1-Wire long wire around 10m.

Thread Starter

FroceMaster

Joined Jan 28, 2012
544
Have this setup with a 16F18887 and a DS18B20 temp probe,
Setup is working fine over 50 cm wire, but when i encrease to around 10m
i get no reading,
Have an old setup with a 16F690 same wire, and that works fine.
Use a 5 k pull up near the sensor,
Have also tried to place the pull up near PIC,

What can i do to get a reading ?

And Spinaker, no need to say not again, ;)

Rgds
Sten
 

Thread Starter

FroceMaster

Joined Jan 28, 2012
544

JohnInTX

Joined Jun 26, 2012
3,824
Those 2 link are not working, dead.
Now point on wireless, to much interference, that is why i switched to wire,

Page 40-41 , all i have found to a AN937 datasheet has only 16 pages ;)
I went directly to maximintegrated.com and none of their ap-notes come up. Server error? Try it again later, maybe.
BTW, some searches return Microchip's AN937. Not the same.

Here's the link to the ap-note page directory.
https://www.maximintegrated.com/en/sitesearch.external.html?sp_q=extending the contact range of iButtons&_charset_=UTF-8
 

Thread Starter

FroceMaster

Joined Jan 28, 2012
544
Dont see that have to do with reading from a ds18b20 sensor.
Btw reading is stillnok up to 0.5 m. But over 5-7 i get problems.(16f18887)

Same sensor reads ok with 16f690.
 

Thread Starter

FroceMaster

Joined Jan 28, 2012
544
Have been playing a lot, and searched all over.
On my desk i have the 16F18877 and a DS18B20
Use a 4,7k pull up near the PIC.
That works like perfect.

Want to extend the wire from PIC to DS18B20.
Have a CAT5E cable 10 meter. Use a Pair for +5v and GND, and another pair for 1-Wire and GND,
When using that, i get the sensor i precent, but no readings, Then i try a smaller resistor, and place it near the sensor,
4k5 3K0 1k5 , and R750, but nothing gives me readings,

Have my "old" setup with a 16F1509 where i just use an old loudspeaker wire, and that works with no problems at 10 meters.
There i just placed the 4k7 resistor near the sensor,

Could someone explain how to get it to work ?
Do i need changes to timing ?
Do i need some CAPS or other thing ?
Can i build an extender or ? and how ?

It's driving me mad.

Rgds
 

shteii01

Joined Feb 19, 2010
4,647
Generally, to make longer distance work, you want to use lower frequency.

How are you implementing 1-wire? Does PIC have hardware module to do 1-wire? Is it software implementation?
 

Thread Starter

FroceMaster

Joined Jan 28, 2012
544
I think it works now. I just took one twisted pair for signal. Before i use one for signal and the other to ground.
Right now it runs perfect but 10m wire is not rolled out yet. Just connected.

Yes PIC use software.
 
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