![]() After placing the transistor in the correct formation, multimeter would show the H fevalue of the transistor.įig.5: Image showing PNP transistor placed in transistor region of multimeter Place the three legs of the transistor in the same manner as discussed above.įig.4: Image showing transistor placed correctly in transistor region of multimeter ![]() The reading is nothing but thr HFE of that transistor.įig. If multimeter shows reading then it’s correct. If the previous method doesn’t work, place the three legs of the Transistor in the B-C-E formation.3: Image showing transistor placed in transistor region of multimeter The multimeter will show the reading if this formation is correct, else it will show over range.įig. Place the three legs of the Transistor first in the E-B-C formation. Transistors can be divided into three groups: small power transistors, medium power transistors, and high power transistors based on their current capacity.Collector, Base, Emitter terminals can also be known. To ease the process, multimeters come with a function where one can calculateH fe or small signal Forward Current Gain of a bipolar transistor.Īpart, from detailing with the forward gain value, the H fe function solves two problems. If the model number is not known, it is impossible to detail about the type of transistor just by looking at it. 2: Image showing Transistor function region in multimeter Step 1: Transistor Function on Multimeter.įig. After reading this, you will be able to find out configuration of the device as well as find out its collector, emitter and base. I am not sure what the actual voltage is at the contacts and hesitate to risk my meter to find out.This tutorial will detail with testing PNP and NPN configured transistors using a multimeter. The author of the circuit says 5 volts is available at the flash contacts, yet flash trigger voltages are usually high enough that they will fry digital camera circuitry, if an old flash is fired from a new digital camera. It works as long as something is not providing a parallel path. ![]() I have, however, used this little test on Q's in circuit. Somewhere, as I mentioned, I read it may show a leaky Q as good. I think the test procedure was offered in the book I have as a simple "go/no go" test adequate for many normal circumstances. I am tempted to build the circuit again laid out just like the schematic, in case I made an error I do not see. The URL I gave borrowed the circuit from another man, and some of the values are a little different in his circuit, but they are not supposed to be critical. They are all new resistors and I checked the number of ohms after ganging them together. If the LED is working properly, then it glows otherwise the LED is defective. Connect the probes of the meter to LED such that it is forward-biased. Place the multimeter selector / knob in diode mode. Identify the anode and cathode terminals of the LED. I had to gang resistors together in series to get the values given. Let us now see how to test an LED using a digital multimeter. An equivalency converter gives 1000 pf as 0.001 mf. The seemingly large value number on C3 is picofarads. It would close an open switch on the auxiliary flash's trigger circuit and the auxiliary flash would fire when the flash sensor cube "saw" the real flash from the camera.Īll three capacitors are ceramic. The first stage would trigger from the pre-flash and start the second timer. The next step is to determine if you are dealing with a npn or pnp transistor technical. Such a bipolar transistor test can be performed either by switching the multimeter to ohmmeter mode (resistance test) or by switching to a diode test in the first case, the limit should be set to 2kOhm. I am thinking of trying a two stage time delay circuit built from two 555 timers or one 556 timer. Read how to test the transistor with the meter. It would be a useful device to have, since I have a couple of working Vivitar 283 flashes. Use a soldering iron to melt the solder holding the base lead of the transistor to the circuit board and pull the base lead out of the board so its not. I have checked my circuit layout to be sure I followed the schematic. The auxiliary flash seems to fire immediately, rather than after a slight delay. My flash is a Vivitar 283 just like the one the author used. A description and a schematic can be found at: Last night I used my own Instructable to find and replace a bad transistor, but it still does not work. The circuit causes the auxiliary flash's trigger cube to ignore the first or pre-flash from the camera and fire on the second flash that coincides with the open shutter. The circuit I have been trying to make work is supposed to fire an auxiliary photo flash in synchronization with the open shutter on a digital camera when the flash on the camera fires.
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