This device is needed for a smooth start of halogen lamps at 12 Volts, so that they do not fail quickly and work longer.The device is made on an NTC thermistor with a resistance of 10 ohms and a 12V relay with normally open contacts.
How it works.When the current passes through the thermistor, it begins to heat up and its resistance drops.The current to the lamp goes through a thermistor.When the resistance drops on the thermistor, the voltage on the relay coil begins to increase.When the voltage on the coil reaches a certain value, the relay contacts will trigger and bypass the thermistor.Now the current will go to the lamp without a thermistor.Smooth activation in my case is about 4 seconds.
The three photos show the voltage on the relay coil at the moment of switching on, when the lamp lights up and when it is fully shining.
