to view it. ) will build kits from Kees for only $20! He does very good work and I recommend this option if you are not up to the fabrication process. Danny will build and test the Encoder for this very reasonable price and if you have special needs are are not physically able to build an Encoder it may even be less. Danny will also build RF Decks. If you have specific needs please contact him for the details.

Note: I do not support nor do I authorize any use of the rev 4.0 Encoder by any manufacture for the purpose of profit. If anyone would like to use the rev 4.0 Encoder for resale in their products please contact me for authorization. You will find listed here anyone that I support, anyone selling products using my Encoder that is not mentioned here is doing so against my wishes.

The RF deck

The RF Deck is the device that is responsible for taking the modulation signal from the Encoder and generating the modulated RF. This RF Deck is designed around a National Semiconductor LMX2306 PLL. The details are pretty standard. The PLL must be programmed on power up and my Encoder provides this function. The RF Deck also allows you to use a small PIC microcontroller and a rotary switch to allow operation in a standalone mode. Here are the features:

  • AM or FM operation
  • 53.1 through 53.9 MHz operation
  • Channel 0 through 9, 50 MHz operation
  • Positive or Negative Shift
  • Lock/RF on LED
  • 1.75" by 2.5" board size

The RF electronics design is the most complex part of this transmitter. It’s not easy to meet the narrow band requirements of these systems. This designed has been analyzed using a spectrum analyzer to insure it meets the FCC requirements.

Status

PC boards are available to allow you to build you own encoder and RF deck. You will find the technical documents on the Download page and instructions on how to order PC boards on the Products page. I only sell blank PC boards, my technical data includes parts lists to allow you to build your own transmitter.

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Copyright © 2004,2005,2006 GAA Custom Electronics. All rights reserved.
Revised: 11/26/07