I've designed the following schematic for my LED emergency lighting project;
I'm planning on building it soon, my knowledge in electronics is short right now (I started learning electronics by reading the book at "allaboutcircuits.com" two days ago).
I would like to know if my design is solid, correct and safe, should I add protection circuit, change the "Relay power OFF circuit", etc;
Do you have any suggestions on how can I make it better?
If changes are needed, could you please add a schematic for the change and how it should be connected to the existing circuit? remember that I'm a beginner.
LED emergency lighting schematics:
Purged delay circuit
Corrections, changed relay symbol to SPST
Changed parts designations
Former schematics
Deprecated-00
Deprecated-01
Deprecated-02
Design explanation:
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The DC power supply is an old 5VDC-Output phone charger, it is going to stay connected to the mains 24/7.
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It is essentially two separate circuits, one for the relay coil with power OFF delay and the other is to drive the LED's with 1.2V*4 AA battery pack. -
Now the relay is connected directly to the 5VDC power supply as suggested;
when the Mains power goes out, the relay will close the LED's driving circuit. -
The switch S1 is when I don't need the light anymore while it is being used as a flashlight.
Best Answer
1) You don't need the switch because if it's an emergency light Murphy will have turned it off at the most inopportune moment.
2) You don't need the delay because it's just adding a lot of unnecessary stuff to something that's supposed to just work and not have reliability problems.
3) You don't really need the 5 volt supply since you can just use a relay with an AC coil. However, it's probably a good idea to use low voltage where you can and minimize the possibility of someone getting zapped.
4) Make sure that, if it's a 5 volt relay, that 6.2 volt supply won't fry it.
Having said that, here's how I'd do it: