First Test of the Sunrise
So I finally got everything together to test the sunrise light bar. I’ve got a microprocessor to do electronic dimming with a rudimentary timer, the high intensity LED bars and a darlington array to handle the higher current loads.
Basically in order to dim LEDs electronically you have to generate a Pulse Width Modulation (PWM) signal. This is a signal where the LEDs are on for a portion of the period and off for the rest of it. So basically it’s flickering but at something like 1000 times a second. This can give the illusion of dimming by varying how much the LED is on – 10% on & 90% off or vice versa… Anyways, the problem is that a microprocessor can only source about 5volts at 20milliAmps, this is fine for one LED but for the array of high intensity LEDs I have, I need 12volts at 300milliAmps. This is where the darlington array comes in, it’s basically a high speed, high current switch that allows me to use the PWM signal from the microprocessor to drive higher current loads.
So, here’s a photo of the set up – the lightbar at the top of the mounting board doesn’t have a clamp – they’re sending me one soon. To the right of the 9v battery is an Arduino development board. This is not the platform I’ll be using in the end, but it’s fast for prototyping. I programmed a simple clock and alarm system into it with a snooze, heh. It generates the PWM signal to drive the lights at the appropriate time. The white breadboard has the darlington array and a small pushbutton for the snooze. and the cord coming in from the bottom is scavenged from an old cell phone charger – this is what provides the power for the LEDs.
And here is a shot of it while the LEDs are at full brightness. The white cord trailing off to the left is a tether to the computer – I feed debugging values to the laptop to make sure everything is working correctly. In the final version I plan for the clock and the sunrise light to be wirelessly communicating. That way the clock can be one place and the lights elsewhere, with the option of adding more lights. I also want to run the clock portion off of batteries while the lights have to run off of house current:
Finally, heres a photo w/ the exposure set for normal room lighting – this show really how bright these LEDs are.. This photo is also off axis – straight on this light is difficult to look at for any length of time. Very bright… ha!
So thats it. Next I want to focus on getting the clock portion finalized and moving the LED controller to it’s final platform w/ some serial communication w/ the clock…Moving along..
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