DS18B20 temperature sensor not recognized

[Jeffrey S. LaFavre]

I am following the instructions at http://projects.privateeyepi.com/home/temperature-sensor-project-using-ds18b20

To connect a temperature sensor to my Raspberry Pi 3 running Rasbian ver. 8 jessie, with recent update and upgrade

I am using a DS18B20 temperature sensor connected to the Raspberry Pi as per instructions and have doubled-checked to determine that all wiring is correct.

at the command prompt I run following:

sudo modprobe w1-gpio

sudo modprobe w1-therm

cd /sys/bus/w1/devices/

ls

this resulted in an empty directory listing

then the following command:

sudo nano /boot/config.txt

and edit file by adding following two lines to bottom of file:

# 1-wire settings

dtoverlay=w1-gpio.gpiopin=4

save, exit and reboot

then repeat the commands at top of this list (sudo modprobe etc. etc.)

but still I get an empty directory listing 

Can anyone advise on why the Raspberry Pi is not recognizing my temp sensor (I have tried two units with same result)

Thanks very much

[Gadjet Nut]

I tested it under Jessie 8 and have no problems. See directory in bold below and Jessie version below. Can you send a picture of your wiring?

pi@raspberrypi:/sys/bus/w1/devices $ ls

28-0415a21f14ff  w1_bus_master1

pi@raspberrypi:/sys/bus/w1/devices $ cat /etc/os-release

PRETTY_NAME="Raspbian GNU/Linux 8 (jessie)"

NAME="Raspbian GNU/Linux"

VERSION_ID="8"

VERSION="8 (jessie)"

ID=raspbian

ID_LIKE=debian

HOME_URL="http://www.raspbian.org/"

SUPPORT_URL="http://www.raspbian.org/RaspbianForums"

BUG_REPORT_URL="http://www.raspbian.org/RaspbianBugs"

pi@raspberrypi:/sys/bus/w1/devices $

[Jeffrey S. LaFavre]

I discovered my problem:

# 1-wire settings

dtoverlay=w1-gpio.gpiopin=4

 

I had a period instead of a comma between gpio and gpiopin=4

I have everything working now and posting to web site.  However, the temperature is reading 85 degrees C for a temperature probe at room temp (about 20 degrees C).  Do you think I have a faulty device or is some kind of calibration needed?

Thanks

[Jeffrey S. LaFavre]

Now I think I have identified problem with 85 degree C readings.  I have part DS18B20+PAR, which I understand can be powered parasitically only.  I was trying to power at pin 3 with 3.3 volts from Raspberry Pi.  Now I am wondering if I can use DS18B20+PAR.  From datasheet, to use parasitically, pin 3 and pin 1 of DS18B20+PAR must be connected.  Just wondering how the 4.7 K resistor fits into the wiring in this case?  Will continue to investigate.