Hydraulic Solenoid Circuit Help: Pushbutton Engagement

Discussion in 'The Projects Forum' started by krp8128, Mar 27, 2012.

  1. krp8128

    Thread Starter New Member

    Mar 27, 2012
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    New here, and looking for a little help.

    O have a hydralic system with 2 solenoid (120v) valves to control forward/reverse movement. I want to be able to walk up to the system, push button 1 (and release) and have solenoid #1 engage.

    I have a separate control that sends in a DC signal at a certain point. At this point, a NO timer relay is triggered . When the NO timer relay closes, I want solenoid #1 to disengage and solenoid #2 to engage.

    Is this possible? I can provide a schematic for the solenoid cable wiring if that would help
     
  2. GetDeviceInfo

    Senior Member

    Jun 7, 2009
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    Define the rest of the states. When does #2 deactivate, or is it on until you push the button again, or the timer resets, or?

    Timers are typically defined as delay on, or delay off.

    Initially it sounds like a simple holding circuit with the timer toggling between solenoid 1 and 2. But I know you've got more to say.
     
  3. strantor

    AAC Fanatic!

    Oct 3, 2010
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    does this relay logic require explanation? Don't be afraid to speak up.


    [​IMG]
     
  4. krp8128

    Thread Starter New Member

    Mar 27, 2012
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    The DC signal triggers a delay on timer, which then activates solenoid #2. #2 can either be left on (my hydraulic pump simple bypasses the pressure @ max stroke), or I may have a 2nd DC output available to shut this down (I need to check the triggering device)
     
  5. krp8128

    Thread Starter New Member

    Mar 27, 2012
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    Yes, a little (never really read a ladder diagram before!)

    It looks like my timer is tied to CR1 (NC), which activates Sol 2 when fed an external signal (not shown?).

    I assume that when PB1 is closed, CR2 activates Sol1. When CR1 is switched, Sol1 is deactivated, and Sol 2 is activated.

    Did I read this correctly?


    I'm a MechE who scraped by in DC circuits, attempting AC logic control, so bear with me!
     
  6. krp8128

    Thread Starter New Member

    Mar 27, 2012
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    If I understand this correctly, I believe that McMaster item #6784T13 will serve as CR1 and CR2
     
  7. krp8128

    Thread Starter New Member

    Mar 27, 2012
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    Taking a second look at the cable that came with the solenoids:

    [​IMG]

    Does this help me in any way?
     
  8. shortbus

    AAC Fanatic!

    Sep 30, 2009
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    What you really need is called a "solenoid operated spool valve". This type valve allows a single valve to be used for both directions. Also instead of four hydraulic lines it only uses three. One line for each cylinder direction and one for the return.
     
  9. krp8128

    Thread Starter New Member

    Mar 27, 2012
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    shortbus likes this.
  10. strantor

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    The timer is tied to the coil of CR1. the rest of the sentence is correct. External signal is not shown because I didn't know any details of it - All I know is that it has a NO contact and that's enough info for me.

    Yeah pretty much - you press PB1 and (as long as CR1 isn't activated) SOL1 engages, along with CR2, which serves as a latch to keep SOL1 activated after you take your hand off the button. SOL1 will remain activated until your timer trips & activates CR1, at which time CR2 will reset & SOL1 will deactivate.


    No, that's a latching relay, not what you need. all you *really* need is a general purpose DPDT relay for CR1 and a general purpose SPST relay for CR2. I however swear by these 4PDT general purpose "Ice Cube" relays (don't forget about the mounting bases) for both, or anything - They leave unused contacts, which leaves room or expansion later or if you burn up a contact you can simply move the wires over to a new one. The price difference is negligible, (actually they are much cheaper than the ones you found) so I keep tons of them laying around but not DPDTs & SPDTs.
     
  11. strantor

    AAC Fanatic!

    Oct 3, 2010
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    I'm slightly puzzled by this question. In what way would that help you? I don't see why you "need help" - You seem pretty much set as far as I can see....
     
  12. krp8128

    Thread Starter New Member

    Mar 27, 2012
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    Strantor,

    I guess I don't "need" help, just takes me some time to work through designs like this, as electronics is not my strong point. Learn something new everyday though! I thought for a second that the solenoid cable might have the switching built in.

    After I posted about the latching relay i re-read the description and it seemed wrong. I actually did purchase 2 1358T731 relays, I suppose I should have just gone with the 4PDT. will this work?

    I could revisit this tomorrow, I know I paid a bit more ordering from McMaster, but we get priority overnight shipping. My hydraulics and motor showed up a week ahead of time, so my design time for the controls has been accelerated.
     
  13. strantor

    AAC Fanatic!

    Oct 3, 2010
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    oh, I see. no, for all intents & purposes, consider those 2 graphics to be "coils" just like a relay. They share a common & have individual signal wires, so 3 total, not including whatever earth ground might be included.

    nope, those are still latching relays. they have 2 coils...
    From mcmaster page:
    That's going to really complicate things. Trying to turn all these steady signals into pulses is more trouble than it's worth. If you have a Fry's electronics near you can can pick up 4PDT or DPDT or SPDT general purpose nonlatching relays, any of those we can make it work, but not the latching ones. If no frys, you can get them for sure from grainger, or any local electrical supply house hotshotted same day if time is of the essence, or just go pick them up.

    I also like mcmaster. If they don't have it, it probably doesn't exist.
     
  14. krp8128

    Thread Starter New Member

    Mar 27, 2012
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    I guess I am missing something, why don't I want a latching relay? Would it work, but just overcomplicated the circuit?

    Enough from me tonight, I'll have the enclosure, fuses, switches, wire etc. and apparently the wrong relays on hand tomorrow. My brain is cooked from the day I had today, after all this is just a side project @ work.
     
  15. strantor

    AAC Fanatic!

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    Ok, your latching relays have 2 coils, meaning it needs 2 seperate signals to latch & unlatch. It also is only rated for intermittent duty, meaning that the signals you send to each of the 2 coils can only be momentary; you cannot leave voltage on the coil for any considerable length of time.

    So, for a regular relay, where you only need the presence or absence of one 120VAC signal, now you need 2 pulsed 120VAC signals. The complication caused by using latching relays is exponential, as creating a pulsed signal requires a oneshot, and creating the inverted signal to unlatch the relay also requires a oneshot, plus a general purpose relay.

    Just to humor you, I've created a new drawing. If you were absolutely determined to use those latching relays, your circuit would look like below. You would need 4 of these 115$ one-shot relays, plus 2 general purpose relays (which is all you need to buy to begin with)

    [​IMG]

    As you can see, it's completely bonkers. I just drew it to put things in perspective. You are going to have to suck it up and go buy the relays.
     
  16. krp8128

    Thread Starter New Member

    Mar 27, 2012
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    Not absolutely determined, just thought that was what i was looking for. After talking with a few other people, I keyed in on "latching" and "relay" along with the general concept of what I wanted to do.

    I still need to source the timed relay to properly set up my test fixture, so while I am doing so I will pick up the 4PDT relay and base.

    Thanks again
     
    Last edited: Mar 28, 2012
  17. strantor

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    Alright, well come back afterwards. I've got some time invested on this thread so I sort of feel like I'm involved in the project. I would like to know how it turns out.
    thanks
     
  18. krp8128

    Thread Starter New Member

    Mar 27, 2012
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    Do I need any sort of diode to safeguard the circuit when the relay opens, or would that only apply in DC?
     
  19. strantor

    AAC Fanatic!

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    yes that's only in DC circuits. Don't put a diode. You can put a quencharc (AKA arc suppressor AKA snubber) across the relay contacts to prolong the life of the relays.
     
  20. krp8128

    Thread Starter New Member

    Mar 27, 2012
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    Strantor,

    I hope to have this circuit running tomorrow at work. Still a little stuck on the 4PDT relay though, could you play connect the dots?

    [​IMG]

    This is the 4PDT relay you linked earlier. Note that my E-stop circuit is incomplete, this will be wired to kill power to the motor.
     
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