PICAXE-18X PROJECT BLOG
Late 2007 Start of the PICAXE repeater controller project
Started this project with a PICAXE-08M chip but soon moved onto a more powerful PICAXE-18X.
5 - MAY - 08 Revised version of the circuit board to host a PICAXE-18X.
A total redesign of this project board. (but not the last!)
30 - May - 08 Schematic Drawing
Completed revision "A" of the schematic and posted on the net.
## - JUL - 08 Some where around this time, etched another board.
Hum.... I think it was to add LED's to the MOSFET switches. PTT, FAN and the Spare.
30 - JUL - 08 Schematic Drawing
Completed revision "B" of the schematic and posted on the net.
22 - AUG - 08 MPF102 JFET change out to 5 VDC relay. Another new board etched!
A new board etched and code changes to suit a new 5 volt relay which switches the audio. I just couldn't get the MPF102 to work properly and yet it seems to be the industry standard in small PIC Repeater controllers!!! The alternative......Yes, I know, it's an electro-mechanical relay with moving parts! But the specs say the relay has a life span of 10,000,000 operations! And it says it has gold contacts too:) I think 10,000,000 operations will out last me! Also, it either will pass audio (zero Ohms, energized) or it will not pass audio! (infinite Ohms, de-energized) Nothing like half on and half off like the problems with the MPF102 JFET. How do you get the JFET to shut off if you don't have a negative voltage??? Lost patients and threw in the towel on this one. I actually like the 5 volt relays, they are actually 6volt relays and seem to work fine. Relays are from Jaycar Electronics here in Australia. I think I will eventually knock up artwork for a PICAXE-18X controller with all relays. (1 - Oct - 08) Artwork done, but not etched and tested.
## - SEP - 08 Some where around this time, etched yet another board.
Hum.....
1] Added 1N914 diodes to 5 VDC relay and COR circuit.
2] Also removed bridging pins/links for the MCLR and added a tiny push button?
3] Added micro toggle switch for Initialising rather then the larger mini toggle.
31 - AUG - 08 Schematic Drawing
Completed revision "C" of the schematic and posted on the net.
13, 14 & 15 - SEP - 08 Bench Testing Controller Card
I think it was here that I benched tested the controller card. Both radios on the bench with the TX 5 watts into the dummy load and the RX with no antenna. Tested all functions and parameters with my HT. A few tiny issues, but all sorted out.
20 - SEP - 08 Took the controller up to the hill for a real test. Seems to work OK. But had a few problems as listed.
1] I think the Mute DTMF tones OFF should be the default cause when you key in the fourth valid tone when making a parameter change, the IRLP thinks you're trying to connect to a node. Valid or invalid, the IRLP will surely let you know!
2] Problems with a buzzing like noise from the 80mm x 80mm box fan getting into the 25 WATT VHF transmitter's audio. I had to heavily bypass the 12 VDC at the fan to stop this. I added the fan on the TX rigs PA heat sink as I don't think it is anywhere near a 100 percent duty! I've also set the "Time Out Timer" from 2 minutes to 1 minute for the time being.
3] About the third day of repeater testing I awoke to a howling dry easterly wind off the outback desert. I turned on my HT to find the repeater going crazy. Key up, unkey, key up, unkey etc. etc. Also, large amounts of static on the TX audio. I talked to a Repeater Guru and he says that these are small static discharges off the antenna caused by the howling dry wind and I need to install an inductor of the right value to bring the antenna to DC earth potential. I hope I can do this in the shack, cause I'm not climbing 100 feet in the air!!!
4]
1 - AUG - 08 More artwork via MS Paint for a relay based PICAXE-18X repeater controller card.
Why do I torture myself with MicroSoft Paint!!!!! Artwork done, but not etched and tested. Need to use the laser printer at work. (on a weekend or night shift!)
2 - OCT - 08 Rewired the home brew rack mount power supply.
Changed out the battery charger section and made it a unregulated auxiliary 12 VDC power source for fans and anything else that may need it. Hopefully this will keep fan noise out of the TX audio. ((How does a brushless DC motor generate so much noise!?!?!? Must be electronics switching inside the fans motor enclosure???))
4 - OCT - 08 TX radio heat sink and fan addition.
Bolted a separate heat sink onto the TX radios existing heat sink. Also, added a different 12 VDC fan to it. Here we go, more noise in the TX audio!
5 - OCT - 08 Installed controller, modified power supply at our local repeater site. Now only time will tell if the controller card is a success.
Still no good, audio problems from the cooling fan. Buzzing noise from the fan getting in the TX audio. Eventually added a couple 4700uf caps and replaced the high speed 12 volt fan with a 24 volt fan running at 14 volts. Seems to be a success.
9 - OCT - 08 Lightning Storm!!!
I was notified at 7:30 at night that the transmitter at our local repeater was stuck on. This was after a fears lightning storm went through earlier in the day around lunch time. I went to the repeater site and found the PICAXE-18X in the repeater controller card had pretty much lost it's way. No all, but most of the outputs were ON and they were on for no reason. Unfortunately the PTT was one of them. I reset all the power and the PICAXE based repeater controller came good. I also let the TX radios cool down for half an hour as it was probably on continuously for 7 - 8 house!
14 - DEC - 08 New Schematic
New schematic for the PICAXE-18X using all relays. Only revision "A" for this board. I'm starting to get things right the first time these days!
3 - JAN - 2009 Happy New Year!
Well were back at it again after a lay off of a few months. I think I've etched out the last and final PICAXE-18X repeater controller board. This one uses relays instead of MOSFETs. I don't know why I did this, maybe for someone who wanted isolated contacts? The code is the same as the MOSFET board, so there is no changes to the code. It's the same for both boards.
10 - JAN - 2009 I think this projects over!
Well, I think this one is about wrapped up. I'm not sure what part of this project I hated most? Torturing myself with MS Paint to draw up the circuit board artwork and schematic? Or drilling 300 holes in a freshly etched circuit board, only to find out I left out multiple traces. Or, working in the 36 degree heat in my workshop? Or maybe it was the time I didn't use a "non- mirrored" image and transferred the artwork to the copper, etched out the board and started to drill the holes, only to realise it was all backwards!!! You just gotta hate that! Anyone who etches back yard circuit boards will of done that at least once in their lives!
11 - MAR - 2009 New Code (Ver.2)
Posted a new version of the repeater code and programming guide. This was due to changing out the codes Morse routine with a new one submitted by Wolfgang, DL8UAD. Many thanks. It will now bang out all punctuation characters! Even a seven element "$" dollar sign! dit dit dit dah dit dit dah.
2 - JAN - 2010 New Code (Ver.3)
Posted a new version of the repeater code. I added the option to have the Fan Relay energize, or not energize, when the controller PTT relay is activated. No sense turning on the controller Fan relay if there is no fan connected to it! Also, a general tidy up for the PICAXE-18X controller code & comments since the controller was going back into service again when we shifted from the old communications building to the new building. And in doing so, we gave up our trusty modified Philips 828 for a UniLab KL150b that the local mining company acquired for us. But one problem, the KL doesn't have a CW ID'er or remote access to the repeater in it's simplest form as a stand alone talk through repeater. Hence, the requirement for an external repeater controller. Also to note, the radio tech said that the KL would supply a set of contacts for a Carrier Detect (COR) and the PICAXE repeater controller would need to supply a set of contacts to the KL for the PTT. So, the PICAXE-18X "relay version" is in use for the first time!
10 - JAN - 2010 Bill of Materials
Not much to do in the hot and humid Outback until it cools off a bit so I made up some Bill of Material for both PICAXE-18X controllers and posted them on the net.
12 - MAR - 2010 Drawings and Artwork Updated
Made a trip up to the repeater site today to check on the Uni-Lab KL150b and the PICAXE repeater controller. Reports indicated some slight audio distortion. We soon found what I think is called "cross over distortion" on the output of the LM358N OpAmp. To fix this problem, a 1K resistor was soldered from pin 7 to pin 4 on the copper side of the circuit board. I am told that this is a inherent problem with these old OpAmp chips and that a new style OpAmp should be used. I believe an TL072 is a drop in replacement, but I haven't tried one yet. The drawings and circuit board artwork have been updated to accommodate this new 1K resistor.
15 - FEB - 2011 Back to Basics! New Code (Ver.5) Actually less code!
The code started to get cluttered with a bunch of rubbish so I deleted all the BS and went "back to basics." Also updated the programming guide and posted both on the net.
18 - DEC - 2011 PICAXE-18X chip is not obsolete!
It is my understanding that the PICAXE18X chip is obsolete and that the PICAXE18M2 is the replacement. I am not sure how that will effect the operation of this project by using this new chip. Please be aware. The PICAXE website says that the new chips are backwards compatible.
Anyone who has any interest in this project, feel free to make changes, fixes, updates, mods, upgrades etc. etc. as you wish. It's only here to be shared. Steve - VK6HV