The objective of this construction project is to build a simple and easy to use Opamp Tester. This test gadget can be used to test the popular general purpose opamp type 741 and other such opamps that are pin to pin compatible to 741.These include the opamp type numbers much as LM 709, LM 201, MC 1439, LM 748, OP-02, LM 318, LM 356 etc. As an opamp finds its existence in almost every project of interest due to a large number of application circuits that can be built around opamps, a test gadget like the one hitheto described is certainly going to be an asset to an electronics experimenter or a hobbyist. Building this project will not only be another construction or learning exercise for them, it will become a very useful tool for them in the other projects they intend to construct. With this gadget available with them, they don’t have to randomly replace the opamps in case the circuit they have built with so much of enthusiasm happens to use a few opamps and is not working. They will be able to testate opamp before declaring it fit for use. One important point: Since the pray has an educational valuator, it could be a very good choice as a project for those doing diploma or an equivalent course in electronics.

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The objective of this construction project is to build simple and easy to use test gadget that can be used to identify good and bad IC TIMERS from a given lot. Like opamps, an IC timer is another widely used electronic device and it finds its place in almost every project of hobbyists’ interest. This gadget not only enables you test the IC timer 555, it will also give you an opportunity to appreciate the tremendous functional potential of the various terminals of this truly versatile IC. Most of the circuits appearing in various magazines or books to test IC timers do the same by wiring the IC in one particular configuration only. Testing the IC timer with the gadget being described here not only tests the IC in all basic configurations, it practically tests the functionality of read more

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Thyristors (SCRs, Triacs) are very popular in AC power control applications where they are used to provide an active control of the AC power being fed to the load. The load here could be anything that is operated from AC mains and whose parameter to be controlled happens to depend upon the amount of AC power. Speed of motors, Temperature of heating elements etc are some of the examples. Here, we would build a simple circuit to demonstrate separately the use of SCRs and Triacs to provide AC power control. SCRs are used for those loads where it is immaterial whether the load current is unidirectional or bidirectional (though the AC input is always bidirectional). Heating element is one such load, an incandescent bulb is another. Remember that amount of heat is always proportional to read more

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Under previous posts, we have already seen how a bipolar transistor, NPN or PNP, can be used as a single pole, single throw switch. The transistor operating in saturation region with voltage across the switch being about 0.2 volt represents the ON-condition of the switch. The transistor operating in the cut-off region, where the only current that can flow through the switch is the collector-to-emitter leakage current represents the OFF-condition of the switch. We also demonstrated how an SCR can be used as a single pole single throw switch of the latching type. Another very important solid state device that can be usd as a switch in a way similar to the operation of a bipolar transistor is the Metal Oxide Semiconductor Field Effect Transistor (MOSFET) briefly mentioned in the last read more

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The objective of this simple exercise is to demonstrate the operation of solid state (or electronic) switches using electronic devices like TRANSISTORS or SCRs. There are many more electronic devices that can be used for the purpose. We have chosen these two as these are the most commonly used ones in this role, more so in the electronics circuits of hobbyists’ interest. MOSFET (Metal Oxide Semiconductor Field Effect Transistor) is another commonly used switching device that has outclassed bipolar junction transistors in many switching applications. It is not covered here but is separately covered in the next project. [caption id="attachment_2035" align="aligncenter" width="300" caption="click the image to enlarge"][/caption] CIRCUIT DESCRIPTION The first part of the circuit read more

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Majority of Electronics enthusiasts and hobbyists wants to build their own AC-DC power supplies to test the electronics circuits built by them. The objective of this easy to build and understand circuit is to familiarise the constructor or the hobbyist with the effect of changing the rectifier-filter configuration on the DC output voltage produced in a conventional mains operable AC/ DC power supply. By opening or closing an appropriate combination of switches (SW-1 toSW-9 in the circuit diagram), this circuit could be configured into any one of the popular power supply rectifier circuits like (i) Conventional Half Wave Rectifier with positive DC output voltage (ii) Conventional Half Wave Rectifier with negative DC output voltage (iii) Conventional Full Wave Rectifier with positive read more

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The losses occurring in a d.c. motor are the same as in a d.c. generator  (i) copper losses (ii) Iron losses or magnetic losses (iii) mechanical losses As in a generator, these losses cause (a) an increase of machine temperature and (b) reduction in the efficiency of the d.c. motor. The following points may be noted: (i) Apart from armature Cu loss, field Cu loss and brush contact loss, Cu losses also occur in interpoles (commutating poles) and compensating windings. Since these windings carry armature current (Ia), Loss in interpole winding = Ia 2× Resistance of interpole winding Loss in compensating winding = Ia 2× Resistance of compensating winding (ii) Since d.c. machines (generators or motors) are generally operated at constant flux density and constant speed, the iron losses read more

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