LED toy/night light project - advice/thoughts..

[PRR]

> I thought that By-Pass Cap would help the battery drain more efficiently.  Based on this quote from Mr. RG:

Filtering caps lower the apparent high frequency impedance of the power supply to the circuit.
The filtering cap keeps the high frequency impedance that the circuit sees low even with the battery getting higher.

Read it carefully. ""high frequency impedance""!

The highest frequency in your lamp is maybe 2Hz, if the kid has a stutter-finger.

In this case, the cap is just another part to fail, and leak, and wire-wrong, and find a place to fit, and pay-for.

> Maybe my night light project doesn't apply?

+1

Battery, switch, resistor, LED. Done.

Resistor value should be greater than 350 ohms to keep LED current to nominal max safe value.

As an indoor toy with a healthy LED, you could probably go 10 times higher, get good light, and much longer battery life.

As Gus says, a good bright LED and an enthusiastic user who may hold it up to his eye can cause temporary or permanent eye damage. Low current and light diffusion are good.

Better battery life could be had with LM3909 LED Flasher chip (obsolete). One D-cell will power a blinker for years, until the battery rots of old age. Modified for high rate and duty cycle, it can appear "steady" yet run for months non-stop. This will also show a stobe effect when kid waves it around.