Servo not responding correctly with Blynk slider

Solved
1

Hi,

I’ve been struggling with this for a few days now. Here’s what is happening - If I move the slider very slowly, it seems to control the servo correctly, but if i move it quickly, the servo doesn’t keep up and it stops moving. I added a short delay and that seems to help somewhat. The strange thing is that the servo.read value appears to be different than the actual physical position of the servo. What i mean is that the servo.read value keeps changing even though the servo is not moving. Any advice?

hardware:
board - esp8266nodemcu
Servo - 17kg large torque. 15 kg·cm (208 oz·in) @6.6V; 17 kg·cm (236 oz·in) @7.4V
servo powered by 9v battery, board powered by usb
note: servo works perfectly when controlled locally with a potentiometer

Code below:


 #define BLYNK_PRINT Serial
        
        
        #include <ESP8266WiFi.h>
        #include <BlynkSimpleEsp8266.h>
        #include <Servo.h>
        
        // You should get Auth Token in the Blynk App.
        // Go to the Project Settings (nut icon).
        char auth[] = "xxxxx";
        
        // Your WiFi credentials.
        // Set password to "" for open networks.
        char ssid[] = "xxxxx";
        char pass[] = "xxxxx";
        
        
        Servo servo1; 
        int ServoPin = 5;
        int currentServoPos = 0;


        
        
        void setup()
        {
          // Debug console
          Serial.begin(115200);
          Blynk.begin(auth, ssid, pass);
          servo1.attach(ServoPin);
          
          
        }
        
        BLYNK_WRITE(V5)
        {
           

              int pinValue = param.asInt(); // assigning incoming value from pin V5 to a variable
              int mappedServo = map(pinValue, 0, 1023, 1, 180);
              currentServoPos = servo1.read();
                  Serial.print(" current servo Position is: ");
                  Serial.println(currentServoPos);
                  Serial.print(" current slider Position is: ");
                  Serial.println(mappedServo);
            

             if ( mappedServo < currentServoPos)
                  {
                      delay(100);
                      servo1.write(mappedServo -1);
                
                  }
                  else if (mappedServo > currentServoPos)
                  {
                     delay(100);
                     servo1.write(mappedServo +1);
                    
                 
                  }
                    
                          }
                        

        void loop()
        {
          Blynk.run();
       
          
        }
'''
2

Try just setting the slider for the servo range of 0-180 (or whatever) and s simpler control function.

You will need BlynkTimer if you also use the myservo.detach(); option. I use it to stop the servo from jittering when not in actual motion…

 //===== Servo Slider Function =====
BLYNK_WRITE(V10) // Servo Slider Function
{
  myservo.attach(servoPin);
  SrvoPos = param.asInt();
  myservo.write(SrvoPos);
  timer.setTimeout(1000L, ServoDetach);
} // END Blynk Function

void ServoDetach() {
  myservo.detach();
}
3

Fast movement means longer, harder, current draw… and 9v batteries are well known for NOT being good current sources.

4

Thanks Gunner, what would you suggest to power the servo. My goal is to run 2 of them for pan/tilt for an outside garden project.

5

A couple of 18650 LiPOs in series will be great I think. In a pinch even a 4 pack of AA will be better than a 9v

1 Like
6

just use a power bank.

7

Power Banks generally only supply 5v The large torque servos are a bit more power hungry… the dual 18650s will supply the best voltage and current combo.

8

Thanks Gunner,
If i got a big LiPO pack with the right voltage such as the kind used for drones and rc cars, would that be better than using 2 small ones in series? I’m not at all familiar with electrical engineering so the less I have to modify, the better.

for example, a product like this:

9

That would work perfectly as well.

You will need a proper charger and a little understanding about the proper care, use and charging, as those can be potentially dangerous.

10

You were right! i got 2 3.7v 18650 LiPOs and connected them in series and now the servo works much better. Thanks!

1 Like