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Topic: Yun + Solar Charger Shield V2.2 (Read 3441 times) previous topic - next topic


Aug 07, 2016, 04:03 pm Last Edit: Aug 07, 2016, 09:50 pm by oscarcuenca2
A few days my micro USB was broken and separated from the yun board. Until this moment it was working correctly.

I bought Solar Charger Shiel V2.2 thinking that adding it on yun, it would work so I was thinking it would be a good way to give power to my yun. I connected solar panel and Li-Ion Poly 2500  mAh 3,7V battery to the Solar Charger Shield V2.2 and the shield to on my YUN- It is correctly charging, but the Yun do not receive power since it still off.Also the shield is delivering power to the circuit, but nothing to the Yun Board.

Anyone could help me or tell me why it is not sending energy to Yun the Solar Shield? :o
Here Attch photo, As you can see, the leds of the wifi activity is not on. Maybe Batery Lion-Ion 3,7V 2500 mAh is not enought and need output 5V, but specifications of solar shield is Maximum Output Power(with battery): 3W(600mA@5V)...?


Aug 10, 2016, 02:33 pm Last Edit: Aug 10, 2016, 02:35 pm by ShapeShifter
This thread should probably be up one level in the "Arduino Yun" forum, not the "Yun Shield" forum. This thread discusses a problem with using a particular shield with a Yun processor board, while this forum is for the Yun Shield product that is a shield that can work with other Arduino processor boards.

Looking at the Seeed Studio Solar Charger Shield V2.2 schematic and board layout, it would appear that this battery charger shield is not compatible with the Yun. The Yun handles it's power supply differently than many other Arduino boards.

In a more typical Arduino board, it can be powered from a raw voltage (usually around 7 to 12 volts) by feeding the VIN pin. The typical Arduino then has an on-board regulator to drop that raw VIN to 5V, which is output on the 5V pin. But, if the VIN pin is not being used, one can feed regulated 5V into the 5V pin to power the board.

The Yun, on the other hand, has no internal voltage regulator. To power the Yun using an external power source (not the USB connector) you must input a regulated 5V into the VIN pin. The 5V pin is strictly an output, with a diode that prevents feeding power into the 5V pin.

The Seeed Studio Solar Charger Shield V2.2 has a boost converter to take the lower battery voltage and raise it up to 5V. That voltage is then fed to the 5V pin, where it can be used to power a typical Arduino board. But with the Yun, this is just trying to back-feed the 5V output, which causes nothing to happen because of the polarity protection diode.

You may be able to get this to work with the Yun by putting a jumper between the 5V and VIN pins. This will feed the output voltage of the shield to the VIN pin of the Yun. You will also be trying to back-feed 5V into the 5V pin, but this shouldn't be a problem: the Yun is actually trying to put about 4.5V out the 5V pin because of a couple of polarity protection diodes. That means that there is 4.5V on the Yun's side of the diode (anode) and 5V on the external pin side of the diode (cathode.) This will reverse bias the diode (cathode higher voltage than the anode) and no current will flow.


Hi ShapeShifter
Thanks for this information.
It has been very useful for me. Specially to understand better Yun. What finally I made is to make a bridge with wires between the solar shield and the Yun just connecting the VIN with 5V out of the Solar shield and GND. In this way the shield delivery 5V regulated to Yun and also I can work with solar energy, it is not so nice but it works. It would be a good idea to find a Solar Shield for Yun. Do you think there is any Solar shield for Yun in market?

Regards and thanks againg for your help.


It would be a good idea to find a Solar Shield for Yun. Do you think there is any Solar shield for Yun in market?
That would be a rather small niche specialty market. I'd be surprised if there were such a board, I don't think it would be economical to develop. Compared to other boards, there aren't that many Yuns in use, and the number of people who would want a solar shield for it would be even less.

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