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18

The VIN pin is directly connected to the USB's 5V supply. Which means that when the board is powered by USB you can take 5V out of that pin. You cannot control that voltage. It is always on, and always 5V (or whatever your USB port happens to provide - 4.75v - 5.25v). You must never ever connect VIN to a power source and connect the USB socket. That can ...


8

You decide which rails are positive and which are negative when you connect them to the + an - from your power supply or battery. A breadboard isn't polarised per se. It's just a bunch of cross-connections inside a perforated plastic case. No active or passive components inside. Some manufacturers may choose to paint indications regarding where to connect ...


6

Based on your schematic, you need to provide a 3.3v power source to the 3.3v side of the logic level converter. You can use the 3.3v pin on the Arduino. Also, it's really hard to evaluate your soldering with such a shaky picture. Just make sure none of the pins are connected. A visual inspection usually will do, but if you want to be sure, use your ...


5

You're misunderstanding what you need to drive a transistor. A transistor will allow up to a specific amount of current through the collector depending on the current that flows through the base. If less is needed by the load then less will flow. Think of it like a tap. If there's not much water pressure it doesn't matter how far you turn on the tap, after ...


5

LVTTL is Low Voltage Transistor-Transistor Logic. In general, the term "TTL" is used for a digital signal. The "Low Voltage" part is special, the ATmega32U4 switches from low to high (and vice versa) at low voltages. Just as it is written. For example, when the ATmega32U4 runs at 5V, then: VILmax = 0.2 * 5 - 0.1 = 0.9 V. VIHmin = 0.2 * 5 + 0.9 = 1.9 V. ...


4

The forward voltage of an LED or diode is the applied voltage of the "knee" in the exponential characteristic at which it starts to substantially conduct, and in the case of an LED, produce light. It is not, under ordinary circumstances of indicator-type LEDs, a voltage that would be produced internally to the LEDs, at least not with any substantial ...


3

-10uS because of the 10uS delay at the end of the loop, and /128 because he has decided there will be 128 possible dimming levels.


3

Assuming you are asking about digital input pins on an Arduino: Digital logic operates at the saturation and cut off regions of the transistor logic used. Most modern day processors use CMOS transistors. The logic levels are Low: 0 V to 1/3 VDD and High:2/3 VDD where VDD is the supply voltage. This information can be found here. So, if your processor is ...


3

He is describing a boost converter which steps up voltage at the expense of current. To quote from the Wikipedia page on that subject: A boost converter (step-up converter) is a DC-to-DC power converter that steps up voltage (while stepping down current) from its input (supply) to its output (load). It is a class of switched-mode power supply (SMPS) ...


3

Is the programming code for A0 to D2 the same as for the other pins ? Then you could put the pin numbers in an array and run them in a for loop. The TP4056 has a CE pin, why don't you use that to turn then on and off ? The accuracy of reading a voltage with an Arduino depends on the accuracy of the voltage reference. You use the VCC 5V as reference. Is ...


3

Measuring voltage Use the following interfacing circuit for measuring voltage: Resistors R1, R2, R3 (1% tolerance or better recommended) will map the voltage input range (-12 to +12V DC) to an output range that can be read will the Arduino ADC (+0.5 to +4.5V DC, in order to have some slack from the top and bottom end of the ADC range). The actual ...


3

You may want to use a boost converter which is a device that can step up voltage. You can get them from eBay for around $US 2. As Chris Stratton pointed out in a comment, the boost converter may run your batteries down quite quickly. Let's say you need 200 mA for your Uno, sensor and LEDs. At 5V power that is 1W of power (0.200 * 5). However to get 1W ...


3

As gre_gor said. A simple breadboard contains of rows and columns of connections but sometimes for convenience manufacturer marks or prints Positive and Negative symbol along the row as they are usually used to power a circuit


3

You have a few options: Use a low-pass filter to round the square wave's edges some so they look more AC-ish. Use a low-pass filter and have your code create steps of voltage that look AC-ish by varying the PWM widths. Use an external SPI DAC chip that you can control with more discrete levels to make smoother looking AC. Look into Direct Digital Synthesis (...


3

wouldnt that then send current through the Vin pin and back to the coin cell battery? Is that what would happen in this instance? Yep, that's right. shouldn't there be a design feature to prevent users from damaging it like that? Fool/fail safe? No. VIN can also be VOUT. You can use it to power other things that want a higher voltage.


3

First you want to take a regulated 24V supply. To that you want to add a switch-mode ("Buck") regulator to drop you down to 5V. You don't want to try using an LDO for this unless you are happy to have a heat sink the size of a small car. A good cheap choice is a "UBEC" that can take 24V in and give 5V out (I use these). That 5V can then be fed direct into ...


3

It's actually very simple, and it indeed does involve using PWM. PWM is just a signal being on for a percentage of a predefined period. That percentage is also, when the PWM signal is averaged out, equivalent to a percentage of the peak voltage of the PWM signal. So if you take a PWM signal and use it to switch a higher power source (say, through a P-...


3

You can make -5 V if you use an external power source, like in the circuit below (untested). Connect the GND (-) from the Arduino to the +5V from the External (5V) source, than 0V will be the GND (with respect to the Arduino), but the GND of the external source will be -5V with respect to the Arduino. I only used the resistors to get no short circuits, you ...


3

void setup(){ Serial.begin(9600); } void loop(){ static unsigned long count=0; static float sum=0; float ave=0; int volt=analogRead(A0); float voltage = map(volt,0,1023,0,2500) / 100.0; Serial.print("Voltage: "); Serial.print(voltage,2); sum=sum+voltage; count++; ave=sum/count; Serial.print(" Average: "); ...


2

Expanding on dannyf's answer, if the pump datasheet does not feature a graph, then you will have to experiment. If a flowmeter is not readily available, an excellent approximation can be calculated by pumping water into a large, known receptacle (e.g. 10 litre bucket) and timing how long it takes. Do this for 20%, 40%, 60%, 80% and 100% Pulse Width ...


2

Running an Arduino board with 12V is almost always too much. With only a few leds the voltage regulator on the Arduino boards gets too hot. The best voltage is 7.5V. Then the voltage regulator has only little power dissipation and it is just high enough to turn off the USB 5V power. Or power the Arduino board with a 5V (from a USB charger, or USB power pack)...


2

The implementation of the digital inputs may depend on what kind of microcontroller you are using. On AVR microcontrollers (most common Arduinos are AVR-based), the inputs go through Schmitt triggers. This means that the voltage seen by the logic downstream is always a valid logic level. You should then not worry about an invalid input causing “unexpected ...


2

It means that a pin can give (source) at max. 40 mA. However, if a components uses more, than the Arduino cannot give it and as a result the pin becomes unusable. So you never should exceed 40 mA. And 20 mA is adviced. +5V and GND pins can take more, however there is also a maximum on 'groups' of GPIO pins. See more information here, below is an excerpt of ...


2

Yes, yes and yes. Will Nodemcu support 4AAA batteries which is 6v approx Yes, it will. However there is no back-powering protection on the USB, so having that connected whilst the board is connected to your computer could potentially damage your computer's USB port. That's why VIN's label was changed to 5V on the newer boards. or should i go with 3AAA ...


2

It looks like VIN connects to a LM2940, 5 volt regulator, so the voltage on the OUTPUT pin (D2) will never be higher than 5V.


2

100 Hz is pretty trivial. See my page about timers. This sketch can detect frequencies up to about 5 MHz: // Timer and Counter example // Author: Nick Gammon // Date: 17th January 2012 // Input: Pin D5 // these are checked for in the main program volatile unsigned long timerCounts; volatile boolean counterReady; // internal to counting routine unsigned ...


2

In principle not. However, the voltage regulators may become quite hot, since you are going down from 12 V to 9 V and 5 V (especially the step from 9 V to 5 V is quite a lot). It depends on the current (in (milli)Amps) how hot they get. For the adapter it does not matter, if it is 1 A or 10 A, the microcontrollers will only take whatever they need. Only if ...


2

Here is my try at this: if your voltage source doesn't mind sinking something like 150 µA, you could try something like this: simulate this circuit – Schematic created using CircuitLab This should map the input range [−70 mV, +50 mV] to [0.04 V, 4.06 V].


2

The Arduino Uno has no on-board battery. The dc barrel jack is provided to give you more options to power the Uno, which is handy for stand-alone applications (without USB-connection to a computer) and/or battery powered applications. It can also supply more current than the USB-connection, which can be necessary when using shields. The current taken from ...


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