Controllers & Sensors circuits and projects

Minuscule circuit of the electronic heater controller presented here is built around the renowned 3-Pin Integrated Temperature Sensor LM35 (IC1) from NSC. Besides, a popular BiMos Op-amp CA3140 (IC2) is used to sense the status of the temperature sensor IC1, which also controls a solid-state switch formed by a high power Triac BT136(T1). Resistive type electric heater at the output of T1 turns to ON and to OFF states as instructed by the control circuit. This gadget can be used as an efficient and safe heater in living rooms, incubators, heavy electric/electronic instrument etc.

This small InfraRed Remote Control Tester circuit is used for checking the operation of an infrared remote control unit. The circuit is based on the idea of connecting a piezo buzzer directly to an IR receiver IC.

This heatsink monitor circuit signals via 3 LEDs when the temperature exceeds 2 boundary levels. When the heatsink temperature is below 50 … 60^oC (122 … 140^oF) the greed LED lights. The yellow one signals that the temperature is within 60 and 70^oC (140 … 158^oF). The red one signals that the temperature has reached beyond 70 … 80^o (158 … 176^oF). At this point a relay can be triggered to break the power supply or otherwise protect the electronic device by turning ON a cooling fan.

When a Relay driver circuit is used in Sensor based electronic circuits, false triggering may occurs due to unwanted relay clicking. The input signal level is not sharp in most sensor circuits and the transition stages are slow. So the relay driver transistor partially turns on / off . The relay coil will not become fully energized leading to vibration of the relay contacts and heating. A Snap Action relay driver with Schmitt trigger action can eliminates this.