MOSFET ON by default when arduino is off.

[TomGeorge]

Hi,
You have the gate to ground which is one of the arduino outputs, now put it at 5V.

Tom...

[tauro0221]

Hi,
Attached it is the drawing I am using for the simulation.The mosfet it is connected to ground or not. I need to know what is in the circle in red.

[tauro0221]

Hi,

Thank you very much TomGeorge that it is what I have been asking. Why in the schematic the mosfet was connected to  ground? Now when he remove the arduino it will zero the mosfet gate and it wii short the battery. I still does not understand why do not let the battery charging than shorting it.I would let the battery charging. The diode will isolate the battery when there is not light and the solar panel will not discharge the battery. I think now we are working as A team.

[tauro0221]

Hi,
I ran a test using a switch to simulate when the arduino was IN and OUT. Everything ran OKAY with no problem.

Attached it is the schematic with the voltages in RED when the Arduino was IN and the BLUE when it was OUT.

[juan3211]

Hi Tauro0221, sorry I forget to mention that SWITCH "I" in my schema is like the output pin of arduino.

SI2302 works with Vgs >= 2.5V, I will work with 3.3V in my arduino.

I have attached two schemas here:

1. one with arduino output LOW --> mosfet OFF, so solar panel current goes to the battery.Charging process.
2. antoher one with arduino output HIGH --> mosfet ON, so solar panel is shorted. No energy to the battery

Gate is connected to ground thorugh R25 to mantain mosfet OFF when arduino is off or missed(just in case)

(in the first schema, you have the solar panel model that you said and works perfect !!!)

So then, could be this a solution for low power panels ?

[tauro0221]

Hi,

Yes, That will work. I have a question. Why you have to short the solar panel? Any reason why you do it.

[juan3211]

Hi,

Yes, That will work. I have a question. Why you have to short the solar panel? Any reason why you do it.

HI, I want to short it to protect battery for overvoltage. For a solar panel there is no problem to short circuit it.

I want to program it this way:

1. if battery is > 4.2V, disconnect solar panel by short circuiting it with mosfet. Mosfet ON
2. If battery is < 3.8V, connect solar panel by mosfet OFF
3. If battery is < 3.6V send a SMS or HTTP GET to a WEB to call for help as the battery will be ruined if there is not more solar power to recharge it.