Electronics > Beginners
Best kits? (and various other questions)
Retkid:
Well I'm getting to the point where I can start to design concepts. Im very fuzzy on transistors and dont quite understand NPN AND PNP.
https://cdn.discordapp.com/attachments/504691699872694273/571113686509289473/unknown.png
I'm at the level at apart from the transistors, and how everything feedbacks into each other, I get it pretty well (also the resistor with the diode, what the hell is that)
but anyway, any suggestion for component kits. I'm planning on getting a de soldering iron and going picking for old pcbs to nab resistors and non electrolyritic caps. I was wondering if i can take an old PCB, cut the top laye with the solder mask off, then draw traces and photo-resist traces onto a used pcb, as well.
Any of these questions, i would appreciate any answers to any of my questions
David Cutcher CEG:
I am currently putting together an introduction course to be presented on Udemy.com
It is specifically for the rank beginner, who is interested in learning electronics, but like many people, don't know where to begin.
My biggest asset is that I approach this as a teacher, not from the technical point of view. Hands on right from lesson 1, and 1st circuit in lesson 3.
The beta test course will be up and running June 1st.
However, Right Now, I am looking for a few more beta testers.
If you are already into electronics, this is not for you. Newbies only, please. My explanations are not deeply technical, but technical enough.
If you are interested, send me a note. My email address is in the header of the attached outline.
DDunfield:
--- Quote from: Retkid on April 26, 2019, 03:12:04 am ---Im very fuzzy on transistors and dont quite understand NPN AND PNP.
--- End quote ---
At a very basic level: Transistors are unidirectional devices. eg: In a common-emitter configuration, a small current between base and emitter controls a larger current between collector and emitter. But ONLY if the currents are flowing in the right direction. Think of NPN and PNP as the "polarity" of the transistor. In the above example an NPN transistor would have the base (and collector) at a more positive voltage than the emitter in order for current to flow in the right direction. For a PNP transistor, the base (and collector) would be more negative than the emitter.
--- Quote from: Retkid on April 26, 2019, 03:12:04 am ---I get it pretty well (also the resistor with the diode, what the hell is that)
--- End quote ---
Are you referring to the device at the bottom of the image which looks like a horizontal resistor with a triangle connection coming off the bottom mid-way?
If so, that is a potentiometer, although in this case it is being used as a rheostat.
A rheostat is simply a variable resistor. Mechanically one connection is at the end of a resistive material, and the other can slide along the material. The closer to the connected end, the lower the resistance, the further away, the higher the resistance.
A potentiometer is just a rheostat with a connection at the other end as well. As the tap connection slides the resistance to one end lowers while the resistance to the other end raises.
In this case, since the "far" connection is connected to the tap it serves no extra purpose and could be left unconnected (*).
(*) The advantage of connecting the far end to the tap is that if the sliding connection between the tap and the resistive material becomes intermittent (common in some pots as the device ages and/or dust gets inside). the rheostat will present it's maximum value instead of "open circuit".
Btw, I can't see where it goes, but assuming the dotted line going from the tap on the potentiometer goes to another tap on another potentiometer, this means it's a "ganged" pot. In other words, two (or more) potentiometers which operate in tandem from a single shaft. An example being the volume control of a stereo amplifier. You want to control the gain of two independent circuirs (left and right) with a single control.
Dave
rstofer:
As to transistors, this tutorial is as good as any other. There's a nice animation about 1/2 way down the page and it really demonstrates switching action very well.
https://learn.sparkfun.com/tutorials/transistors/all
I haven't spent much time with Sparkfun tutorials but from what I see, they are pretty good.
Digilent has a more formal program called RealAnalog - heavy into the math behind all this stuff.
Retkid:
--- Quote from: DDunfield on April 26, 2019, 01:02:02 pm ---
--- Quote from: Retkid on April 26, 2019, 03:12:04 am ---Im very fuzzy on transistors and dont quite understand NPN AND PNP.
--- End quote ---
At a very basic level: Transistors are unidirectional devices. eg: In a common-emitter configuration, a small current between base and emitter controls a larger current between collector and emitter. But ONLY if the currents are flowing in the right direction. Think of NPN and PNP as the "polarity" of the transistor. In the above example an NPN transistor would have the base (and collector) at a more positive voltage than the emitter in order for current to flow in the right direction. For a PNP transistor, the base (and collector) would be more negative than the emitter.
--- Quote from: Retkid on April 26, 2019, 03:12:04 am ---I get it pretty well (also the resistor with the diode, what the hell is that)
--- End quote ---
Are you referring to the device at the bottom of the image which looks like a horizontal resistor with a triangle connection coming off the bottom mid-way?
If so, that is a potentiometer, although in this case it is being used as a rheostat.
A rheostat is simply a variable resistor. Mechanically one connection is at the end of a resistive material, and the other can slide along the material. The closer to the connected end, the lower the resistance, the further away, the higher the resistance.
A potentiometer is just a rheostat with a connection at the other end as well. As the tap connection slides the resistance to one end lowers while the resistance to the other end raises.
In this case, since the "far" connection is connected to the tap it serves no extra purpose and could be left unconnected (*).
(*) The advantage of connecting the far end to the tap is that if the sliding connection between the tap and the resistive material becomes intermittent (common in some pots as the device ages and/or dust gets inside). the rheostat will present it's maximum value instead of "open circuit".
Btw, I can't see where it goes, but assuming the dotted line going from the tap on the potentiometer goes to another tap on another potentiometer, this means it's a "ganged" pot. In other words, two (or more) potentiometers which operate in tandem from a single shaft. An example being the volume control of a stereo amplifier. You want to control the gain of two independent circuirs (left and right) with a single control.
Dave
--- End quote ---
Thanks for the term rheostat, much better than "Pot that's in parallel in a way to change the current".
How do i wire ganged pots? and I cant find a Transistor with the arrow on the top IN EasyEDA...
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