LED Wake Up Light

Now that I’m out of school and working full time, waking up during the fall/winter/spring is getting pretty difficult. It was no problem at all during the summer since I was able to wake up with the sun. That’s no longer the case as the winter months approach. So how could I set up something to try and recreate the sun rising? Hopefully a strip of white LEDs next to my window will do the trick!

These guys are bright!


The lights are currently set up to slowly turn on over a 30 minute period using PWM (Pulse-Width Modulation) control via an Arduino which controls the gate to a MOSFET.

The next step is to switch over to an Electric Imp to allow for pulling the time off the interwebs. Luckily, the Electric Imp has a PWM output on it, so switching over to that entirely can eliminate the need for the Arduino!

Oct 19th 2014 Update

Got everything ported over to the Electric Imp! When going through a test run I noticed that the lights were much dimmer than when I had them plugged in directly to a 12V source. Come to find out that the MOSFET I’m using requires ~5V to fully saturate. The Electric Imp can only output 3.3V. Dang.

No biggy though. I decided to implement an op amp to boost up the voltage from the Imp to the gate of the MOSFET.

But wait… the UA741 op amp isn’t a rail-to-rail device. This means that when I try to pull set the input pin low on the op amp, it won’t properly pull to ground and shut off the output. There’s a turn-on voltage we have to overcome on the internal circuitry. So, now I’m on the hunt for a TTL MOSFET to simplify things a bit! Maybe a high-side switch would work better…

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