User manual

1-Wire Application Guide v1.04 Page 26 of 41
Figure 19 Solar Sensor 2
As can be seen from the figures above, there are two types of solar sensor
designs. The Solar Sensor 1 design in Figure 18 is the more common one. Both
designs work on the same principle however. Light falling on the sensor, either a
solar cell or a photodiode, causes a small voltage to appear at the V
s
inputs of
the DS2438. These inputs are normally used in DS2438 battery monitoring
applications to measure current flow, however, they work equally well in this
application. The amount of light will be proportional to the voltage at the inputs;
so reading the DS2438 V
s
voltage will determine how much light is present.
Obviously, these sensors need to be mounted outdoors to be able to determine
solar radiation. Place them in a position where sunlight is present and rain will
not fall directly on the sensor.
When used with a TEMP08, set the DS2438 type to “V” (voltage).