Step 3: And here comes the solar panel
The solar panel is what powers the LED inside the house. With each solar cell giving out 0.55 volt max, 7 solar cells in series will give out 3.85 V max. Yet, since only the bottom sides of the first and last solar cell are connected in this connection method, only 6 out of 7 cells are used to power the LEDs. The first cell acts as a dummy cell that gives out no power. The maximum voltage is thus just 3.3 V. One addition more cell will make the LED brighter if you LED can take the extra current but I didn't do so because one extra cell will make a panel too large for this roof.
To connect the solar cells in series, I connect successively the bottom side of a cell to the top side of the other. Solar cells are not that good a conductor. To aid the current flow, bus bar, the more conductive white region on the solar cell, is printed onto the cells. That is why you can see that I am only applying the conductive ink onto the bus bar. After applying 2 dots of instant glue onto the cell edge and a dot of conductive ink onto the edge of the bus bar, I placed the second solar cell onto the first with a 1mm overlapping. Repeat this for 5 more times and you will get a panel consists of 7 cells. Note that the more you overlap, the less of the cell is exposed to sunlight and thus the less current you can get from the cell.
Before I put the panel onto my paper house, I measured its current under a light just to see if all connections are good. My panel gives 80 something mA when not shaded by my fingers but you can still see 57.6 mA when I took the photo with my other hand.
Don't worry too much if the current reads zero. It may only be caused by a bad connection or two. If this happens, identify the bad connection with an aid of a multimeter and use a hot air gun to soften that connection. Then, pull the connected cells apart and redo that connection. You may also simply do another panel from the beginning instead, if you prefer so.
To connect the solar cells in series, I connect successively the bottom side of a cell to the top side of the other. Solar cells are not that good a conductor. To aid the current flow, bus bar, the more conductive white region on the solar cell, is printed onto the cells. That is why you can see that I am only applying the conductive ink onto the bus bar. After applying 2 dots of instant glue onto the cell edge and a dot of conductive ink onto the edge of the bus bar, I placed the second solar cell onto the first with a 1mm overlapping. Repeat this for 5 more times and you will get a panel consists of 7 cells. Note that the more you overlap, the less of the cell is exposed to sunlight and thus the less current you can get from the cell.
Before I put the panel onto my paper house, I measured its current under a light just to see if all connections are good. My panel gives 80 something mA when not shaded by my fingers but you can still see 57.6 mA when I took the photo with my other hand.
Don't worry too much if the current reads zero. It may only be caused by a bad connection or two. If this happens, identify the bad connection with an aid of a multimeter and use a hot air gun to soften that connection. Then, pull the connected cells apart and redo that connection. You may also simply do another panel from the beginning instead, if you prefer so.
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