Wiring & diagram Info

D. Mohan Kumar know as his best creations. For beginners, here’s a low-cost multitester that can be used to test the condition of almost all the electronic components For beginners, here’s a low-cost multitester that can be used to test the condition of almost all the electronic components from resistors to ICs. It uses only a few components but can also detect polarity, continuity, logic states and activity of multivibrators.

The schema is extremely simple and exploits the biasing property of bipolar transistors. Transistors T1 and T2 act as transistor switches driving the red and green halves of bicolour LED1 independently to give results of the test.

 Simple Handy Tester Circuit Diagram



When power is applied by pressing switch S1, transistor T1 stops conducting due to the lack of forward bias. At the same time, transistor T2 takes base bias voltage from the battery through resistor R1 and conducts. This allows the red half of bicolour LED1 to illuminate.

When the base of transistor T1 gets positive voltage through resistor R3, it conducts to light up the green half of bicolour LED1. When transistor T1 conducts, the base of transistor T2 is grounded and it cuts off to turn off the red half of bicolour LED1. The functioning of the schema thus depends on the signal obtained at the base of transistor T1. The table gives the testing procedures for various components with the expected indications/results.

Why a lamp tester or fuse tester? Testing cables, wires, lamps… belongs to a repair job and sometimes this becomes too cumbersome since one has only two hands and too often, one has to hold the part being tester and the two probes of an ordinary continuity tester all at the same time.

This fuse and lamp tester enables easy testing of lamps and fuses by using the conductivity of the human body. One of the test probes is connected to the part under test while the other probe is hel dby the normal hand.

When the lamp or fuse is working properly, your eyes will glow in the dark! Just kidding :) . When the lamp or fuse is working properly, a small amount of current flows through the hand which is enough to switch the transistors and light the LED.

With a suitable load, the terminal voltage of a NiCd or lithium-ion battery is proportional to the amount of stored energy. This relationship, which is linear over a wide range, can be used to build a simple battery capacity meter. 

 

Voltage Tester for Model Batteries Circuit Image 

This model battery tester has two functions: it provides a load for the battery, and at the same time it measures the terminal voltage. In addition, both functions can be switched on or off via a model remote-control receiver, to avoid draining the battery when it is not necessary to make a measurement. The load network, which consists of a BC517 Darlington transistor (T2) and load resistor R11 (15 Ω /5 W), is readily evident. When the load is active, the base of T1 lies practically at ground level. Consequently, T1 conducts and allows one of the LEDs to be illuminated. 

The thoroughly familiar voltmeter schema, which is based on the LM3914 LED driver, determines which LED is lit. The values of R6 and R7 depend on the type and number of cells in the battery. The objective here is not to measure the entire voltage range from 0 V, but rather to display the portion of the range between the fully charged voltage and the fully discharged voltage. Since a total of ten LEDs are used, the display is very precise. For a NiCd battery with four cells, the scale runs from 4.8 V to 5.5 V when R6 = R7 = 2 kΩ. The measurement scale for a lithium-ion battery with two cells ranges from 7.2 V to 8.0 V if R6 = 2 kΩ and R7 = 1 kΩ. 

For remote-control operation, both jumpers should be placed in the upper position (between pin 1 and the middle pin). In this configuration, either a positive or negative signal edge will start the measurement process. A positive edge triggers IC1a, whose output goes High and triggers IC1b. A negative edge has no effect on IC1a, but it triggers IC1b directly. In any case, the load will be activated for the duration of the pulse from monostable IC1b. Use P12 to set the pulse width of IC1a to an adequate value, taking care that it is shorter than the pulse width of IC1b. 

If the voltage tester is fitted into a remote-controlled model, you can replace the jumpers with simple wire bridges. However, if you want to use it for other purposes, such as measuring the amount of charge left in a video camera battery, it is recommended to connect double-throw push-button switches in place of JP1 and JP2. The normally closed contact corresponds to the upper jumper position,while the normally open contact corresponds to the lower position.

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