August 2021

I was chatting to an old friend who has two young boys. Both own a night light from Ikea. The light in question is a small yellow house (SOMMAR product code) that glows using a single yellow LED. This light draws 20ma and drains the battery flat over a period of around 10 days. You can see my efforts to extend the length of battery using a JTPS (Joule Thief Power Supply) in another article. I was able to double the length of the run time of the Ikea light but further improvements were difficult with such a bright diffused light.

I decided to design and build a new night light. The new nightlight would be a small black box with drilled holes to spell out the boys names using 5mm low energy blue LEDs. The bulbs draw extremely low current and with just 1ma across the entirety of the bulbs. The light would run 24 hours a day for up to a year.

I built three of these lights. One would spell Dan, one Will and a final test unit spelling Kev to test the battery power and longevity once the other two were given away.

The JTPS was a basic dual coil 1M / 10PF Capacitor supply with a Zener 5v regulator across the output. Driven by a low power BC337-40 transistor, this fed the LEDs in parallel from a single AA battery fitted in a battery holder unit.

The final product is the basis for many other projects that require long duration lights. The brightness is sufficient for a nightlight and is actually a little too bright if aimed directly at the user. On a C or D size cell this light could run for several years.

The LED Love Light consists of a PCB populated with dozens of 3mm red LED bulbs. These are driven by a variable power joule thief power supply regulated at five volts and powered by 1 or 2 AA batteries.

The light will run for several weeks non stop or months when used intermittently.