Temperature wire distance


Active Member
One of my boards does not like to have the temperature sensor very far from it.  When I put the temperature sensor directly on the board, it runs fine for days.  When I put the temperature sensor farther away from the board, it reboots or at least the plc code restarts.  I've checked and changed the wiring twice.  I've used different temp sensors with the same result too.  The sensor works fine when it is directly on the board.
I used some cat 5 cable and put the ground and data pin on one pair and the +5 on another wire.  The cable is about 15 ft long. The board seems to reboot at random times.  I should mention that I also have a humidity sensor on the same cat 5 cable using different pairs going to the same board.  Those are the only sensors I have on the board.  When I take the temp sensor off or wire it on the board, it runs great.  As soon as I put the sensor on the cable, reboots happen. 
Has anyone else had this problem?  Any ideas on how to remedy this problem would be appreciated. 
I have 5 temps on my cai controlling my hot tub with total 30ft cat 5 with no problem. 
Check your power supply,how many amps is it putting out? I had to put bigger (more amps)power supply, the more temp i added. Never rebooted for 2 months all well.
Hi MobileMe,
For power supply labeled one AMP, it does not necessarily output 1AMP.  MAXIM made a publication before about power cube from Sony, Panasonic, etc, most of them could not deliver the labeled amperage AND voltage at the same time. WebControl can only be as reliable as the power supply.  We would suggest you to try a different brand or different rating power supply to see if that problem still exist.
As mentioned look at the voltage being supplied to the WebControl, preferably with a scope to see if it is clean or noisy, rather than just too low.
The reboot problem may be noise pickup by the cable and not be directly related to the 1-wire temperature sensors. I'd try connecting a temperature sensor directly to the controller, so the 1-wire interface is active, and the cable but leave the far end disconnected and see of the board still reboots. If so you probably have a noise pickup problem.
I'm using two WebControl units one with about 35' of cable and 7 sensors and another with 25' and 3. Both operate normally.
I have dehumidifier on the same circuit as one of the WebControl units and on several occasions it caused problems. I'm trying to harden my design to make it more robust.
I had a similar issue with reboots, my temp sensor wasn't the trigger like describe here, mind were seemingly random. It was due to an inadequate power supply. I ended up scrapping a 300W ATX power supply from an old computer and using a 9V voltage regulator with heatsink to supply the voltage to the board and the remaining 12VDC pigtails i'm using to power the 12VDC devices i'm using. I haven't had any issues, that was 2 months ago.