Current-Voltage (I-V) curve tracers areuduseful implements for solar Photovoltaic (PV)udresearch and manufacturing, particularly whenudwishing to ascertain module yield viz-a-viz solarudirradiation falling on the module in different climaticudconditions. This paper presents a simple affordableudand easy to fabricate instrument for tracing I-Vudcharacteristics of a PV module. It comprises ofudrapidly varying resistive loads centred on powerudresistors connected to relays and controlled by anudelectronic circuitry. The circuit consists of a 555udastable oscillator that is used to send clock pulses toudthe clock terminal of a 4017 decade counter which inudturn produces a sequence of pulses. Each progressionudof pulse advances by one bit to sequentially turn onudindividual relays via driver transistors. The speed ofudthe count is made variable from the frequencyuddetermining network of the 555 oscillator. The I-Vudcharacteristics of the module are thus measured byudthe sequential selection of the relays which are eachudconnected to a selected load resistor to determine theudoperating point on the I-V curve. The currents andudvoltages are then recorded simultaneously withudirradiance from a pyranometer, by a datalogger toudwhich the instruments are connected. The circuit wasudtested on two monocrystalline modules to compareudthe effect of Harmattan dust on PV output yield.
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