MacMini Upgrade - Power Supply

From tunertricks.com April 12, 2005. As I’ve mentioned before in other tech posts, I really disliked from the outset that I had to use a power inverter to run the MacMini installed in my 2001 GTi. My thinking is that it was a rather convoluted solution to take an electrical system’s output that is 12 to 14v DC, convert it to 110v AC and then step it back down to 18v DC through the MacMini’s power supply brick to make the computer function in an automotive environment. I got numerous emails and comments (ahhh, slashdot) about this aspect of the install as well, seconding my thoughts on how cool it would be if somebody out there made an 18v power supply designed for the MacMini to function properly in a car.

Aside from my aversion to this aspect of the inverter solution, it also led to simple functionality problems in the car environment, such as the fact that the Monster Cable inverter I used would sometimes go into a protection mode and not allow the Mac to power up normally, the lack of ignition-controlled wake and sleep functions and the quirky workarounds that I had to come up with to allow the computer and inverter to stay on while pumping gas or running in to a store for a quick pickup.

Well, these problems have been solved by Carnetix with the development of the CNX-P1900 dual output 140watt intelligent DC to DC power regulator.

Basically, this unit is a direct replacement (with major upgrades!) for the MacMini’s power brick that accepts 7.5 to 18 volts of constant input, has an ignition sense and pulse trigger input and ouputs a stable and consistent 18.5 volts, a secondary 5 volt or 12 volt output for powering USB hubs or screens, a delayed 12 volt amplifier or accessory turn-on lead and a pulsed ground output for triggering the MacMini’s power button for automated operation of sleep, wake and startup functions. The wide range of voltage input capability allows the P1900 to never sacrifice its ouput based on low voltages encountered during engine cranking, where battery voltage can often drop to as low as 7.5v. This unit is precisely what I hoped somebody out there would develop - but I didn’t expect it so soon! The unit I installed in my VW at the end of last week is a pre-production model using the GTi as a test environment, but production models will be available through Carnetix at the end of April, with a MacMini-specific plug and play wiring harness coming available in August of this year.

The installation process - luckily for me - was really very straightforward, as the unit comes with detailed instructions that are frequently updated on the Carnetix site and are available for download in .pdf form as new information comes available. Through the process of installing this unit in my car and communicating with Carnetix on the finer details of the process, I expect that a MacMini specific installation manual will be perfected within the next couple of days - certainly before any units ship to end users. A clear diagram of the necessary wiring is already available on the site as well, and is posted below.

Essentially, you simply open the MacMini and unplug the power button connector from the board and replace it with the Carnetix-supplied MacMini power button y-cable that connects to the board, the power button, and the output wire of the P1900 power supply for sleep, wake and startup control. You then cut the power supply cable from the Mac’s power supply brick and wire it to the P1900’s output connector. This second step will be simplified when the new harness becomes available in August that will plug directly into the back of the MacMini, eliminating the need to remove the cable from the original Apple power supply. Lastly, you connect the power input wires to the P1900 (battery, ignition, ground and the optional pulse-start input) and the remaining outputs to a USB hub, screen, amplifier or any other applicable accessory that needs power in conjunction with the computer. Change the setting that allows the MacMini’s power button to sleep the computer in the Energy Preferences pane of System Preferences and you’re pretty much done.

The only idiosyncracies of powering a MacMini off this power supply are the required installation of a sleep diode (detailed on Carnetix’s site) and the changing of one jumper that allows a connected powered USB hub to turn off immediately when the key is turned off, preventing the Mac from waking back up when it detects a change in voltage on the USB bus. I would imagine that when this unit is made available to the general public, this setting will already be made based on the user’s requirements before the product is shipped, eliminating the need for any internal tinkering except in special circumstances.

After having this unit in the car for roughly a week, I can absolutely say that I am pleased and impressed by the thought and detail that was put into the design and execution of this little technological wonder. It is smaller than the Apple power supply (not to mention an inverter as well), the internal fan keeps the regulator cool while remaining quiet, it doesn’t induce any audio or video noise, the installation is simple and it functions exactly like the company says it does. Now, I can use the Mac in my car in exactly the same way as a typical car stereo. When I turn on the car, the computer wakes up, and a simple press of the play button in iTunes (or a press on the Griffin Powermate) gets the music going. When I turn off the car, iTunes pauses and the computer goes to sleep with no fuss, no crashes, no hard shutdowns…It’s really a huge change from the previous situation.

I did leave the Monster Cable inverter installed - by the way - for those who noticed it in the photos below to provide power to the AC outlet installed in my rear side panel. This allows for charging of camera and laptop batteries or running any other AC device in the car whem the need arises. Thanks a million to Mike at Carnetix for the chance to try out this early model and for all the tech support, and thanks to everyone for looking. This solves a major issue for easily installing these incredible little computers in cars and enjoying them on a daily basis. Other upgrades are always on the table, so keep checking for more!

1 7 6 5 4 3 2