Noob needing assistance. Looking for a DPDT timed relay. I think :)

Discussion in 'General Electronics Chat' started by Mike Robling, Jul 20, 2016.

  1. Mike Robling

    Thread Starter New Member

    Jun 20, 2016
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    I need to flip the polarity on a DC circuit, every few hours.

    My pool has a salt chlorine generator The plates get covered with mineral deposit every few weeks. At which time they have to be soaked in a vinegar solution.


    I wired in a DPDT to the DC source for the plates. It worked well at first, but it seems my better-half doesn't remember to throw the switch.

    120vac on the timers and pumps.
    12vdc going to the generator plates.

    Any help would be much appreciated.
     
  2. jpanhalt

    AAC Fanatic!

    Jan 18, 2008
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    Mike Robling likes this.
  3. EM Fields

    Member

    Jun 8, 2016
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    Is divorce an option?
     
  4. crutschow

    Expert

    Mar 14, 2008
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    That still wouldn't get the switch reversed. ;)
     
  5. AlbertHall

    Well-Known Member

    Jun 4, 2014
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    It would likely be a lot more expensive than a relay and a '555 ;)
     
  6. jpanhalt

    AAC Fanatic!

    Jan 18, 2008
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    Was exhausted last night (drove to DC and flew back same day). Here's perhaps a better search. I chose DPDT and xPDT relays with AC operated coils and contacts rated for DC: http://www.digikey.com/product-sear...=0&page=1&quantity=0&ptm=0&fid=0&pageSize=500

    You can narrow the search based on DC current needs and voltage. You do not need to use all available poles on a relay.

    A multi-day light timer should work. Is there any reason you cannot cannot regenerate your electrolysis unit every night? That would allow a very simple and inexpensive light timer to be used.

    John
     
  7. Tonyr1084

    Active Member

    Sep 24, 2015
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    First, I know nothing about a Salt Chlorine Generator (SCG). So I am making some assumptions. 12 volts DC is causing some sort of electrolysis, and in doing so the plates load up with minerals (assumed). By reversing polarity those minerals should be released and allowed to migrate in the opposite direction. Question: Wouldn't the minerals continue to accumulate? Why wouldn't they be released into the water (or chemical) stream if you reverse the current?

    Let me ask this: Does flipping the switch manually give you the results you want? To be honest, I'm dubious whether this works or not. Nevertheless, on the assumption it works, all you need is a cheap timer from Lowe's or Home Depot (probably can be picked up in Walmart as well), one of those timers that can be set to be on at certain hours and off at certain hours. Settable in 30 minute increments.

    Snatch a 120 volt relay (coil voltage 120 volts) and wire it in the same way you have your DPDT switch. Set your timer for six hours (or 12 - or however many hours in a day you want polarity to reverse). This sort of timer is good for a single day. If you want longer periods then they sell programmable timers - a little more expensive but certainly doesn't break the bank - that you can program it to switch on certain days, every weekday or every weekend day, however you wish to set it. You can achieve periods of time up to 3 1/2 days where the positive plate is positive and 3 1/2 days where it is negative.

    I'll edit this post when I find the sort of timers I'm referring to.

    [edit]
    Here's a link to the cheaper one day settable timer: http://www.lowes.com/pd/Utilitech-1...-in-Countdown-Function-Lighting-Timer/4176999

    Here's a link to the more expensive 7 day programmable timer: http://www.homedepot.com/p/Defiant-...eyword=7+day+plug+in+programmable+light+timer and Home Depot sells the first timer as well.

    Further thought: With the timer you can set the plates to regenerate for a short period of time while still operating normally for much longer periods of time. Let me clarify with some made up numbers: Suppose you want to regenerate every night at midnight - for four hours. Every day at midnight the timer switches the relay on and reverses the current and holds it that way for those four hours then returns to normal operation.

    I'm assuming regeneration wouldn't take as long as it takes under normal operation to accumulate whatever it is that it accumulates.
     
    Last edited: Jul 21, 2016
  8. AnalogKid

    Distinguished Member

    Aug 1, 2013
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    A lamp timer from Walmart or ebay will switch 110 Vac on and off a few times a day for very low cost. A DPDT relay with a 110 Vac coil wired to a plug and plugged into the timer will do what you want without a circuit board or soldering.

    ak
     
  9. GopherT

    AAC Fanatic!

    Nov 23, 2012
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    - and, boy, are his arms tired.
     
  10. Mike Robling

    Thread Starter New Member

    Jun 20, 2016
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    @Tonyr1084 I found while reading threw info on other systems some employ a self cleaning function. 2hrs is the usual time for most manufacturers. The plates are housed in a clear container so I can see the bubbles being created during electrolysis and when I flip the switch the mineral deposits flake away and the bubbles never stop. The generator is before the sand filter so it traps the deposits or gets vaccumed up.

    The circuit I added for the pool has a outdoor 10a mechanical timer and a gfci outlet. The system runs for 4 hours a day.
     
  11. Mike Robling

    Thread Starter New Member

    Jun 20, 2016
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    Results from new DMM
    9.2vdc
    1.55a

    Well I passed out last night thinking. "Timer and a relay???" Lol
    I was going to ask how to wire a timer and a relay, lol. Took a few moments this morning but I got it. Hahahhaha now it seems obvious I'll pick up a relay today and get this thing going.
     
  12. jpanhalt

    AAC Fanatic!

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    There are two types of timers. One simply closes a pair of contacts. Probably the more common type provides 110 VAC at the set interval and is used to turn lights, coffee makers, etc. on when needed. If you get that type, be sure to get a relay with a 110 VAC coil. That is the route I would go, assuming you have 110 VAC available where you want the relay to be. The contacts need to be rated at your DC voltage, which should be pretty easy to find.

    John
     
  13. Tonyr1084

    Active Member

    Sep 24, 2015
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    OK, understood. Four hours a day running. How often (hours, days) do you want to reverse the current? IF you want four hours running and then two hours cleaning - a cheap timer such as the one I linked to (the timer with the settable slides) should do just fine. It sounds like your system is already on a timer.

    Without knowing HOW your system achieves its control of the power it would be difficult to come up with a good solution. For now I'm assuming your system is powered from an internal timer. It switches on for four hours each day then shuts down. So that's suggesting to me that somehow you have to re-energize the system for the cleaning process. Perhaps someone here might know of a hack to change the time period your system runs - like set it to run 6 hours a day with the first or last two hours spent self cleaning. OR maybe you have control over the time period it runs and at what hours it runs. Otherwise we're going to be re-engineering your system.

    What becomes of the gasses the system generates? Do you know what the gasses are? I'm thinking (just a guess) that you're producing HHO - that's two individual hydrogen molecules along with one oxygen molecule. Such a combination of free hydrogen and oxygen can be very explosive. Back when I saw people claiming 125% increase in gas mileage using an HHO system on their car I experimented with a couple designs of HHO generators. I quickly discovered just how energetic a very small amount of HHO gas can be. Estimating that a half ounce (volume) of HHO could have an ear-ringing pop to it. Twice that much can smart (to the ear). Any more than that and you're approaching hazardous to outright dangerous releases of energy.

    I mention this because messing with a system that has probably already taken into account such production of gasses could present a physical danger to anyone who seeks to change up the operation of such a device. In other words - BE CAREFUL. All such switching circuitry should be in a somewhat sealed box. Placed where gasses generated from the system would not likely enter.

    What literature is available for your system? Perhaps we could find a solution that may be safer than adding a relay (with contacts that can cause a spark). Just want to be sure we don't blow you up.
     
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