‘ERROR: Cookies are blocked or not supported by your browser. You must enable cookies to use WordPress.’

I recently struggled when I tried to add a new website to my WordPress multi-site installation. When I was using a subdomain (newsite.parentsite.com) everything was working fine, but as soon as I moved the new site to its own domain (owndomain.com) I couldn’t log in and I was stuck in a loop with the following error appearing: ” ‘ERROR: Cookies are blocked or not supported by your browser. You must enable cookies to use WordPress.’”
This was quite frustrating and I wasted way too much time trying to solve it. Luckily I came across the following forum post that details a solution: https://wordpress.org/support/topic/changes-domain-and-now-i-get-cookie-error/ .

In essence you do the following:

  1. Under your /wp-content/ folder create a /mu-plugins/ folder if one doesn’t exist already. This stands for “must use” and contains plugins that WordPress must load for all sites.
  2. Create a new file (fix_cookies.php) in the mu-plugins directory.
  3. Paste the following code in the fix_cookies.php file:
<?php
add_action( 'muplugins_loaded', function(){
	global $current_blog, $current_site;
	if ( false === stripos( $current_blog->domain, $current_site->cookie_domain ) ) {
		$current_site->cookie_domain = $current_blog->domain;
	}
});

That’s it. After a refresh you should be able to login to your dashboard.

Removing the Supervisor Password on an Lenovo X131e Laptop

According to the Lenovo Hardware Maintenance Manual a X131e with an unknown Supervisor password, the following applies:

“Attention: If the supervisor password has been forgotten and cannot be made available to the service technician, there is no service procedure to reset the password. The system board must be replaced for a scheduled fee.”

This however is not the case.

Firstly I used this tutorial to get access to the innards of the laptop. [YouTube]

The Supervisor Password locks down the BIOS and prevented me from being able to boot from a USB disk so I had to find a workaround.

Luckily I was able to find a helpful guide on David Zou’s site.

The links detail the process of identifying the BIOS EEPROM storage chip and then shorting out the communication lines at the right time to allow you to change the password without knowing the old one. I love this hack since it is so ingenious and according to the official documentation no solution exists.

So while I cannot claim to have disovered this workaround I can confirm that it works beautifully and I just wanted to thank David for sharing the details.

 

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.

TS-BTDF01 Bluetooth Transmitter Pairing Instructions

Screen Shot 2016-06-20 at 5.57.59 pmI recently bought a TS-BTDF01 Bluetooth Transmitter to use with a pair of Bluedio headphones. At first I thought the unit was DOA, based on the included instructions. Here is how you can troubleshoot any pairing problems you might have.

  1. Connect all the cables (Audio in and power)
  2. Press and hold the white button on the back until you get an alternating flashing blue and red light on the front. This is a loooong press.
  3. The unit is now in pairing mode.
  4. If you get a slow flashing blue light, the unit is on but not in pairing mode. Power cycle and try again
  5. Once the unit is paired it can just be turned on with a long press of the white button.

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!

Disclaimer

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.

References:

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.

References:

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.

Conclusion

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 backup a website on a Mac

Contrary to popular belief the web is not static. Neither does it retain everything. If there is a useful website that you want to save for posterity you can use the following method. Note that these instructions are for a Mac using OSX. I will post Windows instructions in the future.

Instructions:

Download SiteSucker. Get the version for your iteration of OSX. Newer versions are only available through the app store. The latest versions are not free. I’m still using version 2.3.6.

Sitesucker Screen ShotDownload, install and run the app.

Sitesucker Screen Shot 2016-04-13 at 6.21.28 pmYou should be greeted by the window above. Paste the URL of the website you are interested in downloading in Web URL box, and click download.

Site Sucker Screen ShotThe lower half of the screen should start flashing with URLs and filenames. The program will continue to download all the files on the site.

Screen Shot 2016-04-13 at 6.44.16 pmWhen the download is finished the window will look the same as before you started except that the Files Downloaded counter will have a value larger than zero.

Screen Shot 2016-04-13 at 6.45.52 pmYou can now click on Open File to open your downloaded website in your default web browser. The website will have been “localized”, meaning all the links will have been altered to work on your local machine. This makes it possible to browse the offline copy without the internet. Lastly you can click on the Download Folder button to see where the files of the download were stored.

Have fun and use responsibly.

Warnings:

  • Most hosts of websites charge the owner for the amount of bandwidth used. Making a backup of a whole site uses a lot more bandwidth than just viewing a few pages. Thus, only backup websites that are important to be preserved.
  • There are various settings that can affect the operation, including the ability to exclude local files, settings limits etc. Interested parties are invited to view the SiteSucker manual. Make sure you are viewing the manual that matches your version of the software. In most cases the default settings will suffice.
  • It is good to keep an eye on SiteSucker when it is downloading to make sure that it is behaving as expected. Sometimes it downloads large files you don’t want or follows links to parts of a site you are not interested in. You can prevent this behavior by changing the settings.

How to print a webpage onto paper (dead tree paper)

I believe in the strategy of not putting all your eggs in one basket. As such I don’t trust the internet, or the cloud for that matter, to always have a copy of articles or websites that are important to me. Sometimes I save these websites to my computer or clip them to Evernote, but for really good articles I want to print them onto good old reliable paper. Since the printing of websites has become less popular the functionality to do it properly has disappeared from my browser of choice, Firefox.

Here is my tips for printing a website using the Chrome browser.

Step one is to open the website you want to print in Chrome.

Screen Shot 2016-02-07 at 12.58.48 pm

Now select Print… from the three stripes menu in the top right hand corner or by pressing Ctrl + P (Windows) or Command + P (Mac) on your keyboard. Screen_Shot_2016-02-07_at_12_59_13_pm

This will bring up the print dialog. Make sure you have the correct printer and page size selected. Then make sure that you select:

  • Minimum under Margins
  • Tick Simplify page under Options
  • [Optional] If you want the URL to be printed on the pages make sure to tick Headers and footers under Options
  • Click Print

Screen_Shot_2016-02-07_at_12_59_27_pm

For comparison you can see that the print would have been 6 pages without selecting the Simplify page option.

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.

Note:

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.