How to lower the voltage from 12v to 5v?

Question

Electronics

Good afternoon.

Tell me how to connect a small 5v / 0.2a cooler

to a 12v / 1a source? What is the most compact option? Resistor (if so, which one)?

Answer 1

1) The best thing (in terms of efficiency) is to install a DC-DC converter. You can buy a ready-made module, or pick up some kind of car phone charger. There is just 12V -> 5V
2) You can put a 7805 stabilizer (usually it is called a KRENK). A minimum of a body kit, you can solder it with volumetric mounting on your legs
3) If you want a resistor, then you can calculate it.
Current through the entire circuit I \u003d 200mA \u003d 0.2A.
Drop across the resistor Ur = 12V - 5V = 7V
Resistor resistance R = Ur / I = 7V / 0.2A = 35Ω
Resistor power P = I * I * R = 0.2A * 0.2A * 35Ω = 1.4W
T. e. you need a 2W (or more) resistor at 35 ohms (or a little more)
Connect it - in series, through any wire, but usually this is a plus

Answer 2

dc-dc converter

Answer 3

Better not a resistor, but a 7805 with a pair of capacitors, screw the only small piece of aluminum / copper to dissipate 3 W.
Well, or Chinese step-down DC / DC, there almost any running board will provide 0.2 A.

Answer 4

Such a cooler costs 100 rubles, it would be wise to buy a 12 volt cooler and use it.