Pat Anderson
New member
No big deal to PC people, they can get dirt cheap 12 volt adapters for their notebooks. For us Mac types, though, we suffer with Apple's strange reluctance to provide us a similar amenity. They do sell an "airline" 12 volt adapter, but it has two drawbacks: (A) it doesn't charge the battery, and (2) it is the most expensive 12 volt adapter on the planet.
So, I came across the solution while searching for a third party 12 volt adapter - of which there are several but they too are incredibly expensive. The solution is: build your own.
I was a leg up on this project because I already had an old Targa universal laptop adapter, the kind with a bunch of interchangeable tips - the tips not only are different sizes but evidently also regulate the voltage. A Macbook needs 16.5 volts, so I found the 16.5 volt tip using my digital multimeter (the Targa manual does not say voltages, only what models of computers the various tips are for). This tip has a 5.5 mm plug, so I went to Radio Shack and got a little project box and a 5.5 mm jack. Drilled 5/16ths hole in each end of the project box, and stuck a grommet in the hole for the cord.
Now, the essential part is the magsafe cord with the magnetic tip. But most of us have had a 120 volt power adapted die (I am on my third one now). When the last one died, I decided to harvest the cord just for this project. So I stripped the end of the cord, the center wire gets soldered to the center lug on the jack, and the shielding goes to the outer lug. Close up the project box, plug the Targa tip into the jack, and we are done.
This morning was my first chance to use it, working like a charm! First I checked the voltages on the pins of the Magsafe, which is symmetrical. Pins 1 and 5 are negative, pins 2 and 4 are positive, and the middle pin, 3, is probably the controller for the green/amber LED light. Got 16.5 volts with the multimeter right where they were supposed to be, plugged 'er into the Macbook and she has charged the battery right up to 100% and is powering this session!
A small thing, perhaps, but being able to run the Macbook directly on 12 volts on the boat is a big thing to me, now tethered to my iPhone and powered by my homemade 12 volt adapter, I am good to go!
So, I came across the solution while searching for a third party 12 volt adapter - of which there are several but they too are incredibly expensive. The solution is: build your own.
I was a leg up on this project because I already had an old Targa universal laptop adapter, the kind with a bunch of interchangeable tips - the tips not only are different sizes but evidently also regulate the voltage. A Macbook needs 16.5 volts, so I found the 16.5 volt tip using my digital multimeter (the Targa manual does not say voltages, only what models of computers the various tips are for). This tip has a 5.5 mm plug, so I went to Radio Shack and got a little project box and a 5.5 mm jack. Drilled 5/16ths hole in each end of the project box, and stuck a grommet in the hole for the cord.
Now, the essential part is the magsafe cord with the magnetic tip. But most of us have had a 120 volt power adapted die (I am on my third one now). When the last one died, I decided to harvest the cord just for this project. So I stripped the end of the cord, the center wire gets soldered to the center lug on the jack, and the shielding goes to the outer lug. Close up the project box, plug the Targa tip into the jack, and we are done.
This morning was my first chance to use it, working like a charm! First I checked the voltages on the pins of the Magsafe, which is symmetrical. Pins 1 and 5 are negative, pins 2 and 4 are positive, and the middle pin, 3, is probably the controller for the green/amber LED light. Got 16.5 volts with the multimeter right where they were supposed to be, plugged 'er into the Macbook and she has charged the battery right up to 100% and is powering this session!
A small thing, perhaps, but being able to run the Macbook directly on 12 volts on the boat is a big thing to me, now tethered to my iPhone and powered by my homemade 12 volt adapter, I am good to go!
