Solar Garden Light Experiments: A simple light and a Crack in the Gate Post

Over the years I’ve tinkered with a handful of those inexpensive solar garden lights. One of my earlier experiments involved swapping the standard white LED for a red one, that ended up producing a surprisingly pleasing effect. This prompted me to revisit an old challenge, getting one to run a colour changing LED without instantly resetting to red.

The red crack light

I had a cheap (approx. $2.00) solar light, something like this one. Many years ago I replaced the white LED with a red one. It has worked well since then, but I had to replace the battery and bypass the switch. The switch always seems to be the first component to fail. About a year ago, the bottom part of the light broke. I placed it above a crack in our gate post and unintentionally created a really interesting effect.

At night a red glow shines out of the crack. The colour in the image below is not as deep red as it is to the naked eye. It looks like glowing fire coals. For this reason I’ve made sure it is not visible from outside our yard, otherwise we may end up with the rural fire service here. It has also become a home to a huntsman spider that is often seen moving up and down the crack.

I opened it up to show its innards and check how it is going. It looks ugly in there, but is still working. As noted above the only electrical change I have made from the original circuit is bypassing the switch and swapping out the white LED for a red one.

Back together and yes, it still works.

RGB conversion attempt

After the success of the red LED light, I decided to revisit a previous failed attempt of turning a simple solar light into a colour-changer. That attempt just emitted red light. What I didn’t know at the time was that these lights pulse the LED. They use a small boost (pump) circuit to boost the voltage up from the 1.2V cell to a voltage needed by the LED. Every time a pulse ended the LED lost power and the colour changing circuit reset back to red.

Modifying the circuit

Since then, Big Clive has released two videos where he shows how to turn a single colour LED light into a colour changing one. Both are reasonably old. I had made a note of the circuit diagram in the first video and that is what I have used.

In the second video the circuit diagram is different.

I opened up the light. It looks fairly clean compared to the other one, but this one has been outside for many years. The battery has been replaced once and the switch is unreliable.

I’ve highlighted the switch and LED on the back of the board.

It’s immediately obvious why the switch is unreliable. I left the switch there, but added a solder bridge across the terminals on the back of the board to make it permanently on. I’ll have to remove the battery if I want to turn it off.

This is the circuit diagram of a single colour solar light as shown in Big Clive’s first video.

This shows Big Clive’s modification. I used this however, instead of a IN4148 diode I used an IN5819 Schottky diode. I have lots of these and I was hoping the lower forward voltage drop would give the LED more usable voltage.

I also added the 100nF capacitor.

It looks a bit hacky. It looks a bit hacky. The second wire from the LED, along with one leg of the capacitor and the diode, are soldered together above the board..

Here is another view.

And another.

All done. Here it is as it emits blue light.

Summary

With the RGB modification done, both lights are now running as expected despite their age and weathered components. The red LED conversion proved remarkably pleasing. I think that is because the placement of the light is really what makes the difference. In this case I got lucky and an interesting effect happened.

The colour changing mod worked but as yet I haven’t found a good place to really make a good use of it.