Interior signage such as lighted exit signs, plays an important role in keeping clients and staff safe during an emergency. This post shares the design idea of a simple and economical LED exit sign.
This is the circuit diagram of the dark-activated LED exit sign. Pretty simple, self-explanatory, and straight forward!
A 12V battery source is required for this portable exit sign to function properly. Moreover, superbright red (or amber) LEDs are recommended as the light source to illume the exit sign plate.
Note that LEDs provides better visibility in outdoor spaces than most other exterior lighting options. Additionally, LEDs typically cost significantly less to maintain and operate, saving you money in the long run.
Back to the circuitry, it consists of just three transistors – one phototransistor (PT334-6C) and two bipolar junction transistors (S8550 and S8050). The 1MΩ resistor in the circuit sets the light/dark detection threshold of the phototransistor.
The S8050 is a low voltage high current small signal NPN transistor. From datasheet, it can handle collector current up to 700mA. So, you can easily set the LEDs in series or parallel according to the capacity of the LED driver S8050 transistor.
Keep in mind that LEDs wired in parallel have the same singular rated LED voltage across the entire load, but the current requirement will increase or decrease based on the number of LEDs. Also, series-wired LEDs have the same singular rated LED current through the entire load, but the voltage requirement will increase or decrease based on the number of LEDs. Ideally, for reliability and lighting consistency, series-parallel combination of LEDs is the best of both domains.
Another great pick for this exit sign application is the 20mm red LEDs (see below).
Datasheet https://docs.rs-online.com/729c/0900766b80b78dd3.pdf
To get started, I breadboarded the circuit with a 12VDC white LED plate as the output load.
Ultimately, I was quite satisfied with the results…
As you might expect there are two different kinds of exit signs – wall-mounted and ceiling-mounted.
After all of the construction is finished, your exit sign must be placed on any door that connects to a pathway out of the building. Remember, the area must be void of any objects that would make it difficult to read the word EXIT. No matter how small or big your location is you and everyone else in it need to be able to see what is going on!
That is all for now. Hopefully you all found this post interesting and useful. Stay Awesome!
