Hydraulic Solenoid Circuit Help: Pushbutton Engagement

Thread Starter

krp8128

Joined Mar 27, 2012
27
Catch me up on this cycle/cycle stop development. I'm not aware of these. Is this part of the timer circuit? I'm not privy to the knowledge of what the timer's function is. Anyway, I've gone ahead and edited the drawing to what I think should work. Edits in red.


P.S. if your timer is latched and you press stop, it will stop as long as you hold the button in, but when you release the button it will resume operating. You will need to press E-stop. I need more details about the timer (what it's for, how long it's time is, what latches it, etc) to work around this.
Right now I have 3 buttons wired, we previously had them labeled as "E-Stop", "Load" and "Unload". I have re-named the Load momentary switch as "Cycle".

Pressing "Cycle" currently latches the relays and activated sol1 which loads my apparatus. Once a certain load is reached, the timer kicks in and 30-seconds later triggers Sol2. I need to add a "Stop" to this to shut down sol2 and limit needless travel (this distance varies, or I would use a prox switch). Using "E-stop" to stop the motion is a pain and not appropriate as it is not an emergency situation. I could make "stop" a maintained switch, but would rather have it a momentary....

During setup operations the QC tech has requested the ability to jog the cylinder through the use of Sol1 and Sol2 in order to adjust position.
 

strantor

Joined Oct 3, 2010
6,782
Once a certain load is reached, the timer kicks in and 30-seconds later triggers Sol2. I need to add a "Stop" to this to shut down sol2
I need to know what is responsible for this timer, so I can tell you how to stop it. I still have no idea. You obviously have something else in this circuit, I assume a load cell display with some kind of timing function & a relay output obviously. I need to know more about it, because your stop button is going to have to interface with it, and reset the timer or the load threshold or something. I can't do it just with the control circuit (unless you're OK with just using the E-stop button, in which case refer to post 40)
 

GetDeviceInfo

Joined Jun 7, 2009
2,192
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.
It's always best to define your circuit functions before building a circuit.
 

strantor

Joined Oct 3, 2010
6,782
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.
It's always best to define your circuit functions before building a circuit.
Ah, retrospect. Now I know why you've been silent for 40-something posts. You knew this was coming and were just watching it play out. That's the difference that experience makes.
 

Thread Starter

krp8128

Joined Mar 27, 2012
27
GetDeviceInfo is correct, defining the states ahead of time would have made this easier. In my defense, when I started this, our internal discussion was to replicate a manual directional control valve with a solenoid operated one, and add a timer. The scope of the circuit changed as it was built.

As of right now, I have a switch to cycle between "Jog" (gives non-latching activation of SOL1 and SOL2) and "Cycle" (gives Cycle run and Cycle stop options).

However, I am still stuck on the timer side. Assuming that nothing got fried* here is what I have available on my scale:


  • Open collector outputs
  • 24 VDC on terminals at startup (0 lbs)
  • terminals "go to ground" when setpoint (x lbs) is reached, and voltage is 0 VDC
I need a relay that:

  • when 24 vdc is present at the coils the contacts are open
  • when 24 vdc is lost, the timer counts 30 seconds and closes the contacts
  • I also need a way (switch, 2nd timer etc) to re-open the contacts, as this solenoid is latched at this point and it will drive my cylinder to full extent. I might be able to have a 2nd 24 vdc signal for this.

*While we were trying out some relay timer configurations, my co-worker (who had talked to the service tech for the unit) dropped a live 30V output and it shorted. The service tech said it should be fine, just hit reset. However, with the same wiring configuration as before my output now goes from 24 vdc --> 30 vdc when setpoint "x lbs" is reached (it went 24-->0 before). I have to call today to see if a setting has been reset.
 

GetDeviceInfo

Joined Jun 7, 2009
2,192
only because I'm curious;

What's the relationship between the hydraulics and the scale? Is the scale a platform wieght scale or a hydraulic pressure switch? Can you briefly describe the process and how you want to control it.
 

Thread Starter

krp8128

Joined Mar 27, 2012
27
The hydraulics and scale are 2 independent systems. The scale is a load cell/display unit.

I have the hydraulics setup that when engaged they load the system to X pounds. When the load cell reads X pounds, the 24 vdc output goes to ground (0v). At this point I need to trigger a timer, and after the predetermined time interval the opposite solenoid needs to be engaged. This solenoid now needs to be disengaged after a set period of time or via a manual momentary switch.
 

GetDeviceInfo

Joined Jun 7, 2009
2,192
The hydraulics and scale are 2 independent systems. The scale is a load cell/display unit.

I have the hydraulics setup that when engaged they load the system to X pounds. When the load cell reads X pounds, the 24 vdc output goes to ground (0v). At this point I need to trigger a timer, and after the predetermined time interval the opposite solenoid needs to be engaged. This solenoid now needs to be disengaged after a set period of time or via a manual momentary switch.
I'm guessing you have a hydraulic motor turning some feed device (some explaination would help). Do you continue feeding for 30 secs, beyond setpoint?, or do you stop at setpoint, wait 30 secs, then do something else, whatever that is. Getting information is kind of like squeezing juice from an orange, which isn't helping your cause.
 

Thread Starter

krp8128

Joined Mar 27, 2012
27
I'm guessing you have a hydraulic motor turning some feed device (some explaination would help). Do you continue feeding for 30 secs, beyond setpoint?, or do you stop at setpoint, wait 30 secs, then do something else, whatever that is. Getting information is kind of like squeezing juice from an orange, which isn't helping your cause.
The hydraulic motor is always running, force is controlled by a mechanical pressure limiter. When pressure hits the max. setting the system goes into bypass mode and dumps excess pressure back tot he tank.

There are 2 solenoid actuated valves to move the cylinder in and out.

I walk up and push my "cycle" button to to initiate the retract solenoid. This generates X force at the end of my cylinder, and the solenoid remains engaged. I remain at X pounds via the mechanical side of the system.

When the loadcell measures X force, a 24 VDC signal is sent to my timer. After time T, the timer closes its contacts, disengaging SOL1 and engaging SOL2.

I could not activate the 24VDC signal due to the load cell MFG supplying me with the incorrect wiring information. Now that I have the signal operating correctly, my only remaining task is to unlatch the relay controlling SOL2.

It looks like the best way for me to do this is to add a 2nd timer, by which i can control how long my cylinder is extending (unloading the system).

i.e. Setpoint X is reached, 24VDC activates Timer1, time passes and Timer 2 is activated, immediately running SOL2. After a 2nd time period, timer2 shuts down shutting down SOL2.

Think I missed anything?
 
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