Reddit mentions: The best bjt transistors

Honestly you can get a bunch of the individual stuff separately on amazon. Here are some recommendations I have:

Get a volt meter that can measure ohms and current (mA):

https://www.amazon.com/gp/product/B00KHP6EIK/


Red/Green/Blue LEDs:

https://www.amazon.com/gp/product/B0059H5Z5O/

https://www.amazon.com/gp/product/B004UMA60S/

https://www.amazon.com/gp/product/B0059H5Z5O/


Breadboards:

https://www.amazon.com/gp/product/B01258UZMC/


Jumper wires:

https://www.amazon.com/gp/product/B00ZWEFWO8/


pir (motion) sensors:

https://www.amazon.com/gp/product/B017HP88VI/


transistors:

https://www.amazon.com/gp/product/B00R1M3DA4


resistors:

https://www.amazon.com/gp/product/B0185FGTSS/

https://www.amazon.com/gp/product/B0185FGN98/


The multimeter is great, you can make sure you wont fry your GPIO outputs. Try not to pull over 16mA of current per pin to avoid damage. Use a 1k or 330 ohm resister accordingly. You can also do a lot of cool stuff with a transistors and LEDs.


I've been documenting a lot of the electronics stuff I've been teaching myself; About six months ago I was where you were, setting out trying to learn how to use all these components. Feel free to reach out if you have any questions. I'd recommend going to the oldest post on my blog and reading in order if you want some ideas: https://supertechnologyknowledgequest.blogspot.com

PM me with any questions, I'd be happy to point you in the right direction for anything you are trying to do for which I can help! Best of luck!

edit: the multimeter is no longer on amazon, just find one that lets you read resistance AND current (milliamps).

I picked up an awesome cheap tool I forgot to mention and it was only $15:

https://www.amazon.com/gp/product/B071Y5CHPK/ref=ppx_yo_dt_b_asin_title_o00__o00_s00?ie=UTF8&psc=1

You have to assemble it and it doesn't come with instructions, but it's so good. I use it to test parts before soldering them in, that way I know I have properly working parts before putting them on the board so if I have any problems later, I know it's not the parts. It measures resistors, diodes, caps, transistors, etc. It does the same thing as the $60 atlas DCA and more. The atlas DCA only measure semiconductors, this cheap thing measures passive parts too like resistors/caps, etc. The numbers are slightly different than what my atlas measures, like right now I'm measuring a silicon transistor that is reading 290 hfe on my atlas but 250 on this cheap thing, but it's at least in the right ballpark. The atlas goes into way more detail like leakage and stuff, but the cheap thing at least gives you the hfe and the pinout so you don't accidentally connect the wrong lead to the wrong input. I got a cheap DMM from amazon too that will give you an accurate enough reading for like $15. So for $30, you can have two great measuring tools.

You can just buy one of those cheap LCR/component tester jobbies. They're not as good as a real inductance meter but for basic identification they're fine, great for lots of other quick measurements too.


https://www.amazon.com/Multifunction-transistor-Capacitor-Inductance-screwdriver/dp/B071Y5CHPK

I have done something very similar to this, as I have worked on projects where I needed to control common-anode RGB LED strips. You should just need a common NPN Transistor. Here is a link to some I found on amazon that I find tend to work well, and the bulk pack is pretty nce, And Here is the datasheet for those specific transistors.

If all you want to do is be able to turn the LED on and off, the circuit should be fairly simple. Connect VCC (12v) through a current-limiting resistor to the anode (+) of the LED. Then connect the cathode (-) of the LED to the collector of the transistor, (can be seen in the diagram/datasheet) then connect the emitter of the transistor the ground (- of the power source). And connect the output pin from the Arduino through a small-value resistor to the base of the transistor. With that, you should be able to use the Arduino output to control the higher-voltage LED with digitalWrite(pin,HIGH) turning it on, and digitalWrite(pin,LOW) turning it off.

Here is an example of what that would look like. Ignoring however you plan on powering the Arduino itself, you can see how the LED, transistor and output pins are connected.

 

NPN Transistors normally have 2 "modes" per se. They have an analog mode which uses a change in normally very low voltage to change how much "on" they are, meaning they let different amounts of current flow from the collector to the emitter (In this case the voltage path of the LED) depending on how much current is flowing from the base to the emitter (Arduino to ground, as when the output goes high, it allows current to flow through the transistor's base to the emitter). However in this case, the transistor is mostly going to be functioning in the saturation region, meaning that the Arduino is likely going to be putting out enough current that the transistor will either be completely ON or completely OFF, and you wont get much analog function out of it. However if you want to be able to dim your LED, you can use PWM to very quickly turn it on and off, which can give it the effect of dimming it.

 

TLDR: Use a transistor. Likely NPN would work well.

Edit: In the circuit schematic tool I used, they had the ATMega, but not an Arduino itself. Treat the mega shown as if it were an Arduino, Ex. Has voltage regulators, input pull-ups, etc. The VCC is the arduino's RAW or Vin

It will work just fine, but it's expensive. For future reference, a 2N2222 is a good general purpose NPN that is readily available for cheap.

Bingo. Transistors are switches controlled by power.

Not sure EXACTLY what kind of transistor you'll need, but you should be able to find one easily at RadioShack, Frys, or the internets: https://www.amazon.com/S8050-Silicon-Transistor-Voltage-Current/dp/B015E4DJ90

I just ordered the parts I need. [Found a good deal too](
https://www.amazon.com/pcs-2N3904-2N3906-TRANSISTOR-200mA/dp/B00KHMRG5S/ref=sr_1_cc_1?s=aps&ie=UTF8&qid=1480682405&sr=1-1-catcorr&keywords=50+pcs+of+2N3904+%26+50+pcs+of+2N3906+TRANSISTOR+40V+200mA)

Even the same manufacturer can differ on the TO-92 because they can be ordered in any pinout you want, but I think the standard EBC applies generally.

OP, for $15 you can check - worth every penny.

Yeah. You can do it all analog if you can get it down to 26 outputs.

Then you just need transistors for the duplicates. Easy peasy.

Edit: You'll have your work cut out for you if you just set out to Google-learn about transistors and relays. This project would be quick with a bank of four of these, but it would also be unnecessarily bulky and expensive. You can do everything those do with just transistors since you're only powering LEDs.

I got a 100 pack of 2N2222 NPN transistors from Amazon for $4.60. Here's the link.

Here’s a listing of all the included material

eBoot 30 Pieces Photoresistor Photo Light Sensitive Resistor Light Dependent Resistor 5 mm GM5539 5539 https://www.amazon.com/dp/B01N7V536K/ref=cm_sw_r_cp_api_i_-wV6CbC6051BJ

Beadalon Artistic Wire 30-Gauge Bare Copper Wire, 30-Yards https://www.amazon.com/dp/B0048927RI/ref=cm_sw_r_cp_api_i_vEV6CbC9KF2ZQ


MCIGICM 200pcs 2n3904 npn Transistor, 2n3904 Bipolar (BJT) Transistors NPN 40V 200mA 300MHz 625mW TO-92-3 https://www.amazon.com/dp/B06XRBLKDR/ref=cm_sw_r_cp_api_i_UEV6Cb66Z0SC2


3mm Diffused LED Diode Assortment Kit - Pack of Assorted Color LEDs and Resistors (1000 pcs) - Red, Green, Yellow, Blue and White Light Emiting Diode Indicator Lights from Plusivo https://www.amazon.com/dp/B07GBFJ823/ref=cm_sw_r_cp_api_i_dFV6CbWBSS5AD

an npn transistor has 3 pins the emitter base and collector and basically you would take the two pins from where the button should be and connect the emitter and collector (outermost pins) to them then the center pin (the base) goes to an arduino pin and if you pull that pin high then the outermost pins will be connected

they can be bought here

check the datasheet for more information

Why not just buy some? This for ex: https://www.amazon.com/Hilitchi-250-Piece-General-Transistors-Assortment/dp/B06Y4M2N29/

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250 assorted types for $10 is 4c a piece... not worth the time in my mind.

You'd need to disconnect the antenna, yes... but I'd take a guess that the meter you posted won't read capacitance that low anyways. I've had very good luck with this meter when measuring small capacitances, including variables: https://www.amazon.com/Multifunction-transistor-Capacitor-Inductance-screwdriver/dp/B071Y5CHPK it seems to measure down to about 25pf.

The other thing is you might be measuring at the wrong points on the cap. Pay close attention to the mechanism and how it's connected. Put the meter on continuity, and put the leads to the points where you were testing. If you have DC continuity, you're using the wrong points.