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Topic: Basic Transistor with Arduino. Is this accurate? (Read 11957 times) previous topic - next topic

Bittsen


It'd be nice if you'd be so kind as to stay "online" till this gets sorted.

I'm going to turn it over to CrossRoads.



I am "online". I'm having major issues with this website though. I don't know why it keeps booting me to "about blank" every time I post, whether or not the post goes through.

Don't lose faith in me. I am just delving into transistors. I assure that when it clicks it will click.

I have watched over a dozen 15 minute transistor tutorials and they all say pretty much the same thing. And that's nothing helpful. ~LOL~

So, let's cut to the chase. Pretend I am stupid for a second.

I have never understood transistors. I have never understood "factoring" in algebra. Other than that I have assimilated most every topic thrown my way. So I am transistor dumb.

NPN vs PNP (which I was actually taught in high school a few decades ago).

I don't even know what question to ask.

As for buying a book... I bought a few. They all talk like the reader is an engineer. If the reader was an engineer then they wouldn't need the stupid book. Right?


CrossRoads

Bittsen,
The box is the Arduino, the transistor is an NPN (as indicated by the arrow on the emitter leg),  may have said a generic 2N2222 would do, and the top resistor value is not critical. 1K, 2.2K, 5K.
Designing & building electrical circuits for over 25 years.  Screw Shield for Mega/Due/Uno,  Bobuino with ATMega1284P, & other '328P & '1284P creations & offerings at  my website.

Bittsen


Bittsen,
The box is the Arduino, the transistor is an NPN (as indicated by the arrow on the emitter leg),  may have said a generic 2N2222 would do, and the top resistor value is not critical. 1K, 2.2K, 5K.


The ground from the arduino in your drawing is part of what threw me off.

OK, so I think I'm getting it.

The top resistor is just to provide a "load" that will allow the current to flow through the NPN.
Then the drain (or is it emitter) on the NPN provides a +/-12V signal to the gate of the P-channel Mosfet which, in turn, allows positive current to flow through the mosfet to the eventual load.

Or am I still off?

I promise I'm not trolling. THis how I see it happening.

larryd

An important thing to remember with switching transistors or MOSFETs always check (using a DVM, or scope) the collector to emitter or drain to source voltage to ensure they are fully saturating (turning on).  This will confirm you have things wired correctly and the device will be dissipating minimum power.  The ON voltage may be: with regular transistors as much as .4V, with darlingtons this could be 1.4V and with logic MOSFETs you are looking for less than .4V @10+amps.
No technical PMs.
If you are asked a question, please respond with an answer.
If you are asked for more information, please supply it.
If you need clarification, ask for help.

CrossRoads

The top resistor is to pull the Gate of the P-channel MOSFET High to turn it off.
To turn the P-channel MOSFET on, the gate must be pulled low; that's what the NPN transistor is for.
The Arduino High output puts current into the NPN base to turn it on. When it is on, the collector goes from 12V down to ~0.7V, and that low voltage turns on the p-channel mosfet.

So there are two technologies at play - the MOSFET, which only needs voltage level changes at the Gate to turn it off & on, and the NPN, which is BJT, which needs current, and lack of current into the base to turn it on & off.

Do some reading at wikipedia of MSOFET and BJT, it is quite interesting.
The NPN could also be directly replaced with an N-channel MOSFET.
Designing & building electrical circuits for over 25 years.  Screw Shield for Mega/Due/Uno,  Bobuino with ATMega1284P, & other '328P & '1284P creations & offerings at  my website.

Bittsen

No no no....

We aren't going back to talking about N-channel Mosfets. That's where I went off the rails earlier.

Essentially we are back to the beginning. My best option is just to design my project around the NPN transistor and the P-channel mosfets that I can get and are relatively cheap.

I will just have to redesign my project to accommodate more components. At least they are still cheaper than solid state relays and can modulate at 20?S

CrossRoads

Designing & building electrical circuits for over 25 years.  Screw Shield for Mega/Due/Uno,  Bobuino with ATMega1284P, & other '328P & '1284P creations & offerings at  my website.

Bittsen

Well, it would appear that virtualbreadboard is useless for this stuff.

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