Sublight – Powerful SCUBA lamp.

Night diving and wreck diving requires a good torch. When I asked for advice on buying a torch, most divers I told me that “30Watts are great , 50Watts are insane , and anything above is not really necessary…”

If it’s worth doing, it’s worth overdoing.  I started with interpreting what they said , It sounded to me like this: “30Watts are OK , I have it because I could not afford the 50Watts , anything over 50Watts is what I would like to have”

So… what I “needed” was :

  • 225Watts … (3 x75Watt bulbs)  
  • battery time of at least two hour at reasonably high intensity…
  • Variable intensity
  • >20Khz PWM (Pulse Width Modulation) to keep high efficiency and no noise.
  • Internal 28Volt DC-DC converter to improve efficiency of Power MOSFET’s .
  • Multiple bulbs (3), just in case one dies – there are still two left.
  • Voltage monitoring.
  • No disassembly required for charging.
  • Nice software with SOS and maybe a bottom-timer.
  • Self adjusting intensity (not implemented yet)
  • Low battery warning and battery capacity prediction. (not done yet)


So , the project resulted in:
Acrylics pipes with 22mm acrylics ends , with O-rings , 4Mhz RISC Microprocessor that works at 4-5 volts , 28Volt DC-DC pump , 2 optically isolated PWM outputs that uses the 28volts to control 50Ampére low-drop power MOS-FET’s so fast that the MOSFET’s does not require any cooling as they “never” are in linear state. A 2×16 Character LCD display had to be added.

There are no moving parts, the 3 buttons and on/off are magnetically controlled and does not represent a weak point (or should I say leak point ?)  


here is the battery case : two 12Volt 6,5Ah batteries in parallel gives 13Ah ! (could be 2×7.2Ah , but I 6.5Ah was all I had).

Here is the torch ,

the display is showing voltage and intensity. as soon one bulb is 100% on , the other 2 starts helping , that’s to distribute the bulb-burn-time so their life length will be different. those are 3x50Watts “Osram Decostar” (1×10º , and 2×24º)  halogen bulbs ,just because I did not got any 75Watts , of course , the electronics will handle 3x75W (225Watt)

The LCD display is back-lit , (green/blue) , and looks very nice under water. Now booting …


because of the massive intensity of the light , the camera could not do better , the LCD is invisible , It’s normal daylight in the room but “seeing” this bright light source , the camera made this picture so dark.


The Freeware

The design/circuit  should always be treated as freeware, you might build as many as you like , even for your friends.

The author (me) must always be credited as the author.

The compiled program is here. , It is possible to buy preprogrammed controller from me.

The schematics: (right click the picture below and “save target as”)

A little description , it should be everything you need to know:

  • U$3 is the LCD connector , any HD44780 compatible LCD goes , at least 2×16  characters.
  • PADLAMP1 is the pad (output) for lamp1 , padlamp23 is is for lamp 2and3
  • JP2 is the switch/button connector
  • use IRFZ44 or better power MOSFET (BUZ 11 is used on schematics by accident) – they are pin-compatible.


Q: Do you have the container plans ?
A: No ,I just found some material that would fit the batteries worked on it.

Q: Is there a PCB layout ?
A: Yes , I designed a two layer PCB ,but never etched it.

Q: Where did you found the O-Rings you needed ?
A: A hardware store sold them as meter-ware with a special glue, then I made the O-rings I needed.