This project is a small automatic cooling system for home theater rack. It supports 2 temperature sensors for different zones in the rack and 2 12V PWM fans (standard for PC case cooling).
There is a power switch connector for a switch mounted on the casing (will be designed and 3D printed later). A reset button is provided mostly for reprogramming purpose. There are 4 buttons for setting up temp...
Auto PTT on signal (useful for digital modes like RTTY / PSK / FT8).
This project is an automatic line-level audio switch.
It has 2 line-level inputs and 1 output.
When there is no signal on input 1, input 2 will be on the output.
When a signal is detected on input 1, the relais will switch the input 1 to the output.
Then when there is no signal on input 1 for about 15 seconds, the relais will switch again to input 2.
This is a simple circuit powered by a 741opamp. The relay does the switching of the pump or adapter of the water pump. It's a 230V/12V switching relay. Here you can find the schematic and the PCB layout also.