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Need help with a 12v solenoid

  1. Apr 2, 2015 #1
    I'm not so smart when it comes to electrical things, so please forgive my ignorance.

    Here's what I am trying to do. I have a quad axle dump truck, I'm trying to have the drop axles automatically come up when put into reverse. The drops are raised and lowered via 2, 12 volt solenoid valves. I currently have the solenoids 'powered' to lift them and when they are lowered, the current is removed via 2 toggle switches in the cab of the truck. I ran a wire from the back up beeper to one of the solenoids and it now activates the solenoid and lifts the axle when the truck is shifted into reverse, but when I power the solenoid in the cab to raise the drop axles when empty, the back up beeper is being powered and always is beeping.

    I am thinking I need some sort of diode with one lead in and two out, so no power goes to the back up beeper, so I can run one to each solenoid lift valve, but not sure. What do i need to fix this problem? Thanks in advance.
     
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  3. Apr 2, 2015 #2

    sophiecentaur

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    The two solenoids will keep needing current whilst they are activated (obviously) so is it a good idea to use them for a long time? Isn't the purpose of the beeper to tell you that they are lifted (and using current)? I don't understand why you would want to turn the beeper off unless the solenoids are de-activated.
    If I am talking rubbish then I haven't understood the question (haha - nothing unusual there , then). If the problem is just about the beeper going when the lift is down then show us a diagram of the circuit you're using and we may be able to spot something; there's no reason why a beeper should keep going if a solenoid (in parallel with it) is not activated.
     
  4. Apr 2, 2015 #3
    Lol, your good. Perhaps I didn't explain it well. The beeper is just a safety device, to let anyone on the ground know that the truck is backing up and it can only beep when backing up. The beeper is activated via the reverse safety switch located on the transmission, when the truck is shifted into reverse. This same type of switch turns on the back up lights on cars and pickups.

    What i need is to stop the 'backup beeper' from beeping when the 2, 12 volt solenoids are activated.

    Yes the 2, 12 volt solenoids are always activated when the axles are up, which is the majority of the time.
     
    Last edited: Apr 2, 2015
  5. Apr 2, 2015 #4

    sophiecentaur

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    OK. Why don't you just use another beeper (with a different sound) that's just there to tell you when the solenoids are activated? If you don't want it going for ages, you could have a short timer on the bleeper and have an indicator lamp that's on all the time the solenoids are powered. :smile:
    It may be an idea to put an extra (low current) fuse in series with the lamp / beeper to protect the thin wires to them - assuming the solenoid is fused for lots of Amps - which could melt any thin wire.
     
  6. Apr 2, 2015 #5
    I don't need to know when they are activated. I already know this when we lift them or they wouldn't lift. What i am needing is the backup safety beeper to not be powered when I power the 2, 12 volt solenoids to lift them.
     
  7. Apr 2, 2015 #6

    Svein

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    Yes - you connected it that way. Sit down and create a truth table with inputs "backup beeper power" and "solenoid power"; outputs "backup beeper sound" and "raise drop axles". That will give you the start of a solution.
     
  8. Apr 2, 2015 #7
    It has to be connected that way, but what I need is a way to stop the back bleed of power from the 2, 12 volt solenoid to the back up beeper.
     
  9. Apr 2, 2015 #8
    circuit.PNG
    This should do it. Just make sure you install the diode the correct way around.


    Oh and please disregard the battery symbol at the top. That should just be two +12V fuse taps and not a battery with + and - I didn’t see that when I grabbed the symbol and dragged it into the schematic. I guess I need glasses.
     
    Last edited: Apr 2, 2015
  10. Apr 2, 2015 #9

    sophiecentaur

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    Right. So your solenoids can be operated either directly by a switch or as a consequence of selecting reverse - i.e by two independent switches.
    All you need is for a diode in the connection between the vehicle electrics and the solenoids, letting current flow through the solenoid when the reversing beeper etc are activated but blocking current from the 'extra' switch to the beeper circuit so that only the solenoid is activated by your switch. You need the 'arrow' on the diode to point towards the solenoid in the circuit. If that verbal description is not enough then I'll need to draw a diagram but it's pretty simple.

    I see that the last post contains what I meant to get across!!
     
  11. Apr 2, 2015 #10
    Yes Tom, that is how it needs/is connected, thank you for the diagram! Now, what isolation diode would you recommend?
     
  12. Apr 2, 2015 #11
    Yap, I just need to know what type of diode to get. Thank you!
     
  13. Apr 2, 2015 #12

    sophiecentaur

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    Reverse breakdown is no problem for any rectifier diode you can find. (>12V) Forward current to drive a beeper and lamp(?) need only be a few Amps or so. Very easy requirements that many diodes will satisfy. No need to go chasing a specific device number. Anything in an eBay supplier's catalogue to suit.
     
  14. Apr 2, 2015 #13
    I looked, most seem to be something for a circuit board. I need something with coated wire leads, as this goes under the truck cab and will be exposed to the elements to a certain degree. I'll use heat shrink butt connectors to connect. Thank you.
     
  15. Apr 3, 2015 #14
    The diode will also need to handle the solenoid current. Nothing special a run-of-the-mill generic blocking diode with enough current rating to handle the solenoid current. This ebay page has a big selection of them. You just need to know what current the solenoids draw. Check the size of the fuse in the solenoid circuit and get a diode with the same rating or a bit higher so the fuse will blow before the diode pops.
     
  16. Apr 3, 2015 #15
    I just looked again and to me they looked like they are all soldering types for a circuit board. Of the few that might work, are 3 phase. Thank you.
     
  17. Apr 3, 2015 #16
    You can solder leads on to it and heat shrink the whole thing can't you? I've done it before.
     
  18. Apr 3, 2015 #17
    I suppose so, but then I would need to make some sort of enclosure to keep it isolated. I was hoping to be able to use one that was enclosed already that had plugs on it or wire leads.
     
  19. Apr 3, 2015 #18
    Put some long leads on it, heat shrink over it and ty-rap it up inside the engine compartment where it will be safe and dry. You ought to see what my old car looks like!
     
  20. Apr 3, 2015 #19

    jim hardy

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    Do you know the resistance of that solenoid? How much current it draws ? Same for the beeper?

    When you turn off the solenoid its inductive "kick" will try to pull current through the diode and beeper.
    If solenoid's current is much more than beeper expects, it may wreck Mr Beeper.
    A diode across Mr Solenoid would be a good idea.


    If solenoid current is an amp or less, ie Rsolenoid >12 ohms, the 1N4000 series 1 amp diodes are cheap and available most everywhere.

    I can't imagine solenoid requiring more than 5 amps, at that current it'd get really hot. Look for 6 amp rectifiers in a blister pack at electronics shop. Or pillage from a dead PC power supply.
     
  21. Apr 3, 2015 #20

    jim hardy

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    @sedgehammer get one of these, 10A 50V are real cheap.
    70548.jpg
    In TomK's post #8, use it in place of the diode...
    tie the two AC terminals together and run to beeper
    run the + terminal to junction of solenoid-toggle swtch
    tie - terminal to vehicle's ground.
    That'll do both jobs, steering current and suppressing inductive kick.
    And it's easy to mount where you can see it.
     
  22. Apr 3, 2015 #21
    Yes, that looks like I was looking for. Where can I buy it? Thank you!
     
  23. Apr 3, 2015 #22

    jim hardy

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    They're all over Amazon.
    https://www.amazon.com/BRIDGE-RECTIFIER-SINGLE-PHASE-PROFILE/dp/B007Z7LXVQ
    but i dont like that you cant order from Amazon by phone

    Radio Shack has them in blister packs , if you can find a Radio Shack still open
    Lawnmower repair shop might have them

    plenty of mail order electronic shops
    http://www.mpja.com/Bridge-Rectifiers/products/171/
    the lady who answers phone there has always been quite pleasant to me,

    digikey, parts express,,,, search on hobby electronic suppliers

    Get some push on terminals and heatshrink while you're at it, to spread out that shipping cost
    be aware they come in different widths, 1/4 inch most common
    http://www.mpja.com/Quick-Connect-Terminal-Female-Blue-for-14-16AWG-250in-25Pcs/productinfo/18824 TM
    18824.jpg

    same as this bridge
    http://www.mpja.com/25A-100V-Bridge-Rectifier-IR-26MB10A/productinfo/30339 BR/
    you don't need much voltage, 100 is plenty
    30339.jpg
    Harbor Freight's heat gun is on sale right now for under ten bucks,
     
    Last edited by a moderator: May 7, 2017
  24. Apr 5, 2015 #23
    A thought I had would be to add a 12 VDC DPDT relay and wire the beeper N/C. Then power the coil with the same power as the solenoid to raise the drop axles.
     
  25. Apr 23, 2016 #24
    I'm a little too lazy to read through these posts but if all the wiring is there for these devices then it should be easy. The beepers for reverse probably can't handle the amps if you're trying to split power to two solenoids and the beeper.

    Just find the where the power goes to the solenoid under the hood after the fusebox and after other switches and relays in the ciruit (check with ohm meter) and solder an extra wire to it if it's not too big a wire. Now put an inline fuse in there. After (before if you want to be technical) the fuse put a relay in and put the other side to power. Make the relay activate from the reverse wire under the hood or dash or reverse light or reverse beeper or transmission.

    Edit: well it looks like some people answered you. I hope the circuit conected to the beeper is just to power a relay or switch for the solenoids rather than the actual solenoids. But if the fuse hasn't blown yet then you can probably get away with it.
     
    Last edited: Apr 23, 2016
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