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

SunBeam

Hello,
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.
Clinton

terryking228

Quote
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

SunBeam


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.
clinton

tylernt

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...

PeterH

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.

wwbrown

I to what was stated re: contactors, they can be found on ebay for about the same cost as comparable SSR's

Tesla-uncoiled

Hi guys im interested in doing a small scale version of this. Very bare bones, I'm a hardware guy so i have my circuit set up but im trying to find a piece of code to work off. What I plan on is having 1 Ds18b20 set up to trigger a relay at a set temp limit. I have come across some code but most of it is to log the temps.

Could anyone give me some pointers or point me in the right direction?

Thank You

terryking228

Quote
Hi guys im interested in doing a small scale version of this.


Take a look at: http://arduino-info.wikispaces.com/Brick-Temperature-DS18B20

After you have that running, add a variable to hold the value returned by
sensors.getTempCByIndex(0)

And then use an "if" statement like ;
if (temperature > toohot) {//do something } ;

Regards, Terry King terry@yourduino.com  - Check great prices, devices and Arduino-related boards at http://YourDuino.com
HOW-TO: http://ArduinoInfo.Info

PeterH


What I plan on is having 1 Ds18b20 set up to trigger a relay at a set temp limit.

...

Could anyone give me some pointers or point me in the right direction?


It sounds as if you are planning to emulate a thermostatic switch in software. Why not just use a thermostatic switch?
I only provide help via the forum - please do not contact me for private consultancy.

SunBeam


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.....


Grainger has a helpful PDF entitled "Choosing Relays, Contactors and Motor Starters" and clarified some points for me. here is the link: http://www.google.com/url?sa=t&rct=j&q=&esrc=s&source=web&cd=2&sqi=2&ved=0CCwQFjAB&url=http%3A%2F%2Fwww.grainger.com%2Ftps%2Felectrical_choosing_relays_motor_starters_contactors.pdf&ei=Bwt6UI73Dq6p0AHM7YHICg&usg=AFQjCNFTeGMBcA0tosszw9fOhvEOXKdefw&sig2=HW8qHpAJQnmd5B4ve0TJtg

Hope that is helpful. It clarified some stuff for me.

terryking228

You may also want to look at this from the ArduinoInfo.Info WIKI:

http://arduino-info.wikispaces.com/RelayIsolation

Regards, Terry King terry@yourduino.com  - Check great prices, devices and Arduino-related boards at http://YourDuino.com
HOW-TO: http://ArduinoInfo.Info


Tesla-uncoiled

Updates: I have the brick sketch running fine now, I unsure on how to keep the value from the serial port to compare to my limits. Would i use the math library? Sorry for all the questions :)

Thanks again

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