rpm limit

[vegoil]

Has anyone fitted a rpm cut out to a lister CS start o matic to stop a over revving.

[BruceM]

I have rpm monitoring on my CS, for both over and under speed, with closing of the injection pump rack and lifting of the exhaust valve.  Rpm is sensed by a Cherry magnet/hall effect sensor near the spokes, rack and lifter via air cylinders, control via Picaxe 40X2 and hand wired board with logic level MOSFETs for air solenoid valve control.  Over temperature, oil high/low, and excessive vibration also cause an emergency shut down.

The same can be done today with almost no custom hardware via Arduino plus available interface boards.

The commercial engine rpm limit detectors I can find aren't suited for the CS due to it's low speed.  A Picaxe 08M IC (8 pin dip) could do it easily with a few lines of Basic.  Let me know if you need help.

Best Wishes,
Bruce

[vegoil]

thanks for the reply, your way over my head.  I was looking for a simple fix. I have been looking for something that brakes the circuit to the exhaust lifter solenoid and shuts the engine down if she goes over 850 RPM. its a old type lister 8-1 start o matic

regards

John

[BruceM]

If the voltage regulation on the genset is not too good, and AC (or DC) voltage rises when you overspeed, you might use a standard AC voltage sensing relay to trip your SOM solenoid circuit.  Watch AC (Or DC ) voltage while you force an overspeed.  I can probably find one that will work.  Are you generating 230V/50Hz or other?

There are some engine overspeed (tachometer) products, but they are not adjustable down to 650 rpm.

[vegoil]

is this the cut out you are thinking about I have already had a look at them but because they use a currant they might start the engine and keep it on.

[38ac]

thanks for the reply, your way over my head. 

regards

John

Don't feel alone! When Bruce talks engine and power management I get lost right after he says hello! I can only wish that I had his electrical knowledge!

There are tachometers that work from the injector line pulses. I used to own one .  Maybe you could integrate one with a control to pull the rack? But that's in Bruce's territory for sure.

[veggie]

Usually if the engine overspeeds, then the voltage goes up as well. (Depending on the generator head you are using)
Perhaps check for a voltage sensing relay (Ebay ??)

EG: If the voltage on a 240VAC generator raises to =>250 VAC, then trip the relay which energizes a kill solenoid on the fuel rack.

Just a thought

[vegoil]

Hello Bruce,

I am not sure what part of the world you stay but there must be a time difference between us I am in the far north of the UK.

I am generating 220Volt 50 hz it is a old type BKB start o matic
 
Do you think that the photos I sent of the voltage cut out will work on the AC 220volt
I could get one for the 24 volt charging side and set it to trip at 28 volt (that's a guesstimate). you could please advise on the upper voltage trip setting.

the reason that I believe that the 220 volt side wont work as well is because I have one of that device that plugs into a socket then you plug in a load IE: light or heater into it. it has a screen that reads the voltage, amps, hertz . when the unit is plugged in on its own the engine dose not start. then the heater is switched on the engine starts when the heater is switched off but still plugged into the device the engine still runs until the device is switched off. if this makes sense. I only use this plug to test check the volts amps hertz

I am unable to run the engine over rev at the moment because when she over reved she brunt out the charging resistor. I have sent for 0.8mm wire to rewind the resistor.

Regards

John

[BruceM]

Very helpful info, John.  I'm surprised that the minimal power of a voltage and power monitoring circuit would keep the SOM running once the larger load is removed.  Yes, sensing on the 24V side might be a good solution to avoid messing with the SOM start circuit.  There are DC voltage controlled relays which could then do the job. 

If you can connect on the DC generator side so that the relay is only powered when the generator is running that would avoid a load on your batteries.  (Upstream of a diode between DC generator and battery would do this.)  I'm not familiar with the SOM 24V charger circuitry so if you have a schematic/wiring diagram I can look at, that would be helpful.  Ideally we'd like 24VDC to power your overspeed sensing that is only present when the engine is running.

You'll have to test and monitor via VOM to see if DC sensing will reliably detect engine overspeed, once you've repaired your charge current limiting resistor.

If a rise in DC volts with overspeed doesn't look viable in testing, then we might look for an AC over frequency sensing relay powered by 24VDC to avoid the SOM start circuit troubles.  Frequency sensing relays are quite pricey, so I'd look at voltage sensing first. 

AC frequency sensing via Arduino is readily available, and the Arduino 5V could be powered from the 24V side, but hopefully we can avoid that approach.

I'm in central eastern Arizona, USA.

Best Wishes,
Bruce

[mikenash]

Hello Bruce,

I am not sure what part of the world you stay but there must be a time difference between us I am in the far north of the UK.

I am generating 220Volt 50 hz it is a old type BKB start o matic
 
Do you think that the photos I sent of the voltage cut out will work on the AC 220volt
I could get one for the 24 volt charging side and set it to trip at 28 volt (that's a guesstimate). you could please advise on the upper voltage trip setting.

the reason that I believe that the 220 volt side wont work as well is because I have one of that device that plugs into a socket then you plug in a load IE: light or heater into it. it has a screen that reads the voltage, amps, hertz . when the unit is plugged in on its own the engine dose not start. then the heater is switched on the engine starts when the heater is switched off but still plugged into the device the engine still runs until the device is switched off. if this makes sense. I only use this plug to test check the volts amps hertz

I am unable to run the engine over rev at the moment because when she over reved she brunt out the charging resistor. I have sent for 0.8mm wire to rewind the resistor.

Regards

John

John in my industry we have simple diesel engine controllers in use out on farms all over the place.  They're made from off-the-shelf components.  They just do simple stuff like track revs and oil temp & pressure and start/stop on a signal.  Several of them use the Hz signal off the diesel engine's alternator to control revs - ie, as the revs rise, so do the hertz and the controller uses this info to talk to the little ram that's attached to the throttle arm

If you had a google, there might be info about a simple version of this?  If you have or wanted to fit a simple automotive alternator - taking a signal off that might be easy and I guess you could set limits with a simple controller

Folks here who know more about this stuff may chime in?

Cheers

[BruceM]

Good idea, Mike. There are some $55 diesel generator engine monitors on ebay, one at least that senses rpm down to 300.  You'd likely need a hall effect sensor and a magnet or 4 for the tach sensing.   I have zero experience with them.  Chinesium devices can be difficult as documentation is non-existent or unfathomable.  The issues would be how to power it without screwing up the SOM start/stop circuitry, and matching their tach input requirements, plus programming it.  I'll try to help if that's the way John wants to go. 

[vegoil]

Hello,

I have ordered one of each 24volt and 230volt controller shut dawn device I will try one on the 230 volt If that don't work I will put the 24volt one on the exhaust lifter solenoid that closes the pump rack at the same time. I believe this would be the easiest to retro fit.

this is a photo of what I have ordered

[BruceM]

Seems you've done some good research and have a good plan, John.  Let me know if you need a hand.

One issue I've run into with ST generator heads is that the waveform distortions are bad enough to confuse most inexpensive (edit) non-RMS voltage/frequency monitors, particularly on AC frequency.  I solved that by switching to a Siemens RMS voltage monitoring relay, which has been problem free.  I recall that Siemens also makes a voltage monitor that runs on 24VDC, but can monitor 230VAC.  They are spendy but are available in a wide range of models.  So that's a possibility to look into if you have difficulty with the one you found.

[vegoil]

Thanks for the help. it will be about 3 weeks before it's delivered I will let you know how I get on.

Regards

John

[BruceM]

The Siemens product I've used before is a SIRIUS 3UG4 monitoring relay.
They are 24V AC or DC powered, will monitor AC or DC voltages or frequency (down to lister CS/SOM rpm speed) depending on the model.  I don't know the current prices, but they are likely a few hundred new. 

Just passing this on, sorry I forgot the details before.  I used this on my neighbors DES CS clone 8/1 setup, to protect the well pump, etc., from under or overvoltage in case of slipping belt or AVR failure.  I found it used on ebay.