Dimming (non-RGB) LED strips


I am looking to build a motion sensing device that will dim a LED Strip to full brightness when motion is sensed, and dim to off after a timeout has occurred from last motion sense. All the tutorials I have seen just show how to dim via RGB inputs, but I will need to dim via PWM to the 12V input of the LED strip.

I will be using the SparkFun Pro Micro 5V board (https://www.sparkfun.com/products/11098), Armacost LED strips (http://armacostlighting.com/documents/RibbonFlex60-RF3528060.pdf), and the SEN-08630 PIR (PIR Motion Sensor (JST) - SEN-13285 - SparkFun Electronics).

Has anyone attempted this or have any advice on how to PWM the voltage input on a 12V device?


Easiest way is to connect the LED strips + to whatever you are powering them from (like 12V) and control the - with a transistor, rated high enough for the current you are switching.
For up to about 9-12 LEDs in a strip (about 90mA to 120mA of current), a 2N2222A would work fine. Connect the LED strip - to the NPN collector, connect the NPN emitter to the Power Suppy Gnd, connect the Power supply Gnd to the Arduino Gnd.
Connect a PWM pin to a 220 ohm resistor the other end of the resistor to the NPN base.

analogWrite (pwmPin, x ); // with x = 0 ( off ) to 127 ( middle ) to 255 ( full on )