esp8266 with 12 V AC step down converter

[riker1]

Hi
having a question.

Anyone havong an idea how to power supply esp with 5v DC
from a source 12v AC?

Thanks a lot

Thomas

[Micha_he]

Bridge rectifier -> smoothing capacitor -> 12V DC to 5V (or for ESP8266 3.3V) DC step-down-converter.

What is the problem ?

[TD-er]

For the part after the rectifier, you may want to use one of these:
http://nl.aliexpress.com/wholesale?catI ... +step+down

Use one that may be able to handle enough current, since the ESP may need up-to 250 mA and you also need some for the sensors.
So choose one that is able to handle up-to 500 mA or more, just to be on the safe side.


Where the "load" is drawn, you connect one of those DC-DC step down converters.

As capacitor you should use an elco rated for 25V or more and capacity of about 1000 uF. (or more)
The 12V AC should be able to handle 300 mA or more. (to power the ESP you need something capable of delivering 1 Watt, so 1 Watt / 12V = 0.125 A should be absolute minimum)

And make sure to use + and - of the elco in the correct position, or else you will see (and hear) fireworks.

[riker1]

Hi, thanks

How do I calculate the smooting capacitor ?

or would this work?
https://www.ebay.de/itm/LM2596-AC-DC-to ... ctupt=true

Thanks

[TD-er]

The module you linked has it all, so that's fine too.
Make sure you either have one which can be adjusted, or choose a fixed one with the correct voltage for your project.

[riker1]

Thanks a lot

[Shardan]

For the shown circuit (bridge rectifier, capacitor running on 50 Hz)
there is a simple rule of thump for the smoothing capacitor.

The capacitor should have at least double of miliamperes needed in microfarad.

So if you need 500mA current the capacitor should at least have 1000 uF.
More is always allowed

Remember this does not count for switching power supplies,
the high frequency used allows smaller capacitors.

[adampr1]

But why so big module?
In my projects I'm use smaller module
https://www.ebay.de/itm/MP1584-3A-DC-DC ... 0506.m3226

MP1584.jpg (74.15 KiB) Viewed 10435 times

With out extra cooling 2A is supported - max 3A when we put some coolpads. That module working with 1MHz therefore no need so big capacitors. It's very nice and place effective.
If we need concrete output voltage then better remove those small ceramic poti and put SMD Resistor (sieze 805 but 1206 is also ok).
3,2kOhm for 3,2V output, 47k + 560k (parallel) for 5V, 120k + 2M2 (parallel) for 12V.
I'm using successful many of those modules

BR
Adam

[riker1]

Hi Adam,

ok, thanks.

but your recommendation is DC only I think.

Model: DC-DC buck module
Input voltage: 4.5V ~ 28V
Output voltage: 0.8V ~ 20V
Output current: 3A (max)
Conversion efficiency: 96% (highest)

I require an AC-DC

[adampr1]

Hi riker, you are right , sorry. I'm forgot AC and consider only on DC conversion.
BR
Adam