My First Solar Cell Project (Prototype)
Introduction: My First Solar Cell Project (Prototype)
This is a small-scale prototype PV (PhotoVoltaics) project before making a decent and practically useful home solar panel system later.
Therefore, this is the testing purpose of basic circuits made for understanding the operational scheme of a solar cell.
The overall circuit configuration is very basic and power is rated less than 2W (using 5V and 400mA solar cell).
As this is the first time for me to utilize solar cells in a DIY project, I'm wondering how this component is working and really any electricity is produced from it.
I'm using only one small solar panel and produced electricity from it is stored in a single 18650 battery through the TP4056 charger module.
With this circuit, I can understand the basic operational characteristics of a solar cell as well as the method of storing energy in a lithium-ion battery.
Through experiences and knowledge with this circuit, I can make a more useful solar energy generating system someday.
Step 1: Schematics
As shown in the schematics above, the solar power generating circuit itself is simple.
As I'm interested in the operational scheme of the solar cell, several measuring circuits are included such as a voltage meter, ampere meter, and battery capacity level meter.
I'll explain each measurement circuit one by one in the later step or at the other instructable as each device is a little bit complex.
The operational scheme of this solar circuit is simple like below.
- Solar cell produces about 50mA current when it receives sunlight (Although the solar cell specification claims a maximum of 400mA, the actual current I got under the sunlight through windows is 50mA)
- TP4056 lithium-ion battery charger circuit storing electric energy from the solar cell to 18650 battery (This module prevents overcharging and over-discharging of 18650 battery while operating)
- The 18650 battery storing energy from TP4056
- Battery level indicator circuit showing the capacity level of 18650 battery (This circuit was explained in other Instructables)
- 1Watt LED circuit is a load of this solar circuit and consumes energy stored in the 18650 battery
As this kind of solar circuit that charging battery is very common, maybe no further explanation will be necessary.
Step 2: Parts
The most important part is of course solar panels.
For making this experimental solar circuit, I chose a small size solar panel that's dimension is 125mm x 125mm.
The following are used parts.
- 5V and 400mA solar panel
- TP4056 single 18650 battery charger break-out
- 20L15T Schottky diode as blocking current from battery to panel (this is a 20A device but you don't need this much high capacity diode. I only have this device in my inventory)
- 2900mAh Samsung 18650 battery
- 1W LED as the testing load
- Others (Battery level indicator, voltage meter, and current meter circuits)
According to the TP4056 charger IC specification sheet, an additional blocking diode (such as the 20L15T Schottky diode listed above) is not necessary.
Internally power MOSFET is included in the TP4056 and the MOSFET includes a parasite diode that can be acting as a blocking diode role.
But for the reliable solar circuit operation, this additional Schottky diode is used as a safety measure.
Step 3: Wiring Major Parts
As the circuit is simple, no additional wiring diagram will be necessary for explaining the part connection details.
The solar panel is connected with the TP4056 charger via the Schottky diode.
The diode prevents current flow from the battery to the solar panel during night hours.
The 18650 battery is connected to the Battery(+/-) pin and the TP4056 charge current to the 18650 with a regulated 4.1V level. (So output power from the solar panel is less than 4.1V, actually charging seems not occurring)
For a load of battery (Stored energy consumer), 18650 battery level circuit and 1W power LED are used as details explained in the following instructable.
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https://www.instructables.com/1W-Power-LED-Flasher/
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As I was curious about how much current can be produced from the solar panel, voltage and current measuring meters are produced and connected. (I'll explain details about these meters later)
Step 4: Measuring Voltage Produced by Solar Panel
Firstly I'm supposing 5V is produced by the solar panel I bought.
As the specification of the solar panel is rated as 5V and claims to produce 400mA, I naively assume that a constant 5V can be observed when the panel is exposed to sunlight. 267