12v step down to 5v?

[Zythophile]

I assume this is probably a simple problem to folks who know electrical systems - I do not

What would this entail in a electrical system install to accomodate a 5v (I believe) device? Is it just a matter of putting a resistor in the circuit? This would be for a lighting solution that would be a steady draw.

Devices in contention are battery operated, three AA batteries at 1.5v each, and I'd like to ditch the battery-based source of power. I assume that's 4.5v total to take into account, round up to 5v?

If I were to chain two or more of these together, would the power would have to step up to match in a linear fashion?

 

[Qxxx]

All you need is a little USB adaptor that runs off 12V. They can be wired into your system, or plugged into the cigarette lighter socket.

https://www.amazon.com/DaierTek-Charger-Aluminum-Waterproof-Voltmeter/dp/B07SYWRTHJ
https://www.amazon.com/Charger-Adapter-Cigarette-Lighter-Samsung/dp/B08GWZWN6K

Then a USB cable with a power plug.

https://www.amazon.com/12V-Voltage-Step-Converter-Cable/dp/B07J6NYVJV

 

[Zythophile]

Oh nice! So nothing extra really needed as far as the base system. That makes things far simpler. Thank you!

 

[Qxxx]

Yeah, the other thing is, I have a bazillion rechargeable NiMH AA batteries that I use in my portable projects. 3 in series will give a nominal 3.6V which will run most things, and 4 in series will give about 4.8V. I buy holders for these things.

https://www.jameco.com/z/SBH-331-AS-R-3x-AA-Battery-Holder-with-Cover-and-Switch_216144.html
https://www.jameco.com/z/BH-341-2A-R-Jameco-Reliapro-4x-AA-Battery-Holder-with-6-Wires_216152.html

 

[Spaceman Spiff]

Oh nice! So nothing extra really needed as far as the base system. That makes things far simpler. Thank you!

You also need to know how many amps your device uses.  The first one linked delivers 1.5 amps, the second 4.8.  Too many amps is ok, not enough probably won't run your stuff.

You can also use a buck transformer (also called a voltage converter).  Get an adjustable one and you can set it for the voltage you need.

 

[user 423]

Devices in contention are battery operated, three AA batteries at 1.5v each, and I'd like to ditch the battery-based source of power. I assume that's 4.5v total to take into account, round up to 5v?

Rechargeable Ni-Mh batteries are actually 1.2 volts. At least the Energizers and Eneloops I have are.

A while back I bought 2 push lights that use 4 AA batts and plan to switch to USB power.

4.8 volts is even closer, so I make it a point to look for devices that use 4 instead of 3 batts.

No luck for my camera or small flashlights.

 

[MrAlvinDude]

Here are examples of a cheap (but good) buck converter (model mp1584)

https://www.ebay.com/sch/i.html?&_nkw=mp1584

They are so cheap that they are offered in 1/5/10 pcs per lot.

The MP1584 is adjustable, so you need a multimeter in order to read the voltage output, before you connect them to the LEDs.


For LEDS that operate on 4.5V, I always set the output of my buck converter too a little less, like 4.3V or 4.2V
As this will help the LEDs to live about 2-10 times longer.

 

[Qxxx]

Good find, Alvin, I've not seen those converters before. I have several of these other adjustable ones, been using for my projects, usually with LiPo or NiMH cells with 7.2-9.6V series setups.

https://www.ebay.com/itm/2pcs-XL400...er-Constant-Current-Power-Module/152837387238
https://www.ebay.com/itm/1x-DC-DC-S...wer-Supply-Module-3-35V-to-5-45V/383537296766