Design a circuit that detects the presence of the infrared signal. The circuit should light a red LED when infrared signal is detected otherwise it should light a green LED. You may use NPN transistors, IR LED, Photodiode, Red LED, Green LED and a rectifier diode.

This project involves designing a portable device that can inject a 1kHz sine wave signal into a 100V audio line to detect short circuits. The device should be compact (around the size of a smartphone) and include LED indicators to show the status: a green LED for normal operation and a red LED for short-circuit detection. The device will be powered either by a switching power supply or rechargeable batteries.

makes a circuit which has transistors, diodes, relays, IC Timer, LED, which first turns on a green LED lit from 0 to 35 degrees Celsius then turns off and turns on a yellow LED from 35 degrees Celsius to 50 degrees Celsius then turns off the yellow and turns on the red at 50 degrees or more which in turn will turn on an oscillator circuit with IC555 and a Buzzer. In addition it should turn on an exhaust fan at 110 VAC. Translated with DeepL.com (free version)

I want make a board that trigger a green and red LED with three wire, 0V, 24V and output of proximity switch. but i want output wire remain 0V when not connected.

Red, Green, Blue (RGB) 623nm Red, 530nm Green, 472nm Blue LED Indication - Discrete 1.9V Red, 2.7V Green, 2.8V Blue 0404 (1010 Metric)

Greenhouse controller with temperature and humidity control Input voltage 12v led voltage: 12v humidifier voltage: 5V Display: i2c 0.96 OLED display sensor: htu21d i2c