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Touch activated Switches

Discussion in 'General Electronics Chat' started by killivolt, Jan 23, 2010.

  1. Space Varmint

    Space Varmint New Member

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    Scope grid for 20KHz
     

    Attached Files:

  2. killivolt

    killivolt Well-Known Member

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    Ok, that is rock solid in between, However, from zero to peak it slopes upward?

    Edit: I'll bet, I've damaged the 4069's somehow. I know I didn't hookup the Vcc on one of them, who knows what I did.

    Gotta head out I'll be picking this up at the house after dinner.

    Thanks SV

    Cheers.
     
    Last edited: Feb 6, 2010
  3. killivolt

    killivolt Well-Known Member

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    So, I did hookup the Touch Sensor circuit. I tried to check it for any response by hooking up the probe to it. Every setting didn't seem to render a response. Although when I touched the side of the exciter input I got a response that looked somewhat like the exciter waveform.


    Edit: Now if I can get the MOSFET and Relay in tomorrow. The relay I want to use is because I have one:)

    http://www.nteinc.com/relay_web/pdf/R74.pdf

    Do I need to use a regulator off the 9v supply or just a resistor to power the relay?

    Edit:Edit I just found this roaming around to see if someone else tried this circuit, interesting read.

    Capacitance Proimity Switch Technology -Dave Johnson and what I didn't find before I started this Journey
     
    Last edited: Feb 6, 2010
  4. dave

    Dave New Member

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  5. Space Varmint

    Space Varmint New Member

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    Nah, you did not blow the chips. I seriously doubt it. The curve is a function of how long it is taking the capacitor to charge up. It is part of an RC time constant. As long as it is switching high to low and back, then it is working fine.
     
  6. Space Varmint

    Space Varmint New Member

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    If not sure than always use a regulator. Too many variables to consider without one.
     
  7. killivolt

    killivolt Well-Known Member

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    Ok, I have the 20khz and feeding the 2907 to the receiver and have a relay fed with 5v supply.

    My main question is in the diagram, what is the 9v with the cathode of the diode facing it going to other than the supply ?

    Shouldn't it be facing the exciter. Is that a mis-print ?
     
    Last edited: Feb 7, 2010
  8. killivolt

    killivolt Well-Known Member

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    I've built the diagram and am just not sure about it's inner working. I've set up everything and checked and re-checked all my connections. What bothers me is am I supposed to be getting 9v peak at 20khz after the 47ohm resistor. The diagram depicts 9v to 0v at 20khz. I have the 20khz at 0.798v at that point. So, which is it.

    Confused.....

    Here's the Diagram.

    Touch Activated Switch


    Edit: After giving this some thought maybe the reason it's not working is I picked up my parts without consulting with Doug Johnson. I think his selection of components may be the reason I'm not getting this to switch on. It may also be the reason why the voltages are out and why I don't have the desired 9v to 0v even though my oscillator is working.

    On this site which is not the one I got the schematic from, he is selling his small packaged unit "complete". It's comprised of surface mounted components. ( Mine is through hole and voltage rating maybe different )

    After further reading on this site I believe it's time to talk to the designer
     
    Last edited: Feb 8, 2010
  9. Space Varmint

    Space Varmint New Member

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    Surface mount shouldn't make much difference at that frequency. I'm looking at schematic, Will get right back.
     
  10. Roff

    Roff Well-Known Member

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    Are you talking about one of the two diodes connected to the exciter output?
     
  11. killivolt

    killivolt Well-Known Member

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    Yeah.

    But that shouldn't matter I'm only getting 5.6v or so on the Hex inputs and only 2.34v on the outputs. By the time it hits the 47ohm resistor it drops to 0.798v or so.

    If I lift the diodes it comes up to around 6v. (My Dmm is a Fluke 111)

    Edit: I got a meeting in about half hrs or so. Thanks for giving me feedback. I'm hooking everything back up for testing.
     
    Last edited: Feb 8, 2010
  12. Space Varmint

    Space Varmint New Member

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    Yeah I think he is. It looks like the guy is superimposing the 9 volts onto the signal voltage. I've never done it like that. But if you getting .7 volts than that is too small. Probably won't make threshold (switch the logic). What does that signal go to? I'm looking at this thing, and you said there were wires connecting the switches didn't you? This looks lie part of a wireless remote switch. The term "exciter" means to drive a radio frequency amplifier. It looks lie the 2n7000 transistor is a receiver and I do believe he is trying to portray an antenna on the front of it though it is sort of an antenna signal. Now I know what the oscillator is for. To send the signal through the air, but this does not match the description of what you said you were making. Maybe we should start there. Is this just one switch tied to a sending device and one received pulse?
     
  13. Roff

    Roff Well-Known Member

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    The diodes on the exciter output are normally reverse biased, and are there to prevent noise or reflections that exceed the supply voltage from getting back into the 4069 driver, possibly damaging it.
    The system is not wireless. The exciter is wired to the inputs of all the sensors. The receiver is wired to the outputs of all the sensors.
     
  14. killivolt

    killivolt Well-Known Member

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    I'm in the meeting. Now the qeustion re
    ians am I supposed to have 9v to 0v at the exciter?
     
  15. Space Varmint

    Space Varmint New Member

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    No, that is my mistake. I see now. The line drivers are what brings the signal strength up to 9 volts. So make sure you have 9 volts going to the supply pin of the line driver.
     
  16. Roff

    Roff Well-Known Member

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    Roughly. it might be only 1V to 8V, or something like that.
     
  17. killivolt

    killivolt Well-Known Member

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    Line drivers? are you referring to Vcc on Pins 14 of the chips yes. 9v

    I checked and double checked it.

    So, then If I remain at the 0.798v maybe their is a current problem or something. I am using a .049 cap on the Mosfet receiver that I pulled out of a TV because I didn't have one, don't know it that will affect it or not.

    I forgot, so today I'll be heading over to see if I can get a ceramic one.
     
  18. Space Varmint

    Space Varmint New Member

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    Use your scope to measure it. But this is a strange circuit with all the inputs ties together and all the outputs tied together. Not sure why that is but you probably have a "fan out" problem. What that is, is you don't have enough drive to drive all those inverters so your voltage is being loaded down. But if you using your DVM to measure the voltage, remember the voltage is swinging negative to positive so you should be reading an average of 4.5 volts. What you want to do is make sure the input to the inverters is a full 9 volts when it goes high and it drops to zero when low. The check the outputs of the inverter gates to make sure they are the same.
     
  19. killivolt

    killivolt Well-Known Member

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    This all I could get back from Dave at this point I'm trying to see if he can lead me somewhere or not on this.

     
    Last edited: Feb 8, 2010
  20. killivolt

    killivolt Well-Known Member

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    On the input side of the inverters after the 10k resistor I have 5.7v and 2.5v on the output side then it goes into the 47ohm resistor and drops to 0.7v

    I have 9v on both of the 4069's pins 14 ?
     
    Last edited: Feb 8, 2010
  21. Roff

    Roff Well-Known Member

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    The cap on the receiver won't affect the exciter.
    I'm running a simulation for you. I'll post the test circuit and some waveforms when I'm done, probably later today. It's lookin' good!
     

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