Help with SHT11 and SHT75 sensors

LeeW

I've been having an issue with an SHT75 sensor where I cannot get it to read out any values. I've taken the code provided for the SHT sensors from Parallax and only changed the Data and Clock pin values to the appropriate ones, and it still does not seem to work. The values I get are 0 for temp and 0 for humidity.

Now, thinking it was maybe an issue with the SHT75 I switched to the SHT11, but continued to have the same problem.

The weird thing is, wiring up an RHTPG75 (Tracy Allen's enclosed device) I am able to get solid results without changing anything except the pin numbers.

I've added the necessary resistors for both the SHT75 and the SHT11 but without any luck. Anyone have any idea?

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Jay B. Harlow

Don't have an answer; instead I have a question

I have been using mine, the Sensirion Temperature/Humidity Sensor #38018, with a Propeller Demo board. I've noticed that if I start it "cold" (sitting on my desk all night away from my computers) it will generally read 1 degree F lower then I expect; after a while (30 minutes or more) it will be 2 or 3 degree F higher then I expect.

The propeller is polling the sht11 every couple of seconds and updating a OLED display.

WBA Consulting

If you are using the democode for the stamp, you should be getting bogus values (IE: something like 6413 for temp) if communication with the SHTxx device is not working. If you are truly getting "0" as your values, something is incorrect in the code that must be fixed before you can say the sensor itself is bad.

Check my website on the link below for more tips, etc for using the SHTxx sensors.

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Andrew Williams
WBA Consulting
WBA-TH1M Sensirion SHT11 Module
My Prop projects: Reverse Geo-Cache Box, Custom Metronome, Micro Plunge Logger

LeeW

Figured out a mistake on my part - I was using the pin diagram for the sensor itself, not the module... so that fixes the SHT11 issue. I'll take a closer look at the 75 and see if I'm not mixing up diagrams.

Tracy Allen

Hi Lee,

Just as the SHT11 has a different pinout than the Parallax breakout module #38018, the SHT75 has a different pinout than the EME breakout SHT75PG. I think you have both. I'm attaching the diagram for the module that shows how the wire colors map to the pins on the sensor. The "PG" version is mounted in a PG7 gland nut for installation on a tube or enclosure. The photo shows the sensor mounted on the circular circuit board, how it projects from the PG7 gland (note the ventilation holes), and how it is protected behind a Goretex membrane.




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Tracy Allen
www.emesystems.com

Post Edited (Tracy Allen) : 5/29/2010 6:47:12 PM GMT