I've been reading up on different methods of powering a Pro-Mini (or most any Arduino) and a question popped into my head.
This is all hypothetical as I haven't purchased any hardware for the project I'm contemplating. That said, I seem to see a lot of folks asking how to power a board when their supply voltage is larger than the recommended voltage for the Arduino. And in almost every instance, it is advised that a converter be used to drop the voltage to safe levels.
My project would involve a Pro-Mini being soldered (and powered) directly to a larger circuit board. And, at this point, the main board will be powered by 9 volts. That is subject to change, however.
But for arguments sake, let's say I had to up the voltage to 24 volts. Could one use a voltage divider to feed a safe voltage to the Mini? Just thinking it would be much cheaper and easier to implement.
I'm still learning. So feel free to school me on the subject.
Voltage dividers are for signals (very low current), never to drop voltage for powering circuits.
From the Sparfun voltage divider tutorial.
Application Dont's
As tempting as it may be to use a voltage divider to step down, say, a 12V power supply to 5V, voltage dividers should not be used to supply power to a load.
Any current that the load requires is also going to have to run through R1. The current and voltage across R1 produce power, which is dissipated in the form of heat. If that power exceeds the rating of the resistor (usually between ⅛W and 1W), the heat begins to become a major problem, potentially melting the poor resistor.
That doesn't even mention how inefficient a voltage-divider-power-supply would be. Basically, don't use a voltage divider as a voltage supply for anything that requires even a modest amount of power. If you need to drop down a voltage to use it as a power supply, look into voltage regulators or switching supplies.
Could one use a voltage divider to feed a safe voltage to the Mini?
No not really. In general you need ten times the current draw through the voltage divider as you will take out across the bottom resistor. This means that the resistors burn up a lot of power and get hot. This needs expensive higher wattage resistors and wastes a lot of power.
And in almost every instance, it is advised that a converter be used to drop the voltage to safe levels.
There is a good reason for this. Just get yourself a switching, sometimes called buck, regulator board, problem solved.
groundFungus:
Voltage dividers are for signals (very low current), never to drop voltage for powering circuits.
From the Sparfun voltage divider tutorial.
Grumpy_Mike:
No not really. In general you need ten times the current draw through the voltage divider as you will take out across the bottom resistor. This means that the resistors burn up a lot of power and get hot. This needs expensive higher wattage resistors and wastes a lot of power.
There is a good reason for this. Just get yourself a switching, sometimes called buck, regulator board, problem solved.
I guess that makes perfectly good sense. Thanks fellas!