Watching closely, it is not a single LED, but twenty single 1-W dies tied in series and parallel in a single package. The seller offers also a 50W model arranged in the same fashion

The setup i rigged up for a quick and dirty test of the 20W led

These are the parameters of the led from the vendor; there is no official datasheet, even if the page of the seller cites the luxeon brand. The following information however is all I needed to make a quick try:

Lens Color: Water Clear
Emitted Color : Warm White
DC Forward Voltage (VF): 13.5 ~ 15.0 VDC
Forward Current (IF): 1400mA ~ 1800mA
Viewing Angle: 140 Degrees
Color Temperature: 5500K
Intensity Luminous (Iv): 1000LM

After some rough calculations I found that a 18V power supply and a couple of 1 ohm resistors (what I had lying around) was just about right to turn the led on and keeping inside spec. The heatsink (coming from an AMD processor box) keeps the led cool, and prevents it from frying up in a few seconds: this little beast puts out a lot of heat.

See for yourself the comparison pictures between a conventional light and the led ligt from the test setup:

My room lit by my every day lighting (six fluorescent light bulbs)

my room lit by the 20W led

As you can see a single led can replace a whole chandelier of six light bulbs, giving comparable results and a clearer light. This is definitely going to be the lighting system of the future, because duration and consumption are far more efficient than conventional systems. I wonder what the 50W model could do.

A final word of recommendation: if you decide to try one of these leds, make sure you don’t watch it directly… it is like when you watch the sun with your bare eyes. Always wear sunglasses when you’re tinkering with these things.

Here is the schematic [click to enlarge]:

The top left connector is for input from a microcontroller, which determines which coils are turned on. The rest is divided in four identical sections, each having a BC337 NPN transistor driving a TIP122 power darlington pair, which in turn is attached to the motor coil through the bottom right connector. Collectors of the power transistors are connected to a sense power resistor which allows fixed current to flow in the motor, independently of the voltage.
As for now the motor I am using is underpowered: its spec says 24v but I am giving this circuit a 18v supply, so speed and torque may be affected. For now I can reach a speed of about 10 revolutions per second of the stepper.

Here is how it came out on a breadboard, attached to an arduino and to a stepper motor [click to enlarge]:

The little trimmer in the picture has been added for controlling a delay in the firmware, so to test different speeds of the motor. In fact the speed can be raised until the motor reaches resonance, and just a tad before that point the motor is going at full speed. This is the code:

void setup()   {
 DDRB = DDRB | B11111111;
}

int sensorPin = 0;
int sensorValue = 10;

void loop()
{
  sensorValue = analogRead(sensorPin);

  PORTB = B00000001;
  delayMicroseconds(sensorValue*10);
  PORTB = B00000011;
  delayMicroseconds(sensorValue*10);
  PORTB = B00000010;
  delayMicroseconds(sensorValue*10);
  PORTB = B00000110;
  delayMicroseconds(sensorValue*10);
  PORTB = B00000100;
  delayMicroseconds(sensorValue*10);
  PORTB = B00001100;
  delayMicroseconds(sensorValue*10);
  PORTB = B00001000;
  delayMicroseconds(sensorValue*10);
  PORTB = B00001001;
  delayMicroseconds(sensorValue*10);
}

As you can see the code is very simple: it just does a full step sequence delayed by the value read from the trimmer. It is good for testing different speeds and step sequences, to see which one is best for achieving maximum speed.

The next steps for beta version will be:

• add PWM to software
• port software to avr-gcc and optimize timings
• determine if BC337 are really necessary or not
• add filtering caps for PWM
• add diodes for coil protection

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!