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Member #156819

Member Since: October 17, 2010

Country: United States

  • Hey who took the bars down from his cage.

  • I got this device running on a arduino breadboard clone running a Mega1284P chip. I am using the code from here bildr. You have to modify the clearRegisters to set all of the 74HC595 pins High so the relays are off. Then to turn on the relay set the output to LOW.

    I ordered the connector that was in the "Customers also purchased" section(PRT-08506) for this with out looking at the specs, it is wrong my fault Digikey I guess.

    SO I have some twisted pair wire jambed in the end of the provided cable for the time being. Here is what I came up with for pins on the cable.

    I have pin3 to GND, Pin 4 to 5v, Pin5(RCLK) to D9 , Pin7(SER) to D8 , Pin9(SRCLK) to D10, and finally pin10 to GND.

    Hope this will help someone else.


  • thank god that is over

  • Got the new shipment of RHT03 and I got them to work fine on 3.3 volts.
    I had ordered 3 ea.
    I unplugged the original RHT03(from above) then plugged in the new. it worked.
    so plugged in the second it did not.
    So reading your GND issue above i connected both pin 3 and 4 to GND and it worked.
    Plugged the original back in with pin 3 and 4 connect to GND and it worked.
    Problem solved at least for me.
    So to recap at 5 volts the device works with pin 4 to GND at 3.3volts the device works with pin 3 and 4 hooked to GND.
    I wont even pretend to know why.

  • Thanks for the heads up. I thinking the production side of things might be a bit rough. The sensors I have do work at 5V with pin 4 being ground. I spent about 8 hrs trying all the suggestions and anything else I read about to get those two to work at 3.3v no luck at anything less than 3.9 volts for the humidity to report correctly. Temp worked above 3.42 volts.
    I am going to order a few more. This package is perfect for what I am doing and I like the price to.

  • I was never able to get the sensor that I had running at 3.3v but Thomas sent me photos of the RHT03 running at 3.3v, I will assume it is something with the batch.
    I will use the two I have up for a 5v project and wait for the a new batch to arrive and try the new batch at 3.3v. Looks like Sparkfun only has one left at the moment so shouldn't be too long

  • Thomas
    I understand what you are saying that they should be one and the same but they are not. The ones I am calling DHT22 were bought from sparkfun at the first of the year and match the picture above and will run at 3.18 volts(battery was getting low) and report correctly.
    The one I am calling RHT03 has that with the MaxDetect logo on the bottom of it and were bought in July from sparkfun. It will not run at 3.31 or 3.46 volts correctly, measured at the vcc pin for the sensor.
    I checked voltage using an ideal 61-361 meter.
    I even reset up the original bread board that I had, and used sparkfun's FTDI break out board for power. the 5 volt version the RHT03 and DHT22 works, for the 3.3 volt version only the DHT22 work. I then hooked up a lipo for power putting it through a N4001 diode the voltage was 3.46 and the temp was right but the humidity was a little over double on the RHT03 the DHT22 reported correctly. I am using a ATMEL ATMega328P with ardiuno boot loader on some PCB I had made and the bread boards using Ben Adams version 4 DHT22 library.
    The Temp and Humidity values are checked against a sensiron SHT15 on another bread board using a arduino boot loaded Atmega32p with the sensiron SHT15 library.
    I have 3 more PCB boards that I need to populate and run at 3.3 volts so I am looking for some DHT22, I am going to use the RHT03 that I have for some green house controls I am going to make but they will be run at 5 volts so wont be an issue.
    Plain and simple I can't get the last shipment to run at the same voltage the original ones I bought run at using the same set up...

  • Don't bother trying to run the RHT03 at less than 5 volts.
    It doesn't report the humididty correct at the 3.46 I said it was giving me values at..

  • To add one more final thing I found that the RHT03 does seem to work at 3.46 volts, Close to the upper end of where my 3.3 volt LCD is not going to be happy. I hope they fix this issue and get the sensor back to what the DHT22 was doing.

  • I just found the same thing to be true that the RHT03 version does not work for 3.3V. They do work for the 5V..
    I am going to contact sparkfun tec support and see if they have the DTH22 version hanging around so I can complete my project 3.3v.
    By the way did some testing and the DTH22 reports back at 3.1 volts just not sure how accurate didn't have anything handy to check the temp or humidity against.

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