Issue
162 January 2004
Remote
Observation Station
CONFIGURATION
SOFTWARE
I
developed a simple configuration utility in C/C++ using
Microsoft Visual C++ 6.0 that allows me to configure
the PVCC board’s behavior (see Photo 5). Therefore,
I eliminated the need for buttons and LCDs that would
be required to implement a user interface. The trade-off
for this low-cost approach is the inconvenience of needing
a computer with a RS-232 serial port when I want to
change a setting in the field.
|
|
Photo
5—My PVCC configuration program is a simple MFC
dialog app. It uses two threads, the main GUI thread
and a communications worker thread. Inter-thread
communications is handled via semaphores and messages. |
When
I click the Get Configuration Data button, the program
requests the configuration data currently stored in
flash memory and displays it on a dialog. Then, I can
enter any desired changes to the settings and click
the Send Configuration Data button. This sends the revised
data to the microcontroller to be programmed into flash
memory, overwriting any previous data. A CRC16 check
is used in both the get and send data packets in order
to avoid accepting corrupt data.
UPDATE
I
have implemented some improvements since I built the
original Remote Observation Station. After several weeks
of field-testing, it became obvious that the original
21-W solar panel was too small for this project, mainly
because the camera now draws about 500 mA, which is
350 mA more than the original camera. I found my current
camera—an older Sony handycam—on eBay for $65. Although
the camera’s tape mechanism is broken, the video section
still works; it provides an excellent 10× zoom for the
station.
In
addition, the need for a low-voltage disconnect feature
became obvious while operating with the undersized panel.
LVD, a common feature on charge controllers, disconnects
the loads if the battery’s voltage gets too low. This
not only protects the system from a total shutdown caused
by a dead battery, but also prevents the battery from
being discharged to a level that will tend to shorten
its service life. The specification for the MK 8G24
valve-regulated, gelled-electrolyte battery states that
the battery can be cycled about 500 times if the depth
of discharge (DOD) is 100%. It can be cycled 1100 times
for 50% DOD, or cycled a whopping 6000 times for a 10%
DOD.
I
added two set points to the configuration software to
support the LVD feature. This provided the needed hysteresis.
To reduce the load on the battery, the station uses
a photocell to sense the ambient light level to turn
off the camera and transmitter at night. The remaining
load from the PVCC control board is about 30 mA in Charge
mode with OSD active.
