# Servo motor overheating

**URL:** <https://forum.core-electronics.com.au/t/servo-motor-overheating/3329>\
**Category:** Raspberry Pi\
**Created:** [30 August 2018 04:13 UTC](https://forum.core-electronics.com.au/t/servo-motor-overheating/3329 "2018-08-30T04:13:06Z")\
**Posts on this page:** 3\
**Page:** 1

<div class="post-metadata">

**Author:** ![Brian58843](https://avatars.discourse-cdn.com/v4/letter/b/9f8e36/32.png) [@Brian58843](https://forum.core-electronics.com.au/u/Brian58843)\
**Post date:** [30 August 2018 04:13 UTC](https://forum.core-electronics.com.au/t/servo-motor-overheating/3329/1 "2018-08-30T04:13:06Z")

</div>

Hi everyone, I’m new to the whole Raspberry Pi scene and only started a couple of months ago. I’m attempting to build an RC car with the Raspberry Pi Camera Module v2, that I can control from my smartphone regardless of distance (e.g. 40-50km) for agricultural monitoring.

I’ve connected a Servo Hat to my pi, and have attached a servo motor to the Hat (for the camera). When i ran the script my servo started vibrating loudly and after about a minute started to overheat (burns my finger after a few seconds of contact). Since then the servo continues to vibrate and overheat as long as it’s plugged in - even after the Pi is shutdown or as it’s booting up. The only way i can get it to stop is to unplug the power completely.

I ran a second test script to try and reset the position, but the buzzing continued. After a while the servo stopped responding altogether to the script.

Does anyone know what might be causing the buzzing, and what is the normal operating temperature for a servo?

The script I ran initially was:

#! /usr/bin/python

import os.path  
import tornado.httpserver  
import tornado.websocket  
import tornado.ioloop  
import tornado.web  
import RPi.GPIO as GPIO  
import smbus, time  
from numpy import interp

#Configure the servo hat for use  
bus = smbus.SMBus(1) # the chip is on bus 1 of the available I2C buses  
addr = 0x40 # I2C address of the PWM chip.  
bus.write\_byte\_data(addr, 0, 0x20) # enable the chip  
bus.write\_byte\_data(addr, 0xfe, 0x1e) # configure the chip for multi-byte write

directionPin = 18  
enablePin = 16  
pwmPin = 12

#start address for servo  
panServoStartAddress = 0x06  
tiltServoStartAddress = 0x0A  
steerServStartAddress = 0x0E

#stop address for servo  
panServoStopAddress = 0x08  
tiltServoStopAddress = 0x0C  
steerServStopAddress = 0x10

#Initialize Raspberry PI GPIO  
GPIO.setwarnings(False)  
GPIO.setmode(GPIO.BOARD) #use gpio numbers as shown on board  
GPIO.setup(pwmPin, GPIO.OUT) #gpio pin for motor pwm  
GPIO.setup(enablePin, GPIO.OUT) #gpio pin for motor enable  
GPIO.setup(directionPin, GPIO.OUT) #gpio pin for motor direction

#Initialise servo positions (start time, then centre servos)  
bus.write\_word\_data(addr, panServoStartAddress , 0)  
bus.write\_word\_data(addr, tiltServoStartAddress, 0)  
bus.write\_word\_data(addr, steerServStartAddress, 0)  
bus.write\_word\_data(addr, panServoStopAddress , 1250)  
bus.write\_word\_data(addr, tiltServoStopAddress, 1250)  
bus.write\_word\_data(addr, steerServStopAddress, 1250)

#initialise motor settings  
frequency = 20000 #(PWM frequency) Max is 20KHz for motor driver  
speed = 50 # this is the duty cycle of the PWM output (100 is max speed)

#initialise PWM signal  
pulseWidth = GPIO.PWM(pwmPin,frequency) #pwmPin as PWM output, with set frequency  
pulseWidth.start(speed) #start PWM at set speed

#initial servo settings  
panAngle = 0 #centre pan servo  
tiltAngle = 0 #centre tilt servo  
SteerAngle = 0 #centre steer servo

#Tornado Folder Paths  
settings = dict(  
template\_path = os.path.join(os.path.dirname( **file** ), “templates”),  
static\_path = os.path.join(os.path.dirname( **file** ), “static”)  
)

#Tornado server port  
PORT = 8080

def setSpeed(speed):  
#set the vehicle speed  
pulseWidth.ChangeDutyCycle(speed)

def forward():  
#move the vehicle forward  
GPIO.output(enablePin,GPIO.HIGH) #enable the motor driver  
GPIO.output(directionPin,GPIO.HIGH)#set direction of movement

def backward():  
#move the vehicle backwards  
GPIO.output(enablePin,GPIO.HIGH) #enable the motor driver  
GPIO.output(directionPin,GPIO.LOW)#set direction of movemet

def steerLeft():  
#steer the vehicle left  
SteerAngle-=1  
if SteerAngle \< -90:  
SteerAngle = -90  
count = mapServoAngle(SteerAngle)  
setServoAngle(steerServStopAddress,count)

def steerRight():  
#steer the vehicle right  
SteerAngle+=1  
if SteerAngle \> 90:  
SteerAngle = 90  
count = mapServoAngle(SteerAngle)  
setServoAngle(steerServStopAddress,count)

def centreSteer():  
#centre the steer servo  
SteerAngle = 0  
count = mapServoAngle(SteerAngle)  
setServoAngle(steerServStopAddress,count)

def stop():  
#stop the vehicle  
GPIO.output(enablePin,GPIO.LOW)

def panleft():  
#pan the camera left  
panAngle-=1  
if panAngle \< -90:  
panAngle = -90  
count = mapServoAngle(panAngle)  
setServoAngle(panServoStopAddress,count)

def panRight():  
#pan the camera right  
panAngle+=1  
if panAngle \> 90:  
panAngle = 90  
count = mapServoAngle(panAngle)  
setServoAngle(panServoStopAddress,count)

def tiltUp():  
#tilt the camera up  
tiltAngle+=1  
if tiltAngle \> 90:  
tiltAngle = 90  
count = mapServoAngle(tiltAngle)  
setServoAngle(tiltServoStopAddress,count)

def tiltDown():  
#tilt the camera down   
tiltAngle-=1  
if tiltAngle \< -90:  
tiltAngle = -90  
count = mapServoAngle(tiltAngle)  
setServoAngle(tiltServoStopAddress,count)

def mapServoAngle(angle):  
#function to map the desired angle to servo count  
#it calculates and returns the count for angles in the range -90\<angle\<90  
count = interp(angle,[-90,90],[836,1664]) #4.6 counts per degree  
return int(count)

def setServoAngle(address,count)  
#sets the servo at the given address to the specified angle  
bus.write\_word\_data(address, count)

class MainHandler(tornado.web.RequestHandler):  
def get(self):  
print “HTTP User Connected.”  
self.render(“index.html”)

class WSHandler(tornado.websocket.WebSocketHandler):  
def open(self):  
print ‘[WS] Connection was opened.’

def on\_message(self, message):  
print ‘[WS] Incoming message:’, message  
if message == “m-forward”:  
forward()  
if message == “m-backward”:  
backward()  
if message == “m-left”:  
steerLeft()  
if message == “m-right”:  
steerRight()  
if message == “m-up-off”:  
stop()  
if message == “m-down-off”:  
stop()  
if message == “m-left-off”:  
centreSteer()  
if message == “m-right-off”:  
centreSteer()  
if message == “pt-up”:  
tiltUp()  
if message == “pt-down”:  
tiltDown()  
if message == “pt-left”:  
panleft()  
if message == “pt-right”:  
panRight()  
if message == “speed-25”:  
setSpeed(25) #allow the speed to be set  
if message == “speed-50”:  
setSpeed(50) #allow the speed to be set  
if message == “speed-75”:  
setSpeed(75) #allow the speed to be set  
if message == “speed-100”:  
setSpeed(100) #allow the speed to be set

def on\_close(self):  
stop() #stop vehicle movement if connection is lost  
print ‘[WS] Connection was closed.’

application = tornado.web.Application([  
(r’/’, MainHandler),  
(r’/ws’, WSHandler),  
], \*\*settings)

if **name** == “ **main** ”:  
try:  
http\_server = tornado.httpserver.HTTPServer(application)  
http\_server.listen(PORT)  
main\_loop = tornado.ioloop.IOLoop.instance()

```
    print "Tornado Server started"
    main_loop.start()

except:
    print "Exception triggered - Tornado Server stopped."
    GPIO.cleanup()

```

#End of Program

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<div class="post-metadata">

**Author:** ![Clinton](https://yyz2.discourse-cdn.com/flex028/user_avatar/forum.core-electronics.com.au/clinton/32/1515_2.png) [@Clinton](https://forum.core-electronics.com.au/u/Clinton)\
**Post date:** [30 August 2018 04:42 UTC](https://forum.core-electronics.com.au/t/servo-motor-overheating/3329/2 "2018-08-30T04:42:46Z")

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Hey Brian,

Servos should not be getting hot enough to burn your hands. I have a feeling something has gone a bit funny somewhere. Are you about to tell me what Servo Hat and servo you are using and how you have wired them together so i can compare what the code is doing to what the hardware is doing?

---

<div class="post-metadata">

**Author:** ![Brian58843](https://avatars.discourse-cdn.com/v4/letter/b/9f8e36/32.png) [@Brian58843](https://forum.core-electronics.com.au/u/Brian58843)\
**Post date:** [30 August 2018 08:08 UTC](https://forum.core-electronics.com.au/t/servo-motor-overheating/3329/3 "2018-08-30T08:08:09Z")

</div>

Hey Clinton,

I’m using the sparkfun pi servo hat (link [here](https://www.sparkfun.com/products/14328)) and a this is the sub-micro servo im using ([link](https://www.sparkfun.com/products/9065))

I’ve also attached a photo of how it’s wired up (hooked up to #0 on the servo hat).

 ![IMG_1927](https://canada1.discourse-cdn.com/flex028/uploads/core_electronics/original/2X/5/5489506e1d35c614746b345679ec025a6bf30908.jpeg)