12v timers and relay wiring

Discussion in 'The Projects Forum' started by Crazywizard, Feb 26, 2018.

  1. Crazywizard

    Thread Starter New Member

    Jan 21, 2015
    17
    1
    Hi all,

    I am hoping someone can help me design a circuit using timers and relays. I wish to start a generator from inside our RV, set a run time via an EBay
    programmable 12v timer/relay and using a second timer have the cooling fan for the generator enclosure run for several minutes after the genny has stopped. Starting it and running time I have worked that part out. The genny has its own 12v output when running and I plan on using it to power the run timer - genny stop, timer turns off also. When that happens I want a second timer to take over the cooling fan and turn itself off after a set period.
    I don't want the timers to be active when not in use as it could be days or a week or two between genny runs. These timers hold their setting when turned off so they won't need re-programming every time.

    Hope you get the idea of what I am trying to do. If you copy and google this it should show you the timer.
    12V LED Automation Delay Timer Control Switch Relay Module with case

    M
    any thanks,
    Jan
     
  2. eetech00

    Senior Member

    Jun 8, 2013
    1,535
    304
    Hi

    So is it the second timer for the fan you need to design?

    What will be the power source?

    eT
     
  3. Crazywizard

    Thread Starter New Member

    Jan 21, 2015
    17
    1
    Yes, the second timer is my problem. The power to it will be 12v from the rv battery system.
    The first timer will start itself when the genny starts as it will be powered by the gemmy output.
    Once the genny starts I will trigger the timer from a switch inside. somehow I need the second "fan" timer
    to start when the genny stops. So it will need both power and a trigger signal. But I want it to loose power again
    once the time has elapsed.
     
  4. eetech00

    Senior Member

    Jun 8, 2013
    1,535
    304
    How long does the timer need to run? and what type of load?
    Wait...the load is the cooling fan. Fan Part number?
     
    Last edited: Feb 27, 2018
  5. Crazywizard

    Thread Starter New Member

    Jan 21, 2015
    17
    1
    The fan will run for 10 minutes. It draws 4 amps and is an aftermarket motorcycle radiator cooling fan.
    It needs to cool the generator enclosure for a period after the generator has stopped. I can do that without
    a problem using a timer and relay. My problem is I don't want the timer to stay on when not in use and I don't
    want to have to remember to turn it off manually. I can turn it one when I start the genny but I want it to
    turn itself off at the end of the timed period.
    Many thanks for your help.
     
  6. eetech00

    Senior Member

    Jun 8, 2013
    1,535
    304
    A little difficult to understand the write up on ebay.
    I think we might be able to design a timer that will be held in "reset" when the generator output goes active.
    Then, when it goes inactive, the time would start (because its no longer in "reset") and shut off the Fan power
    after 10 minutes.

    But you might be able to use another timer like you've purchased (they are pretty cheap).
    Do you have a doc/manual that explains how it can be used?

    eT
     
  7. Crazywizard

    Thread Starter New Member

    Jan 21, 2015
    17
    1
     
  8. AnalogKid

    AAC Fanatic!

    Aug 1, 2013
    7,842
    2,205
    Just to be clear, the fan runs only after the gen has stopped? If so, then a SPDT relay with a coil that matches one of the gen outputs can produce a switch closure when the gen stops. Connect the fan power and timer power in direct parallel to the timer's NO contacts. Now all than is needed is a capacitor to diode-OR enough power into the timer for it to wake up and close its own contacts. I'll sketch this later today.

    Do you want to build the fan timer and control from scratch or mostly use assembled modules?

    Can the RV battery system and the gen 12 V output share a common ground?

    Does the gen 12 V go away when the gen stops?

    1 - CD4060
    1 - p-channel power MOSFET, 30 V, 20 A
    2 - 1N4148
    1 - 4700 uF / 25 V cap
    R's, C's, connectors

    ak
     
    Last edited: Feb 27, 2018
  9. Crazywizard

    Thread Starter New Member

    Jan 21, 2015
    17
    1
    Excellent. I don't mind either way. I guess building from modules would be less time consuming.
     
  10. Crazywizard

    Thread Starter New Member

    Jan 21, 2015
    17
    1
    I have it working. Added an extra relay than I thought may not be needed and it is working great.
    Thanks for your help.
     
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