DC Fuse and DC MCB

A fuse is an electrical safety device that operates to provide overcurrent protection of an electrical circuit. Its essential component is a metal wire or strip that melts when too much current flows through it, thereby stopping or interrupting the current. It is a sacrificial device; once a fuse has operated it is an open circuit, and must be replaced or rewired, depending on its type.

DC Miniature Circuit Breaker (DC MCB) is particularly designed for DC over-current and short-circuit protection in an electrical circuit. DC MCB and the AC MCB have the same functions. Only application scenarios are different. DC MCB is mainly used for direct current (DC) systems applications, line Solar Photovoltaic (PV) and Solar Battery Energy Storage Systems (BESS). The voltage state of DC MCB is generally DC 12V-1500V.

Reference:
[1] https://en.wikipedia.org/wiki/Fuse_(electrical)

Array and Array Junction Box

We commonly use 72 Cell panels or 144 Half-Cut Cell Panels. A 72-cell panel produces 46-50 Volts while not under load. At maximum power point, it drops around 37-42 Volts. A standard On-grid Inverter requires a much higher voltage than this. Sometimes off-grid inverters also require multiple modules in series. 
A solar photovoltaic array is formed by a series/parallel combination of SPV modules to attain the desired voltage and current level. Usually in an Array modules are kept in series to obtain a certain voltage. Arrays are kept in parallel to increase the current.
Before connecting to the inverter sometimes protection is required (if it is not built in the inverter). Like DC Fuse, DC MCB, DC SPD and Current Measurement Unit. These are installed in an Array Junction Box or String Combiner Box. 

Reference:
[1] https://creativestudio1973.blogspot.com/2021/06/introduction-to-solar-panel.html
[2] https://creativestudio1973.blogspot.com/2021/06/on-grid-systems.html
[3] https://creativestudio1973.blogspot.com/2021/09/surge-protection-device.html
[4] https://creativestudio1973.blogspot.com/2023/11/dc-fuse-and-dc-mcb.html

Hydrometer

 A Hydrometer is a device for measuring some characteristics of a liquid, such as its density (weight per unit volume) or specific gravity (weight per unit volume compared with water). 

A hydrometer usually consists of a sealed hollow glass tube with a wider bottom portion for buoyancy, a ballast such as lead or mercury for stability, and a narrow stem with graduations for measuring. The liquid to test is poured into a tall container, often a graduated cylinder, and the hydrometer is gently lowered into the liquid until it floats freely. The point at which the surface of the liquid touches the stem of the hydrometer correlates to relative density. Hydrometers can contain any number of scales along the stem corresponding to properties correlating to the density.

A simple hydrometer consists of a glass float inside a glass tube, as shown above.

The hydrometer float is weighted at one end and sealed at both ends. A scale calibrated in specific gravity is positioned lengthwise along the body of the float. The float is placed inside the glass tube, and the fluid to be tested is drawn into the tube.

As the fluid is drawn into the tube, the hydrometer float will sink to a certain level in the fluid. The extent to which the hydrometer float protrudes above the level of the fluid depends on the specific gravity of the fluid. The reading on the float scale at the surface of the fluid is the specific gravity of the fluid.

The point at which the surface of the liquid touches the stem of the hydrometer correlates to relative density.

Hydrometers are calibrated for different uses, such as a lactometer for measuring the density (creaminess) of milk, a saccharometer for measuring the density of sugar in a liquid, or an alcoholometer for measuring higher levels of alcohol in spirits. In our application, we measure the Specific Gravity of Battery Acid.

Reference:
[1] https://en.wikipedia.org/wiki/Hydrometer
[2] https://www.britannica.com/technology/hydrometer
[3] https://instrumentationtools.com/how-to-measure-specific-gravity-of-battery/
[4] https://www.batteriesinaflash.com/how-to-measure-specific-gravity

Soil Moisture Sensor interface with Arduino

 The soil Moisture sensor is widely used in measuring the water content in the soil. Soil moisture sensors do not measure water in the soil directly. Instead, they measure changes in other soil properties related to water content in a predictable way. Today we will see how it works and how we can use it in our way.

This sensor mainly utilizes capacitance to gauge the water content of the soil (dielectric permittivity). The working of this sensor can be done by inserting this sensor into the earth and the status of the water content in the soil can be reported in the form of a per cent.

The soil moisture sensor consists of two probes which are used to measure the volumetric content of water. The two probes allow the current to pass through the soil and then it gets the resistance value to measure the moisture value.

When there is more water, the soil will conduct more electricity which means that there will be less resistance. Therefore, the moisture level will be higher. Dry soil conducts electricity poorly, so when there will be less water, then the soil will conduct less electricity which means that there will be more resistance. Therefore, the moisture level will be lower.

Specifications

Operating Voltage: 3.3-5V

Current: <20mA

Output: Analog and Digital

The sensor comes with an LM393 comparator chip mounted on a module. This helps to generate a Digital Output as per the threshold setting value. The threshold value can be adjusted from the pot mounted on the module.

Pinout:

Vcc : +5V

Gnd: Ground

A0: Analog Out

D0: Digital Out

How to use Sun Path Finder

Sun path diagrams can tell you a lot about how the sun will impact your site and building throughout the year. Stereographic sun path diagrams can be used to read the solar azimuth and altitude for a given location. Sun path finder is a device that helps you to read the Stereographic Sun Path Diagrams ans shading analysis.

Azimuth Lines - Azimuth angles run around the edge of the diagram.

Altitude Lines - Altitude angles are represented as concentric circular dotted lines that run from the centre of the diagram out.

Date Lines - Date lines start on the eastern side of the graph and run to the western side and represent the path of the sun on one particular day of the year.

Hour Lines - Hour lines are shown as figure-eight-type lines that intersect the date lines and represent the position of the sun at a specific hour of the day. The intersection points between date and hour lines give the position of the sun.

Step by Step Guide to use Sun Path Finder:

1. Locate the required hour line on the diagram. 

2. Locate the required date line, remembering that solid are used for Jan-June and dotted lines for July-Dec. 

3. Find the intersection point of the hour and date lines. Remember to intersect solid with solid and dotted with dotted lines. 

4. Draw a line from the very centre of the diagram, through the intersection point, out to the perimeter of the diagram. 

5. Read the azimuth as an angle taken clockwise from north. In this case, the value is about 62°. 

6. Trace a concentric circle around from the intersection point to the vertical north axis, on which is displayed the altitude angles. 

7. Interpolate between the concentric circle lines to find the altitude. In this case the intersection point sits exactly on the 30° line. 

8. This gives the position of the sun, fully defined as an azimuth and altitude.

Battery Management System

A battery management system (BMS) is an electronic system that controls the charging and discharging of a rechargeable battery (cell or battery pack) by protecting the battery from operating outside its safe operating area monitoring its state, calculating secondary data, reporting that data, controlling its environment, and balancing it.

Basic Features of BMS:

Overcharge Protection: Protects the cells as well as the battery from overcharding beyond its safe limit.

Deep Discharge Protection: Protects the cells as well as the battery from deep discharding while powering a load.

Cell Balancing: When a cell is fully charged bypass that cell to let the other cells to be charged.

Types of BMS depend upon the type of cells as well as the number of cells in series. As per the number of cells in series, BMS is classified as

1S: Only one cell

2S: 2 number cells in series

3S: 3 number cells in series

and so on...

The voltage of BMS depends upon the cell type like for Li-Ion 1S BMS its rated voltage is 3.7V. For 2S it would be 7.4V. On the other hand for lithium ferro-phosphate cell (LiFePO4), 1S BMS would be 3.2V and 2S would be 6.4V, and so on...

 Every BMS has it's terminal marked connection needs to be done as per marking. 

 

 

For this lithium ferro-phosphate 1S BMS
B- Terminal is for Battery Negative
B+ Terminal is for Battery Positive
P+ is for Power Positive
P- is for Power Negative 

B+ and B- connects with the battery and P+ and P- go to the load or charger.

For the above Round type Li-Ion BMS also B+ and B- connects with the battery and P+ and P- go to the load or charger.

 This lithium ferro-phosphate 2S BMS has five terminals apart from B+, B-,  P+, P- it has one extra terminal that is BM. This BM terminal goes to the middle terminal of the battery series.

 The Li-Ion 2S BMS also has the same pin configuration.

 For 3S Li-Ion BMS, the Connection diagram is shown above. The lithium ferro-phosphate does not come with a 3S configuration.

Instead lithium ferro-phosphate BMS comes with 4S configuration. The connection diagram is shown.

Surge Protection Device

A voltage spike is a transient event, typically lasting 1 to 30 microseconds, that may reach over 1,000 volts. Lightning that hits a power line can give a spike of over 100,000 volts and can burn through wiring insulation and cause fires, but even modest spikes can destroy a wide variety of electronic devices, computers, battery chargers, modems and TVs etc, that happen to be plugged in at the time. However, lightning and utility power anomalies only account for 20% of transient surges. The remaining 80% of surge activity is produced internally. Although these surges may be smaller in magnitude, they occur more frequently and with continuous exposure can degrade sensitive electronic equipment within the facility.

A Surge Protector or a spike suppressor, surge suppressor, surge diverter, Surge Protection Device (SPD) or transient voltage surge suppressor (TVSS) is an appliance or device intended to protect electrical devices from voltage spikes in alternating current (AC) circuits. 

Typically the surge device will trigger at a set voltage, around 3 to 4 times the mains voltage, and divert the current to earth. Some devices may absorb the spike and release it as heat. They are generally rated according to the amount of energy in joules they can absorb.

There are three types of power surge protectors:

• Type I: This Power surge protector is installed at the origin such as the main distribution board.

• Type II: It is installed sub-distribution boards.

• Type III: This power surge protector is installed at the protection load.

Reference:
[1] https://en.wikipedia.org/wiki/Surge_protector
[2] https://new.abb.com/low-voltage/products/surge-protective-devices
[3] https://www.se.com/in/en/product-subcategory/1615-acti-9-surge-protection-devices-spds/