Archive for October, 2008

TRACE SWCA, an Expensive device to break.

Posted in Problems, Solar Power on October 7, 2008 by wizbandit

I had one of my two $175 TRACE/XANTREX SWCA Inverter RS232 interfaces quit working on me a few weeks back.  I had opened these units up once to install power through an isolation low voltage drop diode to power a Bluetooth serial adapter.  They are mostly SMT inside with the exception of the MPU which is an Atmel AT89C2051.  The other SMT chips include a 74HC14, 232ACBN, 74HC86, 24LC04B, DG417, and on the back side a PCF8574AT.


The interface uses a standard 4 conductor flat telephone cable.  How the RJ11 terminal is crimped on the wire is important. Here is the pin-out as it ends up at the RJ11 to DB9F (provided with the SWCA): RED = PIN2, BLACK = PIN3, YELLOW = PIN5.  The GREEN in all I have seen is not connected.  I use this to provide 5V on PIN9 of the DB9 to power my Bluetooth to Serial converter which accepts 4-9 volts on PIN9 as POWER.  I found +5V on the PCB off a SMT Capacitor on the power rail.

The SMT part that had failed was the DG417 Analog switch.  From what I can see it is what turns on the DATA OUT line which is the RED wire when the SWCA is selected using its preset address.  The address is set using the antique DOS software that comes with it.  You can actually command up to 8 SW series inverters (SW5548 for instance) which requires you to connect the SWCA as the ONLY device on the serial port to “SET” the ID from 1 to 8 in the flash memory.  If you Parallel SWCA’s with the same ID there is no communication because of data collisions.  When I put my defective SWCA on with my good one the good one quit working so it was simple enough to trace back the data wires from the DB9 to the PCB.  I found the RED wire going directly to PIN-1 of the DG417.  PIN-8 is the data in so I just measured across the pins and got like 84 ohms.  The good SWCA measured infinite ohms so I knew the chip was shorted.  I ordered some from Digi-Key for $2.28 each, they should be here tomorrow.  I’m hoping the suspected ESD didn’t get past the DG417.  I could still send commands to the inverter so I know that part is working fine.  Just no data back at me.  The DG417 is an 8 pin SMT device, not real hard to remove. 

I have installed ESD protection on both the DATA LINES.  I use P6KE27CA Solid State devices in all my RS232 projects for ESD protection.  This is the very same device used in the Radio Shack RS232 inline surge protector from many years past.


24LC4B (4K I2C Serial EEPROM),  PCF8574AT (Remote 8-Bit I/O Expander for I2C BUS),  AT89C2051 (2Kbyte Flash Microcontroller),  DG417 (Precision CMOS Analog Switch),  232ACBN (High Speed +5V Powered RS-232 Transmitter/Receiver,  74HC14 (Hex inverting Schmitt trigger),  74HC86 (Quad EXCLUSIVE-OR Gate).


The part came from Digi-Key right on time.  I soldered in a new DG417 and I’m happy to report SWCA #2 is back in service and fully functional.  The only quirk I have is my two are different versions and the UP/DN arrows on one are reversed which is a pain.

Clay Archer reverse engineered the REMOTE PORT on the SWxxxx TRACE inverters and was kind enough to provide the information on the port.  Here is his letter and the details. 

Here are some of my notes on the SWCA.   I’m in the process of putting together my own interface, initially with a parallel port interface to a PC, and eventually a stand-alone PIC processor with an ethernet interface, when I can find time to work on it.  I don’t intend on making a commercial product with this, but if you develop anything with it I would appreciate some feedback. 


SWCA interface pinout: (DB25)

01) V+  5V

02) NC or Gnd

03) Gnd

04) Gnd

05) Gnd

06) NC

07) DB7 (14)

08] DB4 (11)

09) DB2 (9)

10) DB0 (7)

11) NC

12) NC

13) NC

14) LCD Enable (6)

15) Reset

16) LCD Read/Write (5)

17) LCD RS Data/Instruction (4)

18] Read Switch/Enable

19) Write LEDs enable (latch)

20) DB6  [13]

21) DB5  [12]

22) DB3  [10]

23) DB1  [8]

24) NC

25) NC 


LED and switch bits:

      LED                     Switch

DB0   over current              set+

DB1   float                     set-

DB2   AC2                       menu up

DB3   inverting                 menu down

DB4   error                     menu ->

DB5   line tie                  menu <-

DB6   AC1                       on/off

DB7   bulk                      Gen



LCD is an HD44780 based LCD display (I think) with 2 lines &40 chrs.  Numbers in () are LCD module pins. 


 You can find documentation on the HD44780 based LCD on the internet. The SW inverter interface (DB25) port was initially designed as an external keypad and display, basically a  duplicate of the internal keypad/display.


 The SWCA is a PIC processor designed to emulate the keypad/display and interface to a serial port as a display terminal emulation. To talk to the SW inverter you will need to emulate the HD44780 registers to read data and emulate the pushbutton switches to request data from the SW inverter. You could also just build an external display. Parts used in the internal display are two 74HC573  (8 bit latches to latch the LEDs and pushbuttons) one 74HC14 (to debounce & buffer the enable for the LCD display) and an LCD display with assorted resistors & cap’s etc. I have a rough schematic of the internal display, if you want I can scan it and send you a copy. 


Good luck,

Clay Archer


MORE is BETTER! Solar Power That is!

Posted in Solar Power on October 7, 2008 by wizbandit

Solar Power Tracker #4 went ON-LINE this past Weekend on temporary wiring.  I still have to dig the conduits back to the main junction box where the home runs are.  Since I have the construction down to a semi-fine science I timed the construction of number four, working at a daily pace with 90% of the materials needed on-site.  The time required, 10 days from start to power-up.

Base construction.


For now I only have six Kyocera KC130’s to put on it.  I have 24 Siemans SR90 Photovoltaic panels from my orginial roof setup, 4 are now on tracker #4 feeding my Advanced Energy GC-1000 grid-tie inverter still mounted on tracker #2.  I’m thinking I need to move it.  Since I don’t own enough PhotoWatt PV panels to make six panel arrays, just eight still on the roof feeding the old four panel array system, I’m going to put all eight on a smaller tracker just for the GC-1000 to use.