Revitalising a Sun Jar and the Joule Thief Revisited

A few things to note: Firstly, you’ll see the PCB only shows a single LED; the LED is connected to the board through flying leads ending in a 2-pin JST connector that the LED plugs into. This is to allow it hang inside the diffuser. So, the JST connector will be soldered into the two LED pads (D1). I then soldered together three LEDs in parallel leaving just two legs extended that can be pressed in to the JST connector, see Figure 6. Before connecting these LEDs I put a heat-shrink sleeve over one of the sets of legs to ensure no short-circuit between them was possible.

Fig 6 the LEDs

Secondly, halfway along the battery holder you can see two larger pads that are not electrically connected to anything else. These are so that the leads from the solar cell can be fed through from the copper side and then soldered in place to the smaller adjacent pads.

Figure 7 (lhs) shows the routed PCB just before removal from the router bed, and Figure 7 (rhs) shows it in place in the sun jar.

Fig 7 the routed PCB on the left, on the right . . . it fits!

Figure 8 shows the completed PCB.

Comparing this with Figure 6, you can see the JST connector soldered into the LED (D1) pads.The black and the red wire loops on either side of the battery box are the connections to the solar cell which will sit on the opposite (copper) side of the PCB to the rest of the components.

Fig 8 the completed PCB

Figure 9 shows the assembled and powered circuit in the light and in the dark.

Fig 9 the assembled circuit in the light (left) and in the dark (right)

All that is needed to finish things off is to attach the solar cell to the copper side of the PCB with double-sided sticky pads and insert the JST connector into the diffuser; see Figure 10.

Fig 10 the circuit in place with the LEDs hanging in the diffuser
Fig 11 this what ’sand’ coloured LEDs look like.

The solar jar in action (Figure 11). Now that I have one, I want more. Mason jars are not very expensive and it would be easy to design a 3D-printable insert for the neck to hold the solar PCB.