Hydraulic Solenoid Circuit Help: Pushbutton Engagement

Thread Starter

krp8128

Joined Mar 27, 2012
27
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
 

GetDeviceInfo

Joined Jun 7, 2009
2,192
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
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.
 

strantor

Joined Oct 3, 2010
6,782
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

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


 

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Thread Starter

krp8128

Joined Mar 27, 2012
27
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.
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)
 

Thread Starter

krp8128

Joined Mar 27, 2012
27
does this relay logic require explanation? Don't be afraid to speak up.



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!
 

shortbus

Joined Sep 30, 2009
10,045
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.
 

strantor

Joined Oct 3, 2010
6,782
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?).
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.

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?
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.


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

strantor

Joined Oct 3, 2010
6,782
Taking a second look at the cable that came with the solenoids:



Does this help me in any way?
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....
 

Thread Starter

krp8128

Joined Mar 27, 2012
27
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.
 

strantor

Joined Oct 3, 2010
6,782
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.
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.

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? ]
nope, those are still latching relays. they have 2 coils...
From mcmaster page:
they don't require a constant control voltage to stay switched. Also known as latching relays, a momentary signal to one coil transfers and sets the latch; a momentary signal to the other coil releases it. For intermittent use only.
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 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.
I also like mcmaster. If they don't have it, it probably doesn't exist.
 

Thread Starter

krp8128

Joined Mar 27, 2012
27
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.
 

strantor

Joined Oct 3, 2010
6,782
I guess I am missing something, why don't I want a latching relay? Would it work, but just overcomplicated the circuit?
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)



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.
 

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Thread Starter

krp8128

Joined Mar 27, 2012
27
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:

strantor

Joined Oct 3, 2010
6,782
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
 

strantor

Joined Oct 3, 2010
6,782
Do I need any sort of diode to safeguard the circuit when the relay opens, or would that only apply in DC?
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.
 

Thread Starter

krp8128

Joined Mar 27, 2012
27
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?



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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