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Need some guidance with relays and timers

Discussion in 'General Electronics Discussion' started by Rudyeb, Oct 7, 2015.

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  1. Rudyeb


    Oct 7, 2015
    I have a problem in winter with the city water supply to my home. It runs underground and under a river. Last year it froze and I had no water for 5 weeks.

    I've been told to keep my water running at a very slow rate continuously. I would like to put a solenoid valve inline to my sink faucet and it would have a timer and a relay. I want to be able to adjust the timing between actuation of the valve and the length of time the valve is open. I'm thinking the valve would be on for 5 seconds and then go off and come back on in 3 minutes and be on for 5 seconds and repeat this cycle.

    I have no idea what items I need to make this setup other than the solenoid valve and am hoping someone here might be able to provide me with some guidance to let me know what I need to buy.

    I thank you in advance for your help.
  2. Old Steve

    Old Steve

    Jul 23, 2015
    Google "555 astable". The 555 could switch a relay, or even the solenoid directly if it's DC and uses less than 200mA.
    (If I say more, I'll end up designing the circuit, and I'm too busy right now. :) )
    Last edited: Oct 7, 2015
  3. Harald Kapp

    Harald Kapp Moderator Moderator

    Nov 17, 2011
    If you don't want to build your own circuit, use a time switch with suitable resolution. I doubt you will get 5sec/3min resolution, but a 1min/30min duty cycle should be almost equivalent. You'll probably need an electronic time switch, not a mechanical one, to be able to make such a setting.
  4. Nicholas Schlensky

    Nicholas Schlensky

    Oct 7, 2015
    Linear Technology have a nice type of timer that can make 1ms to 9.5hrs pulses, LTC6995 and ltc6993. This will allow you to set the time on and time off to be any size between ms and hrs.
    Allthough a 555 has the advantage of being easily available
    The output of this could go to a Nch Mosfet then to solenoid
  5. AnalogKid


    Jun 10, 2015
    There are three basic ways to do this. You can buy industrial timer modules, the kinds of things in industrial control panels that wire together; or buy a programmable timer pc board device from china on ebay for around $12, and a small power supply for it and a small solid state relay and wire all of that together, or you can start from scratch and build a circuit to do the timing (plus the power supply and SSR). #1 is highest cost/lowest effort; #3 is lowest cost/highest effort.

    So first question set - what is your skill set / how much effort do you want to put into this / is this a learning project as well as a practical device for your home, or do you just want to get on with it?

  6. hevans1944

    hevans1944 Hop - AC8NS

    Jun 21, 2012
    I would try to find a geared synchronous clock motor such as this one and attach a cam to its output shaft. Use the cam to actuate a microswitch that energizes your solenoid valve for a few seconds once per revolution. In the example shown, this would occur once every six minutes. The problem will be finding just one of these on a distributor's shelf somewhere. You could contact the manufacturer for suggestions, maybe even wangle a "demo" unit from them.
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