Simple short circuit protection with just one relay

The simplest, reliable short circuit protection, without logic electronics, transistors and everything else. LEDs are used as an indication only.
This device can be used in low-voltage circuits where there is a risk of shorting contacts with an output voltage of 6 - 18 V.

Will need

• 12V relay.
  
  
  
  
• Two 10 kOhm resistors.
  
  
  
  
• Two LED different color.
  
  
  
  
• Momentary button.

Making simple short circuit protection

Let's look at the schematic diagram of the device:

It works like this: When power is applied, the relay remains unchanged, only lit red Light-emitting diode. There is no potential coming out. To start the work, you need to briefly press the button. After this, the relay will change its state, close the button contacts in parallel and will remain in this state until the short circuit. The red light will go out and come on green. The output will supply voltage to power the load.
If a short circuit occurs, the total circuit voltage will drop to zero. The relay contacts will release and disconnect the load.To restore the output voltage, you will need to press the button once again.

We solder the device on a universal board:

On the left is the input for the power supply, on the right is the output for the load.

Job

Connect the power. Lights up red Light-emitting diode.

A small 12V electric motor is used as a load. Press the button once: Light-emitting diode The red one went out and the green one came on.

If the motor was connected, it will work. If you close the output contacts now, the green LED will go out and the red LED will light up. The output power will be lost until the tact button is pressed again.

That's all! An incredibly simple and reliable device. It will also turn off the load if the incoming power from the source is briefly lost. This feature can also be very useful.

Watch the video