8
votes
Accepted
What's the function of this transistor on Arduino Mega?
It's a P-channel MOSFET. It's job is to act as a "dropless" diode.
The principle is this:
MOSFETs have a built-in diode across them in reverse bias (an effect of the chemistry)
The P-channel MOSFET ...
- 106k
8
votes
Accepted
LED not blinking when using a transistor
Without a common reference (ground) between the Arduino power supply and the external power-supply, again, you have a floating base, as you can't know what the Arduino's 5v output (or local ground) ...
- 15.3k
7
votes
Accepted
Switching a Solenoid Using Arduino's 5V Output?
Low-side switching an inductive load (such as a relay) using a microcontroller (such as Arduino), NPN BJT transistor (with full base resistor calculations), and snubber/flyback diode
Note: this answer ...
- 1,369
7
votes
Accepted
Controlling a 5V fan and ultrasonic fogger with an arduino - do I need an external power supply?
About the ultrasonic fogger:
The product description is misleading. This is a pure transducer. That means it does not generate its own ultrasonic frequency and is thus not DC. You need to provide an ...
- 16.5k
6
votes
Newbie Arduino DC motor problem
I see a couple of issues here, which are related to your questions. I will use numbers here, but these do not necessarily correspond to the numbers you have used when asking.
The first thing you need ...
- 161
5
votes
Transistor amplifier to drive speaker using Arduino PWM
Your amplifier arrangement is fundamentally flawed. At the moment you are "tickling" the top end of the electromagnet in the speaker - that is, you are energising it when the Arduino outputs a HIGH, ...
- 106k
5
votes
Accepted
How can I connect nearly 450 LEDs to an arduino without drawing too much current?
First you should consider changing your whole idea so that your LEDs don't draw nearly 10A.
I am assuming that for each segment you have 14-20 LEDs wired in parallel, each with its own current ...
- 106k
5
votes
Accepted
How come my transistor doesn't work?
Is there the only wire from Arduino to the Base of Transistor?
Basically you need something like this:
If you reverse the transistor (E and C), builtin protection diode will be in forward direction, ...
- 4,777
5
votes
Accepted
How to detect if LED is switched on in external circuit using Arduino NANO?
I'm afraid your circuit does not work.
In fact, the base of the transistor is always connected to the power, regardless the LED being ON or OFF. Therefore the BJT would be always in the ON-state. Also ...
- 411
5
votes
Accepted
Vary voltage using relay. Is this possible?
No, you can't vary the voltage with a relay. The only way you could do it with a relay would be to have a selection of different voltages available, and then use multiple relays to select which ...
- 106k
5
votes
Accepted
Switching fan on with transistor, fan running very slowly
With a 2.2K resistor you're massively limiting the current that can flow through the transistor.
I haven't looked up the specs on that transistor, but taking typical values for Vbe (0.6V) and Hfe (100)...
- 106k
4
votes
Accepted
Why is my circuit working only when I touch it?
Sounds like you have guessed it: although it's very hard to say from those photos, it doesn't look like you have the circuit grounded.
Connect a ground from the Arduino to the black wire from the ...
- 2,181
4
votes
Do I need a transistor if my relay has an optocoupler?
That isn't just a relay you are linking to. That's an entire board that, among others, contains a relay (blue box). This board already has a transistor to drive the coil inside the relay. It also has ...
- 11.3k
4
votes
Accepted
How to eliminate noise from PWM controlled 12V fan at low speed
I had the same problem with a 5V fan. Something simple worked for me: To decrease the PWM frequency. You probably want to do this using pin 9 or 10 (for the Uno) as changing the frequencies of other ...
- 56
4
votes
Using a transistor to get 100mA on a IR led
Increasing the power to the LED isn't the best way of increasing the distance. In fact it's the worst way.
The 100mA is only for a small duty cycle. You can power it with 100mA but only for a ...
- 106k
4
votes
Accepted
Using a transistor to get 100mA on a IR led
Here is a diagram from Peter Bennett's answer to an Electronics Stackexchange question, How much voltage to give my IR LED?:
As you can see, the current-limiting resistor is in series with the IR ...
- 8,890
4
votes
Accepted
Solenoid "vibrates" instead of pushing
From your schematics it looks like:
you connected the power supply backwards (on both schematics actually, I wonder how come you did not fry your Arduino)
the external supply and the Arduino do not ...
- 44.3k
4
votes
Accepted
Why is it I need transistors and resistors to turn a DC motor with an Arduino but I can connect it directly to a battery?
If you want the motor to rotate continuously, without using PWM, and without switching the motor on and off from the Arduino, you can connect the motor straight to 5 V and ground. If you then add a ...
- 1,795
3
votes
Control a 5 volt water pump with an Arduino
To use an NPN, connect a power rail of 5V to the pump's positive terminal, and from its negative terminal wire it to the transistor's collector pin. Wire emitter to GND, and place a >=220 ohms ...
- 311
3
votes
Accepted
How can I switch a 1.5V buzzer with my Arduino?
You simply need to ground the circuit. In row E on your breadboard just under where you connect the - of the battery, connect that to the ground pin on the UNO. This causes the buzzer to start working....
- 168
3
votes
12 V relay using Arduino
If it's working with 12v on the input but not 5v, it sounds like the base resistor value
(which is missing from the diagram) might be too high. A value of around 1k should ensure the transistor is ...
- 76
3
votes
Why does the transistor burn out
TinkerCAD may have mislead you on the pinout for the transistor
TinkerCAD
PN2222A
- 170
3
votes
Why does the transistor burn out
By this, does it mean that you still have a problem turning the pump on? Because a PN2222A should handle up to 1A through its collector, as the datasheet states http://www.mouser.com/ds/2/149/PN2222A-...
- 193
3
votes
connecting a small motor to arduino using a transistor
I like your thought process (even though it might not be completely correct), I've seen how little thought were put in for such simple circuit design in the Arduino community, including from some ...
- 1,549
3
votes
Why are transistors necessary before LEDs?
The port pins of your Nano can deliver current in a quite limited range, and six LEDs need a lot more to shine brightly. The transistors are amplifying the available current.
However, 4k7 resistors in ...
- 2,200
2
votes
How to ground a arduino with an external power-source?
I would be careful about "ground loops" when using two supplies connected to the mains electricity. You may get strange results. If you are using a lap top then maybe disconnect it from the charger ...
- 217
2
votes
How to ground a arduino with an external power-source?
Majenko explained how to figure out what is what. I'm just repeating the shematics again with "additional" description:
Current limiting resistor R1 is REQUIRED, if you don't want to destroy Arduino ...
- 4,777
2
votes
Accepted
How to ground a arduino with an external power-source?
Ground is usually (though not always, but in your case it is) the point of lowest potential in a circuit. In your circuit that is the "negative" connection of the power supply. Note that the "negative"...
- 106k
2
votes
How come my transistor doesn't work?
The program is fine.
Looking at the first photograph - The Ground of the Arduino needs to be connected to the ground of your circuit.
I do not understand the two-transistor part of your circuit, so ...
- 773
Only top scored, non community-wiki answers of a minimum length are eligible