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delay off timer for bathroom fan

Discussion in 'General Electronics Discussion' started by goffery, Aug 4, 2013.

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  1. goffery

    goffery

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    Aug 4, 2013
    Dear friends,
    I need help.
    First, confession: My skills in electronics are rather poor.
    Well, What I want to build is a times off delay for bathroom fan, frequently called extractor.
    Originally, I had a fan with internal delay off control, but it went bad.
    The fan is powered by 220V mains, through a relay from the 12V electronic circuit. The circuit is built around 4060 oscillator/counter.
    The common wiring in Israel for these kinds of devices is a three prong outlet containing permanent phase and zero, plus switched additional phase (same phase), which is driven on when the lights are turned on, and turned off, accordingly when the lights are gone off (when the customer goes out).
    Operation: as the lights in the bathroom switched on the fan goes on, and stays on as long as the lights are on. After switching the lights off, and after a preset duration (5-30 min), the fan turned off as well.
    The main idea is that the controller is always hooked to mains supply, and the phase-on when light turned on, and then off provides the signal for clocking.
    I tried on my own several configurations, with "beautiful" failures. For instance I thought of using logic "not" inverter on the delayed output (one-shot configuration) preset time, but the switched phase (bathroom lights) brings the reset to low, and resets the timer…
    Many of you there have enough know-how and ingenious ideas as to how to work it out. Will you please enlighten me?
    Thank you all in advance,
    BTW: one important thing to remember. There is no momentary switch there to use for resetting. Only the three outlets: L (line) and 0, both permanent, and LT (switched line) witch turned the bathroom light, and delivers signal to the fan, and stayed on (latched) till tight turned off.
    Yossi
     
  2. CDRIVE

    CDRIVE Hauling 10' pipe on a Trek Shift3

    4,960
    652
    May 8, 2012
    Welcome to EP Yossi. Please post your schematic.

    Chris
     
  3. goffery

    goffery

    8
    0
    Aug 4, 2013
    Schematics

    I am afraid that I do not have any schematics. In fact, the aim of my post is to request anyone who has an idea to propose a circuit , or at least a concept.
    Thanks,
    Yossi
     
  4. CDRIVE

    CDRIVE Hauling 10' pipe on a Trek Shift3

    4,960
    652
    May 8, 2012
    You must have drawn something when you attempted this......

    Chris
     
  5. KrisBlueNZ

    KrisBlueNZ Sadly passed away in 2015

    8,393
    1,271
    Nov 28, 2011
    Hi Yossi.

    So the fan will connect to a connector that has three terminals: Phase (always present), Phase switched, and Neutral. So it can get its operating power between Phase and Neutral, and use the switched phase to tell whether the light is ON or OFF.

    This board with the CD4060 on it, is that the board that was inside the fan? Do you want to repair that board, or design a new one? Is the 4060 circuit a design you've found somewhere? If so, can you link to it?

    What you want can be done - in various ways.

    Your circuit needs to be powered from 220 VAC mains. It needs to monitor the voltage coming into the switched phase input. It needs to switch an extractor fan ON and OFF.

    A conventional way would use a transformer to create a 12V DC supply for the circuitry, use an optocoupler to monitor the voltage coming in the switched phase signal, implement the delay using one or two 4060s or similar, and use an electromechanical relay to switch the extractor fan. The fan would be enabled while the switched phase was present, and for a presettable length of time afterwards.

    Have a look on Google or Wikipedia for some of those keywords if you want more details.

    Other options for switching the fan would be an SCR or triac, and a solid state relay (SSR). How much current does the fan draw?

    Can you draw out the schematic of the original board from the fan? Or start by posting a photo of it?
     
  6. CDRIVE

    CDRIVE Hauling 10' pipe on a Trek Shift3

    4,960
    652
    May 8, 2012
    Personally I think an attempt to repair the original circuit should be made.

    Chris
     
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