Hardware Reference
In-Depth Information
Figure 9.27
Light-level threshold detector based on a photodiode
Figure 9.28
Comparsion of typical spectral response of LDR and photodiodes
Figure 9.29 shows how temperature thresholds can be sensed using the
AD590 sensor described earlier. This arrangement generates a logic 0 input
whenever the temperature level exceeds the threshold setting, and vice versa.
AC sensing
Finally, Figure 9.30 shows how an external AC source can be coupled to an input
port. This arrangement produces TTL-compatible input pulses having 50% duty
