10 W LED with Tinkerkit MOSFET

Other Hardware LEDs and Multiplexing
1

Hi all,
I am new in the forum and have a problem with controlling 10 watt Cree LED with Tinkerkit MOSFET.

I have connected the MOSFET to a power supply (220 V in, 8.4 V out) with 1.5 A. I can control the brightness of the LED by sending values between 0 and 1023 but there is always a weak "flickering". What could be the reason for that ? Can I do something to get rid of it ?

Thanks for your help.

Andreas

2

Using a simple MOSFET to control such a powerful LED is not going to work in the long term. You need a constant current driver to drive it reliably and consistently.

but there is always a weak "flickering". What could be the reason for that

The inability of your LED / MODFET combination to respond quickly enough to the PWM signal.

3

8,4V DC - regulated ? (should be)
Put a capacitor parallell to led.
PWM dutycycle out to MOSFET is 0/255..255/255

Post code and schematic..

4

knut_ny:
8,4V DC - regulated ? (should be)
Put a capacitor parallell to led.
PWM dutycycle out to MOSFET is 0/255..255/255

Post code and schematic..

It is the current that needs to be kept constant, not the voltage. Otherwise you'll kill the LED in time.

5

Have a look here at how I controlled a 9W RGB LED using a tiny85. Depending on your LED characteristics the PSU(s) sections may need altering but I link to the article that outlines the way to calculate them.

6

Here the very simple source code for my tests:

// include the TinkerKit library
#include <TinkerKit.h>
TKMosFet mos(O5);
void setup()
}
void loop()
{
mos.write(1023);
}

I attached a DC source to the MOSFET. The maximum current at 8.4 V is only 0.5 A (should be about 3 A) and it flickers with a frequency which can be easy seen. By the way, 1023 gives most light. Below is less and 2000 gives no light at all.

Do you know what's wrong with that ?

Thanks

Andreas

7

Yes I told you in reply #1