How to fit LED kitchen lights with fade effect

Step 2: Fader

When the lights were switched on, I wanted a gentle fade up to full brightness.  This would provide a bit of interest and be a contrast to the buzzing, flickering startup of the flourescent lights.

Pulse Width Modulation or PWM is the simplest way to fade LEDs and MOSFETs are the simplest way to rapidly switch large(ish) currents.  By combining a MOSFET with a microcontroller, I had the most flexible way of controlling the fade.  

I used an Arduino to test the concept and my test rig is shown in the photo.  I got the circuit idea from here: http://www.ladyada.net/products/rgbledstrip/  I only used 1 channel (White) instead of 3 (RGB).

Using this rig, I was able to develop the fader software easily.  It is described in the next step.

Comments

[FLAN]

I have a question.. I bouhgt this SMD leds and I want to use a power supply 12v 65w, I conect it and LED light up, but the strip is getting to hot, This is normal?

[samaddon]

you need to decrease the voltage to 11 volts and 35w if you are using a single led then after some time the led will blow up!

[diy_bloke]

I don' t think the Wattage makes any difference

[samaddon]

you need to decrease the voltage to 11 volts and 35w if you are using a single led then after some time the led will blow up!

[Esterill]

Hi, It depends on what you mean by 'too hot'. All LEDs get warm or hot when on. Because there are a lot of quite high power LEDs on the strip, we would expect some heat. Once the strip is fixed to a surface be it metal, wood etc. I would expect the heat to be reduced. However, if you are worried about the level of heat you should contact the supplier for advice.

[bennyj121]

I have pretty much the same setup and used an old iomega supply ffrom an old drive. It has a 12v output at 2.5A and another 5.1v output that does not light up my 9 foot string. I am not sure which SMD LED's my strip has, but I thought I would do the dim thing the easy way but they will not loght at such a low voltage. I hacked the microwave and used the built in lights on it to power the iomega, so when i turn the microwave/counter lights on, my cabinet strips also power on. The 'dimmer' switch I added (to the 5.1v line) acts as an off switch now.

[dxlrant]

In your testing environment with the segment of 3 LEDs would 5 volt be sufficient to power all? I realize the strip is rated for 12 volts, but just wondering.

[PyroMonger]

you can use 9volts and it will work fine. I have blue strips like the ones used here and they run on a 9volt battery with more than adequate brightness

[Esterill]

Hi, thanks for the interest. It may be sufficient but if the LEDs come on at all, they certainly won't be very bright.