1. that the 7805 can be used as is to drop the 12v to 5v,
2. that one should add 2 capacitors to the step-down circuit.
Quote1. that the 7805 can be used as is to drop the 12v to 5v,Wrong
There is no difference in safety, 12V and 5V are equally safe. Remember a child's train set has 12V exposed rails.Local regulation however is better to minimise line volts drops.
Pesonally, I would connect the LEDs in string of 4 or 5 with a current limit resistor and run them from 12V if that is an option.
Are you saying the 7805 should not be used to drop 12v to 5v, or only when used with 2 capacitors in the circuit to stabilise it ?
are you saying better to run the 12v and avoid the drop to 5v until the last possible point,
If you only want 1 per room, I'd find the specs for the LEDs (foward voltage, recommended safe current) and feed it with 12volts through a series resistor of suitable value. LEDs aren't rated by voltage, using a suitable resistor you could run them off 200 volts if you chose to (not recommended). Personally I'd wire 3 in series with 12 volts and a smaller resistor (it would use the same amount of electricity for 3* the light . Buying small (5mm) high brightness LEDs is cheap in comparison to the effort involved in positioning and wiring them. They can be had for pennies apiece on ebay. Running 1 LED from 12V is no more wasteful than using a 7805 to step down the voltage.
QuoteAre you saying the 7805 should not be used to drop 12v to 5v, or only when used with 2 capacitors in the circuit to stabilise it ?only when used with 2 capacitors in the circuit to stabilise it.Quoteare you saying better to run the 12v and avoid the drop to 5v until the last possible point,Yes, that way any volts drop getting to the regulator is eliminated. If you regulate before your long run then you might not get 5V at the end.
Any links you can point me to for the correct diagram and capacitor selection
If you are looking to conserve energy, than 2-3 ultrabright white LEDS, capable of 15,000mCD on just 20mA, are the way to go.
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