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A PICAXE-18X REPEATER CONTROLLER

Programmed in "BASIC"!!!

 

The older PICAXE-18X chip is now obsolete but the PICAXE web site says the new PICAXE-18M2 chip is backwards compatible, but it's NOT for this project! You need to use a PICAXE-18X chip. At some point in the future I will etch out a new version of the controller for the PICAXE-18M2 chip.

 

Controller PCB Art Work      Controller Etched Board     Controller Schematic    Controller Programming Guide  Controller "BASIC" Program

                                                                                                                                                                                                            

Controller in use   Controller Bill of Material     Link to Controller Board w/RELAYS

 

PROJECT BLOG PAGE

 

MORE PICTURES AT THE BOTTOM OF THIS PAGE

 

I know, I know.... not another repeater controller! After all there are at least a half a dozen very good 16F84 PIC based Amateur Radio repeater controllers on the net. But I haven't seen a PICAXE based repeater controller. That may not be totally true as I have seen some chatter on a web site that said it was using a PICAXE based repeater controller in their repeater system. But I haven't seen it as a project and I was looking for something different in my next PICAXE project. So after many months without a project on the work bench, I decided to quench my curiosity and see if a PICAXE-18X chip running at 4Mhz. was capable of this application. I also wanted to have a go at a project from the ground up.  Designing the circuit, drawing up the printed circuit board artwork, etching the circuit board, programming the PICAXE in BASIC and hooking up the circuit board to a couple of surplus VHF radios as a repeater. Being that I am only one of four amateur radio operators in a 300 mile radius that uses our NHRC-4 controlled 2 meter repeater here in the outback in North West  Australia, it's possible that I will never use this circuit. So I encourage anyone to make improvements to any part of this project.

 

THE DESIGN 

(I tried to keep it  "Basic")

The audio section of this project is not my design but was found on another Amateur Radio Operators web site elsewhere on the net. Thanks K5LXP. Also, I think it was a featured article in the magazine "QST" about 10 years ago. So it seems to be the standard OpAmp audio circuit for a simple PIC approach to controlling a Amateur radio repeater.  This project uses a MC145436 DTMF chip for remote control and remote program changes. This basic controller features standard features in many others repeater controllers. Adjustable Time Out Timer, adjustable ID Timer, Morse Code Id'er with 11 available spaces for the call, i.e. DE_XX#XXX/R, adjustable Hang Timer delay, 3 programmable Roger Beeps, 3 digit password, all programmed in decimal.... not HEX!!! All programmable via DTMF tones once the "BASIC" program has been downloaded into the PICAXE chip with the program and defaults settings.  It also ID's to a small speaker if required. I found the Speaker Output handy while programming. There are 3 power MOSFETs as switches, 2 used and 1 spare. There are 9 status LED's for such things as 5 volts OK, COR active, Morse ID, DTMF Tones OK, Mute DTMF Tones, Repeater Muted, PTT Active, Fan ON and a spare status LED for the spare MOSFET switch. 

 

DRAWING UP THE ART WORK

Oh, this was very painful. It was all done with the MicroSoft "Paint" program. No special PCB layout software was used.  (but I've purchased some software now!) It took hours and hours.... and more hours  to draw up.  There are actually  two versions. A bare bones PICAXE-08M version and this PICAXE-18X version. The photos of the artwork were .BMP files but they are huge, so I've converted them to smaller .JPG files to save a little space on my 20 Megs of free web space. NOTE: One thing I found during this ongoing project was not to print the .BMP artwork file from MS Paint.... it's crap! A helpful hint I found on the internet was to import the large .BMP file into a Word .doc file and resize it to the exact size required before printing. It prints so much better from Word! I'm not sure why? But no more crude and jagged edges as when printed from MS Paint. Also, do a test print to paper first and place the18 pin IC socket on it. Make sure the socket pins line up with the socket holes on the paper. If this is correct, all the other part spacing will be OK. Now you're ready to print to the special blue paper. Printing to the special blue  "Press & Peel" paper from a laser printer seems to require a good or new toner cartridge. The "Press & Peel" people say that using a photocopier machine to transfer pre-printed artwork printed on plain paper, to the special blue "Press & Peel" paper works too, but I haven't tried the photocopier scheme yet. The repeater controller art work link at the top of this page is a "Mirrored Images" but NOT TO SCALE!.

 

ETCHING THE PRINTED CIRCUIT BOARD

The "Press & Peel" technique was used with good results. Only a few touch ups were needed on the board before etching. Good enough for "back yard" circuit boards! Make sure you clean all the oxidation off the circuit board copper with steel wool or very very fine sand paper. I used 400 grit wet & dry sand paper and then gave the shinny copper a wipe with alcohol to remove any oils from fingers before you iron the "mirror" image onto the copper. Remember... it needs to be a MIRROR IMAGE! I  If you hold your artwork up in front of a mirror and any "normally" printed text in the art work  is upside down or backwards.... then it's wrong! Trust me!  

 

THE PROGRAM AND PROGRAMMING THE PICAXE

It's been fun programming the PICAXE-18X chip. Lots and lots of late evenings!  By no means am I a programmer by profession or as a hobbyist. I simply toyed around with the program until I finally got it to work and do what I wanted it to do. So, please feel free to add, change, optimise, delete  as you require. 

 

All programming is done with the "FREE"  PICAXE software through a serial download cable. I believe there is a USB download cable for those too modern to have a DB9 serial port. One great feature of the PICAXE Microcontroller is it can be programmed right in the circuit and does not need any special programmer. And the second great feature is I can add or control any feature of the repeater controller! Note: I believe the programming software is free for non commercial use. Check out their site for yourself.  http://www.rev-ed.co.uk/picaxe  The software is free and the PICAXE chips are cheap!

 

THE SURPLUS RADIOS TO BE USED AS A VHF REPEATER

The surplus mobile radios below were made by AWA. That's Amalgamated Wireless Australaisa (Limited) They are model M8-1540. 

(I'm not sure they are up to the task, but I'm going to give them a go)

 

IN CLOSING.....

This was the test set up for the PICAXE Repeater Controller. Although the M8's seem to be somewhat up to the task, the RX radio did appear to be a bit deaf. And the TX radio's heat sink got very hot even when running at 5 watts output for a timeout setting of 3 minutes. Hence the reason for the additional heat sink and fan on the back of the TX radio. The M8's are now turned off but sit in the rack as a back up to our normal Philips 828 radio and NHRC-4 controller.

 

 

 

 

 

 

 

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