The MagSafe adapter in MacBooks and MacBook Pros is probably the greatest single advancement in laptop technology in the last 10 years. Interestingly, the MagSafe port is also a an analog volt meter that can be read by the OS, and it’s not just limited to monitoring battery voltage; with the right software, you can turn a MagSafe port into a terrible and expensive analog sensor, letting scripts on the computer run based on analog values.
[Peter] created a voltmeter application for his mac after realizing the System Management Controller – the chip responsible for charging the battery – was accessible through low-level kernel calls. If you care enough to chop an Apple power adapter in half, the MagSafe port can read other analog inputs.
The SMC Voltmeter app [Peter] wrote samples the voltage every second and displays values on a graph. This app also allows you to run scripts. While you won’t be able to do much with an extremely expensive, very slow, one-channel data logger (the battery is going to run down eventually), we’re sure we’ll see something that’s held together with duct tape and prayer that uses this weird tool.





The standard power adapter for Apple laptops is a work of art. The Magsafe connector has saved more than one laptop owned by the Hackaday crew, and the power brick with interchangeable plugs for different countries is a work of genius. Being a miracle of modern manufacturing doesn’t mean Apple gets it right all the time; the UK adapter doesn’t use the ground plug, leading to the power supplies singing at 50 Hz when plugged in. [Gareth] had had enough of the poor design of his charger 

