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












1















Having the 11~ pin on OUTPUT mode that delivers a varying voltage (from 0 to 5 : 0 to 255).



and the A0 pin on INPUT mode to read the voltage, I find that the value read by A0 being either 0 or 1016 instead of it gradually taking multiple values between the two. what is the catch?



The circuit and the code i am using:



https://i.ibb.co/dDMJJCg/Cir.png



int volt = 0; 

int sign = 1; //values: (1, -1), increments or decrements "volt" by 5.

float potential;



void setup() {



  pinMode(11, OUTPUT);

  pinMode(A0, INPUT);

  Serial.begin(9600);





}



void loop() {







if (volt == 0){sign = 1;}

if (volt == 255){sign = -1}





volt = volt + sign * 5; //raises brightness to 255 from 0, then to 0 from 255.

analogWrite(11, volt);











potential = analogRead(A0);



Serial.println(potential);



delay(30);

/*

*/



}





arduino-uno analogread







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  • even filtered, you won't see a value between the LED's Vf and 5v, keep that in mind.

    – dandavis
    1 hour ago


















1















Having the 11~ pin on OUTPUT mode that delivers a varying voltage (from 0 to 5 : 0 to 255).



and the A0 pin on INPUT mode to read the voltage, I find that the value read by A0 being either 0 or 1016 instead of it gradually taking multiple values between the two. what is the catch?



The circuit and the code i am using:



https://i.ibb.co/dDMJJCg/Cir.png



int volt = 0; 

int sign = 1; //values: (1, -1), increments or decrements "volt" by 5.

float potential;



void setup() {



  pinMode(11, OUTPUT);

  pinMode(A0, INPUT);

  Serial.begin(9600);





}



void loop() {







if (volt == 0){sign = 1;}

if (volt == 255){sign = -1}





volt = volt + sign * 5; //raises brightness to 255 from 0, then to 0 from 255.

analogWrite(11, volt);











potential = analogRead(A0);



Serial.println(potential);



delay(30);

/*

*/



}





arduino-uno analogread







share|improve this question







New contributor




Huskarnov is a new contributor to this site. Take care in asking for clarification, commenting, and answering.
Check out our Code of Conduct.





















  • even filtered, you won't see a value between the LED's Vf and 5v, keep that in mind.

    – dandavis
    1 hour ago
















1












1








1








Having the 11~ pin on OUTPUT mode that delivers a varying voltage (from 0 to 5 : 0 to 255).



and the A0 pin on INPUT mode to read the voltage, I find that the value read by A0 being either 0 or 1016 instead of it gradually taking multiple values between the two. what is the catch?



The circuit and the code i am using:



https://i.ibb.co/dDMJJCg/Cir.png



int volt = 0; 

int sign = 1; //values: (1, -1), increments or decrements "volt" by 5.

float potential;



void setup() {



  pinMode(11, OUTPUT);

  pinMode(A0, INPUT);

  Serial.begin(9600);





}



void loop() {







if (volt == 0){sign = 1;}

if (volt == 255){sign = -1}





volt = volt + sign * 5; //raises brightness to 255 from 0, then to 0 from 255.

analogWrite(11, volt);











potential = analogRead(A0);



Serial.println(potential);



delay(30);

/*

*/



}





arduino-uno analogread







share|improve this question







New contributor




Huskarnov is a new contributor to this site. Take care in asking for clarification, commenting, and answering.
Check out our Code of Conduct.












Having the 11~ pin on OUTPUT mode that delivers a varying voltage (from 0 to 5 : 0 to 255).



and the A0 pin on INPUT mode to read the voltage, I find that the value read by A0 being either 0 or 1016 instead of it gradually taking multiple values between the two. what is the catch?



The circuit and the code i am using:



https://i.ibb.co/dDMJJCg/Cir.png



int volt = 0; 

int sign = 1; //values: (1, -1), increments or decrements "volt" by 5.

float potential;



void setup() {



  pinMode(11, OUTPUT);

  pinMode(A0, INPUT);

  Serial.begin(9600);





}



void loop() {







if (volt == 0){sign = 1;}

if (volt == 255){sign = -1}





volt = volt + sign * 5; //raises brightness to 255 from 0, then to 0 from 255.

analogWrite(11, volt);











potential = analogRead(A0);



Serial.println(potential);



delay(30);

/*

*/



}





arduino-uno analogread




arduino-uno analogread






share|improve this question







New contributor




Huskarnov is a new contributor to this site. Take care in asking for clarification, commenting, and answering.
Check out our Code of Conduct.











share|improve this question







New contributor




Huskarnov is a new contributor to this site. Take care in asking for clarification, commenting, and answering.
Check out our Code of Conduct.









share|improve this question




share|improve this question






New contributor




Huskarnov is a new contributor to this site. Take care in asking for clarification, commenting, and answering.
Check out our Code of Conduct.









asked 3 hours ago









HuskarnovHuskarnov

262




262




New contributor




Huskarnov is a new contributor to this site. Take care in asking for clarification, commenting, and answering.
Check out our Code of Conduct.





New contributor





Huskarnov is a new contributor to this site. Take care in asking for clarification, commenting, and answering.
Check out our Code of Conduct.






Huskarnov is a new contributor to this site. Take care in asking for clarification, commenting, and answering.
Check out our Code of Conduct.













  • even filtered, you won't see a value between the LED's Vf and 5v, keep that in mind.

    – dandavis
    1 hour ago





















  • even filtered, you won't see a value between the LED's Vf and 5v, keep that in mind.

    – dandavis
    1 hour ago



















even filtered, you won't see a value between the LED's Vf and 5v, keep that in mind.

– dandavis
1 hour ago







even filtered, you won't see a value between the LED's Vf and 5v, keep that in mind.

– dandavis
1 hour ago












2 Answers
2






active

oldest

votes


















3














The PWM output pin does not vary voltage - it only outputs 0, or 5V. The amount of time that 5V is on, from 1/255 of about a 2mS period, to 255/255 of the same period, determines how bright the LED is perceived to be.



You really need a current limit resistor in series with the LED to keep from burning out the uC output pin, or from burning up the LED.






share|improve this answer
























  • Thanks, if the OUTPUT voltage isn't really varying, how does the LED brightness vary? streamable.com/vc106

    – Huskarnov
    3 hours ago








  • 1





    @Huskarnov It flickers too fast for your eye to catch, the more it is on the brighter it seems.

    – ratchet freak
    3 hours ago








  • 1





    The amount of on-time is perceived by the eye as dimmer or brighter. It's the way our brain works.

    – CrossRoads
    3 hours ago











  • @Huskarnov this GIF might help visualize it.

    – Gerben
    2 hours ago



















3














As CrossRoads says, there really isn't any such thing as analog output on an Arduino. (Any Arduino.) It uses pulse-width modulation to vary the "duty cycle" of the output from 100% on to 0% on, which simulates an analog voltage.



If you drive an LED with PWM (and the required current limiting resistor) your eyes will not see the flashes, and will average out the brightness based on the duty cycle of the PWM signal.



If you want an actual analog voltage from PWM you will need to add a filter capacitor to average out the voltage over time. With a simple single capacitor filter you'll still have flutter in the output but it will be closer. If you want a clean constant voltage you'll need a more complex filter.






share|improve this answer


























  • @Gerben you edited my answer to talk specifically about Arduino Uno. My answer applies to all Arduinos. (Arduini?)

    – Duncan C
    13 mins ago











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2 Answers
2






active

oldest

votes








2 Answers
2






active

oldest

votes









active

oldest

votes






active

oldest

votes









3














The PWM output pin does not vary voltage - it only outputs 0, or 5V. The amount of time that 5V is on, from 1/255 of about a 2mS period, to 255/255 of the same period, determines how bright the LED is perceived to be.



You really need a current limit resistor in series with the LED to keep from burning out the uC output pin, or from burning up the LED.






share|improve this answer
























  • Thanks, if the OUTPUT voltage isn't really varying, how does the LED brightness vary? streamable.com/vc106

    – Huskarnov
    3 hours ago








  • 1





    @Huskarnov It flickers too fast for your eye to catch, the more it is on the brighter it seems.

    – ratchet freak
    3 hours ago








  • 1





    The amount of on-time is perceived by the eye as dimmer or brighter. It's the way our brain works.

    – CrossRoads
    3 hours ago











  • @Huskarnov this GIF might help visualize it.

    – Gerben
    2 hours ago
















3














The PWM output pin does not vary voltage - it only outputs 0, or 5V. The amount of time that 5V is on, from 1/255 of about a 2mS period, to 255/255 of the same period, determines how bright the LED is perceived to be.



You really need a current limit resistor in series with the LED to keep from burning out the uC output pin, or from burning up the LED.






share|improve this answer
























  • Thanks, if the OUTPUT voltage isn't really varying, how does the LED brightness vary? streamable.com/vc106

    – Huskarnov
    3 hours ago








  • 1





    @Huskarnov It flickers too fast for your eye to catch, the more it is on the brighter it seems.

    – ratchet freak
    3 hours ago








  • 1





    The amount of on-time is perceived by the eye as dimmer or brighter. It's the way our brain works.

    – CrossRoads
    3 hours ago











  • @Huskarnov this GIF might help visualize it.

    – Gerben
    2 hours ago














3












3








3







The PWM output pin does not vary voltage - it only outputs 0, or 5V. The amount of time that 5V is on, from 1/255 of about a 2mS period, to 255/255 of the same period, determines how bright the LED is perceived to be.



You really need a current limit resistor in series with the LED to keep from burning out the uC output pin, or from burning up the LED.






share|improve this answer













The PWM output pin does not vary voltage - it only outputs 0, or 5V. The amount of time that 5V is on, from 1/255 of about a 2mS period, to 255/255 of the same period, determines how bright the LED is perceived to be.



You really need a current limit resistor in series with the LED to keep from burning out the uC output pin, or from burning up the LED.







share|improve this answer












share|improve this answer



share|improve this answer










answered 3 hours ago









CrossRoadsCrossRoads

1,1977




1,1977













  • Thanks, if the OUTPUT voltage isn't really varying, how does the LED brightness vary? streamable.com/vc106

    – Huskarnov
    3 hours ago








  • 1





    @Huskarnov It flickers too fast for your eye to catch, the more it is on the brighter it seems.

    – ratchet freak
    3 hours ago








  • 1





    The amount of on-time is perceived by the eye as dimmer or brighter. It's the way our brain works.

    – CrossRoads
    3 hours ago











  • @Huskarnov this GIF might help visualize it.

    – Gerben
    2 hours ago



















  • Thanks, if the OUTPUT voltage isn't really varying, how does the LED brightness vary? streamable.com/vc106

    – Huskarnov
    3 hours ago








  • 1





    @Huskarnov It flickers too fast for your eye to catch, the more it is on the brighter it seems.

    – ratchet freak
    3 hours ago








  • 1





    The amount of on-time is perceived by the eye as dimmer or brighter. It's the way our brain works.

    – CrossRoads
    3 hours ago











  • @Huskarnov this GIF might help visualize it.

    – Gerben
    2 hours ago

















Thanks, if the OUTPUT voltage isn't really varying, how does the LED brightness vary? streamable.com/vc106

– Huskarnov
3 hours ago







Thanks, if the OUTPUT voltage isn't really varying, how does the LED brightness vary? streamable.com/vc106

– Huskarnov
3 hours ago






1




1





@Huskarnov It flickers too fast for your eye to catch, the more it is on the brighter it seems.

– ratchet freak
3 hours ago







@Huskarnov It flickers too fast for your eye to catch, the more it is on the brighter it seems.

– ratchet freak
3 hours ago






1




1





The amount of on-time is perceived by the eye as dimmer or brighter. It's the way our brain works.

– CrossRoads
3 hours ago





The amount of on-time is perceived by the eye as dimmer or brighter. It's the way our brain works.

– CrossRoads
3 hours ago













@Huskarnov this GIF might help visualize it.

– Gerben
2 hours ago





@Huskarnov this GIF might help visualize it.

– Gerben
2 hours ago











3














As CrossRoads says, there really isn't any such thing as analog output on an Arduino. (Any Arduino.) It uses pulse-width modulation to vary the "duty cycle" of the output from 100% on to 0% on, which simulates an analog voltage.



If you drive an LED with PWM (and the required current limiting resistor) your eyes will not see the flashes, and will average out the brightness based on the duty cycle of the PWM signal.



If you want an actual analog voltage from PWM you will need to add a filter capacitor to average out the voltage over time. With a simple single capacitor filter you'll still have flutter in the output but it will be closer. If you want a clean constant voltage you'll need a more complex filter.






share|improve this answer


























  • @Gerben you edited my answer to talk specifically about Arduino Uno. My answer applies to all Arduinos. (Arduini?)

    – Duncan C
    13 mins ago
















3














As CrossRoads says, there really isn't any such thing as analog output on an Arduino. (Any Arduino.) It uses pulse-width modulation to vary the "duty cycle" of the output from 100% on to 0% on, which simulates an analog voltage.



If you drive an LED with PWM (and the required current limiting resistor) your eyes will not see the flashes, and will average out the brightness based on the duty cycle of the PWM signal.



If you want an actual analog voltage from PWM you will need to add a filter capacitor to average out the voltage over time. With a simple single capacitor filter you'll still have flutter in the output but it will be closer. If you want a clean constant voltage you'll need a more complex filter.






share|improve this answer


























  • @Gerben you edited my answer to talk specifically about Arduino Uno. My answer applies to all Arduinos. (Arduini?)

    – Duncan C
    13 mins ago














3












3








3







As CrossRoads says, there really isn't any such thing as analog output on an Arduino. (Any Arduino.) It uses pulse-width modulation to vary the "duty cycle" of the output from 100% on to 0% on, which simulates an analog voltage.



If you drive an LED with PWM (and the required current limiting resistor) your eyes will not see the flashes, and will average out the brightness based on the duty cycle of the PWM signal.



If you want an actual analog voltage from PWM you will need to add a filter capacitor to average out the voltage over time. With a simple single capacitor filter you'll still have flutter in the output but it will be closer. If you want a clean constant voltage you'll need a more complex filter.






share|improve this answer















As CrossRoads says, there really isn't any such thing as analog output on an Arduino. (Any Arduino.) It uses pulse-width modulation to vary the "duty cycle" of the output from 100% on to 0% on, which simulates an analog voltage.



If you drive an LED with PWM (and the required current limiting resistor) your eyes will not see the flashes, and will average out the brightness based on the duty cycle of the PWM signal.



If you want an actual analog voltage from PWM you will need to add a filter capacitor to average out the voltage over time. With a simple single capacitor filter you'll still have flutter in the output but it will be closer. If you want a clean constant voltage you'll need a more complex filter.







share|improve this answer














share|improve this answer



share|improve this answer








edited 14 mins ago

























answered 3 hours ago









Duncan CDuncan C

1,5211617




1,5211617













  • @Gerben you edited my answer to talk specifically about Arduino Uno. My answer applies to all Arduinos. (Arduini?)

    – Duncan C
    13 mins ago



















  • @Gerben you edited my answer to talk specifically about Arduino Uno. My answer applies to all Arduinos. (Arduini?)

    – Duncan C
    13 mins ago

















@Gerben you edited my answer to talk specifically about Arduino Uno. My answer applies to all Arduinos. (Arduini?)

– Duncan C
13 mins ago





@Gerben you edited my answer to talk specifically about Arduino Uno. My answer applies to all Arduinos. (Arduini?)

– Duncan C
13 mins ago










Huskarnov is a new contributor. Be nice, and check out our Code of Conduct.










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