This proximity detector circuit is designed using a temperature sensor and TLC272 op amp. The temperature sensor can react to any heat generated by body heat. The sensor used in this TLC272 proximity detector circuit has a sensitive surface which was divided in two, so that it can sense if the heat source is coming from the left or right.
This water sensor alarm circuit diagram is designed using common electronic components. The water sensor alarm circuit may operate an active buzzer, to make a sound when is reached a certain level of water.
Because water sensor and control circuit for buzzer are located on the same printed circuit board, indicator, together with 9 V battery and buzzer can be mounted in a compact case.