ESP32 Feather S3 servo

nigeljohnson73 · July 6, 2022, 9:12pm

I am trying to get an SG90 micro servo to run by attaching it to my S3.

Initially, I tried powering from the USB and GND connection on the S3, and the signal in pin 12. Since this didn't work I tried a separate battery pack supplying 6.4v from 4AA batteries.

I have a socket soldered to the S3, and with an extension plugged in, I can measure 6.4v at the end, and 49.94Hz on the signal line with my multimeter. (I also measured a stable 5v when it was connected to the USB pin) This rules out dodgy wiring or a busted S3 - I also tried this on an LOLIN D1 mini, and it didn't work there either.

I also wondered whether I was struggling with the pin, but moving it around did not help anything - other than maybe blowing up an S2 board while walking through pins, and now won't respond to the serial cable plugged in... that's another story.

This leaves 3 options
1: The servo is broken: I swapped servos and still nothing. I invested in a servo tester and they're both fine.
2: Logic level voltages: The servo specs say that they are logic level (3v3) and 5v tolerant... Could it be wrong?
3: I'm an idiot: Let's explore this a bit more.

Here is a sketch that covered multiple things, but as configured, should just be the same "sweep" example with some Serial output and the LED blinking... both of these work.

#include <ESP32Servo.h>

int led_pin = 13;
int servo_pin = 12;
bool led_on = true;

Servo myservo;

void setup() {
  Serial.begin(115200);
  delay(500);
  Serial.println("\nServo sweep and LED blink");

  pinMode(led_pin, OUTPUT);
  digitalWrite(led_pin, LOW);

  //  pinMode(servo_pin, OUTPUT);
  //  digitalWrite(servo_pin, LOW);

  //  myservo.setPeriodHertz(50);
  //  myservo.attach(servo_pin, 500, 2400);
  myservo.attach(servo_pin);
  myservo.write(0);
}

void loop() {
  int pos;
  Serial.println("loop(): on");
  digitalWrite(led_pin, led_on);
  //digitalWrite(servo_pin, led_on);
  led_on = !led_on;

  for (pos = 0; pos <= 180; pos += 2) {
    myservo.write(pos);
    delay(15);
  }

  Serial.println("loop(): off");
  digitalWrite(led_pin, led_on);
  //digitalWrite(servo_pin, led_on);
  led_on = !led_on;
  for (pos = 180; pos >= 0; pos -= 2) {
    myservo.write(pos);
    delay(15);
  }
}

What have I missed?

I'd rather not plug in something like a pca9685 as I need to keep weight and component count down. Also, the sweep example is an official example, and lots of websites explain exactly this example.

What else can I try?

Any help very much appreciated.
Kind regards
Nigel

UKHeliBob · July 6, 2022, 9:20pm

A voltage level shifter in the servo signal line

nigeljohnson73 · July 6, 2022, 9:22pm

Yeah. I had thought of that but it involves me going and looking for one somewhere in my pile of boxes. With all the examples of being directly plugged in though, I was hoping it was just me being an idiot - which is infinitely more fixable tonight

UKHeliBob · July 6, 2022, 9:35pm

The common factor would seem to be your servo, but not all SG90s are made equal and I would be very suspicious of the stated 3.3V lower limit of the signal voltage

Idahowalker · July 6, 2022, 10:53pm

I've run the metal geared servos directly driven by an ESP32's GPIO pins.

Post a schematic and images of the wired project and describe the issue, please.

Also your setup is a bit different than the ESP32 servo example.

void setup() {
	// Allow allocation of all timers
	ESP32PWM::allocateTimer(0);
	ESP32PWM::allocateTimer(1);
	ESP32PWM::allocateTimer(2);
	ESP32PWM::allocateTimer(3);
	myservo.setPeriodHertz(50);    // standard 50 hz servo
	myservo.attach(servoPin, 1000, 2000); // attaches the servo on pin 18 to the servo object
	// using default min/max of 1000us and 2000us
	// different servos may require different min/max settings
	// for an accurate 0 to 180 sweep
}

github.com

madhephaestus/ESP32Servo/blob/master/examples/Sweep/Sweep.ino

/* Sweep
 by BARRAGAN <http://barraganstudio.com>
 This example code is in the public domain.

 modified 8 Nov 2013
 by Scott Fitzgerald

 modified for the ESP32 on March 2017
 by John Bennett

 see http://www.arduino.cc/en/Tutorial/Sweep for a description of the original code

 * Different servos require different pulse widths to vary servo angle, but the range is 
 * an approximately 500-2500 microsecond pulse every 20ms (50Hz). In general, hobbyist servos
 * sweep 180 degrees, so the lowest number in the published range for a particular servo
 * represents an angle of 0 degrees, the middle of the range represents 90 degrees, and the top
 * of the range represents 180 degrees. So for example, if the range is 1000us to 2000us,
 * 1000us would equal an angle of 0, 1500us would equal 90 degrees, and 2000us would equal 1800
 * degrees.
 *

This file has been truncated. show original

nigeljohnson73 · July 7, 2022, 5:20am

Thanks @Idahowalker I did start with that sketch. As for the schematic, I've tried a few, starting here:

nigeljohnson73 · July 7, 2022, 5:29am

After a couple of fo hours of sleep, I think I'm resigned to the fact I need a voltage step-up or another servo. I have ordered these (3-6v):

I also have a PI hut order coming and some of these are on there.

They specifically say they can be run directly off an Arduino

Finally, I have a couple 2.2gm servos which (supposedly) work off a single LiPO battery (but only have 0.2kg/cm torque)

So I will see what happens

nigeljohnson73 · July 7, 2022, 5:34am

Oh, this was the example I was looking for where it had a D1 mini driving a servo direct. It does specifically state the Tower Pro SG90.

UKHeliBob · July 7, 2022, 6:41am

Are your original servos genuine or clones though ?

nigeljohnson73 · July 7, 2022, 7:04am

I thought I was being efficient and reusing stuff in my box-o-spares but they are most likely cheap clones so I've ordered some probably-more-proper ones from PI hut. fingers crossed

Idahowalker · July 7, 2022, 10:49am