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G6Tanuki · 16th Jul 2018, 7:57 pm

I've never really liked the "resistor-ahead-of-a-classic-78xx-3-terminal-regulator" thing - it doesn't do anything to protect the regulator from initial peak-input-voltages at switch-on.

OK, you can possibly avoid this by fitting a *big* electrolytic between the resistor and the input of the 3-terminal regulator.

These days there are plenty of much-better-than-78XX regulators that can happily handle more-aggressive input voltages.

16th Jul 2018, 7:57 pm	#13
G6Tanuki Dekatron Join Date: Apr 2012 Location: Wiltshire, UK. Posts: 14,007	Re: Dropping voltage I've never really liked the "resistor-ahead-of-a-classic-78xx-3-terminal-regulator" thing - it doesn't do anything to protect the regulator from initial peak-input-voltages at switch-on. OK, you can possibly avoid this by fitting a big electrolytic between the resistor and the input of the 3-terminal regulator. These days there are plenty of much-better-than-78XX regulators that can happily handle more-aggressive input voltages.