The purpose of this circuit is to test NPN and PNP transistors and to identify their pin layouts, ie ECB, EBC. I find myself testing a lot of transistors to determine their pin layout and type and as such find that building the test circuit on a breadboard has become a hassle so I wanted an easy circuit that would be more permanent and would allow me to test transistors.
The transistor type NPN/PNP determines the polarity of the connections. The orientation of the transistor is the pin layout. I define the pin layout when looking at the top of the transistor with the flat side facing toward you. That is probably not the official way to classify them but it makes more sense to me when I am placing them in a circuit.
- EBC stands for Emitter Base Collector. When I use this acronym I am saying that the pin to the left is the emitter, the middle pin is the base, and the right pin is the collector.
- ECB similar to the above acronym stands for Emitter Collector Base. The emitter pin is again on the left but the middle pin is the collector and the right pin is the base.
I have gone through about 100 transistors that were pulled from old electronics and have never found any other orientations so i have found that there is no need to test for anything but these two orientations.
The transistor type NPN/PNP determines the polarity of the connections. The orientation of the transistor is the pin layout. I define the pin layout when looking at the top of the transistor with the flat side facing toward you. That is probably not the official way to classify them but it makes more sense to me when I am placing them in a circuit.
- EBC stands for Emitter Base Collector. When I use this acronym I am saying that the pin to the left is the emitter, the middle pin is the base, and the right pin is the collector.
- ECB similar to the above acronym stands for Emitter Collector Base. The emitter pin is again on the left but the middle pin is the collector and the right pin is the base.
I have gone through about 100 transistors that were pulled from old electronics and have never found any other orientations so i have found that there is no need to test for anything but these two orientations.
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This circuit requires few parts and it should be easy to obtain many of the required parts from your own supplies or pick them up locally. I had all the parts on hand that were leftover from previous projects or where recovered from old electronics. If you need to buy these parts I suggest ordering from a supplier on eBay. Only the circuit board you will have to find at Radio Shack if there is one locally or use a different prototype board. While you are ordering parts pick up more then you need, these parts are useful to have on hand.
You will need:
- 1x Radio Shack Printed Prototype Board 276-150
- 2x 8 pin IC Socket
- 4x tactile switch
- 4x 10k ohm resistor
- 4x 470 ohm resistor
- 4x 3mm LEDs
- Solid core wire
- CR2032 battery and holder
- NPN and PNP transistors to test
You will need:
- 1x Radio Shack Printed Prototype Board 276-150
- 2x 8 pin IC Socket
- 4x tactile switch
- 4x 10k ohm resistor
- 4x 470 ohm resistor
- 4x 3mm LEDs
- Solid core wire
- CR2032 battery and holder
- NPN and PNP transistors to test
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Google "Mouser Electronics", a well known electronics distributor. Go left to "Product Finder". Click on "Discrete Semiconductors" and then click on "Transistors Bipolar" and "Show Products". Select page 4 and look at left images 13 and 14 from top. The 6th column from left says "Data Sheet" (click to open)and you will see a TO 92 package (plastic) and TO 39 package (metal) respectively. Kind of confusing. The article deals only with plastic packages. When it comes to metal (TO39), my rule of thumb is that the lead physically closest to the metal tab is the Emmiter but I am not sure that this is always true.
1) There is a standard numbering system for IC sockets that avoids any possible confusion. It is based on the half circle notch (indent) in the plastic frame seen pointing downwards on the parts picture (shown under Step 1). (A) Place the socket in front of you so that the slots will be in two horizontal parallel rows. (B) Orient the socket so that the half circle notch is at your left. (C).Starting from the left on the lower row, the slots are 1, 2, 3, ...x. When you reach the end of the lower row, jump counter clock wise to the top row and continue numbering x+1, x+2,.. to the end. If you have to insert an IC, look at its top surface and you will see a tiny embossed circle (ususally) or some other mark. That mark must point the same way as the half circle notch.
Okay, ive stumbled upon a problem, i've only just started learning electronics and finding it extremely difficult !
But i'm tring to follow the exact specs as this transistor tester as to avoid any mistakes but im cnow confused to heck and back !
Problem 1:
- Very Early-on, the diagram showing the simple schematic of the NPN Transistor tester circuit shows the BASE of the NPN being connected to the 10K resistor but in all the photo's the BASE of the NPN transistor (bottom-right test circuit on prototype-board looking at it from non-solder-side!) is connected to the 470 OHM Resistor.
PLEASE please please can anyone confirm why this is ?
Problem 2:
On the same circuit (bottom-right test circuit on prototype-board looking at it from non-solder-side!) the LED's 'Notch' {meaning the Cathode} is facing upwards... No matter how i orient the LED on my setup {using the same components, no substitutes!} instructions say 'Make sure the Anode is connected to the resistor' but how can this be possible for the LED's Notch facing up ? I really cant make head-nor-tail of this...
Please help as this is an excellent learner project for me and i have many transistors to test, lol, but go easy on me, Learner-Here, lol x2!
Many thanks in advance for the help with what will seem like child's-play to you folk, but rocket-science to me !
Problem 1:
From the simple test schematic I have the base of all the transistors are connected to the 10K resistor. In this schematic the base pin is always drawn as the middle of the three transistor pins. No when we go to real life components the pin layout is not the same. For the bottom right transistor the pin layout from left to right is; Emitter, Collector, Base. So the base moves from the middle pin to the right pin.
Problem 2:
The picture in step 6 appears to be playing tricks on my eyes. It looks like the bottom right LED has a flat facing up. I am sure this is not the case. Just make sure to place you LED with the correct polarity. I like to use a button cell to quickly check the polarity of LEDs before placing them, I never trust the makings on any of the LEDs I pull from old electronics.
Obviously your circuit works as others have made it too and even made some changes but because ive only just started learning electronics this year its playing havoc with my old brain trying to learn new tricks, lol !
I'll be resuming this project over the weekend and am quite determined to make an enclosure for it as well because of the great practical use of this very important circuit !!!
Once again many thanks for your kind patience with assisting a complete noob and making it a few good steps closer for me to make this awesome circuit !!!
;-)
Also i have a bunch of rechargeable LIR 2032 Coin Cells to finally start making use of them !!
Thanks so much and Keep making your instructables with extremely outstanding high-res pictures !!! (2mb per pic - nicely done !!!)
!!! "A Simple Yet VERY Effective Piece of Work" !!!
Long story short I was never able to figure out how to make this method work. I am not sure if it is even possible to do but my simple understanding of circuity prevented me from going any further.
It's well written and very easy to follow.
I made a transistor tester that uses four socket pins to test both EBC and ECB.
the leftmost three pins (see pic) test transistors to see if they are EBC. To test your transistors to see if they are ECB, simply rotate the transistor 180 degrees and move the transistor to the rightmost pins (see pic).
I would have used a battery almost identical to yours, but I didn't have any button cells that weren't dead.
That is my version of your transistor tester! XD
HIGH RES PIC
HIGH RES PIC
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First the circut would have to be altered, the IC sockets would need to be on a separate smaller board so that I could place then on the underside of the box lid while having them stick out of cut outs through the top. I have tactile switches with longer buttons so I could leave them as they are and build some wooden pegs on the box lid to press them. Also the LEDs would need to be extended.
By skiping an enclosure I was able to simplify the circuit and keep the tester in as small a package as I could solder. I have these flat plastic organizers that I place all my components in and as an added bonus this tester is just small enough to fit in one of the compartments next to my transistors.
That being said, I'd like to see one for Flame Emitting *ahem* ... I mean, Field Effect Transistors... slip of the metaphorical tongue...
"- ECB stands for Emitter Collector Base. When I use this acronym I am saying that the pin to the left is the emitter, the middle pin is the base, and the right pin is the collector.
- EBC similar to the above acronym stands for Emitter Base Collector. The emitter pin is again on the left but the middle pin is the collector and the right pin is the base. "
But a great project!