RS485 meets Radio.

Presenting a less-wires approach to automation and computer control of radio equipment

By: Kerry Richens (VK1KRF) http://www.qsl.net/vk1krf Thanks to B&B Electronics http://www.bb-elec.com

Preamblestick to a microprocessor family and get the most out of it

Modularise circuit boards and designs so that they can be used in many applications

standardise pinouts, layouts, software routines

A one chip microcontroller can be considered as a customisable IC

eg: why buy a $16.00 Stepper motor controller when a $1.20 PIC16C56 can do the job

an $11.00 hex keypad decoder is not a bargain if you can do the job better with a $1.20 Micro

BY the way: The PIC acronym "Programmable interface controller/Circuit/Chip"

Don't be affraid to have more than one Micro (Customisable IC) on the board

Too many hardcore programmers out there telling us what to do

Why?

Automation is what I do This project stemmed from my desire to convert an

old security camera pan/tilt head into a satellite tracking rotator

Ever run out of ports for rotators rig controls modems TNC’s mouses etc?

Sick of wiring up 8 wire rotator cables? Like home-brewing? (Hic!!) Would you like all remote devices on the one cable

Topics of Discussion

My Radio Shack/ Workshop Background on RS422 and RS485 Converting RS232 to RS485 The Benefits of RS485 Making it Robust Programming DDE

Devices controlled by RS485 in my Station

Dual Axis rotator with 2m crossed Yagis, 70cm Helical, 2.4GHz down converter.

Hills rotator. 2M Phasing Harness. 5 port,3 port,2x 2 port remote coaxial relays. Preamp bypass relays for 2m, 70cm and 2Ghz. FT707 Digital VFO (on the workbench). FRG9600 on it’s own serial port (At Present).

Phasing harness and preamp control.

Remote Coaxial Relays

Dual Axis Rotator

No calibration potsNo calibration pots 2 IC’s2 IC’s NetworkableNetworkable No ADC (Explain Pot Command)No ADC (Explain Pot Command) 22ndnd Order Polynomial linearising in Order Polynomial linearising in

16 bit integer basic16 bit integer basic

Background on RS485 USB, Older 2Mb networks like Lantastic Building management, Dedicated print networks Security Systems, Camera Control.

RS485 levels

Benefits of RS485

Multidrop: 32 devices on a single line without boosting Runs on a single 5 Volt rail Data-rate of 100KBps at 5,000 Feet Differential line means it has High noise immunity Easily implemented Can be easily made robust in harsh environments

The actual data format and type of network can be any level of complexity (Master Slave is the easiest)

Converting RS232 to RS485

There are 2 types of send control systems.

Automatic

RTS/Software

Schematic of my Converter

The 75176 Line Transceiver

An example of a simple network

Active Termination

When the Master is inactive the line is completely tristated.

The line must be actively forced to a ‘0’ to ensure that noise does not present as data to the slaves.

Common Ground Surge Protection An example of single wire protection.

Four Line Surge Suppressor

Optical Isolation

Visual Basic and the real world

A Visual Basic program can send and receive data from other programs via Dynamic Data Exchange (DDE)

Visual Basic can send and receive data via the MSComm Visual Basic Extension (VBX)

Examples of programs that support DDE Winorbit satellite tracking Mixw digital modes Microsoft Office

VB object properties

My Station Control Panel

The possibilities are endless

Weatherstations Mast Lights Rig control including homebrew equipment Power control and monitoring Antenna Tuning units If it doesn’t work, Put a Microprocessor in it Imagination is more important than Knowledge