Go Down

Topic: Help with DS18B20 sensors running relay and logging data (Read 1 time) previous topic - next topic


Arduino newbie here respectfully bringing my project here for guidance. I wish I knew how to do this, but need help getting going. Want to make sure I do not go down the wrong path. From watching this site, there is some incredible knowledge here, so am hoping to tap into just a tiny bit of that!

  • Am building a temperature monitoring system that will use data from one sensor to operate a 1/2 hp 110v electric motor.

  • Sensors are DS18B20s.

  • Will monitor temperatures from about a dozen DS18B20s.

  • Data will go via modified cat6 cable to an Arduino Mega1280. (DS18B20s, time stamp, temp.)

  • Data from one of the DS18B20 will operate a relay for ½ hp 110v motor.

  • Data will transfer via ethernet shield from Arduino Mega1280 to Ubuntu/Mint/Debian PC for storage/analysis.

  • Other sensors will have data read and logged every 30 seconds.

What type of relay works best here?

Regarding the Arduino code, 're-inventing this wheel' makes no sense to me and I learn best using a solid code base to work and learn from.

IMO, having a proven solid code base to start with and then testing / learning / experimenting off of this would be far preferable.

Anybody agree with this? I know I work best starting with a proven thing and using that to learn.

I would be very grateful for any and all suggestions.

Thank you. Looking forward to this.


What type of relay works best here?

Look at: http://goo.gl/lkfoi  which is rated 1 HP at 120VAC 

Typical 10A rated relays are probably not OK for the startup surge on the motor.

DISCLAIMER: Mentioned stuff from my own shop...
Regards, Terry King terry@yourduino.com  - Check great prices, devices and Arduino-related boards at http://YourDuino.com
HOW-TO: http://ArduinoInfo.Info


Look at: http://goo.gl/lkfoi  which is rated 1 HP at 120VAC.  Typical 10A rated relays are probably not OK for the startup surge on the motor.

Good link. I agree, a 10A relay would not be good. Even if it worked, I do not believe it would last long as it would  be stressed hard.

Now hoping some people have examples of a similar setup with regards to a code base to start from.   :)

Thank you Terry.


Agree that a hefty relay is required. Motors require more amps on startup, I recommend a 20amp relay for good safety margin. In fact, I'll be using a RIB2401b "Relay-inna-box" for my own 1/2 horse motor application. I'll be using DS18B20s too. Haven't started yet though so no code advice, sorry...


Big electric motors typically use something called a 'contactor' rather than a relay. They seem to be fundamentally the same thing (solenoid operated switch) but are presumably optimised for switching high current inductive loads. The ones I looked at were surprisingly expensive. This may be a good reason to keep looking for an ordinary relay and hope you find one that is up to the job, but I can't help thinking that they're probably expensive for a reason.
I only provide help via the forum - please do not contact me for private consultancy.

Go Up