Temperature alarm with time delay able to warn of open widows or doors

摘要

An indoor living space ambient temperature sensitive alarm system is able to detect relative temperature rise or fall and is arranged so that an alarm signal is only triggered after a delay period has lapsed and the temperature is found to be still dropping or rising. Figure 1 shows an example alarm circuit with thermistor sensor 3 feeding an operational amplifier which differentiates the input signal over a delay period set by RC pair 5, 6. The system may be a stand alone unit (fig 2, not shown) or may comprise remote sensors mounted on doors or windows (figs 3-6, not shown). The system may trigger a door bell sounder to play a particular chime as an alarm. The system may also log occurrences of alarm events.