Cornbread,

PLC's are for this purpose, to control complex things in a relatively cheap, efficient and elegant way.

 

I have an old worktruck/hobby/best friend. A 1989 Ford F-350 with 7.3L IDI diesel...completely w/o all the fancy electronics to bog it down. Just typical and necessary electricals. Something like a PLC seems like an ideal thing for a truck pre-computer chips. Plus its not one size fits all, half the fun of working on things is being able to tweak it like you want or need. Sheesh!..even adding functions to turn on AC, heater, honk the horn to wake me up after I hit the snooze button.

 

Cornbread,

You can start a new thread if you want ask help on something specific you want to build but not in this thread.

 

Just a few caveats here.
I'm not a Diesel mechanic or anything of that sort.
However, I've noted that on the Diesel-powered vehicles we have at our local museum, the on-time for the glow plugs varies considerably, and appears to be mostly dependent upon the engine temperature.

If an engine has been inactive and the weather is cold, it may require 30 to 40 seconds for the glow plugs to heat up sufficiently. However, if the engine has already been warmed up, the glow plugs may require little or no time to heat.

Quite frankly, I do not know precisely how this time delay is determined, but I suggest that this is worth doing some research on. Leaving the glow plugs on too long may result in early burn-out. Not leaving them on long enough will prevent the engine from starting.

Another item to consider is runaway. If there is an automatic speed controller on board the generator, this may be a non-issue for the current project. However, high-time Diesel engines can be prone to runaway (we had this happen to one of our Diesels, but we got it turned off in time).
Wiki article: http://en.wikipedia.org/wiki/Diesel_engine_runaway
More: http://mercedesshop.com/Wikka/RunAwayDiesel

 

I agree with Sgt about the glow plugs.
Franco, you need to study what do you need well before start to design the electronic controller. As, you see as you study it more you find that you need more situations to monitor and control. Thus I suggest you the PLC as a perfect solution.
Sgt,
What do you think about the PLC solution?

Franco,

If you want to see how a Crouzet PLC looks like have a look at my pictures in my profile in the "Candle Machine" project.

 

Mik3,
I don't know anything about PLC's, nor do I have the time to research them at the moment.

The glow plug timing may call for a remote input from the Diesel engine's controller, or some kind of time/temperature input. If a PLC could handle that, along with the RS485 interface, it could be a nice and easy solution.

 

If an engine has been inactive and the weather is cold, it may require 30 to 40 seconds for the glow plugs to heat up sufficiently. However, if the engine has already been warmed up, the glow plugs may require little or no time to heat.

I have observed the same with my little diesel pickup truck. Takes 20 or 30 seconds after being parked for hours in the cold. Takes 5 or 6 seconds if I've made a quick stop on the way home.

I've read cold resistance of a glow plug is about 1.5 Ohms, and that their "ready" temperature is 1500F (816C). I wonder if glow-plug current draw could be used as an indicator?

 

Morning Guys,

Instead of using buttons for switching it on and of, why not use a regular ignition swicth at the remote location and control all the electronic parts from there? On an automotive diesel engine, there is a temp sensor on the radiator connected to a timer connected to the glow plug light indicator. Some tractor ignition switches have a "anti-clockwise" position for the heaterplugs. You simply turn the key anticlock wise for as long as you think needed, depending on temperature, then start the engine. there is an ordinary 30Amp relay for the glowplugs.

 

On an old Mercedes I had, to start the engine, first you turn the switch to one position and wait until the engines warms (glow plugs on). Then a lamp indicator showed that the engine is warm and you turned the switch one step more to start it. If this engine has a lamp indicator then Franco has to monitor it and not use a timer.

 

Please forgive me if I am missing some details, but you might find the Scytek Galaxy 5000RS a suitable off-the-shelf piece. It taps into the Wait-to-Start lamp circuit normally found on diesel equipped cars and trucks. I am not sure if your genset has a similar circuit and indicator lamp.

http://www.scytek.net/galaxy.php?pic=images/products/galaxy/g5000RS.png

 

Guys, thanks for all your input. My 2 gensets are kubota 12kva unit and i had a very good look at the electrics before attempting any modification. The glow plug circuitry is basically feeding 12v to the glow plugs line via a shunt to limit the current. Even in middle of summer (and gets very hot here) i need at least 6sec of preheating to be able to start the engine within 4sec of cranking. If i try to start it with no preheating i need to crank it for about 9 to 11sec to make it start. In winter if i keep the glow plugs for 10sec i can achive the same remaining below 4sec of cranking. I did connect already relays in parallel to ignition key and "stop" button to play with. Using the parallel port i can drive the relays (via an obvious interface card) with a simple VB program but it is an overkill using a PC to control one engine. The timing i chose is a result of all my testing. Keeping in mind that these engines have a very basic "emergency relay" to shut engine off in case of malfunction, i am just trying to achieve the start and stop sequence using one switch or button only. If something goes wrong the emergency relay will shut engine down. If i am able to make a simple circuit to do what i want it would be my first step to automate the all functions of my power house. Using a PLC is a neat and easy solution but i am still unsure if worth investing in it at this stage. Mik, these Crouzet PLC look very nice and i am tempted to get one and play with it! DO you know any place selling online?

 

I think you can buy it from Crouzet's website but first decide how many inputs and outputs you want.

 

Ok, here it is what i think may work. (and so far the best i can do)
I am using a decade counter with the outputs driving the different stages.
The counter start when a trigger input arrives and should handle all the steps for starting. It should all work in sequence as i am kicking the counter at the end of every stage.
Out0 is unused, 1 control the ignition, 2 the glow plug and crank timing, 3 the power. At this point genset should run. When next trigger arrives, move the counter to 4 and shutdown start taking power off, wait few secs before sending stop signal and stepping counter to 5 to remove ignition. Step 5 is then resetting the counter and system is ready for next start. I haven't worked out yet some feedback from engine and am looking to use Out0 to inhibit the trigger while the counter is in sequence. Also i am not sure if i need the first 555 (U3) to generate RST at startup. Would a RC network good enough? So far it looks ok on LTSpice, any advice criticism or suggestion is needed. Mik, thanks for all your inputs, Bertus not sure if caps will fry the gates....

 

I would use an 8-bit binary counter and clock it with a 1 Hz oscillator. The output of the counter will increase every one second and a logic gate circuit will check the output of the counter until a specific combination arrives. Each combination will arrive after a delay of some seconds. You can choose at which combination of the counter output each function of your machine has to start and stop.

 

Tried it and got lost, couldn't get the simulation running and went in this way, do you think i should not build it? Is it wrong?

 

I haven't check it yet but I will have a go.

 

I had a quick look at your circuit and I don't see it working! Did it worked correct in the simulation?

Also, by trying to hold all the 555 reset during power with U3 does not make sure that none 555 will trigger because real 555 have different time delays and so on. Also, when the output of U3 goes from high to low there is a chance for U9, U11, U15 and U16 to trigger simultaneously.

I believe that the best and more reliable solution is a circuit like what I suggested. Just my opinion.

 

It works on ltspice, didn't build anything yet. If you have the simulator i can post schematic in here. If not i may need your help to get me starting with the counter. This one i made is incrementing only once the steps are all done. Have no feedback yet from the engine tho. Pic would be the easier and cheaper way to make it!

 

It works on ltspice, didn't build anything yet. If you have the simulator i can post schematic in here. If not i may need your help to get me starting with the counter. This one i made is incrementing only once the steps are all done. Have no feedback yet from the engine tho. Pic would be the easier and cheaper way to make it!

I know PIC is an easy solution but the easiest is the PLC because you don't need to make a pcb board (just wiring). Have you ever used a PIC?

Send the spice file, I will try to open it. But even if it works in spice it won't be safe to run it in reality.

 

Never wrote any code for it, pcb boards are not a drama... as long as i use dil and not SMT. As per PLC, just a smart relay with 4 out and 8 inp will cost about $350 (australian) with no cable or anything and have to program it the hard way. Surely if i can make something wont cost that much. Is any tutorial on the web to learn pic programming?
Here is the file. keep in mind that i am not an engineer and may have done some silly mistake, as far as i can check this runs on the simulator but may need some twik to make it better