Sensor and control circuit diagrams

Digital Remote Thermometer

Remote sensor sends data via mains supply Temperature range: 00.0 to 99.9 °C

Cellular Phone calling Detector

Flashes a LED when detecting an incoming call Powered by one 1.5V cell

Dark Activated Switch

This circuit will activate a relay when light falls to a preset level. Light level can be adjusted with VR1 and the relay contacts may be used to operate an external light or buzzer.

Electronic Night Light

This circuit for an electronic night light was submitted by Adam from Canada.

Temperature-controlled 12V dc Fan

Suitable for computer cooling fans. LED motor speed indicator

Voice Operated Switch

This circuit is a voice operated switch (VOX) and designed for audio frequencies within a commercial telephone bandwidth of 100Hz to 3000Hz. Input amplitude is sensitive down to 10mV and the output comparator can drive a relay or interface to micro processors and TTL switching between 0 and 5Vdc.

Temperature Monitor

A simple op-amp circuit that will trigger a relay when a preset temperature is reached. Please note that there is no hysteresis in this circuit, so that if the temperature changes rapidly, then the relay may switch rapidly.

Arduino MQ-7 Carbon Monoxide Sensor Circuit

The carbon monoxide sensor we will use is the MQ-7 sensor. This is a sensor that is sensitive to effects of CO. Carbon monoxide (CO) is a very dangerous gas which is odorless, colorless, and tasteless, so it cannot be smelt, seen, or tasted. A person really would have no idea that they are breathing in CO besides the fact that they would start to feel horrible.

Latch Switch

In this circuit a non-locking push switch is used to activate a load. The load remains switched on until power is removed from the circuit.

Energy Leak Detector

High sensitivity, portable temperature comparator Detects draughts around doors, windows, etc.