Temperature sensor power
26 November, 2012 - 15:42
I have been having trouble with HAH board locking up, and after discussion on this forum I have come to the conclusion it is caused by my extensive network of temperature sensors possibly cause a spike on the 1 wire bus.
To resolve this I tried to use a separate 5v power source to power the temperature sensors, but when I connect it up all the sensors show "?". If I unplug the 3.5mm sensor lead and plug my test sensor directly into the port it reads correctly, so I know that the 5V line is wired and working correctly.
Why is it that my multiple temperature sensors only work with the HAH sourced 5v line?
26 November, 2012 - 19:12
#3
Mines ok
I had the same issue with my very long and poorly shielded 1wire bus.
I added a 5v line using a regulator on a nearby 12v line and reduced the number by a few devices.
All been ok for 12 months now.
Double check your wiring as it can be done.
Garry
26 November, 2012 - 19:46
#4
One wire topology can be an
One wire topology can be an art, OK so no schematic, so I'll take a guess your using a backbone cable (what type of cable and length) and then jointing off of this at required points (if so how & how many) thus a linear topology.
With such a system you can get a lot of signal reflections due to cable impedance, and resistance from the joints adding more impedance so fitting a 100ohm resistor on the data lead of the sensor reduces reflections here's a link http://www.maximintegrated.com/app-notes/index.mvp/id/148 see (Distributed Impedance Matching) from the Maxim website hope this helps.
I understand connecting a test sensor direct to the 3.5mm jack works OK, short lead direct connection min. impedance etc. but try connecting your furthest sensor first on your network if OK then start loading it up.
Steve
Are the gnd's connected together ? i.e new PSU and HAH's
Do you have a quick schematic
Steve