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Member #492383

Member Since: November 26, 2013

Country: United States

  • I built something similar, but I’m monitoring 16 plants. And, instead of connecting to the internet, there’s a blinky light in each plant to indicate that the soil is dry. There are 13 plants in my window though, which exceeded the port count of my Arduino, so I used a pair of shift registers for LED power, and a couple of 16-port multiplexers (one to power the probes, and one to do analog reads) so that I could hook 16 sensors to one arduino. I didn’t hook it to the internet. The cost in Arduino parts was more like 25 dollars (a little over a dollar per plant) from Sparkfun. Admittedly, the wire running to each plant from the Arduino aren’t the most beautiful thing in the world, but it does the job fairly well.

  • If you paint the border red, I wonder who owns the copyright on that? Maybe you should submit a copyright for red-bordered multimeters before it’s too late…

  • Same problem, same fix. If I was really good, I’d try to resolder the battery holder, using less solder. But the aluminum foil trick worked so well, why bother :)

  • ok, I spent a day getting this working, thought it might help to lay out what worked for the next person.

    My config can be described like this:

    transmitter connected to an arduino pro mini 3.3v, 8 mHz Receiver connected to an arduino uno redboard from the inventor’s kit.

    The final wiring config

    Pro mini

    • transmitter connected to 3.3v, gnd and signal(pin 10)
    • I didn’t add an antenna line.


    • receiver connected to 5v, gnd and signal(pin 9)
    • I didn’t connect the extra grounds, or the antenna line here either.

    the KLP walkthrough did not work for me, and neither did the AVR tutorial. I think this may be because it relies on the rx/tx pins used by the usb serial port, and I was most likely corrupting the signal while troubleshooting.

    The http://letsmakerobots.com/node/12336 did work, but with slight modifications. I had to change from pin 23 since my Uno only goes to 13, and I randomly selected pin 2 (this was a mistake, I’ll get to why below). I still wasn’t getting a transmission across, so I dragged out the oscilloscope. I measured signal on pin 9, and it was only getting to about 0.5 volts on the “high” signal. I decided to try a different pin, 11, as it’s got the tilde next to it. Suddenly I had it working, but only partly. I’m guessing that PWM (pulse width modulation) is the difference, so selecting pin 2 (no PWM capability) was an unlucky choice. At this point, switching pins is nothing more than a cargo-cult thing for me. I’m not confident that it was the solution, but I believe so. Can anyone help me prove/disprove that conclusion?

    So now I was getting output, but instead of the correct characters from the test message, I was getting their integer equivalents. I modified the letsmakerobots example as seen below. I marked the lines I changed with “mod:tim”:

    char temp=0;//mod:tim:added a temporary character    
    for (i = 0; i < buflen; i++)
    {   temp=(char)buf[i];//mod:tim:convert uint to char
        Serial.print(temp);  //mod:tim:changed buff[i] to temp here

    So now I have a decent connection between an arduino uno and an arduino pro mini, using VirtualWire-1.20. As far as I can tell, nothing special needs to be done to talk between an 8mhz and a 16mhz arduino. Next task is setting up 315 receiver/transmitter pairs to make the communication go both ways. Wish me luck :)

    edit:correct inaccuracies.

  • Finally, headgear that will distract from my beauty. I’m sick of being just a pretty face. Hey girls, my eyes are up here!

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