How to best power nrf+arduino (from 12V)

[LastSamurai]

Hey I am currently trying to find the best solution for powering a mysensor node consisting of arduino pro mini and an nrf24L01+. There could also be a sensor or 2 and/or whatever current some mosfets need for switching.
This is not going to be battery powered but instead should be powered from a 12V power supply thats also used to drive and RGBW led strip (in this case).

What is the best/cheapest/smallest solution to powering such a node from 12V (or perhaps even more)?
Possible ideas:

• Some DC-DC Buckconverter like a LM2596 => efficient but needs additional parts due to high frequency ripple, also not that cheap
• Some buckconverter + a linear regulator => needs even more space and money but should be really efficient
• Just a linear regulator => cheap, small but what about the heat? Does this work without a heatsink for these small devices?
• 2 linear regulators? e.g. 12V to 5V and 5V to 3.3V => is that in any way better than the above version? I guess the overall heat would still be the same right?
• Special case: the onboard regulator of the arduino pro mini I am using: Has anyone tested this? Does it provide enough current?

How did you guys solve this problem? While powering with a battery has other problems ripple shouldn't be one of them (I guess). I still see lots of questions where a bad powersupply seems to be the problem so this thread might help others too.
Thanks!

[soward]

I've been using a 12V supply and a 5V linear regulator to power a RGBW+W strip and a pro-mini for over a year now. And I use the 3.3v regulator on the mini to drive the radio. No problems and while a buck converter might be more efficient, there's no significant (or even noticeable) heat on the linear regulator and it's a pretty small amount of power in general.

[m26872]

@LastSamurai AMS1117-3.3 won't heat much more than 40'C. I don't think it's worth to bother with anything else than a linear regulator. Power supply ripple rejection seems to be satisfactoring as well.

[TheoL]

I'm using a LD33v with heat sink. I'm powering this regulator as well as the pro mini directly from the 12V adapter. I've found a schematic for this that uses the 10uf capacitores. One before and one after the ld33v. The antenna and the other sensors get their power from the ld33v. Cheap and works like a charm.

[LastSamurai]

Guys, I need some help here (again). I have build a RGBW Controller (schematics in the pdf or my openhardwareio project) that uses the 12V for the leds and an AMS1117 to create 3.3V. I also added a 22uF cap at the output (like descriped in the datasheet).
When I started the node with the 12V input and no LEDs connected yet it seemed to work for some seconds before the AMS suddenly got really really hot and now the input and ouput pins of the AMS seem to be connected (at least my multimeter says so) and it output ~7V.

So I am pretty sure the AMS overheated and got destroyed. It's only powering the pro mini and and NRF24L01+ though.. do you guys have any idea how this could have happened? I really hope I can fix the error on my boards as I want to use them as soon as possible

RGBWController.pdf
Openhardware IO

[TheoL]

@LastSamurai I'm really curious about the answers.

[LastSamurai]

@TheoL Then we are 2 already. I can't find any error in my schematics and the arduino + nrf should not use more than ~50mA max afaik. So this should be no problem for the AMS (even though its a small smd component), right?
Did anyone else use the AMS1117 in similar way?

[LastSamurai]

Ok the issue seems to have been a broken AMS. I just finished a second pcb and that one is working. The AMS gets hot but not so hot that you can't touch it any more. Seems to work now Now I just have to test the lighting part