Bdtyktl

I want to power an Arduino (Wemos D1 Mini) with 5 or 3.3 V from my garage door opener, which has 24 VDC available.

As far as I understand, this can be solved in the following ways:

1. Step down buck converter


2. Linear voltage regulator


3. Voltage divider circuit

What are the pros/cons of each of these?

I'm concerned about heat, and I don't want to burn down the garage. I haven't measured how much current my Arduino draws, but I guess it's very little like 250 mA or less(?). I'm only using the built-in Wi-Fi module and no external sensors/relays.

1. This is the most efficient solution, will provide good conversion rate but is a little bit more complex to do and also more expensive. Although you can find modules that are already soldered with components saving you the trouble of calculating everything.




2. This is less efficient, it basically acts as a regulated resistor, dissipating the power you don't use through heating. Only need 3 components usually, the voltage regulator and 2 capacitors and it is cheaper than 1.




3. Won't work for you, voltage divider is not regulated and depends on the load, thus the resulting voltage may vary.

For your case, I would buy a DC/DC buck converter module already assembled like this one.

Note there are also capacitor based voltage converters.

One point to consider between choosing a DC-DC buck converter or a linear regulator is the quality of the output. Because of how they work DC converters will always have some amount of high frequency ripple on the output while linear regulators are extremely smooth.

So, DC converters are very efficient, but noisy, and linear regulators are very smooth, but inefficient (they basically "waste" the voltage difference as heat; stepping down 24V→5V a very large amount of heat).

Whether the ripple matters or whether you can smooth out the DC converter output enough depends on the device you're powering. In your case, an Arduino with no sensors, it doesn't really matter that the power rail is somewhat noisy.

But if other cases if you have sensors that depend on exact input voltage, or other devices that are sensitive to ripple it may matter. With very sensitive devices you might even have to use a combination of a DC converter to drop the voltage down to close to your target, and then use a low dropout linear regulator to get the final stable voltage without losing a lot of efficiency in the linear stage (since it's only a small step down, instead of a large step down).

Option 3 doesn't work at all. It combines all the disadvantages of linear regulator inefficiency (you're dissipating the voltage difference in the resistors) with an unregulated output voltage that varies depending on the load. The load will vary considerably depending on what the Arduino is doing, and especially whether the WiFi module is sending data or not.

I would suggest you to go with DC-DC buck converter.
I have mentioned a link here
https://www.itead.cc/lm2596-dc-dc-buck-converter-step-down-power-module-output-1-25v-35v.html
[This is an LM2596 DC-DC buck converter step-down power module with high-precision potentiometer, capable of driving a load up to 3A with high efficiency, which can work with Iteaduino UNO, other mainboards and basic modules. When the output current keeps greater than 2.5A (or output power greater than 10W), please add a heat sink on it.]
If you feel this PCB breakout module is big, you will also get LM2596 IC's you can add them in your own PCB.