The light beacons for nocturnal scuba diving can get quite expensive if bought at the store. Here’s a much cheaper alternative using easy to find / junk parts.
It is necessary during a night dive to have an always on flasher tied to the tank to be always visible by dive buddies. This circuit does just that: flash two high-brightness blue LEDs whenever it comes into contact with water.
The circuit is very simple: a first section detects water contact and gives current to the second section, a basic ne555 astable oscillator. No more than that, but it works great. The water detection part is accomplished by just a single transistor and two contacts. The circuit itself is throw-away, since when the battery will be dead, the water tight enclosure will not allow its replacement. However the cost of the circuit is in the 5$ range, and it will last several dives! Here’s the schematic. The battery used is a small 6V battery for cameras. It should last long! The resistors and the capacitor set the 555 to a 20% duty cycle, in favor of battery life.
I did everything on a piece of perfboard. Here’s another picture.
Ok, I think this is all for now. Go ahead and build yourself this flasher, next I will detail the enclosure and the results from the dive :)
Remember to dive safely and responsively. And have Fun!
This circuit is a good flashing circuit but i wanted to ask weather i could modify the circuit and my main objectivve would be to get a flash as well as the battery would last long. say about 6 months.
Could you help me on that.
To make battery life even longer you have to calculate a longer period for the 555 and a shorter duty cycle.
In this way you will have brief flashes, say every one or two seconds, and battery life will significantly improve.
There’s many online calculators to do that, and will tell you the values for the capacitor and the two 555 resistors.
Then you can obviusly use a fatter battery of course :)
to make a flasher which can last 6-12 months on a single battery one can use
this circuit
http://www.discovercircuits.com/DJ-Circuits/1vled3.htm
this is also a simple circuit to pro-long the battery life and keep it flashing with no worry about its battery for atleast a year.