help with a switch

Discussion in 'The Projects Forum' started by chasle, Oct 10, 2013.

  1. chasle

    Thread Starter New Member

    Oct 10, 2013
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    Hello everyone i am new and need help,i am working on a project right now building a hydro electric generator, i have water running through my property but id like to conserve water as much as possible and the only way for me to do that is with a inline electric valve that runs off of 12v, the only problem im having is that i cant find a switch or whatever i need to have the valve open when my batteries get low amd close when they are full. If anyone has a schematic and parts list or where i can find a switch like this please let me know.
     
  2. chasle

    Thread Starter New Member

    Oct 10, 2013
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    If anyone can please help me i need to find or make a switch for a 12v valve that needs to open and close at certain times. I want it to connect to 12v batteries but only open when the batterries get low to 12v and close when the batterries are fully charged at 12.5v if possible. Can anyone figure out how to do this and draw me a schematic and parts list and how everything works woild be very helpful. Thanx
     
  3. Wendy

    Moderator

    Mar 24, 2008
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    The Completed Projects Forum is for Completed Projects only. It is meant to allow members to show plans for projects they built so other members can duplicate them if desired. New threads are also automatically moderated per Moderator review for this reason. Your thread does not belong in this forum, and was moved here.
     
  4. MaxHeadRoom

    Expert

    Jul 18, 2013
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    I don't quite get what opening/closing the valve has to do with the batteries getting flat, I must be missing something?
    You mention opening and closing at certain times and then throw in when batteries are flat?
    Max.
     
  5. crutschow

    Expert

    Mar 14, 2008
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    I think the OP is charging the battery so he wants to shut off the value when the battery is charged.

    Sounds like a comparator with hysteresis would work such as here. The comparator could be an LM339.
     
  6. #12

    Expert

    Nov 30, 2010
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  7. tubeguy

    Well-Known Member

    Nov 3, 2012
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    That certainly qualifies for "You can't make this stuff up".
     
  8. #12

    Expert

    Nov 30, 2010
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    I predict increased sales of rain coats, umbrellas, and waterproof hats in Oregon so individuals can avoid being arrested for stealing rain to cool themselves. If the rain belongs to the government, ALL the rain belongs to the government.
     
  9. chasle

    Thread Starter New Member

    Oct 10, 2013
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    This is for a hydro electric project im working on. To conserve water mostly in summer im using a 12v 1" silenoid valve. The hard part is when i want it to come on, id like it to be able to open the valve at 12v and stay open till the battery is full at 12.5 or 12.8 volts whatever is a fully charged battery. Thats where the switch comes in so that when it hits 12v its supplying enough power to open the valve which allows water flow, spins a turbine at high preasure turning an alternator charging the batteries, and cycling through the process automatically hands free system. Thanks for any info u can give me.
     
  10. MaxHeadRoom

    Expert

    Jul 18, 2013
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    As previously suggested, a simple comparator set to turn it on over 12v.
    The trick would be to use a couple of zeners also as your power supply for your circuit is also going to be varying from below to above the 12v.
    One zener on the supply rail and another on the sense input.
    A LM311 is a single comp. with 50ma output.
    Max.
     
  11. crutschow

    Expert

    Mar 14, 2008
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    Instead of a couple zeners it might be better to use a voltage reference IC for the comparator reference input voltage. That would be more stable than a standard zener diode and give a stable comparator trip point, basically independent of supply voltage and temperature. With that you don't need a zener on the supply voltage, since the comparator supply voltage has little effect on the comparator operation (as long as the voltage is withing the comparator operating limits).
     
  12. Sensacell

    Well-Known Member

    Jun 19, 2012
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    Use a motor driven ball valve that consumes no power unless it's cycling- solenoid valves eat a lot of power while engaged- especially large ones!
     
  13. Alec_t

    AAC Fanatic!

    Sep 17, 2013
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    Here's a suggested circuit, using a comparator with hysteresis as suggested above. Vtrim sets the 'fully-charged' voltage trip point and Htrim sets the hysteresis amount. The valve is modelled here as a 12 Ohm resistor for simplicity.
     
  14. MaxHeadRoom

    Expert

    Jul 18, 2013
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    The thing that is unknown is when and how the charging is going to take place, if only the batteries are connected during normal use, then the 12v rail is going to drop, the idea of zeners is to register and stabilize the power supply until it drops down to the minimum range, also the reference input of the comparator could have a zener reference. This would make sure the any comparison only occurred at above 12vdc.
    I have used a similar approach on to regulate a 240vdc generator field that builds from 0 to 240vdc.
    It would be needed to know at what time is the charging introduced or just a battery change out?
    Max.
     
  15. cornishlad

    Member

    Jul 31, 2013
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    The long term success of the project relies on the quality of the battery charging circuits which cant properly be done by voltage sensing alone. An "intelligent" battery charger circuit will be needed such as that in an automobile alternator..

    Is the hydro power to be considered the prime source, ie will it be engaged automatically when a load is applied - rather than waiting for the battery voltage to fall to some predetermined level. This would be more electrically efficient.

    In both cases current sensing may be a better way to operate the switching relay. ie.An outgoing current operates the switch. FALL in charging current to float charge level de-activates the switch.
     
    Last edited: Oct 22, 2013
  16. chasle

    Thread Starter New Member

    Oct 10, 2013
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    Yes the charging will be done with a car alternator, the one i have is a delco remy 1 wire self exciting aternator, it also has a built in regulator so no overcharge will happen. And yes hydro power is the main drive of the alternator. Ive been looking at voltage controlled switches which might be the way i need to go cause i have little experience building circuits and little knowledge of the coponents.
     
  17. chasle

    Thread Starter New Member

    Oct 10, 2013
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    Can i use the alternator as the switch i need to activate the valve since the alternator has a voltage sensor in it for charging?
     
  18. cornishlad

    Member

    Jul 31, 2013
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    I had to google 1 wire alternators as I'd never heard of them.
    http://www.madelectrical.com/electricaltech/onewire-threewire2.shtml
    Interesting ! Wonder if it's an oldie that you've rescued from somewhere?
    Like modern 3 wire alternators the one shown charges at 14.2 volts. My Merc ambulance/camper charges at 14.4v. In a vehicle, while the engine is running, all systems take power only from the alternator, up to it's rated output current.
    The only reliable way to use battery voltage as a guide to its state of charge is to measure it when it's been idle for an hour - especially when charging is first disconnected when over 13v may show for a while. figures derived from the net state: 12v or less = dead flat battery- should never be allowed to reah this state.
    12.1v = 25% charge,
    12.2v = 50% charged - for long battery life charging should always begin here.
    12.4v = 75% charged
    and 12.6v 100% charged.

    All these figures vary a bit depending on the battery type. ie flooded, Gel, AGM - and battery temperature

    An alternator will need to be turned at speed to produce the required output. I don't know the speed but guessing that a vehicle fast idle might be 1000rpm and the belt gearing perhaps 3:1. You will need to find that out and arrange your hydro drive accordingly.

    Next thing to tell is how will this system be used. If for example it is a battery back up for emergency lighting and will only be used occasionally. If so monitoring the battery voltage while offload and offcharge should be ok . But I would have thought that would be better done by simply putting your battery permanently on a 3 stage mains charger that would float charge it when fully charged. Or is not mains available ? tell us more about the use of the battery power..
     
  19. chasle

    Thread Starter New Member

    Oct 10, 2013
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    I beleive my 90 jeep cherokee has the same alternator, i salvaged this one from a wreckingyard, the cool thing about this alternator if i have my info right is that it will charge at any speed but first needs an inital 500 rpm to get it going, after its going and activates its charge, it will charge at any speed, i am working on the gearing of the hydro generator to be able to go faster than that hopefully, none of this is built yet im still designing and gathering parts and peices for it, the main goal of this project is for off the grid power, i live in a 5th wheel and the whole thing runs off a 30 amp fuse but ive been living with 20 lately, i dont have the batteries for this project yet gonna take some time for me to gather enough money to buy atleast 4 deep cycle batteries, if u have any suggestions on what type of battery i should use for this please let me know. I beleive my alternator is a delco remy cs130 or a cs121 but im not sure its very similar if not. I have a circuit diagram of the alternator but i dont know how to post pics on here but heres a link to to it. http://alternatorparts.com/cs130_sbpage1.htm
    Once u get to the page it has 6 other pages to look through that are located in the middle of the page u should be able to find the diagram in there.
     
  20. cornishlad

    Member

    Jul 31, 2013
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    I realise this is not helping much with the 12v switch question but the answer does depend on how the system is to used.

    You are currently using a max of 2.4Kw ? Are you hoping to meet that demand with your scheme ?
    At battery voltages that would require about 190 amps. Your alternator on provides 70 amps according to your link. Batteries would need to provide the rest. Battery sizing would depend on how long that demand might last.

    I suspect all your higher power appliances would be best kept on the mains particularly if they are 120v ac devices. Inverters present a whole lot of other issues.
    If you want 12v hydro power whenever a load is applied that should be simple to arrange. Up to 900 watts (ie within the alternator capability) then the alternator should handle the load and nothing from the battery. with current sensing it could be arranged that a very small load, such as led lighting would not trigger the hydro as even a single 120Ah battery would last for many hours.
    The alternator you linked to in you last post looks a lot smarter than the 1 wire example I found.
    I must have too much time on my hands this morning. I'm imagining your park plot there in Oregon with a FREE piped feed of high pressure water available that surely will run to waste on exiting the turbine or whatever ?? really.
     
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