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15 votes
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Does ADC conversion to a voltage rely on the actual value of the +5 V pin?

The ADC inside the Arduino does not measure voltage, but rather a voltage ratio. Namely the ratio from the voltage at the analog input to the voltage at the Vref pin. In the default configuration, ...
Edgar Bonet's user avatar
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11 votes
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Why analogue pins affect each other?

This is to be expected. The other pins have nothing connected to it, so their voltage is floating. The Arduino MCU only has a single ADC. To read the different analog pins, it uses a multiplexer to ...
Gerben's user avatar
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11 votes

What is the most efficient voltage divider for Arduino?

The most efficient is not to have a voltage divider at all. Or at least to only have a voltage divider when you actually need one. My preferred schematic is this: simulate this circuit – ...
Majenko's user avatar
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11 votes
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Analog read not working while using WiFi

The ESP32 has two ADCs. One of them, ADC2, is actively used by the WiFi. From the IDF documentation: Since the ADC2 module is also used by the Wi-Fi, only one of them could get the preemption when ...
Majenko's user avatar
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9 votes

Does ADC conversion to a voltage rely on the actual value of the +5 V pin?

A USB-powered Arduino Nano will have an ADC voltage reference which can't be relied on, due to the +/- 5% tolerance of the incoming USB voltage. On top of that, the Nano has an MBR0520 Schottky diode (...
Enric Blanco's user avatar
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8 votes

A question about resistance measurement with arduino

If you know Ohm's Law (which you should) and you realise that the ADC measures voltage, you should be able to work it out from there. But I will go into minute detail for you to ensure you understand. ...
Majenko's user avatar
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8 votes

what is arduino adc reference?

The AD converter in the ATMega microcontroller (as used in Arduino) converts an input voltage to a number. This ADC happens to be 10 bit that means 2^10 states which is 1024. The number 0 (zero) ...
Bimpelrekkie's user avatar
7 votes
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How can I create a battery level circuit

Firstly, if I understand your schematic right, you're not "dividing" anything there. If the ringed red symbol is where you are connecting the ADC then either you will see near 4V on there (if it's ...
Majenko's user avatar
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6 votes
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Arduino: Read frequency of input from audio jack

You can measure a single "pure" frequency by counting the number of times that the pin changes, by using the inbuilt timers. Here is a sketch from my page about timers that accomplishes that: // ...
Nick Gammon's user avatar
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6 votes

Uno - measure the voltage, NOT connecting GND

If I understand the description correctly, neither side of the resistor is at ground potential. There's a wide gamut of methods of dealing with this, for example using a differential ADC unit, or ...
James Waldby - jwpat7's user avatar
6 votes

How to measure the supply voltage of Arduino without using an analog pin

Yes, you can do it. You can measure the voltage of the internal (approximately) 1.1V reference voltage using the ADC and use the results of that to calculate what the reference voltage you used (VCC) ...
Majenko's user avatar
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6 votes
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Is it possible to measure analog output?

First: Why would you need to measure the PWM value. You already know it; it's saved in the val variable. Why not just use this variable for later use in code? Second: Doing the analogRead on the same ...
chrisl's user avatar
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6 votes
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Can I test if something is connected to analog pin?

The input stage of the analog-to-digital converter is a sample-and-hold capacitor. When you take an analog reading, the capacitor is connected to the input pin, it is charged to the voltage you want ...
Edgar Bonet's user avatar
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5 votes

Arduino unstable analog reading when using power supply

I solved a similar issue by adding a pin from supply to AREF and it's now stable. This fixed a frustrating pH meter issue on my Mega that every time I plugged USB in it would be right, but as soon as ...
Jamey's user avatar
  • 51
5 votes

Arduino: Read frequency of input from audio jack

If your signal is a pure 1 kHz tone, then you should use Nick Gammon's counting method, as it is the most straight-forward solution. If, however, you are picking the signal through a microphone, ...
Edgar Bonet's user avatar
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5 votes

AnalogRead value constant for a varying voltage (for LED brightness variation)

As CrossRoads says, there really isn't any such thing as analog output on an Arduino. (Any Arduino unless it has a built-in DAC.) It uses pulse-width modulation to vary the "duty cycle" of the output ...
Duncan C's user avatar
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5 votes
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ADC register always returning high

First, let me give a couple of suggestions on the programming style. There is no point in defining your own variables for accessing the hardware registers: the avr-libc does that for you, you just ...
Edgar Bonet's user avatar
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4 votes
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Maximum potentiometer resistance

There is a lengthy discussion about this on the Arduino Forum. As I understand it, the input impedance is only important if you are sampling a rapidly varying signal, as it takes a finite time to ...
Nick Gammon's user avatar
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4 votes

Can I connect a PWM pin on one Arduino to an analog input on another?

For greater precision, less code, faster execution and no need for capacitors read the PWM "analog" signal on the other Arduino from a digital input pin with pulseIn(pin, HIGH, timeout) The timeout ...
CORTEX Systems's user avatar
4 votes
Accepted

10 bit PWM on Arduino UNO

On your code, you using analogRead but declaring the pin (A3) as output. Change it to pinMode(A3,INPUT); Aside from that, PWM is basically a digital output which changing (HIGH and LOW) at specified ...
duck's user avatar
  • 1,258
4 votes
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Not getting proper readings on Arduino from MAP Sensor

The ground does need to be connected. I have also added a RC filter to stabilize the sensor reading. Connection : Arduino 5V ----> MAP Vcc Arduino GND ----> MAP GND Arduino Analog Pin A0 <--...
Hasan's user avatar
  • 1,476
4 votes
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What is the definition of these arduino commands, and how do they affect the circuit?

These are a lot of different questions. However, you can find most of the Arduino related answers in the official reference: Arduino reference Guide Some other answers: how to declare variables: ...
Michel Keijzers's user avatar
4 votes
Accepted

Analog thermistor readings are wrong

One possibility that has not been mentioned yet: the issue may be the calibration of your ADC converter. Your code carries the implicit assumption that the voltage you measure is V = Vref × RawADC ÷ ...
Edgar Bonet's user avatar
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4 votes
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Arduino continuously reading ADC value using interrupt

reset the resultNumber to 0 after you have written it to serial. and turn interrupts back on void loop () { while (resultNumber < MAX_RESULTS) { } for (int i = 0; i < MAX_RESULTS; i++)...
ratchet freak's user avatar
4 votes

Lowest voltage applicable on AREF pin on Uno and Mega

According to the datasheet (page 375) the minimum voltage you are allowed to have as a reference voltage for the ADC is 1V.
Majenko's user avatar
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4 votes
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Arduino UNO - analogRead() returning mixed results

The analogWrite function, despite its name, outputs PWM (pulse width modulation) which is either fully on or fully off, with varying duty cycles. If you run that through a RC network (eg. 4.7k in ...
Nick Gammon's user avatar
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4 votes
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How can I differentiate between multiple circuits?

First, let's consider the logic of your program. You have two groups of pins: 6 pins connected to the wires and 6 pins connected to the terminals. The first thing I would do is forget that ...
Edgar Bonet's user avatar
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4 votes
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How to boil down analog input to just three cases?

The simplest fix to your problem is to change the map() call to byte alrmSet = map(alrmSwState, 0, 1024, 0, 3); In the call above, the mapped intervals are of the semi-open type, e.g. [a, b), ...
Edgar Bonet's user avatar
  • 43.1k
4 votes

How to convert digital signal to analog value

The problem seems to be clear to you: for slow systems a pwm signal can be considered analog, but measuring at higher rates and without a filter reveales the digital nature behind pwm and all you see ...
Sim Son's user avatar
  • 1,859
4 votes
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Noise on piezo analog read due to Arduino power supply

The 9V wall adapter is in most cases a switched power regulator with a high frequency. That's like a radio transmitter direct beside the wire. So there is nothing mystical, when the smooth USB Voltage ...
Peter Paul Kiefer's user avatar

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