Convert Car Charger to USB

[Boolean90] hacked a cheap USB car charger into a variable power supply. His proof of concept is to use this as a variable-speed motor controller. The best part is that nothing is being abused, the regulator inside is still running within manufacturer’s spec.
While we’ve seen similar hacks before, [Boolean90]s video is pretty cool and provides a nice insight into the components used in these cheap devices. Rather than a linear regulator, which would dissipate too much heat the device uses a common jelybean MC34063A (PDF) switching DC-DC converter which costs about 10 cents on eBay (about two dollars for twenty, shipped). Here it’s used to step the car batteries 12 volts down to 5, but can also be used in step-up and inverting configurations.
Like all switching buck converters the MC34063A uses a PWM (pulse width modulated) signal to drive an inductor and capacitor, which effectively form an LC filter. By controlling the pulse width, the output voltage can be regulated. [Afrotechmods] has a great tutorial on the basic principle. The regulation is controlled by feedback resistors. [Boolean90] simply added a variable resistor to allow the output voltage to be controlled.
BESTEK 2-Socket Cigarette Lighter Power Adapter DC Outlet Splitter 3.1A Dual USB Car Charger for iPhone6s/6/6 Plus,iPad, Samsung Galaxy S6/S6 Edge and More Automotive Parts and Accessories (BESTEK)
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DROK 3A/15W Dual Power Adapter 8-22V to 5V Double USB Cable Connector Car Charger For IPhone/iPad/Nokia/HTC BISS (DROK)
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