Hello,
I am a beginner with Arduino, but have purchased a sparkfun inventor's kit and would like to try out an idea:
I have a reverse osmosis filter on my kitchen sink that goes very slow. I can set it's lever to the hold position so that I do not have to hold it down, and I can walk away while it fills a glass of water. Often times, I forget and come back to a glass that is overflowing onto my countertop. I would like to set up a sensor that will trigger a servo motor when the water reaches the full height in the glass. This servo motor will turn 180 degrees to flip the lever into the off position.
I am wondering if I can use two separated jumper cables as the sensor so that when they touch the water, current from a battery pack flows through them and triggers the arduino UNO board to move the servo. If this is possible, how can I:
determine what size batter pack to use?
if I need a resistor?
where to plug the components into the UNO board?
I have attached an image showing my desired setup to help explain what I am talking about.
Thanks in advance for any help / advice with my first arduino project!!
It sounds like relying on the cup of water as a conductive element is actually more complicated than I wish to go at the moment. The soil moisture sensor looks like a simpler solution that would allow me to just supply input to the arduino board as opposed to supply power. I will use a 9V battery to power the arduino UNO (range is supposed to be between 7-12V?) and then when the soil moisture sensor touches the water it should send an input signal to the board. Then I need to program the board to output a 180 degree turn on my servo and possibly sound a buzzer when this input is received.
Does anyone have a link to a tutorial that accomplishes this goal or something similar?
To use this, you could cut out a section of strips, join every second one to 1 wire, and the ones between to another wire, and hook it up like you see in the link above. There's even some code to do the sensing there.
9V is too high for most servos (3-6V). Don't try to power a servo through the Arduino's built-in 5V voltage regulator (too much current/noise). Also, 9V batteries have a hard time supplying more than a few mA of current whereas a servo requires a lot (~1A). I would definitely prefer to use an 5V AC adapter because otherwise you'll be buying 9V batteries in bulk and replacing them every day or two (the UNO wastes a ton of power).
If an AC adapter is not an option, I would ditch the Uno in favor of a more power-efficient board that you can put to sleep most of the time. Then you could use 4xAA (preferably LSD NiMH).
As for the water sensor, normally tap water is quite conductive (TDS or Total Dissolved Solids of 200ppm+), which is why people get electrocuted when water and electricity mix. However pure water by itself is an insulator and RO filters most of the conductive elements out of tap water (resulting in a TDS of about 10ppm). So, RO is still conductive but the resistance is quite high and analogRead may have trouble distinguishing it from air. Go ahead and give it a try but be aware that you may need to use the analog comparator or add an op-amp or use a soil moisture sensor to get good reliability.
Honestly, an RO membrane is really not suited to "on demand" use. You have to "waste" the RO output (let it run down the drain) for 1-2 minutes after you first turn it on because during this time, it produces high TDS water resulting from membrane "creep". If you turn it on and immediately fill your glass, you're not getting 10ppm R/O, you're getting 150ppm+ and you might as well be drinking straight from the tap.
Usually RO is made in a bulk/batch process and stored in a tank under the sink for on-demand use (and then your glass fills in seconds).
Now transfer some of this to the Arduino. You could use the analog inputs and sense when the water is present. It will not be enough to switch a digital input but you can clearly sense it with the analog pins.
I haven't tested it yet, I just got it in the mail... http://forum.arduino.cc/index.php/topic,203054.0.html is a water level sensor I plan to use to have an autofill on my fish tank. Also, RO water may have a hard time conducting electricity - just an fyi. Without many minerals, water isn't a very good conductor. Good luck, I'll be curious to hear if that works out for you.
Super_Sonic:
I haven't tested it yet, I just got it in the mail... http://forum.arduino.cc/index.php/topic,203054.0.html is a water level sensor I plan to use to have an autofill on my fish tank. Also, RO water may have a hard time conducting electricity - just an fyi. Without many minerals, water isn't a very good conductor. Good luck, I'll be curious to hear if that works out for you.
