I'm a little bit lost with transistors... need help

FramingFrame

Jun 30, 2015
4
Hallo to everyone, this is my first post, so i'lld say that i'm starting to learn electronics on my own, and now i'm at a point that i found out that there are trillions of different transistors, and i dont know how can i know easely the differences between each one, to know which one to pick, by now i'm designing a circuit that runs on 9 or 12v from a dispossable battery, (i didnt decide it yet) and i need just a NPN transistor that makes the current flow when receives the signal to the base and it closes when the signal is gone.

I'm looking to order a package of transistors and there are all those:

10 x S9012
10 x S8050
10 x S9013
10 x S8550
10 x S9014
10 x S9015
10 x C945
10 x S9018
10 x C1815
10 x 2N2222
10 x 2N3904
10 x A42
10 x 2N3906
10 x A92
10 x 2N5401
10 x A733
10 x 2N5551
10 x A1015

So, which one should i use? there's some easy way to know the particularities of each one? how do you manage it? because for me it looks really crazy...

Thanks and regards

brevor

Apr 9, 2013
87
Since you are just starting to learn about transistors I suggest you buy 1 bag of 2N3904 and 1 bag of 2N3906. That will give you 10 each general purpose NPN and PNP transistors.

FramingFrame

Jun 30, 2015
4
Since you are just starting to learn about transistors I suggest you buy 1 bag of 2N3904 and 1 bag of 2N3906. That will give you 10 each general purpose NPN and PNP transistors.

Ok, so that ones are the normal general purpose transistors, good... thanks for the info, and now, where can i easely learn what is the particularity of the other transistors? like that one does that, that one does that, and so on, or there's no other way of studying the datasheet of each one...? because it looks a little bit hard and long task...

brevor

Apr 9, 2013
87
there's no other way of studying the datasheet of each one...? because it looks a little bit hard and long task...

Some transistor manufacturers publish selector guides to help engineers find a transistor that meets their needs, however since you state you are "starting to learn electronics on your own" I would ask what you want to do with the knowledge you learn? If you are just interested in doing "hobby" electronics you don't need to have a complete knowledge of dozens of different transistors.

Minder

Apr 24, 2015
3,479
You might also want to look into Mosfets, for starters and interfacing with low drive TTL/CMOS/μproc electronics there is a 2n7000 'Fetlington' mosfet version of the darlington.
it does not impose the same level of required base/gate drive that a bi-polar does.
M.

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hevans1944

Hop - AC8NS
Jun 21, 2012
4,890

This chart of typical small-signal transistors, all available in bulk packages at very reasonable cost, gives you most of the information you need to select a particular transistor for your small-signal transistor applications. The only major parameter missing is the typical hfe (beta) specification, which will generally be somewhere between 20 and 200 depending on collector current and transistor type. So, pick something that has the proper Vcbo, Icm, and Pcm specs and Google that part type for a datasheet. The image above was a result of this search string which yielded dozens of images to peruse. Later on, you may also want to explore inexpensive power transistors and other semiconductors such as MOSFETs, SCRs, and TRIACs. Just qualify your search string and Google away until you find something interesting and affordable.

FramingFrame

Jun 30, 2015
4
Some transistor manufacturers publish selector guides to help engineers find a transistor that meets their needs, however since you state you are "starting to learn electronics on your own" I would ask what you want to do with the knowledge you learn? If you are just interested in doing "hobby" electronics you don't need to have a complete knowledge of dozens of different transistors.

I am mechanic by profession, and in my free time i like to design and build machines by hobby, i know about electricity and also i've done some things programming in Pascal and Java, so i want to learn about electronics to improve my field of knowledge and to be able to build some machines i have in mind that requires some electronics to drive them. I'm also looking forward to receive my arduino to learn to work with it... And... i dont need to know to design a computer motherboard, but an intermediate, decent circuit with the time will be so useful.... and that along with the arduino then i will have free way to realise my projects... as you say i dont need to know every transistor, but i think to have a decent knowledge of what they can do will be good...

Ah, and thank you all for the answers, now i have quite a bunch of things to look at...

PD: As my begginner electronic project i want to build a simple circuit with 4 PIR sensors and a buzzer to not let my cat jump over the bed when i'm not at home...

Minder

Apr 24, 2015
3,479
I think you will find the likes of the 2n7000 very useful for interfacing with micro's etc, I tend to use mosfets over bi-polar where possible.
There is also 7 & 8 Darlington drivers in DIP packages such as ULN2803 etc. these include the BEMF diodes for inductive loads also.

M.

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hevans1944

Hop - AC8NS
Jun 21, 2012
4,890
... i dont need to know to design a computer motherboard, but an intermediate, decent circuit with the time will be so useful.... and that along with the arduino then i will have free way to realise my projects... as you say i dont need to know every transistor, but i think to have a decent knowledge of what they can do will be good ...
PD: As my begginner electronic project i want to build a simple circuit with 4 PIR sensors and a buzzer to not let my cat jump over the bed when i'm not at home...
It sounds like you are well on your way with the Arduino! I would recommend purchasing a "beginners kit" such as this one that I bought at Radio Shack, but also available on-line. You will probably want to eventually purchase a few Arduino Shields and these are also available from Seeed Studios (China) at Radio Shack. There are many online hardware and software resources for Arduino. Two popular sites are Adafruit and SparkFun.

A "cat buster" alarm sounds interesting! I have a cat that loves to go where he knows he shouldn't go, most especially at night or when no one is home. I have a rather expensive high-resolution TV camera that I am thinking about connecting to my home LAN for recording his nocturnal and stealthy activities, but nothing beats positive and immediate feedback like a PIR connected to a loud buzzer! I also happen to have a PIR that I purchased at Radio Shack for use with my Arduino Unos (I have two of those), but it seems like it would be a simple matter to rig some more up in appropriate places with the Arduino setting each of them up, silencing the alarm after a few seconds, and then re-arming the PIRs as needed. Maybe even include a few "silent" alarms that just light an LED a few times before sounding an audible alarm. That ought to keep my Simon guessing! You could even leave your Arduino connected to a laptop or desktop computer after you program it to send text messages back to the computer. So go have some fun!

Hop

FramingFrame

Jun 30, 2015
4
It sounds like you are well on your way with the Arduino! I would recommend purchasing a "beginners kit" such as this one that I bought at Radio Shack, but also available on-line. You will probably want to eventually purchase a few Arduino Shields and these are also available from Seeed Studios (China) at Radio Shack. There are many online hardware and software resources for Arduino. Two popular sites are Adafruit and SparkFun.

A "cat buster" alarm sounds interesting! I have a cat that loves to go where he knows he shouldn't go, most especially at night or when no one is home. I have a rather expensive high-resolution TV camera that I am thinking about connecting to my home LAN for recording his nocturnal and stealthy activities, but nothing beats positive and immediate feedback like a PIR connected to a loud buzzer! I also happen to have a PIR that I purchased at Radio Shack for use with my Arduino Unos (I have two of those), but it seems like it would be a simple matter to rig some more up in appropriate places with the Arduino setting each of them up, silencing the alarm after a few seconds, and then re-arming the PIRs as needed. Maybe even include a few "silent" alarms that just light an LED a few times before sounding an audible alarm. That ought to keep my Simon guessing! You could even leave your Arduino connected to a laptop or desktop computer after you program it to send text messages back to the computer. So go have some fun!

Hop

Sorry, i didnt had much time those days,

Yes i actually ordered something like this, i looked adafruit before, but the sending costs to Europe are more than the price of the product itself, so

Hahaha, yes i think every cat owner asks himself what he does in the house when he feels alone, i'll do it also some day, but first what i want to do is that, a camera and the arduino, but attaching a PIR sensor and focus it to the door for if someone enters one day in my house, to let everything recorded, it would be good to program the arduino to upload the video to the cloud by streaming, just in case the one who enters takes the computers (and even the arduino) with him xD
I'm going to start studying it to set it up as soon as possible.

For the cat i just want to make a small box, with a simple and cheap electronic circuit and one small cheap led-style PIR sensor on each side of the box, to leave it over the bed when i go, that when the cat jumps over the bed it starts buzzing and in like 3 seconds after having any detection of the sensors, (the cat is gone) it resets itself again to passive mode.

But i think i will start first with the camera thing...

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