While traveling recently, my family had trouble powering the 5 smartphones, 2 tablets, and 2 laptops while driving 2500mi through the southwest. Route 66 and the Grand Canyon are pretty, but in between there are whole lot of straight highways that are not as scenic. This regulator, with the addition of some USB connectors would have been useful to keep our gear charged and ready to go in between stops.
If you need a power and stable power supply in your car this circuit will fit the bill. It’s components are inexpensive and easy to acquire. Although it has a drop of 2 volts, it can handle loads of up to 100 watts at voltages between 1.8V and 10V. The 2 2N3055 transistors handle that power and need to be driven by a transistor. These are controlled with the 741 opamp and the voltage level is controlled with a potentiometer. If you are always going to output the same voltage, you can also set up a voltage divider to the input of the 741. The switch is used to provide the supply voltage, unregulated, if you need the full 12V from the battery.
|RefDes||Name||Value||Digi-Key Part Number||Description|
|R1||VARIABLE||10K||P3Y103CT-ND||TRIMMER 10K OHM 0.15W SMD|
|R2||RESISTOR||0Ω1||P.10AHCT-ND||RES 0.1 OHM 1/10W 5% 0603 SMD|
|R3||RESISTOR||0Ω1||P.10AHCT-ND||RES 0.1 OHM 1/10W 5% 0603 SMD|
|R4||RESISTOR||1K||P1.0KACT-ND||RES 1K OHM 1/8W 5% 0805 SMD|
|R5||RESISTOR||100K||P100KACT-ND||RES 100K OHM 1/8W 5% 0805 SMD|
|C1||NON POLARIZED||100nF||399-4872-1-ND||CAP CER 0.1UF 6.3V 10% X7R 0402|
|C2||NON POLARIZED||100nF||399-4872-1-ND||CAP CER 0.1UF 6.3V 10% X7R 0402|
|C3||NON POLARIZED||100nF||399-4872-1-ND||CAP CER 0.1UF 6.3V 10% X7R 0402|
|U1||OPAMP||741CN||LM741CNNS/NOPB-ND||IC OP AMP HI PERFORMANCE 8-DIP|
|Q1||NPN||2N3055||497-2612-ND||TRANSISTOR NPN 60V 15A TO-3|
|Q2||NPN||2N3055||497-2612-ND||TRANSISTOR NPN 60V 15A TO-3|
|Q3||NPN||BD241B||BD241CTU-ND||TRANSISTOR NPN 100V 3A TO-220|