Monthly Archives: November 2014

Yet another spectrum analyzer!

THE SPECTRALIZER. OK, I know it’s been done before (as my partner kindly reminded me) but I thought I’d share my unique version of a light spectrum analyzer.

Music: Heart of Gold by Snarky Puppy

The video may give you some idea of what it looks like but really doesn’t do the piece justice, The display really is very impressive and an open invitation for like-minded geeks to hack! Anyone know how to get rid of the light bloom on a phone camera?

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CNC – Update 6: Making circuit boards

One of the principal reasons for purchasing the CNC machine was so that I could make circuit boards. I modified the wall clock ATmega328 design that I used to try Dirty Boards (see previous article). Using the Fritzing PCB board layout software, I added a 5v regulator and some passives, and altered the layout so that all traces were on the bottom side.I also added a copper fill ground plane to minimize the amount of copper that had to be removed.  The new design files were then exported in “Extended Gerber” format.

Wall Clock v2 PCB Layout

Wall Clock v2 PCB Layout

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CNC – Update 5: Jog Box

The USB CNC Controller has a 14 pin connector for connection to an external “Jog Controller”. This controller allows the user to move the spindle along each of its three axis, and control the speed at which the movements are made. While there were no instructions for this, a little trial and error established the connections and the necessary circuitry to perform axis movement.

Even though I’m waiting for the 14 pin connectors and big fat momentary switches (on order from China), I made a prototype. It consists of a sloped-top wooden enclosure with an engraved fascia (CNC’ed, of course). I have populated it with LEDs, small momentary switches (which I have previously found to fail intermittently !!) and the jog speed control. The Jog Box connects to the CNC USB Controller with a 14 conductor ribbon cable.

CNC-USB Jog Box-Final

CNC USB Controller Jog Box: Final version with large toggles

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CNC – Update 4: Limits & homing

I have been playing with the CNC machine and all too often I’ve accidentally hit both X and Y extreme limits of travel. I don’t know if there is any damage being done but felt I should do something about it.  The controller software has a panel in the setting menu for both positive and negative limit switches for all three axis so I needed to find the associated hardware connections. The company I bought the machine from claimed not to have hardware schematics for the CNC controller or the USB interface. However, I did receive an image of the CNC Driver Board board indicating where limit switches may connect (top left).

CNC Drive Board

CNC Drive Board

Through trial and error, I found that the model of my controller only provides one input per axis for a limit switch. This means that in the X and Y axes, a limit switch only works when the unit is traveling in a positive direction (i.e. towards the back and right edge). For the Z-axis, the limit switch only works when the spindle moving downwards.  In normal operation the limit switch input is open circuit. If and when the machine moves to a limit, the switch shorts the input to GND and this stops the movement immediately.

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Nano with CH340G USB chip driver

For those of you familiar with buying Arduino-related products on eBay, you probably would have seen a slew of cheap Arduino Nano boards (specifically the V3.0 ATmega328 16M 5V) being sold ($4 vs. $7.50).

So, what’s the catch?

Well, instead of the more common FTDI (FT232) chip, these modules include a CH340G USB interface chip, which is apparently much cheaper. Now, while the FT232, and specifically the FT232R, can throw driver errors (see this post for discussion), the CH340G requires a specific driver. I found the driver online although there were only Chinese instructions. However, installation is very straight-forward (on a Windows 7 (64 bit) machine, at least.


I cannot attest to the quality of the download files. I have tried it, successfully run a Microsoft Security Essentials scan and it does not trigger any issues with virus protection. Please proceed at your own risk!

Click here for the driver software

Before connecting the Nano to your USB port:

  1. Download the “ch341ser,exe” file and run it.The software extracts about 8 files.
  2. The software asks whether it can install the CH341SER.INF driver for the CH340 chip (Version 11/04/2011, 3.3.2011.11). Click INSTALL
  3. A Windows message asks whether the driver has installed correctly. Click YES.
  4. Connect your Nano.
  5. From Control Panel, open Device Manager and Ports. If installed correctly you should see an entry “USB-SERIAL CH340 (COMXX)

That’s it… Cheap Nanos for all!

CNC – Update 3: Cutting images in plastic

If only Matisse had his own CNC machine…

The CNC Controller software has the ability to import 2D images in .bmp, .jpg and .png formats. I chose one of my favourite Matisse’s black and white line drawings of a woman’s head and shoulders, called “La Pompadour” (see note below) and uploaded it into the software. The following screen shots show the sequence of windows and screens as the image was converted to a cutting pattern.

CNC image details

CNC image details

CNC image processing

CNC image cutting control

CNC image pattern trace

CNC image cutting pattern






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