Using a Ublox Chipset USB GPS Receiver on Mac

I recently bought a small USB GPS receiver from eBay. The listing does not give an indication that it can work on OSX but after a bit of detective work I was able to get it working on OSX 10.13.
  1. In terminal run the following command ls /dev/tty.usb* , this will list all the USB serial devices on your system. In my case there was nothing listed after I plugged in the GPS so I knew there was a problem with the driver.
  2. I was able to figure out that my particular unit uses a Prolific chipset
  3. Download the driver from here: [Driver Page] [Direct Link]
  4. Run the installer and remember to allow the driver to be loaded in System Preference–> Security & Privacy
  5. Run the ls /dev/tty.usb* command again. You should now have a new entry along the lines of /dev/tty.usbserial
  6. You can now view the output of the unit with the following command screen /dev/tty.usbserial 9600 
  7. Success!

Maximum Memory on Mid-2007 Macbook Pro A1226

I just thought I’d share this since I had trouble confirming it myself. There are rumours online that the mid-2007 Macbook Pro (Model A1226) can support up to 6GB of RAM. I have been using 4GB and the possibility of an extra 2GB could not be dismissed out of hand.

I ordered the cheapest possible 4GB RAM module from Ebay. Thankfully it was compatible. Apple computers can be a bit finicky with RAM.

screen-shot-2016-09-28-at-12-30-33-pmI just swapped an existing 2GB module with my new no-name 4GB module. My laptop booted up with no problems. The About This Mac  menu confirmed that the upgrade was successful.

Macbook Pro Memory ScreenSo in conclusion, the mid-2007 Macbook pro can indeed support 6GB of RAM.

How interchangeable are AC and DC circuit breakers?

A friend recently asked my engineering opinion on the matter of using DC (Direct Current) circuit breakers in the place of AC (Alternating Current) circuit breakers in a circuit. Now I’d be there first person to tell you that my engineering skills are a bit rusty, but I guess like learning to ride a bicycle it never quite goes away. Forward, onto the breach!


I’m not an expert even though I sometimes pretend to be one online. This advice is for information only and it is up to YOU to ensure that your electrical installation meets local laws and guidelines.

AC in the place of DC

Now this seems to be the most common situation. People want to use the more commonly available AC MCB (Miniature circuit breaker) for their DC based system. This is a bad idea. For exhibit one I call the following video:

This video shows the fundamental difference between AC and DC currents. AC current has a handy zero crossing every half cycle that makes it easy to extinguish an arc. DC on the other hand is full on, all the time. It takes a lot more effort to extinguish the arc in a DC circuit. DC circuit breakers are specially designed to extinguish DC arcs and have special magnets to pull the arc away to get it extinguished.  Thus, don’t use AC MCB’s for DC circuits. For a more in depth explanation have a look at the links below.


For further reading have a look at

DC in the place of AC

This arrangement is a bit more tricky. From the outset it looks like this arrangement should be fine as long as the breaker meets the required voltage isolation levels. However therein lies the rub, if the device does not meet the required isolation levels or have the right approvals, it does not meet legal requirements. There are certain MCB’s that can be used for both AC and DC circuits but these would be clearly marked. Information on this arrangement was a bit harder to find. Have a look a the thread below.


For further reading have a look at

Other considerations

This diagram from an ABB MCB datasheet shows how the trip curves differ for AC and DC. So in other words the performance varies depending on the current type. This is another reason not to use these breakers interchangeably without proper design consideration.

Screen Shot 2016-05-09 at 8.44.31 pmThis is for a circuit breaker that is designed for both AC and DC. You can find the datasheet here.

For a much more detailed discussion on the intricacies of DC circuits and safety I can heartily recommend the ABB circuit-breakers for direct current applications technical application papers.


My recommendation would be to use DC MCB’s for DC and AC MCB’s for AC. There are special design considerations that go into the design of these devices and as an ex-colleague told me when I asked him to check this article: “I got burnt with 110V DC in a panel so don’t play with that thing. Make sure its the right breaker that trips fast.
Can’t argue with real world experience.


How to get a quick idea of future sea-level rise using Google Earth Pro

Our benefactors at Google were kind enough to make Google Earth Pro available for free. Just agree to the terms here and get the version that works on your system.  Just use your e-mail and GEPFREE as the license key to start working.

Firstly make sure that you have the correct settings (Look under Preferences… in the Google Earth Pro Toolbar Menu. Here are mine:

Screen Shot 2015-11-04 at 2.05.09 pm

You can customize the settings to your needs but ensure that the Terrain settings are the same as mine. Also ensure that the Terrain layer is turned on under the Layers box. You can turn the other layers off.

Screen Shot 2015-11-04 at 2.08.20 pm

Then navigate to the area you want to consider. I wanted to look at Auckland, New Zealand.

Screen Shot 2015-11-04 at 2.09.31 pmNext, download this image file that I made. You could use any image file but this one is blue and square, which is perfect for our application. SeaLevelThen you need to insert this image onto the map using the Add Image Overlay tool in the toolbar at the top. That’s the one on the Left in this picture:

Screen Shot 2015-11-04 at 2.19.48 pmGive your object a title, click Browse and point to SeaLevel.png (or the image file of your choice). You could also change the transparency if you want.

Screen Shot 2015-11-04 at 2.26.10 pmClick on the Altitude tab and set the desired sea level height. Make sure Absolute is selected.

Screen Shot 2015-11-04 at 2.26.46 pmMake sure that the image covers the area you are interested in. If it doesn’t, use the green handles on the map windows to change the size and rotation.

Screen Shot 2015-11-04 at 2.33.06 pmIf everything looks good press OK. The map will look a bit splotchy but as soon as you zoom in the terrain data should resolve and the border between the land and the new sea-level should become clear.

Screen Shot 2015-11-04 at 2.36.30 pmAs you can see Auckland won’t cope well with a 50m rise in sea levels.


This method is “quick & dirty”. The terrain data used in Google Earth is not super accurate. Also, I will leave the research up to you, dear reader, to determine what scenario of sea level rise is the most accurate. It works well for sea-level rise in the double digits but single digit rise does not even register above the inaccuracy of the terrain data. At some future date I will describe how to determine the sea-level rise more accurately using digital terrain data.

An adventure in repair and 3D printing

First off I need to apologise for the lack of photos. I should really have documented this process better.

The new apartment I moved into had a broken extractor fan above the hob in the kitchen. The problem was a little plastic part that pushes past switches turning lights and fans on and off.

I thought that this would be a good opportunity to try 3D printing. I extracted the offending part and took some measurements with a digital caliper. I then used these measurements to model the part in Autodesk Inventor. The model was exported and sent to 3D printing service in Melbourne but due to a scaling mix-up the part was printed at the wrong scale. So after the hilarious unboxing of the huge part I went back and made sure I exported the part at the right scale.

This was printed with a different service using a different printer which leaves a much harder support material that supposedly dissolves in water (but doesn’t actually).

After carefully trying to scrape all this material off I tried to screw in the replacement screw only to have the part split! A bit of super glue and some hope took care of this problem.

Lessons learned:

  • 3D printing is great for making small plastic parts that usually break and incapacitate large machines.
  • 3D prints are strong but not invincible.
  • Make sure you and the printer are using the desired scale.
  • Drill out the support material and screw holes. That material has nowhere to go and will split your part if not removed.


What time is it in Melbourne?

The time difference between South Africa and Melbourne is between 8 and 9 hours. Melbourne uses Daylight savings time and thus the time varies between summer and winter. Here is a table showing the differences.

An easy way to list this clock in Windows 7 is to load Melbourne as a second time zone. Here is a tutorial on how to do that: Link. Melbourne is listed under (UTC + 10:00) Canberra, Melbourne, Sydney in the drop-down menu.

And lastly for the people who don’t want any hassle here is the current time in Melbourne.

How to replace a Citroen C2 brake light bulb

To match my previous post on headlight replacement I present this post on brake light replacement. Thankfully these are much easier to reach than the headlights.

  1. Open the boot and locate the nut holding the brake light assembly in place. Loosen the nut and store it somewhere it won’t get lost. Make sure the car and lights are turned off.
  2. Disconnect the brake light assembly power cable. Just wiggle the black connector until it’s free.
  3. Remove the bulb assembly by gently pinching the two pairs of black tabs toward each other. Remove the reflector housing after the tabs are released.
  4. Flip the cover assembly over and replace the dead bulb. Be careful when replacing the assembly in the housing and ensure that the waterproofing gasket is seated properly.
  5. Replace the black bulb assembly and the reflector housing, ensuring that all four clips engaged.
  6. Reconnect the power cable
  7. Replace the assembly into its place and tighten the nut in the boot.

How to import a new parts database to Bentley Substation V8i

Use the following instructions to import/load/add an additional parts database (*.mdb) to Bentley Substation V8i.

  1. Put your *.mdb parts  database file in C:\ProgramData\Bentley\Substation V8i\Substation Data\Databases. This path may be different in a non-Windows 7 environment.
  2. Click “Setup…” in the “Welcome To” window.
  3. Go to the “System Paths” tab.
  4. Click the “New” button.
  5. Give your database a name under “Parts Database Name:“.
  6. Click on “Browse…” and navigate to your database in the directory from step 1.
  7. Select the applicable table from the “Table” dropdown menu.
  8. Click “Next” and then click “Default Mapping“.
  9. Click “Finish“.
  10. Select your new parts database from the “Parts Database Path” dropdown and click “Apply“.
  11. Click “OK“.