15 votes
Accepted

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
  • 43.1k
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
  • 2,114
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
4 votes
Accepted

Inaccurate and non-precise voltage reading from Arduino Analog pin

This should be a lot of fun but you might consider doing some research on analog circuits and A/D circuits. You have way too many digits to the right of the decimal, the accuracy is not there. The ...
Gil's user avatar
  • 1,833
3 votes

what is arduino adc reference?

The default behaviour is for the analog reference to be Vcc which on many Arduinos is 5V. In that case do not connect anything to AREF. However if you have a precision voltage reference then you can ...
Nick Gammon's user avatar
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3 votes
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Nature of the voltage reference instability of internal 1.1V reference of ATmega328P (Nano)

I would say it was "stable but not accurate". The internal reference uses a bandgap voltage reference, which is pretty stable over the operating temperature range of the IC. The output of ...
Majenko's user avatar
  • 105k
3 votes

analogReference(INTERNAL) configuration

Changing the analog reference does not change the resolution. All it does is change the measurement range. It compresses the existing resolution into a smaller voltage range. If you then compress ...
Majenko's user avatar
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3 votes
Accepted

Can i supply the AREF pin with an Analog pin from the same board?

With an input voltage between 0 and 2.2 V, you can use a 2:1 voltage divider to cut the voltage in half. In your code, use analogReference(INTERNAL) to set the analog reference voltage to 1.1 V. The ...
James Waldby - jwpat7's user avatar
3 votes

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

I have a page about the ADC converter on the Atmega328P. Somewhat down the page I describe voltage references. You can use the TL431 chip to provide assorted reference voltages, for example 4V: By ...
Nick Gammon's user avatar
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2 votes
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Arduino protecting analog input with internal voltage reference

Yes, it is safe. The reference voltage is only used as a comparison. The ADC is still powered by, and limited by, the chip's supply voltage (5V). The AREF voltage has no bearing on what limits there ...
Majenko's user avatar
  • 105k
2 votes

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

Does the conversion of adc count to voltage depend on the actual voltage of the +5v pin? yes and no: the adc module cares about Vref, which can be supply via Vdd, internally, or externally. If yes ...
dannyf's user avatar
  • 2,770
2 votes

Is AREF a stable output Ref voltage with analogReference(INTERNAL)

No, it is not acceptable. The datasheet states: AVCC is connected to the ADC through a passive switch. The internal 1.1V reference is generated from the internal bandgap reference (VBG) through an ...
Majenko's user avatar
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2 votes
Accepted

How to work with analog readings using RPi and Firmata?

It does not appear that Firmata has proceeded with the ability to change the analog reference source. You referenced one of the issues opened for it, but I don't see anywhere where it committed to the ...
jose can u c's user avatar
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2 votes

Vcc measurement with internal 1.1V reference fails on 3.3V powered Atmega328

Thanks for your answers! Jot gave the solution: wADC must be a uint16_t. Here is the corrected code : void setup() { Serial.begin(9600); Serial.println(F("Internal Voltage Sensor")); } void ...
feuille osier's user avatar
2 votes

what is arduino adc reference?

The AREF is a reference voltage input pin. The reference voltage is maximum voltage when you measure analog signal. In other words, you can measure 0V ~ AREF voltage by using ADC port. Be aware that ...
Blue Cloud's user avatar
2 votes

Voltage at AREF pin

I was using a 9V battery and a voltage divider made with a 1k resistor and a 2k one. Using a battery is not a good way of getting a stable voltage. A battery's voltage will change over time. Using a ...
Majenko's user avatar
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2 votes
Accepted

Powering the Arduino with a battery and reading the battery voltage

AFAIK, Arduinos are set up to use their operating voltage as the analogRead reference voltage by default. So what I think is happening is that you are trying to measure the battery voltage with the ...
ocrdu's user avatar
  • 1,775
2 votes

Extremely unstable analogRead() on Arduino Nano when powered from an external source

You can use a branded 5 V charger made for cars. You can directly connect this to 5 V pin of the Arduino. By doing this: you are protecting the Arduino from the noise as well as high voltage spikes ...
ArduinoFan's user avatar
  • 1,059
2 votes

Arduino Uno, does a lower Aref voltage work well for measuring current? without increasing ADC integral non-linearity

If you used the 3.3 volt pin as external AREF a 1.5Ω resistor would drop 3V @ 2 Amps, 3V would produce an ADC value of 930 or 2.15mA per ADC count. If you use the 1.1V internal AREF, a 0.5Ω resistor ...
JC Allen's user avatar
1 vote

adc arduino using reference voltage to read stable/constant lithium battery voltage

I want the whole system to run on lithium battery If you power the Arduino from the battery, then you can indirectly read the battery voltage by reading the internal voltage reference. This requires ...
bigjosh's user avatar
  • 1,553
1 vote

Arduino , python , pyfirmata , standard firmata

No, not as far as I know. The firmata protocol does not include a command to set the analog reference. However, you can of course modify the firmata firmware to your liking. In the simplest case, just ...
PMF's user avatar
  • 1,286
1 vote

Is AREF a stable output Ref voltage with analogReference(INTERNAL)

Now, having had the benefit of a support ticket and subsequent discussion with an engineer at TI on this subject, I can confidently offer a qualified YES to my own question. It turns out my case is ...
Randy's user avatar
  • 407
1 vote

what is arduino adc reference?

Well, I think you should read the manual first before you use (and even perhaps brake it). Generally speaking, analog reference is a voltage value between 0.00 and 5.00V, which will be used as ...
Jakey's user avatar
  • 196
1 vote
Accepted

Voltage divider for 6 non intrusive current sensors

I assume you refer to a circuit like this: simulate this circuit – Schematic created using CircuitLab The "reference" you speak of is not a reference - it is a virtual ground. A ground ...
Majenko's user avatar
  • 105k
1 vote

Using Li-Poly battery to run UNO + Adafruit data logger

You can't run the Arduino UNO directly from 3.7V. You can use a boost regulator to step up to 5V and feed that into the 5V pin - in which case your question becomes null and void, since you are ...
Majenko's user avatar
  • 105k
1 vote

Arduino protecting analog input with internal voltage reference

As far as I know, no one uses a zener diode in a analog circuit that is used to measure a voltage. Well, at least no one who is serious and knows what he/she is doing. The zener diode will start ...
Jot's user avatar
  • 3,246
1 vote

Analog Reference (AREF) pin on Arduino MKR1000 not working?

In fact, the documentation suggests that for SAMD boards (MKR1000 is based on Zero) a different enumeration should be used where each value is prefixed with AR_ so for example you should use ...
Jason Crocker's user avatar
1 vote
Accepted

Analog Reference (AREF) pin on Arduino MKR1000 not working?

The compiler error MKR_001:161: error: invalid conversion from 'int' to 'eAnalogReference {aka _eAnalogReference}' [-fpermissive] Is actually really simple once you understand what it means. ...
Code Gorilla's user avatar
  • 5,637
1 vote
Accepted

analogRead values all over the place, while measuring light

The problem you are facing is that the output of the LED is too high impedance for the ADC to work reliably. Basically the LEDs can't produce enough current to charge the S&H capacitor properly, ...
Majenko's user avatar
  • 105k

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