There are times at that I get mad about empty AA batteries or accumulators losing their capacity too early. And since the gaming computer is running anyway, I thought about using one of the molex connectors to run a wire out of the computer casing and use it as power source for the currently battery-driven gamepad.
The plan:
Molex connector gives 12V/5V, convert the 5V to 1.4V
My tests:
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AA akku, Multimeter, Gamepad: the gamepad drains roughly 60mA
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power supply, Multimeter, electronic parts:
5V of power supply are converted to 3.3V by a MCP1702-3302;
the remaining 1.9V shall be reduced by ~30 Ohm resistors in series.
As the power supply is switching power to the 5V and the MCP1702 is also switching to 3.3V, I added a 10V/2200 microFarad capacitor at the end, before running power to the gamepad and connecting is to ground.
Result:
The gamepad's power Led is fading/blinking, the device is not working.
I understood that resistors reduce power and current, thus I took the current into account:
R= U/I = (3.3V-1.4V) / 0.06A = 31.67Ohm
Measuring the resulting voltage with the gamepad attached was driving my multimeter crazy.
Is my approach okay?
Does the capacitor flatten the switched power enough to simulate a battery?
Best Answer
You don't want to use a simple resistor to drop your voltage because this is very dependent on current draw. And your controller is drawing varying amounts of current, depending on which buttons are pressed, and LEDs, etc.
For example, the controller might be drawing 60 mA when idle, but much more when active. If it draws more, this will cause the resistor to drop more voltage, and the circuit could starve.
What you want it to use a voltage regulator that outputs what you need. To use the same family of parts that you are currently using, try a MCP1702-1502 instead of your MCP1702-3302.
If it turns out that the device uses more than 200 mA, perhaps if it vibrates (?), then even the MCP1702 won't be able to provide enough current.