First of all, I'm a noob but i want to learn electronics with all of you guys.
I want to make a project to make an automatic switch from dc adaptor (that converting from ac supply to dc) to battery for turning on dc LED light. The LED light must keep turning on.
In a condition:
1. When the electricity black out, dc adaptor will off because ac supply is down.
2. LED light will turn off.
3. After dc adaptor off, battery will automatically supply the LED light.
4. LED light will turn on because the power from battery.
5. When the electricity is up, dc adaptor will on because ac supply is up.
6. LED light will turn on and the power from dc adaptor.

I just thought, maybe i can make this project with 2 relay but i lack that. What should i do?
or maybe you have another solution that can help me.

 

This has been running in my living room for the past 12 years, duitifully turning the LEDs on when there is a power failure then turning the LEDs off when the power comes back on. When the power line is working a small trickle charge of a few milliamps is fed to keep the battery charged.

In the circuit on top the "AC INPUT AND CHARGER" can be a low voltage transformer secondary with a resistor in series to limit the peak current charging the Nicd battery. The current should be about 2% to 5% the amp-hour capacity of the cells.



For the transformer you can use almost any ferrite core. Compact Florescent Lamps (don't break the glass, only the plastic base) are a good source of these. Descriptions of this circuit can be found by searching for 1.5 volt white LED.

 

This has been running in my living room for the past 12 years, duitifully turning the LEDs on when there is a power failure then turning the LEDs off when the power comes back on. When the power line is working a small trickle charge of a few milliamps is fed to keep the battery charged.

In the circuit on top the "AC INPUT AND CHARGER" can be a low voltage transformer secondary with a resistor in series to limit the peak current charging the Nicd battery. The current should be about 2% to 5% the amp-hour capacity of the cells.
View attachment 190162

View attachment 190163
For the transformer you can use almost any ferrite core. Compact Florescent Lamps (don't break the glass, only the plastic base) are a good source of these. Descriptions of this circuit can be found by searching for 1.5 volt white LED.

i'm sorry that what i mean is the LED light must turn on 24 hours. If the power failure, the Battery will automatically supply the LED light. when the power back on, the adaptor dc will supply the LED and the battery will cut off. I just wrong to type on point 1.

 

Simple Shottkey diodes will do the job..led on all the time, when mains fail battery takes over..