![]() Rechecking should then yield the right outcome using any transistor at random. It's vital to utilize the transistors in the exact order: first, adjust the BC184 and BC214 until the tester indicates that both are accurate, then adjust the TIP31 and TIP32 more finely, and then tune the TIP3055 and T1P2955 to the tiniest degree possible. Then RV1 is steadily tweaked until the LEDs display the proper order. The RV1 is in the nominal middle position.Įach transistor is placed into the socket one at a time, then the test button is depressed. The simplest method is to modify RV1 until the desired response is obtained for all devices while using a set of known perfect transistors.īC184, BC274 (high gain NPN and PNP small signal), TIP31, TIP32 (3 A NPN and PNP medium gain power), and TIP3055, TlP2955 (15 A NPN and PNP low gain power) make up a common set. If not, you must have made some kind of error. The transistor tester may be set up in two different ways: a simple manner and a more complex yet dependable one.īoth times, the circuit is tested by simulating a C-E short (by pressing the battery test button), and the trimpot RV1 is adjusted until the circuit functions as needed.Īt about 3Hz, the two LEDs should alternately flash. This is crucial because, once the battery is in place, the other LED might glow very faintly if a good transistor is being tested (owing to reverse conduction) or if the correct one is quite dim. When I discovered that my new set of red LEDs used far more current than the green ones did, I gave up on the project.Ĭonfirmed intensity-matched LEDs are more expensive as a substitute, use red and green LEDs with the same average light output (measured in mcd: millicandelas) and in mA). A previous prototype employed a green LED for NPN and a red one for PNP, which appeared a lot better, but using intensity-matched LEDs is necessary if you are interested in a dual-colour display. In the end, I utilized two 0.2-inch green LEDs with the labels NPN and PNP as the indicators. However, various pin-compatible devices, such as the 353 dual J-FET amp, can be used in its place. The tester utilizes an 8-pin dual op-amp chip, in my instance the IC 1458, which is dual 741's equivalent. If the battery is healthy, pressing this button will flash both LEDs to mimic a C-E short. To differentiate between a dead battery and an open circuit transistor, a battery test button is provided. The transistor under test's collector and emitter are subjected to fluctuating bipolar signals in a common base circuit by the tester, which causes current to flow in the LEDs while the transistor is conducting. The two LEDs' condition displays the test outcome (Table 1). The tester is activated by pressing the iest button, which is actually the on/off switch, and the suspicious transistor is connected into a panel socket. The tester will test bipolar transistors, however it is unable to work with FETs. The focus of the design is on ease of use and simplicity, and it can function continuously for more than a month on a single PP3 battery. Additionally, certain common failure types are recognizable. ![]() ![]() If you know a transistor's pinout, you can use this op amp based highly accurate transistor tester to quickly determine if it is good or bad and whether it is PNP or NPN. ![]() Precision Transistor Tester using Op Amps The LED need to be dimly or not lit at all. If it fails to illuminate or illuminates very dimly, it indicates a low-gain BJT. I can just use something like "SP" for speaker, "MIC" for microphone, "ANT" for antenna, etc.Simply determine the transistor type's base, emitter, and collector pinouts, adjust the slide switch to PNP or NPN, insert the device in place, and wait for the push buttons.įor medium to high gain transistors, pressing PB1 is going to turn on the LED. For more obscure things, I figure using an "official" single/double-letter designator is more likely to cause confusion when people aren't familiar with it. Anything that fits into multiple categories takes the more descriptive (a Neon lamp or VFD is DS, not V, for instance, just like an LED is DS rather than D). I make subcategories in cases where a component is significantly different in operation or use (Zener diode, variable passives, etc) but otherwise don't need a million different names. Code: BT Battery C Capacitor CV Capacitor - variable D Diode (forward) DS Display/indicator DZ Diode (Zener) F Fuse J Jack / female connector JP Jumper (configuration jumper, not jumper wire) K Relay L Inductor P Plug Q Transistor/other discrete semiconductor R Resistor RT Resistor - thermistor RV Resistor - variable SW Switch T Transformer TP Test point U Integrated circuit V Valve/tube May have missed a couple.
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