0
\$\begingroup\$

I would like to monitor the temperature outside my home. The sensor has to be located at least 20m cable length from the display unit. Whole system should be powered by a battery (doesn't matter which) and should have a decent display.

I would like to have an accuracy of <=0.5°C but it's ok if it's not as good. I would like to create a display unit myself (as fun project). But it's also OK if there is an off-the-shelf component.

All components should be obtainable from cheap online shops from china and should be cheap.

  1. Which sensor should I select? Digital? Analog?

  2. How much resistance is acceptable per 'm of the cable?

  3. Can arduino nano handle displaying part? Would it be possible to log temperatures using arduino?

I've never done anything like this, I've tried a little research, but I know there are people here who can answer this without to much effort. Great, thanks a lot.

so i found this sensor: and I guess there is some info about it here

Still remains question of cable type/dimension.

\$\endgroup\$
0

2 Answers 2

Reset to default
0
\$\begingroup\$

You can easily use STP cable with RJ 11 or Ethernet jacks and SMT CM choke and large Pi filter caps to 0Vdc, using a linear LM75 but I suggest you model it to ensure low Q anti-resonance, which is achieved by low impedance ratios.

I can use Falstad to inject 50/60 Hz + square wave in series with CM transformer to simulate results.

Use the best sim you know how to use.

Then log T min,max ,mean and trigger from dT/dt threshold with time stamps to minimize the data collection to your specifications.

Look in depth (search schematics and Arduino code) or look at cheap weather clocks for their features. They can use remote sensors.

\$\endgroup\$
2
  • \$\begingroup\$ Those sound like pretty good ideas, what's a SMT CM and Pi filetr? I think i will try to make my own arduino powered display unit, which should AFAIK connect directly to the sensor via digital IO on the board. \$\endgroup\$
    – poppycockears
    Oct 25, 2018 at 12:16
  • \$\begingroup\$ Poppy you can easily google unknown terms by copy and paste or highlight and lookup. You can accelerate your wisdom by learning how. Search “common mode noise” “Texas instruments”. Or SMT CM choke. And PI FILTER for signals \$\endgroup\$
    – Tony Stewart EE75
    Oct 25, 2018 at 16:03
1
\$\begingroup\$

Because you want to have 20m Cable, I would use a digital sensor. Temperature is measured most of the time with temperature dependent resistors so the cable would distort the measurement.

Also you will have EMI problems with long cables!

P.S. You know that you can buy a cheap weather station which includes wireless sensors and a display unit? You will not get any cheaper if you try to build the system yourself. Maybe you can also find one with datalogging.

\$\endgroup\$
4
  • \$\begingroup\$ Thanks for your comment! I read that cable resistance can be compensated for since you actually know it's value (can be computed from cable length). I suppose arduino has digital inputs that can handle this sort of thing? I would actually like to do this as a fun project, not necessarily to save money but to learn about this stuff. I am cheap on the other hand :). \$\endgroup\$
    – poppycockears
    Oct 24, 2018 at 9:52
  • \$\begingroup\$ Yes you can also measure the resistance of your cable if you have a good enough multimeter. What I don't know is how the cable resistance is influenced by aging and temperature. \$\endgroup\$
    – A.R.C.
    Oct 24, 2018 at 10:11
  • \$\begingroup\$ Arduino should have analog and digital inputs for all possible solutions. \$\endgroup\$
    – A.R.C.
    Oct 24, 2018 at 10:11
  • \$\begingroup\$ Oh OK. I was looking at link: and I guess there is some info about it here \$\endgroup\$
    – poppycockears
    Oct 24, 2018 at 10:27

Not the answer you're looking for? Browse other questions tagged or ask your own question.