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Author Topic: Beginner Transistor Question  (Read 1722 times)

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Offline VegaObscuraTopic starter

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Beginner Transistor Question
« on: February 03, 2010, 05:50:17 PM »
I'm ready to start experimenting with transistors, but I've read a lot about how easy they are to fry.  I'm not very well funded and I can't afford to keep buying new transistors.  I'm getting most of my parts by unsoldering them from PCBs in old electronics.  So far its been working great, but I tend to have issues knowing how much electricity I can put through things.  So far I've been doing things by trial and error, but I think if I do that with transistors I will quickly run out of parts.  I have all the basic tools.  Soldering iron, continuity tester, multimeter, etc.

I have a robot, but its entirely remote controlled so its more of an RC car that looks like a little robot for now.  I made its controller by taking an old remote control, drilling through the PCB around the buttons directly on the copper lines, and soldering a wire in so when the button is pressed, current goes through and the robot moves.  The harder the button gets pushed, the faster the bot goes.  The problem is, even pushing so hard the controller is about to break, it still has a lot of resistance and the robot doesn't go nearly as fast as it would if it was wired straight from the battery to the motors, without the buttons.  I just really need to know how to use transistors without frying them.

Offline Razor Concepts

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Re: Beginner Transistor Question
« Reply #1 on: February 03, 2010, 06:05:48 PM »
It is best to do things right and calculate as you said, but transistors are cheap! You can buy 500 2n2222s on mouser for $8.50.

Offline MangoBot

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Re: Beginner Transistor Question
« Reply #2 on: February 03, 2010, 09:19:21 PM »
type in the numbers on the transistor and you may be able to find it, then you could find out all of the specifications, and what leads are what, etc.

Offline galannthegreat

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Re: Beginner Transistor Question
« Reply #3 on: February 04, 2010, 02:01:53 PM »
Transistors either amplify (operate in the linear region) or switch (operate in cut-off (open switch) or operate in saturation (closed switch) ). If you want to drive loads, such as a motor that draws more than 200mA I'd suggest either a power transistor (TIP31 is an example of an NPN one) or even a darlington transistor (TIP112 is an example of a good NPN one I use), if you don't require that kind of transistor I'd recommend a 2N2222A as a good general purpose NPN transistor.

This page shows a good example of how to use them properly for your purposes:
http://www.rason.org/Projects/transwit/transwit.htm
Kurt

Offline Soeren

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Re: Beginner Transistor Question
« Reply #4 on: February 04, 2010, 07:11:47 PM »
Hi,

I'm getting most of my parts by unsoldering them from PCBs in old electronics.  So far its been working great, but I tend to have issues knowing how much electricity I can put through things.  So far I've been doing things by trial and error, but I think if I do that with transistors I will quickly run out of parts.

If you type in the numbers in Google plus the word "datasheet" (less quotes), you will be able to get most datasheets.

That said, you might need to shave off some letters or add some depending on the transistor.
Japanese transistors are often marked with eg. Dnnnn or Cnnnn (where nnnn is some number) and the letter is not allways in-line with the number - if you find one of those, add "2S" in front of it to get eg. 2SCnnnn which is the full name. Sometimes pre- and postfixes are for differentiating variant pinouts or special selected devices and for the best results, don't use those in a search.

Sometimes you only get rudimentary info on the more obscure devices, but hey, as long as you desoldered it from trash, you can just put it in the "may-bin".
Trash is aplenty these days - endless supplies of second hand transistors ;D


I just really need to know how to use transistors without frying them.

You might wanna read this Transistor Tutorial.
Regards,
Søren

A rather fast and fairly heavy robot with quite large wheels needs what? A lot of power?
Please remember...
Engineering is based on numbers - not adjectives

 


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