Raspberry pi 2 B won't detect temp sensor DS18B20

Question

I have a rasp pi 2 b+ and a temperature sensor DS18B20.

I can't get my ls /sys/bus/w1/devices command to show anything other than w1_bus_master1.

I suspect it is a problem with my set up but I've tried a number of combinations but still no results.

I'm using a 10kOhm resistor, a Vilros cobbler and just updated raspbian (4.1.19-v7+).

I've tried adding this to my /boot/config.txt dtoverlay=w1-gpio

Pics of setup:

The crocodile clips go to the three connections for the DS18B20

[ enter image description here

Have you a meter? If so check the breadboard voltages. Is 5V actually 5V and 3V3 actually 3V3? A common error is to connect the ribbon cable the wrong way around. — joan, Jul 24, 2016 at 16:43
I don't currently have one but is there another way to tell if it's the wrong way around? I'll set everything up and try flipping it — darkace, Jul 24, 2016 at 16:58

Domme · Accepted Answer · 2016-07-25 10:59:50Z

1

Try this:

Edit your /boot/config.txt line to contain:
```
dtoverlay=w1-gpio,gpiopin=4,pullup=on
```
sudo lsmod, check for w1_therm. If it's not loaded, edit /etc/modules to contain:
```
wire
w1-gpio
w1-therm
```
Use a 4.7k resistor instead as recommended in datasheet. If you only have 10k ones, try to use 2 of them in parallel for a resulting impedance of 5kOhm, for testing purposes.

Reboot after each change. Good luck!

answered Jul 25, 2016 at 10:29

Domme

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Sounds good. Will check when I'm home tonight but I remember that I currently already have dtoverlay, gpiopin and the lsmod has everything you suggested. Will try pullup and paralleling the resistors!
– darkace
Jul 25, 2016 at 10:52
@darkace I used kompf.de/weather/pionewiremini.html for setting up my DS1820. It's in German but you should get the point. I also operate my DS1820 in parasite-powered mode so another idea could be to connect the yellow wire that leads to your DS1820 to GND. (edit: works fine in both modes)
– Domme
Jul 25, 2016 at 11:01

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