RS 485 meets Radio n n n Presenting

RS 485 meets Radio. n n n Presenting a less-wires approach to automation and computer control of radio equipment By: Kerry Richens (VK 1 KRF) http: //www. qsl. net/vk 1 krf Thanks to B&B Electronics http: //www. bb-elec. com

Preamble stick 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 PIC 16 C 56 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? n n n 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 n n n My Radio Shack/ Workshop Background on RS 422 and RS 485 Converting RS 232 to RS 485 The Benefits of RS 485 Making it Robust Programming DDE

Devices controlled by RS 485 in my Station n n n Dual Axis rotator with 2 m crossed Yagis, 70 cm Helical, 2. 4 GHz down converter. Hills rotator. 2 M Phasing Harness. 5 port, 3 port, 2 x 2 port remote coaxial relays. Preamp bypass relays for 2 m, 70 cm and 2 Ghz. FT 707 Digital VFO (on the workbench). FRG 9600 on it’s own serial port (At Present).

Phasing harness and preamp control.

Remote Coaxial Relays

Dual Axis Rotator n n n No calibration pots 2 IC’s Networkable No ADC (Explain Pot Command) 2 nd Order Polynomial linearising in 16 bit integer basic

Background on RS 485 n n n USB, Older 2 Mb networks like Lantastic Building management, Dedicated print networks Security Systems, Camera Control.

RS 485 levels

Benefits of RS 485 n n n n Multidrop: 32 devices on a single line without boosting Runs on a single 5 Volt rail Data-rate of 100 KBps 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 RS 232 to RS 485 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 n n 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 n An example of single wire protection.

Four Line Surge Suppressor

Optical Isolation

Visual Basic and the real world n n 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 n n n Winorbit satellite tracking Mixw digital modes Microsoft Office

VB object properties

My Station Control Panel

The possibilities are endless n n n n 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