Murphy Solenoid control

[veggie]

Ref: Simple solenoid shutdown for fuel rack lever

For those of us who are not proficient with microprocessor controls, can anyone recommend a simple way of energizing a Murphy solenoid switch that would be activated on the closure of temp switch contacts or a switch gauge.
My interest is in how to temporarily energize the pull-in windings for 3 seconds or so, then open the pull-in circuit and energize the hold-in windings.

veggie

[mobile_bob]

if the solenoid is adjusted properly, it will disconnect the pullin winding itself
leaving the run winding to hold it in

to adjust it otherwise invites a burnt out pull in winding

bob g

[BruceM]

I would want a time out on the rack closer solenoid; long enough for the engine to come to a complete stop.  Otherwise, if you are away, and an emergency occurs, it could run down your 12V battery.   For a 6/1 with decompression, this is about 60 seconds.  With compression and/or air shutoff, maybe 15 seconds?  

I looked at the Murphy push/pull 12V solenoid spec-  it draws 624 watt inrush- your control device needs to handle that- which is 52 amps at 12V.  This is beyond most of the timer (one shot) relays.  There are relay types for this function for $35 at alliedelec.com  But then you still have to do a driver/SS relay for the solenoid.

I would implement the timer via a cmos one shot or cmos 555 one shot circuit, and drive a 20V mosfet to handle the solenoid.  About $10 in parts.  I can help with this, but I don't know if this is within your skill set/electronics comfort zone.

Best Wishes,
Bruce M

[veggie]

Thanks for the tip gentlemen,

Jens, if I understand you correctly, you energize your solenoid to run the engine.
Any interruption in the solenoid circuit (a shutdown device that opens on activation) will disengage the solenoid and kill the engine?
I have an adjustable temp switch which opens on temp rise. Assuming it can handle the amp load, would a simple setup like the one in the attached picture make sense?
(I would have to confirm that my Murphy RP2309B soenoid pull-in winding is self de-energizing).

veggie

[veggie]

*** UPDATE ***

According to the attached spec sheet on Murphy 2300 series solenoids, I will need separate pull-in and hold-in circuits.

veggie

[veggie]

Jens, this diagram is more in line with your suggestion of using a solenoid.
All that would need to be added is a manual or automatic way of activating the pull-in winding for 3 seconds.?

veggie

[veggie]

BruceM,

I took a look at the cmos 555 you pointed out.
That puppy would require a circuit board. The term "some assembly required" comes to mind.
A bit outside my skill set.

thanks,
veggie

[mobile_bob]

if you are using electric start, such as a gm starter
simply attach the pullin winding to the relay terminal on the starter solenoid
it will be the one marked "I" or "R" and not "S"

it is only energized while the starter is engaged, this will keep the solenoid pullin
winding energized till the engine starts, and then both the fuel solenoid with its internal switch disconnects
and also the relay terminal on the starter solenoid disconnects, providing two levels of diconnect

setting up a latching relay would also be pretty easy, that way if the temp switch opens
the latch relay releases and then you have shut off all power to the system as well, that way you
don't drain the battery if it shuts down on overheat and you are not there to turn the key off.

the latch could be set with the start circuit as well, it would energize on cranking position and latch
after startup and stay latched until you temp switch opened

you could also daisy chain in a safety Estop cable around the rig, which would release the latch relay
should an animal or child get too close and trip the cable, or some other safety mechanism.
this type of cable Estop with latch is very common in and around mechanized equipment for protection
of workers that sometimes get into places of hazard or slip/fall into a machine.

it would be very simple to impliment using one or two of those iso automotive relays that are very common and
inexpensive.

bob g

ps be sure to use a "clamping" diode (aka flyback or freewheeling diode) across the fuel solenoid connections
the flyback is hard on relay contacts and can cause them to stick unexpectedly, some of the fuel solenoids incorporate
the diodes and some do not, can't hurt to add one in either case.

[BruceM]

I missed the boat on this Murphy actuator.  Jens has the right configuration for a generator setup.

I don't have a typical generator setup; my 6/1 often only runs an air compressor. My controller runs off of a small 12V battery and PV panel, and is designed to be low power.  Continuous holding current on a solenoid all the time the engine is running is not OK for my setup.  I forgot to "switch gears" mentally, to a conventional generator only setup before I commented.  Sorry, Veggie.

Jens-  is this the same actuator that you had some trouble with-  not fully closing the rack? Or is this what you replaced that one with?

[BruceM]

"Yes, it is the same actuator I had trouble with but the issue was slightly different - the actuator OPENs the rack and it does that fine. When the solenoid releases, the governor spring goes slack and the engine governor has to close the rack and that is the part that was giving problems."

This sounds like your Murphy actuator is holding the governor spring- which is not what any diagrams on this discussion have shown.  I'm familiar with the "release the spring for shut down" arrangement as I did some experiments with a brass wire holding the governor spring (fuse link) for emergency shut down over 3 years ago, and posted about it on LEF.  I thought it might be useful for guys wanting a simple emergency shut down method.   It did seem to work reliably, but the spring was totally released- which the Murphy rack unit doesn't have enough extension to do.

Do you have any pictures of this setup?

[veggie]

Veggie,  I think we need to start over with a better understanding of your system and what you are trying to accomplish.  Is your engine a 6/1 or   Is this for emergency shut down only (overtemp, low oil, etc?) or also for operational (remote?) shut down?  

Do you have a 12VDC battery available for control? Is it charged by the AC generator or an alternator?


We all bring our preconceptions to this sort of situation, but it's important that we address YOUR needs.

I just printed out the Murphy datasheet so I can study it. It has a fairly short throw (1"), with about 10 lbs of force, there are both push and pull units.  You originally suggested moving the rack closing lever.  I have doubts about that;  it has a lot of friction due to the cam-like arrangement, and I think it will take too much force if the total throw of actuator is only 1".  (Very short lever arm.) You can check this with a fish scale and string.

Hi BruceM

To clarify:

- Yes, the engine is a 6/1

- The main reason for the solenoid is a high temp shutdown.

- If it could be incorporated into a starting procedure to open the rack during starting,  that would be nice too.( Eg: Flip the fuel rack switch on the gauge panel to energize the system just before I engage the air starter.)

- A 12 volt battery with charger is available. Later plans are for an automotive alternator. Near term, it could be a charger plugged into the 120 outlet of the ST5 head.

- I agree regarding the rack lever. I would like to rig the solenoid to act directly on the rack plunger (as shown in my revision 2 drawing above). I can rig up some opposing spring linkage to assist with closing of the rack when the solenoid is de-energized (if necessary).

Thanks BruceM,

veggie

[BruceM]

Wow, 20 lbs of force for the Syncro Start model is impressive, and the 1.5" throw is handy, too. 

The extra linkage for the twin and two IPs would be a challenge, perhaps the extra linkage drag is what keeps the rack(s) from fully closing. 

I wonder if Veggie just needs emergency shut down if the brass wire fuse link wouldn't do the trick.  It doesn't get an simpler or cheaper.  I made a plastic block holder with clamping screws for the wire. A piece of wire insulation covers the wire where the spring contacts it.  The only minor annoyance is that the engine speed has to be re-adjusted after an emergency shut down, as it's hard to get the wire position exactly right.

Alternately, a small solenoid could be used as a "latch pin" to release the governor spring. A "one shot" type timer relay could be used to drive it.

[potter]

I would put my overheat sensor on the engine  not on the coolant line in case of coolant loss.

  Potter

[BruceM]

Thanks for the photo, Jens.   I hope you can get the rare non-stop solved.  It must be related to the dual linkages and IPs, a tricky mechanical situation to sort out.  It's hell to debug an intermittent problem!