I want to make a 9V DC from 48V the battery bank that will be used to power dc volt meter. I'd used the 9.1 zener and 24K resistor, if I manage to post pictures you will see a diagram. my problem is how to isolate the 9V from 48V.
I hope that someone might help or I'll have to use a 9v battery and switch. Voltmeter consumes 1mA, which means not much power so it can be on permanently.
Thanks for any help!
This sort of simple zener regulator is ok dropping from 12-15V, but it's HORRIBLY inefficient for higher voltages. Your dropping resistor will get very hot, and you'll be wasting (roughly) 5 watts for every 1 watt you're using.
Given you also want to achieve isolation, by far your best option (and most efficient, reliable, safe etc) will be to use a small transformer-based DC-DC switching converter. These are widely available and cost only a few bucks in the sort of power range you want. 48V input are not as common as many of the lower voltages, but ebay item 370130553510 is 48V to 12V, 15W buy now for $9. Component suppliers in your area may have them even cheaper for lower power units.
