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    Is this where I use an Optoisolator?

    Guys, I can use some of the eletrical guru stuff on this board.

    Here's what I am trying to do.

    I have a littermaid automated litter box for our cat. When the box of poop fills up and holds the lid open a little (read STINK), it buzzes a little piezo electric sounder.

    I have attached leads in parallel to the sounder and it will power an LED but that's about it. So I would assume that I won't find a relay that will work at the voltage and amperage of an LED.

    I want to connect the output to my SECU16 so I can have the hiphone place an internal call to the house and get people's attention.

    Will an optoisolator work here? IS that what I should be using?

    Help! It stinks in here!

    SteveP

    #2
    I would wire the LED of the optocoupler in series with your visible LED, making the appropriate change to your current-limiting resistor. I would use a mosfet output opto (pretty much a solid-state relay), so that you don't have to worry about diode-drop or polarity.

    If you want, I can give you specific sources, but I would need to know the voltage that drives the LED/opto combination.

    Comment


      #3
      Since its probably a piezo that's making the sound, it could be the signal is AC at a few kHz. You wont be able to see that with an LED because your eye is too slow. However, your SECU16 may be able to see it, and flash on/off really quickly (but I don't know, it may average). If it does flash quickly, you will be flooding HS with updates. So, you might need to do a little more work if that's the signal you realy want to use. A universal module might do it.

      Comment


        #4
        I put a digital VOM across the leads of the piezo electric sounder and got about 1 volt. It's probably higher but my Radio Shack meter doesn't give me a peak reading that I can find. It does light an old PC LED well but not too bright so I was assuming it's in the range of the voltage required for an LED. I can try running the optoisolator I have (4N35) in series with the LED and see it the LED still goes (will post results later tonight).

        I could use some pointers here. I could put 5 volts on the NPN transistor side of the optoisolator so that seemed like a way to go feed a relay. But your mention of the mosfet output opto (pretty much a solid-state relay) is smarter I'm sure, I'm just not familiar with them. I found the 4N35 locally and figured it was a starting point.

        Thanks for your input.

        BTW, what happened to the motor controller that was discussed a while back?

        SteveP

        Comment


          #5
          It could be AC. An oscillator modulating a five volt supply to excite a piezo could give you a 1 volt DC reading. Try taking both an AC and DC reading. Also measure the voltage with the piezo disconnected, as the low voltage could be due to low impedance of the piezo.

          If the voltage really is that low, driving an optocoupler could be a problem, as the LEDs in most optos need 1.6 volts typically, and as much as 2.2 volts.

          You do not mention how the litterbox is powered. If it is powered by batteries, you do not actually need the isolation that an optocoupler provides. A simple transistor circuit may do. Possibly a low pass filter as well (a capacitor & resistor) if the output really is AC.

          BTW: The motor controller is in process, but have too many commercial projects to allow me to spend much time on it. USB is out for now. Looking to build a ZigBee version after the X10 version.

          Comment


            #6
            <BLOCKQUOTE class="ip-ubbcode-quote"><font size="-1">quote:</font><HR>It could be AC. An oscillator modulating a five volt supply to excite a piezo could give you a 1 volt DC reading. Try taking both an AC and DC reading. Also measure the voltage with the piezo disconnected, as the low voltage could be due to low impedance of the piezo.

            If the voltage really is that low, driving an optocoupler could be a problem, as the LEDs in most optos need 1.6 volts typically, and as much as 2.2 volts.

            You do not mention how the litterbox is powered. If it is powered by batteries, you do not actually need the isolation that an optocoupler provides. A simple transistor circuit may do. Possibly a low pass filter as well (a capacitor & resistor) if the output really is AC.<HR></BLOCKQUOTE>


            Ok, ran some tests. I took the litterbox apart again (ugh) and removed the piezo buzzer from the board. Without the buzzer in the circuit, I attached the VOM and then plugged that into my computer. It's a Radio Shack model with serial output. I let it cycle for about 10 minutes and had the computer track the max voltage ever received. I got 2.50 volts max and 0 in min mode in DC mode. Then, I switched the meter to AC and let it measure for 10 more minutes so I got a few samples. The reason for this is that the meter only records once a second. In AC mode, I got 2.48v max and -0.00 min volts. Also, the piezo buzzer is marked for positive and negative terminals. And, an LED works fine connected one way and does not light at all when connected the other way.

            As a possible solution, I connected a 5 volt reed relay up but there isn't enough voltage to drive it. So I do need some kind of solution.

            In summary, looks like I have 2.5volts DC.

            I have some 4N35 optoisolators which might work as part of the solution.

            I would like to see this come about as a generic solution. There are a lot of situations where devices have LEDs to indicate conditions that would be great to connect to HS via the Ocelot or 1-wire or Powerflash. If this could be setup as an isolated low voltage input circuit that closed a small relay it would be great. It would be nice if it could run on 5-12volts input.

            Rocco, if you can describe this well enough to me I will build it and describe it in the general automation section of the board for others. I would think others could find this useful. In fact, once I get the litterbox done, I want to wire up contacts to the LEDs on my waterbug water detector so I can feed that into HS.

            SteveP

            Comment


              #7
              Ok, 2.5 volts, both AC and DC. That means the output is 2.5 volts DC, but modulated to drive the piezo (probably around 1kHz).

              Does the litterbox runs off of batteries?

              Does the unit do anything other then buzz when it's full? Is it motorized or something? What I'm thinking is that, if all it does is buzz, then hook the SECU16 directly to the switch and disconnect the piezo circuit altogether.

              If not, then we need to go with a circuit with:
              1) a fair amount of sensitivity,
              2) isolation if the litterbox is powered by AC,
              3) a low pass filter to remove the modulation.

              The filter could be a simple RC circuit. The rest is either a high sensitivity optocoupler, or a transistor, depending on the need for isolation.

              An optocoupler like the 6N139 would provide the sensitivity (.5ma input current) as opposed to the 4N35 (10ma input current). The darlington output would have no trouble driving the SECU16.
              To do the transistor approach, I would need to know more about the SECU16's input.

              Comment


                #8
                I think most pizeo buzzers are self contained and just need voltage to make a sound. I would try a generic NPN transistor as a switch (2222A or 3904 Radio shack types). Attach a 2.2K resistor to the transistor base. Then connect the other end of the resistor to the + wire on the buzzer, and the transistor enmitter to the - wire of the buzzer. Connect the transistor collector to the + side of your sensor gizmo, and the transistor emitter to the - side of the sensor gizmo. To test this setup, put your volt meter in the resistance mode and use it across the transistor instead of the sensor. It should show high resistance. Then make the buzzer sound and see if it goes to a low resistance. If this works, then it is probably all you need.
                Why I like my 2005 rio yellow Honda S2000 with the top down, and more!

                Comment


                  #9
                  <BLOCKQUOTE class="ip-ubbcode-quote"><font size="-1">quote:</font><HR>Ok, 2.5 volts, both AC and DC. That means the output is 2.5 volts DC, but modulated to drive the piezo (probably around 1kHz).<HR></BLOCKQUOTE>

                  It is probably modulated as you say. First, it seemed harder to get a good clean meter reading. Second, there are two quick tones and then a pause between. The second tone is slightly lower in note.

                  <BLOCKQUOTE class="ip-ubbcode-quote"><font size="-1">quote:</font><HR>Does the litterbox runs off of batteries?<HR></BLOCKQUOTE>

                  Yes, it can. Holds 8 D cells. But it comes with a wall wart of 12volts AC. I run it off the wall wart.

                  <BLOCKQUOTE class="ip-ubbcode-quote"><font size="-1">quote:</font><HR>Does the unit do anything other then buzz when it's full? Is it motorized or something? What I'm thinking is that, if all it does is buzz, then hook the SECU16 directly to the switch and disconnect the piezo circuit altogether.<HR></BLOCKQUOTE>
                  Nope, just buzzes on full (shame it can't empty itself). The only time the motor runs is to move the rake back and forth through the tray to move the poop to the box. (Littermaid web page). You're right on hooking to the SECU16 as it can handle 5volts. But, I think part of what I am thinking here is that the development of a generic low voltage, low draw module that contains a contact closure could be used a number of places and could feed into a number of sensors like the 1-wire DS2405 and the X10 Powerflash. That way more people could use this approach. I am willing to overdevelop the 'litterbox' solution if it's a generic module that I can use in other places where all I have for sensing is an LED to feed off of.

                  <BLOCKQUOTE class="ip-ubbcode-quote"><font size="-1">quote:</font><HR>If not, then we need to go with a circuit with:
                  1) a fair amount of sensitivity,
                  2) isolation if the litterbox is powered by AC,
                  3) a low pass filter to remove the modulation.

                  The filter could be a simple RC circuit. The rest is either a high sensitivity optocoupler, or a transistor, depending on the need for isolation.

                  An optocoupler like the 6N139 would provide the sensitivity (.5ma input current) as opposed to the 4N35 (10ma input current). The darlington output would have no trouble driving the SECU16.
                  To do the transistor approach, I would need to know more about the SECU16's input. <HR></BLOCKQUOTE>

                  See my comments in last paragraph. I am shooting for contact closure as the lowest common denominator. Would be usable by the most people regardless of SECU16, 1-wire, or Powerflash input.

                  SteveP

                  Comment


                    #10
                    Zoomcat is right about most piezo buzzers being self contained, but I figured this one was the cheaper "circuitless" type because of your voltage readings. The fact that the second tone is a lower pitch reinforces that theory, and means that a microcontroller is probably doing the modulation.

                    So the ideal circuit would have a two-wire 'universal' input, and a contact-closure output. I have a few ideas. I will digest.

                    Comment


                      #11
                      <BLOCKQUOTE class="ip-ubbcode-quote"><font size="-1">quote:</font><HR>So the ideal circuit would have a two-wire 'universal' input, and a contact-closure output. I have a few ideas. I will digest. <HR></BLOCKQUOTE>

                      That's it exactly. Just like the discussions on the motor controller. If we go through the effort to do this thing, it will be usable by the most people.

                      I would add that it should be powered from 5-12volts so that it could be fed from a multiple of sources again to satisfy the most people. Hope that doesn't complicate it too much more.

                      I will be eagerly awaiting your 'digestion'!

                      SteveP

                      Comment


                        #12
                        This circuit has a few advantages:
                        1) it's simple.
                        2) it's cheap ($2.80 for the three components).
                        3) it needs no power of it's own.
                        4) it's input is isolated from it's output.
                        5) it will take an input from 2 to 30 volts.
                        6) it's input is current limited to 16.6 mA.
                        7) it's output behaves much like a switch.
                        8) it's solid-state (for what that's worth).

                        It's disadvantages:
                        1) it has different input pins for 2v to 3v and 3v to 30v.
                        2) it's input requires a polarized signal.
                        3) it's input needs at least 8 mA to operate.
                        4) it's output has a resistance as high as 200 ohms.

                        The fet-output optocoupler data sheet is here:

                        http://www.fairchildsemi.com/ds/H1/H11F1.pdf

                        I will try again soon with a reed-relay approach.

                        Comment


                          #13
                          <BLOCKQUOTE class="ip-ubbcode-quote"><font size="-1">quote:</font><HR>This circuit has a few advantages:
                          1) it's simple.
                          2) it's cheap ($2.80 for the three components).
                          3) it needs no power of it's own.
                          4) it's input is isolated from it's output.
                          5) it will take an input from 2 to 30 volts.
                          6) it's input is current limited to 16.6 mA.
                          7) it's output behaves much like a switch.
                          8) it's solid-state (for what that's worth).

                          It's disadvantages:
                          9) it has different input pins for 2v to 3v and 3v to 30v.
                          10) it's input requires a polarized signal.
                          11) it's input needs at least 8 mA to operate.
                          12) it's output has a resistance as high as 200 ohms.<HR></BLOCKQUOTE>

                          Some comments on your points.
                          1) good news for construction but not critical.
                          2) seems under $10 for parts of a generic device such as this is acceptable
                          3) That is really great as long as it would not affect the detected circuit.
                          4) yep, required
                          5) excellent
                          9) circuit variations would be bad, rather not have to make circuit variations or have selective inputs.

                          Had some trouble viewing the circuit. Said that there were too few operands?

                          SteveP

                          Comment


                            #14
                            At the below link, down the page, is an optical isolator switch thing I made from Radio Shack MOC3010 (276-134, $1.99). This is the only optoisolator Radio Shack carried, so I had to make do. I was able to get it to work with only ~4 ma in from the serial port TXD line by cascading 2 NPN transistors on the output side, and limiting the current from a 9V source through the transistors using a 10K resistor. Used it to isolate the serial port from a sequential video switcher. The MOC3010 is usually used with much higher currents on the input side, but I did get the thing switch as desired.

                            http://www.geocities.com/zoomkat/RSswitcher.htm
                            Why I like my 2005 rio yellow Honda S2000 with the top down, and more!

                            Comment


                              #15
                              Zoomcat: Yeah, that's the ticket . . .

                              I will need to do something like that for the reed-relay approach. A transistor amplifier driving the relay. But it would have to be powered. I would like to do it with 3 AA batteries.

                              A high-performance MosFet instead of the relay may reduce drain on the batteries, but then I would need an optocoupler again.

                              Do you have a schematic of your transistor amp?

                              Steve: I have no idea why you would have trouble viewing the schematic, it's a plain-vanilla .PDF file.

                              Comment

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