Electronics & Instrumentation

Charge controller with Automatic Load switching

Conventionally, a solar panel is connected to a battery with load, through a charge controller. The latter is used to protect the battery against overcharging. Likewise, the load and battery are also disconnected from the panel if its voltage falls to a very low value. However, the charge controller does not have a provision to disconnect the battery from the load. We have developed a Charge Controller using an Arduino board to include this additional function as shown below. The status of the battery and solar panel are monitored continuously at all times. The battery is charged by the solar panel, if necessary and if solar power is adequate. However, if the battery or solar condition is found to be unsatisfactory resulting in very low output, the battery is isolated from all loads to prevent possible damage on account of under-voltage operation.

The connected loads are classified into four groups, depending on the assigned priority level, the highest priority being accorded the lowest rating.

% State of Charge Battery voltage level
100 12.89
75 12.59
50 12.19
25 11.59

Table 1. Charge levels

  • If the solar panel output is not sufficient, it is disconnected from the Battery by the charge controller.
  • If the panel voltage is okay and the battery is fully charged, it is allowed to energize the connected loads.
  • If the panel voltage is okay and the battery is not fully charged, the loads will be disconnected in proportion to the discharge level as per their assigned ratings. This will ensure that loads with higher priority take precedence over others.
  • If the battery is totally discharged i.e. < 10.5 V, all loads are disconnected.

Automation of Arc Discharge Setup for Synthesis of Carbon Nano tubes

A DC Arc discharge setup is employed at ARCI for the production of carbon nano tubes. An arc is produced between two Carbon rods arranged vertically inside a double walled stainless chamber. The upper rod, which is the anode, is moved by a motor and gear mechanism so that it can be moved towards or away from the lower carbon cathode. The cathode deposits that are produced during the arcing contain multi walled carbon nano tubes.

This production set up has been automated using a PLC and touch screen type HMI panel as shown below.

Development of a PC /PLC based system for Detonation Spray Coating process

The denotation method of depositing coatings relies on gaseous explosion to heat and accelerate fine particles of a powder material which, on collision with a fixed target, bond with it to form a coating on its surface.

The complete sequence of operation is as follows:-

  • 1st Stage: Inert Nitrogen gas is let in to flush out retained particles, if any.
  • 2nd Stage: Fuel gases i.e. Oxygen and acetylene are simultaneously introduced
  • 3rd Stage: Nitrogen is let in again to forward the fuel gases in to the detonation chamber and to form a protection barrier.
  • 4th Stage: The gas mixture is ignited by a spark and powder is injected axially into the barrel

The sequence described above is implemented by opening and closing a series of solenoid valves that control the flow of different gases and the ignition circuit. Fig.1& Fig. 2 shows the front panel and block diagram of a PC controlled DSC system developed using National Instruments LabVIEW software.

A PLC program as shown in Fig.3. has also been developed using a Siemens micro PLC and tested by conducting experiments on existing Detonation Gun.

Hardware is implemented using MOSFETs for driving solenoid valves and ignition control and the same has been utilized for both PC and PLC.

Design and Development of a test set up for comparison of Solar PV panel parameters

A simple microcontroller based test facility was set up for comparing the power outputs of two solar PV panels each 12V, 40Wp under identical test conditions as shown in Fig.1. The two devices under test are placed side by side so as to receive the same solar radiation. The outputs of both were connected to a single charge controller through rectifier diodes and current sensors. A battery and load were connected to the charge controller, as is done conventionally. In this way, the same load shares the solar energy generated by the two panels. If the voltage generated by any of the panels is more, the corresponding current drawn from that panel is more and vice versa.

The values of current and voltage with desired sampling rate and with respect to real time clock are continuously logged to a memory card whose stored data can be transferred to any PC in excel format to be used for post analysis as shown in Fig.2.

Front Panel of DSC Virtual Instrument

Block diagram of DSC Virtual Instrument

Portion PLC ladder logic for DSC

Basic scheme of the test setup

Plot of logged data