is the L7812 a suitable power supply IC for a nano 33 ble?

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1

hi all,

from nano 33 ble spec
https://store.arduino.cc/usa/nano-33-ble-with-headers
Microcontroller nRF52840 (datasheet)
Operating Voltage 3.3V
Input Voltage (limit) 21V

need to support following and ALL supply voltages:
12 VDC, 24 VDC and 24 VAC
peak voltage of 24 VAC x SQRT(2) = 33. 94 V

Any thoughts?

source:
https://www.st.com/content/st_com/en/products/power-management/linear-voltage-regulators/standard-voltage-regulators/l78.html

2

Buck/boost converters come to mind, as do MOSFETs. You may have to through a bridge rectifier and some capacitors in the mix as well.

3

In short, the L7812 is old, linear technology. You would run into heat problems very soon.

4

Thanks for the reply
Since L7812 is inefficient and old, may I ask you please to advise suitable power IC?

For 24VAC, we will fit a bridge rectifier + capacitors to get a DC voltage output prior to connecting to a diode based adding circuit (24 VDC OR 12 VDC OR 24VAC x SQRT(2))

Thanks
Trajano

5

traja47:
Thanks for the reply
Since L7812 is inefficient and old, may I ask you please to advise suitable power IC?

As said, get a buck converter. Old or not, all such linear converters have to burn off all the excess power somehow. Get one that takes up to 36V or more as input, and produces 12V which goes to your other devices, and a second buck converter (or does the Nano BLE have one on board?) for the 12V to 3.3V step (or of course direct from 34V to 3.3V).

For 24VAC, we will fit a bridge rectifier + capacitors to get a DC voltage output prior to connecting to a diode based adding circuit (24 VDC OR 12 VDC OR 24VAC x SQRT(2))

That indeed will give you over 34V on the output...