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Motion sensor to control HV to Nixie Tubes

Discussion in 'Sensors and Actuators' started by DBK, Jan 29, 2011.

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  1. DBK


    Jan 29, 2011
    Need help with a PIR motion sensor to turn off and on the HV supply to the display anode rail of a Nixie tube clock I built. I was thinking about the waste of energy and reduction in tube life having the clock display on when I am not home for most of the day, when I sleep or not in the same room as the clock.

    One suggestion was made by the designer of the clock "If you want to switch the HV supply to the tubes, you can go the cheap and easy way and break the connection between the transformer pins 2 and 3 (see the pdf schematic). Install a small TRIAC between the two connections (available from radio shack) and control it with a logic level signal or motion sensor. A TRIAC is very cheap, and very effective. And there won't be any noise that may back flush into the receiver that would affect reception." I asked "Would there be any current drain if the secondary winding is disconnected with the primary still receiving the 9 volts from the wall transformer? Could I achieve the same result of powering off the display by breaking the connection between pins 6 and 7 on the "primary" side of the transformer and inserting the triac there?"

    His reply "Good question, the result opening the primary side would be a large reverse EMF 'kick' that would likely initiate a complete reset of the WWVB receiver. The effect is somewhat like how an ignition coil functions. That was why I recommended the modification be done on the secondary side of the transformer. As far as losses, when the secondary is opened, the primary side does have a minimal loading due to losses. That might be 5% of normal drain."

    You can see the schematic at

    Just scroll down toward the end and click on the schematic at the above address

    This is the WWVB controlled clock made by Jeff Thomas with very expensive tubes that are no longer obtainable.

    I need help deciding which PIR module to get and a simple schematic as to how I connect it to the circuit above. Ideally, I would have some way of adjusting sensitivity and time to turn on or off after sensing or not sensing motion or heat.

    I think a battery operated type would be good since I could put it next to the clock without need for additional outlets.

    What kind of TRIAC would I need?

    Thanks for any help.

  2. ot1


    Jan 29, 2011
    PIR module

    You could use an SB0061 PIR module, all the modules I have seen work of of 12VDC.
    Notice the the transformer in installed backwards to provide a step-up function. The secondary actually has 12V on it, the primary has 180V on it.

    Get a 12v zener (1n4742) and a 10uf cap and .1uf cap, 100 ohm resistor... on the transformer side of R57 220ohm 1w resistor build the 12V supply, duplicated similar to the existing 6 volt supply. Make sure you get 12VDC on the cathode of the 12v zener.

    use the schematic below, contacts of the relay between transformer pins 7 and 6.

    Last edited: Jan 29, 2011
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