Daily Archives: 2014-11-10

RGB LED Strips

On another topic, I recently purchased a 5 metre strip of RGB LEDs.

RGB LED Strip (5m)


These are quite different from the addressable LED strips used in my clocks. These strips consist of multiple tri-colour LEDs (in this case, 60 per metre) wired so that all like-colour LEDs are connected together – often 3 LEDs of the same colour, connected in series. The flexible substrate has four connections: +12V, Red, Green and Blue, that can be cut every three LEDs.  Pulling these colour connections (RGB) to ground illuminates all of the LEDs of that colour in the strip. Driving each LED colour with a Pulse Width Modulated (PWM) signal allows you to precisely control the intensity of each colour, so that the entire strip can display myriad colour combinations. Using an Arduino, for instance, due to the current required to illuminate the LEDs (300 per colour for a 5 metre strip @10mA/LED = 3A!) you will need to drive each colour signal from a PWM output pin connected to a power NPN Darlington or an N-type power FET. Driving the LEDs hard will also mean you need a hefty 12V poser supply and heatsinks for the power devices.

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CNC – Update 1: Cutting heart shapes

So, I was playing with my CNC machine and its control software and started to cut some shapes and designs. I make no excuses, as i’m starting to learn how to use the machine and software. Here is a very amateur video (sorry about the quality) of the CNC machine cutting a heart shape into some primed MDF. The tool is a 1/8″ spiral upcut so consequently the shape outline is quite thick.

As you may be able to see, one of the screens of the USB CNC Controller software shows the G-code (on the left side) and a real-time graphic of the cutter position (x-axis in green, y-axis in red and z-axis in blue) and the heart-shaped path it is taking.

I’ve set up the machine properly so that step size is now accurate in X, Y and Z axis and have been playing with different g-code designs. As an example, here’s a heart within a heart (just for Lili).

CNC Hearts

CNC Hearts

Hearts cut from 3/16" MDF

Hearts cut from 3/16″ MDF

Using a 1mm bit, the inner heart was cut to a depth of about 4mm and the second to nearly 8mm. This outer path was actually created by scaling the first by 200%; a feature of the software.

I guess I’ve just passed my first test – I broke my first 1/32″ milling bit (sob). [Note to self: remember to turn the spindle on before starting the cut!].

I also cut two hearts from 3/16″ MDF using the 1/8″ (3mm) end mill cutter. I used the multi-pass feature to make 7 passes, each pass lowering the mill by 1mm. The results were very impressive, yielding parts with clean features and sharp edges.

Onwards and upwards (or is that side-to-side?)

Cool huh?