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DS10 as water detector.. revisited

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    #16
    Originally posted by viclick
    Stuart tested the Powerflash and found that one drop would trigger it. That would indicate that the resistance goes much lower than 50K (the Powerflash won't trigger with 50K). Since the Powerflash can be triggered, I think the leaf sensor would be able to trigger the DS10. It really depends on the DS10 input circuit.

    Vic
    Does anyone have a leaf sensor and a ds10a?
    Could they try and see if water on a leaf sensor is enough to trigger a ds10a?
    Dick
    HS PRO 2.5.0.81, WinXP, IE8, Shuttle XS35V3, 2.13GHz, 4GB, 40GB SSD drive, AC-RF2, ADIOcelot, Message Server, TI103, SNEVL CID, pjcOutlook, MCSTemperature, Powertrigger, BLBackup, BLFloorplan, BLIcon, BLOccupied, BLRadar, BLRfid, BLLogMonitor, ACPUPSD, UltraECM, WeatherXML & Stipus' script connector. 500+ devices, 260+ events, 1-wire weather station + temp/humidity sensors & Oregon Scientific temp & humidity sensors & 2 Brultech ECM-1240s

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      #17
      The solenoid part no is 215141CK ($10.95) from Jameco. This is the 24volts version. I also ordered the 24 volts power supply part no.228970CK ($13.55). Hope this helps.

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        #18
        Electrical Guru Guidance please...

        While waiting on my leaf sensors, I have been messing around with a Watchdog Water Alarm

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          #19
          May get there yet...

          Originally posted by zoomkat
          To increase sensitivity, an NPN transistor could probably be used in the circuit.
          Good point about being flush on the floor. In my tests with the clothes pin approach the water really needed to be a pool of about 1/8" before it would trip which is WAY too much water IMO. I am sure your approach with the paper towel would work much better in that regard. Your point about the transistor peeked my interest. Could you post a diagram of the circuit with the transistor, and make a recommendation regarding the size (or spec's) of the NPN transistor please?

          Thanks
          Gary

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            #20
            I'd try using the Radio Shack generic 15 for $2.59 NPN transistors. Connect the + lead from the contact sensor to the transistor collector, and the - lead from the sensor to the transistor emitter. Connect the water detector gizmo between the transistor collector and base. When the water detector gets wet, the current flowing thru it and the transistor base should cause the transistor to pass a significantly larger current flow from the collector to emitter. I've thought about making the detector using screen mesh on the bottom, salt saturated and dried paper towel next, then a regular piece of paper towel on top of that for a little extra seperation, then covered with the top mesh screen. This would be sewn together using a needle and thread to keep it all flat and close together. Place it on the floor with something with a little weight on it to keep it flush with the floor. When the bottom paper towel gets wet, the salty water from it should soak up into the upper paper towel and make contact with the top screen. I haven't made one of these, but it made for some good day dreaming.
            Why I like my 2005 rio yellow Honda S2000 with the top down, and more!

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              #21
              That water sensor might be a small change in a high resistance - in which case you need a more elaborate circuit.

              transistor is a switch - between collector and emitter.
              The transistor switches "on", providing a low resistance from collector to emitter, only when the base has a voltage applied that is about +0.7V or more, relative to the voltage on the emitter.

              So the normal NPN switching transistor arrangement is, verbally:

              Emitter at "ground" - common with whatever it is connecting to.
              Collector has a resistor to a plus voltage, say, 1,000 ohms to a 9V battery's positive terminal. Negative terminal is "ground", i.e., connected to the emitter.

              Transistor's base is connected through a resistor (say, 4.7K) to a voltage source. When there's more than about 0.7V (+) the transitor turns on and the collector voltage falls to about 1V relative to the emitter.

              So if you have a relay or some such contact closure, you wire it to the resistor to the base with the other contact lead going to +V (say 9V).

              Another way to do this is with an opto-isolator (50 cent part). This arranges a LED inside the opto-isolator to turn on when the contact closure happens. The LED shines on a phototransistor inside the opto-isolator. That turns the transistor on as discussee above. The benefit is that there need not be a common ground and this is a safety consideration in some situations.

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                #22
                Here is another circuit I ran into to. Untested but it adds fuel to the fire...
                Stuart
                Attached Files

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                  #23
                  Originally posted by zoomkat
                  If you are going to do some electronic tinkering...
                  I have one. Now, effectively using it is another matter.

                  ... the current supplied by the DS10 contact leads might be enough to make the transistor work with out the battery.
                  That would be preferable. I measured the voltage across the DS10 leads to be a hair over 2 volts. Of course the charge of the batteries may affect that measurement some.

                  What is shown is with the flat side of the transistor facing you.
                  Yeah based on the way I labeled the pins the flat side would be facing the front. I picked up a pack of transistors at RS yesterday. I believe the picture actually shows the transistor with the flat side at an angle and more to the back so I think I revised my picture to show the pins accordingly. The numbers are the pin numbers as shown on the back of the pack. See if this diagram is correct.
                  Attached Files

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                    #24
                    beware that the E, B, C leads on transistors are not standard.

                    That circuit shown above won't work, I suspect. If there is enough water to cause enough current flow to turn on the transistor, the collector voltage will go to about 0.7 relative to the emitter. Thus, it will kill its own supply of base current.

                    But more over, I think the water sensor may provide a resistance of 100-300 hundred K ohms according to how much surface area is wet, and megohms when dry. You'll need more gain and a bit more sophisticated (more gain) circuit, I suspect.

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                      #25
                      Gary, have you tested whether the DS10a direclty connected to the water sensor can detect anything?

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                        #26
                        I would beware of acting only on advice that is "speculation" vs what is actually tried. My test sensor (which I actually made) measured ~5k ohms (analog and digital meter) and not a speculated 100-300k ohms (but this may depend on the sensor one makes). Also the RS multipack transistors have the correct pinouts on the pack. If you lay them flat side down with the pins sticking out to the left, the top pin is the collector, the middle pin is the base, and the bottom pin is the emitter. I suspect the DS10 provides very little current to the leads other wise it would probably run its battery down after a while on a closed contact condition. I tried a 1.5v battery in the detector circuit and it seemed enough to probably trigger the DS10 thru the transistor. You could get a two AA battery holder at RS (270-408) to hold the batteries and have it sit on the top of the sensor to keep it flush on the floor. These types of discussions tend to keep ratcheting up in complexity until the gizmo cost more to make than a ready made commercial unit. My challange is to keep it simple.
                        Why I like my 2005 rio yellow Honda S2000 with the top down, and more!

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                          #27
                          Originally posted by zoomkat
                          If you lay them flat side down with the pins sticking out to the left, the top pin is the collector, the middle pin is the base, and the bottom pin is the emitter.
                          Right. So if you rotate it 180 degrees so the pins are sticking out to the right the emitter should be on top. I believe that is the way I have depicted in my (2nd) diagram on page 2 of this thread, right?

                          I will give that a try and see what happens.

                          Gary

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                            #28
                            Just looking thru my parts box I notice that I have a RS pc board that has some alternating traces some what like the leaf moisture detector. The part number is 276-168. This might be worth looking at as you probably can get at a local store for ~$3.
                            Why I like my 2005 rio yellow Honda S2000 with the top down, and more!

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                              #29
                              IT Works!...

                              Originally posted by zoomkat
                              Just looking thru my parts box I notice that I have a RS pc board that has some alternating traces some what like the leaf moisture detector. The part number is . This might be worth looking at as you probably can get at a local store for ~$3.
                              Great! I saw those boards there when I picked up the transistors. I need one to make this thing production ready. Which...

                              In my testing the transistor seemed to do the trick quite nicely. It not only works but it works very well. I used the bare wires for the sensor and placed them about 1/4" apart. It trips the DS10 with only a drop of water. In fact my wife dipped her finger in water and it triped the DS10 when I touched the two wires to her damp finger. Thanks much Zoomcat for your contribution here. Its greatly appreciated. I will test the leaf sensors as being a viable water pickup when they arrive but I also intend to progress building a package that can be replicated many times for placement throughout the house. Here is a picture of my test unit:
                              Attached Files

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                                #30
                                Excellent! Can you update your drawing with the appropriate wiring (or take the tape off for a picture!) I want to try this this weekend.
                                Last edited by JeffCharger; June 8, 2006, 10:47 AM.

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