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AEMLOVE Revision 1

A project log for Designing a solar harvesting blinking gadget

Based on earlier solar harvesting projects I wanted to design a solar harvesting gadget

Jasper SikkenJasper Sikken 05/23/2019 at 20:112 Comments

It's December 2018 when I wanted to design a solar harvesting gadget.

Specifications:

Since I have 2 children and no time I designed a quick and dirty PCB and ordered from Elecrow. Below is revision 1 schematic.

Every 5 seconds the status2 pin goes high when the IC does MPPT evaluation (check solar panel open circuit voltage), I have no idea what applications would need this information but I can use it toe blink a LED with low duty cycle. The LEDs are switched through a DMG1012UW N channel mosfet.

I designed LED on the 1.2V and the 1.8V output of the IC. It was silly to design it on the 1.2V becaise there is no LED that works at such low voltage.

The battery can also be charged from the USB 5V. I used a voltage divider to make a 2.7V voltage for the supercapacitor and a diode to prevent reverse current. 

In January 2019 I received the PCB

On the left is the supercpacator A 1F 2,7V through hole supercapacitor from Aliexpress (CXHP2R7105).

On bottom is the solar cell. 

On left side is the AEM10941 IC and it's large boost inductor.

The other two large though hole capacitors I did some experimentation with that I won't explain here.

The PCB has 2.0mm thickness. That is not enough for the USB connector so I had to manually add more solder paste. 

As you can see she solar cell is surface mount solderable. 

What I've learned from revision 1 PCB

PCB revision 2 you will find in the next project log.

Discussions

Jasper Sikken wrote 05/24/2019 at 22:01 point

You are welcome. I am not sure I understand your question. Ofcourse you can put two supercapacitors in series, they need some kind of balance circuit so they each have 1/2 of the voltage. Normally the test of the circuit  connect to the most positive terminal

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Simon Merrett wrote 05/24/2019 at 21:46 point

Hi @Jasper Sikken thanks for the helpful feedback on rev 1. I was planning on using a 2.0mm PCB for a usb connector for V1.1 of #Yapolamp  but will review that plan now.

I have been experimenting with a constant current charging circuit on two supercapacitors in series. Could you implement something similar but only connect the rest of the circuit to the midpoint between the capacitors? 

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