@AWI Ha, I forgot about that...I remembered that you actually need a minimum load on the output of the switching regulator for it to even run. I created a spreadsheet just taking into account the quiescent currents and assuming 70% effciency for the lm2596 (a "bit" optimistic. Datasheet says 80% at 3A load for 12V-5V operation). Quiescent current for the LM2596 is much higher. Considering the mini pro takes about 12-20mA running, I am sure to opt for the 7805 or LM317 from now on ;) (If there is nothing else drawing current). I think nano etc are comparable but the FTDI USB to serial converter probably adds some current that the mini pro is missing. [image: 1491471718042-upload-90fd958b-83f1-4af4-abbc-f4103ec1e2fc-resized.png] 0_1491471734938_analysis7805.xlsx

Here are some scientific messurements: http://cc.oulu.fi/~kmikhayl/site-assets/pdfs/2012_NTMS.pdf Table on last page says: SoftSPI consumes about double the electricity of a Hardware SPI on a PIC system. So, desoldering the LED is the thing to do. Thx for the hint.

[image: 1462555359580-p_20160506_191958.jpg] [image: 1462555397674-p_20160506_192036.jpg]