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I have a device with two possible output pins with max. rating 60V/1A and 12V/100mA that I would like to connect to an ESP8266 (that sends notifications when ON). To keep it simple, I would connect it as a regulated source (3.3V) directly (without transistor or optocoupler) to Vcc and so on so It's not necessary to use another external source. (Maybe I should, as an amateur I'm listening to you.)

Can you please give me a direction how to regulate the source? Linear regulator (as the main part) seems to be inefficient in this case so maybe a switching (buck) regulator? The 60V seems to be high for that and 12V has only 100mA that seems to be low for the ESP (even with a capacitor?) as it needs about ~50-170mA with ~350mA spikes (thats what I have found)? Is there a way how to lower the voltage to rise the current (transformator, inductor or anything? )?

to keep the answer one and clear: How would you regulate/use 60V/1A or 12V/100mA to get ESP's 3.3V/~300mA?

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    \$\begingroup\$ ESP8266's current burst spikes may be higher than 350mA. Use a power source that can source at least 500mA @ 3.3V to be safe. \$\endgroup\$ – anrieff Aug 8 '18 at 8:47
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How would you regulate/use 60V/1A or 12V/100mA to get ESP's 3.3V/~300mA?

60V/1A = 6 Watt
12V/100mA = 1.2 Watt
3.3V/~300mA ~+ 1 Watt

To supply 1 Watt from the available 12V supply you need an efficiency of 1/1.2
or >= 83% end to end. This is doable but various losses can make it harder than desirable. In addition, as Andy noted, the ESP8266 has (very) significant current spikes during operation. An energy source with a bit more headroom or LARGE capacitors are in order. If the 300 mA nominal is always significantly lower in practice then the 12V supply may suffice but otherwise the 60V supply is 'safer'.

Andy suggested an LT8631 which is an acceptable if somewhat expensive IC. It is important to note that 60V input is more than most regulators can accept (more than once) and a Vinmaxwkg >> 60V is needed.

Here is a list of Digikey switching reguator ICs with Vinmax >= 95V sorted in order of ascending 1 off cost.

I'd be 'just a little' concerned about the prospect of the 60V supply getting into the 3v3 system if things gang aglae. Murphy has a way of managing these things. I'd consider either fuse + crowbar-ing the 3V3 output or consider an isolated output switcher. eg The not otherwise marvellous NCP1032 flyback converter has the advantage of independent output. It requires a 3 winding transformer (input + IC Vcc supply = output but makes it hard to get 60V on your 3V3 rail.

NCP1032 data sheet

enter image description here

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How would you regulate/use 60V/1A or 12V/100mA to get ESP's 3.3V/~300mA?

There are many options from many main chip suppliers such as this one from AD/LT: -

enter image description here

TI have offerings of a similar nature too.

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