Driver for 10 Watt Led

Other Hardware LEDs and Multiplexing
1

Hi there,
I am planning to use 2 x 10 Watt Leds in my ROV project.
I have bought a 10 W Led. Now I need to build a constant current driver to drive my Led.

Forward Voltage of Led : 9-11 V.
Forward Current : 1050 mA.
Input Voltage : 12 V.
+PWM is a digital pwm pin from Arduino.

I found a good guide for building a driver circuit here. (Circuit Schematics attached)

For my 10 W led, I calculated R2 is 0.5 own.
The problem is I can't find 2N5088 (T1) and BUZ71 (Q1) in local electronic stores. I could find only 2N222, BC547 and IRF640N.
If I use these transistors instead of the ones in the guide, what changes do I have to make?

Led Circuit.PNG
Led Circuit.PNG606×557 3.18 KB

2

You can't use the IRF640N because it takes 10V to turn it on fully, you need a logic level FET.

3

I would put a smallish resistor, 1k or so, between the base of the 2N5088 and the 0.8 ohm resistor. It would protect the 2N5088 in over current situation. Normally there are no such situations, but rare things happen.

If the fet runs hot, you need to attach it into an alumiun plate. Ebay and so on sells constant current sources.

4

I've used these with 10W LEDs + Arduino: http://www.ebay.com/itm/380236759063

Connect Arduino GND to the "GND" pin and the PWM output to "DIM". Job done.

You can use transistors to build your own but remember a circuit like that is really just an "automatic resistor". All excess power is turned into heat, your power transistor is going to get very hot!

Assuming an "ROV" is going to work with batteries, that's wasted power.

5

fungus:
I've used these with 10W LEDs + Arduino: http://www.ebay.com/itm/380236759063

Connect Arduino GND to the "GND" pin and the PWM output to "DIM". Job done.

You can use transistors to build your own but remember a circuit like that is really just an "automatic resistor". All excess power is turned into heat, your power transistor is going to get very hot!

Assuming an "ROV" is going to work with batteries, that's wasted power.

Thank you for your suggestions.
Yes, the MOSFET gets very hot during in operation. I'd consider buying a driver. The one in your link says 1.5 A; is it maximum current or supply current?

6

The one in your link says 1.5 A; is it maximum current or supply current?

It is the current which will flow through the LED, so your power supply has to be capable of supplying more than this.

7

Grumpy_Mike:
It is the current which will flow through the LED, so your power supply has to be capable of supplying more than this.

My LED's forward current is 1.1A. So if the driver supplies 1.5A, there would be over current?

8

So if the driver supplies 1.5A, there would be over current?

No the current rating of a power supply is only what it can supply not what it will supply. That is down to the resistance of the load you connect to it.