A numerical processor based control for a solar monitoring and test station.

Abstract

With the increased interest in the area of solar energy, a definite need exists for a unit which would make the testing of systems easier and less time consuming. This paper presents the basic design of a unit, a numerical processor based control, which will work both monitoring and testing stations. The recent advances in processor technology makes possible the ability to acquire, process, and analyze great amounts of data rapidly. This permits the design and mplementation of data acquisition systems to be realized more economically than was previously possible. Although a minicomputer could easily be connected on-line to perform the same duties, the dedicated processor is a much more economical approach. The numerical processing unit (npu) is readily available today and it can be used widely to free the engineer of many of the repetitive tasks sometimes associated with data acquisition. The engineer is then able to devote his time to more important aspects such as design and optimization. The npu provides for an economical solution in control and data acquisition systems because it is easily adapted to many different situations. The main advantage of an npu based system is that the operation of the unit may easily be changed by altering the microprogram. A microprogram is a series of instructions which is stored in memory and controls the operations of the npu. Since many suitable memories are available in integrated circuit form, the operation of the unit may readily be changed by replacing the original memory with another which has different bit patterns stored in its registers. The circuit presented here is used to control a solar monitoring and test station. The function of the npu is to gather all input data desired, make it available to the user, process it, and compute control signals. The output signals are made available in several forms to allow connection to different display devices. Two common examples are digital panel meters and teletypes. However, if an external digital to analog converter is added, analog devices such as strip chart recorders may also be used. Since the npu is digital in nature, all input signals must be in digital form before they can be accepted by the processor. In solar experiments, as in many others, few of the variables of interest are in electrical form. To convert information from its natural form to that suitable to the processor, transducers are used. A transducer is simply an element capable of converting one form of energy into Potentiometers are common examples, they convert a mechanical displacement into an electrical signal. This unit will accommodate any transducer whose output is a voltage within a specified range. This provides the user a certain amount of latitude when using this device. This paper will show an economical yet effective controller, which should find wide application considering the upward trend in solar energy studies.