Faulting from cold weather?

I am using Micrologix 1200's on highway milling machines and this is the first season with them installed. There is a 4 channel analog input card, 16 point input card and a 8 relay output card attached the 14 input and 10 output processor which is 24 volt dc.

On two different occasions with two different machines, when the machine arrived on the job and the operator started the machine, the processor faulted. The fault was "unable to communicate with expansion I/O. Unable to determine which one." I went online, cleared the fault and the processor went into run mode and there were no more problems the rest of the day. These machines are transported on lowboy tractor trailers going down the interstate in temps below 30F. The operator said that the engine fired right up and wasn't cranking slow so I don't think it was a voltage problem. I think there is a specific fault for that anyway. I have a sinking feeling that it is temperature related and that makes me nervous because it was my idea to add automation to these machines.

I have since set the S1/8 bit to reset faults on power up. I am not sure that this was a recoverable fault.

I am quite sure that everyone in this forum has more experience than I do, so I welcome any and all suggestions. Thank you for your time.

Wait, are you one of the ones responsible for I-75 always being torn up between Toledo & Dayton? I see those milling machine grinding up the pavement. Its never ending! just kidding

I haven't run into your situation but I think you probably did all you could do. I wonder about vibration too, while traveling and working.

We are the ones who make your drive a comfortable one after the roads are resurfaced. Speaking of I-75, I personally walked from Troy to Piqua and back to Troy in one night putting rumblestrips in.

The ride on the tractor trailer to the job is a rather smooth one so I don't think it is a vibration problem. However something is happening from the time the machine leaves the shop and arrives on the job. I even wondered about static electricity building up while being transported... I dunno. What I do know is, I can't explain it and that bothers me because we cover several states.

Is the processor sharing a common power supply with the planer ? if so , I'm not surprised that you are gaving problems . The planers that I have dealt with have (wirtgen) have pretty massive diesel engines (750kW ish in some of them) and I can imagine that the voltage goes all over the place not to mention nasty spikes when starting . If this was the case , I would tend to install a split charge relay and a little gell battery that would supply the control system only .

Thanks for your reply 10baseT. You hit the nail on the head with the Wirtgen comment. It is indeed a Wirtgen W2000 with a 660hp engine.

Could you give me some more details on the gell cell and relay scenario that you mentioned? Or could I tie into the power supply for the existing inter-control PLC's? Maybe that would be best.

Thanks for your time.

Kyle,

I would suspect vibration would be much more likely than temperture causes. PC chips can stand a lot of cold, but not much vibration or HEAT. You said the ride to the job was "smooth", but what about afterwards? I cannot imagine that pavement grinding is very smooth. Just because the problem showed up at the time the machine arrived on the job does not mean that that is when the damage was done. It could be the accumulative result of many hours of severe bouncing around in rough conditions.

Definitely provide a clean power source, and mount the PLC cabinets on vibration shock absorbers, if possible.

Your best bet for power would be a gel cell battery charged by a solar panel, that way it is 100% isolated. That and you will always have a abundant amout of sun. Good luck.

Hi Lancie,

I ran small PICO's last year without any problems. The 1200's are fine all day when milling (so far). The processor is faulting when the machine arrives to the job and is started. Was fine when it left the shop. Takes a smooth but cold tractor trailer ride to the job. The operator starts the machine and it faults. Cannot communicate with expansion I/O. What I don't know yet is if the fault occurs at power up or during cranking.

Thanks for your time Lancie.

I would be 100% sure that it is during cranking , and on initial charge from alternator have a bit of a wobble .

If you have an alternative power source that is clean , I would give that a go temporarily - I'm sure it will solve your problems , remember , a 24V battery will get a dood deal more than 24V out of the alternator , particularly after cold cranking 660HP , so you will go from a very low voltage condition (maybe as low as 16V) during cranking , up to 27+ volts after start .

As 10baseT and others have said, the problem is most likely a power issue. Good 24V regulated power is something your PLC definately needs. Some things to consider are that the engine probably takes a longer time to start when it is cold, cold causes expansion and contraction (as in connections to your expansion I/O), and cold also causes condensation, which could cause problems if it happens to connections on your PLC.

Kyle, I also suggest that you set the S:1/18 (Fault override at power up) and the S:1/12 (On Power up goto Run) bits so that the fault can be cleared by cylcing power to the processor instead of you making a trip out to the field.

Actually the detail necessary to tell for sure is scant, but I would first suspect a power supply issue caused by static discharge or buildup. If you can earth ground the frame somehow, it couldnt hurt. What do they do for fuel trucks??

I would think if it were a vibration issue the damage would be perminent, and the unit would not restart, or would become dramitacly worse in short order. Also I would tend to discount cold, unless condensation were building up on the the electronics.

I certainly appreciate all of you taking the time to help.

Most of you are saying it is a voltage problem. I think there is a fault for low voltage. Do you think spikes or drops within a good voltage range could be causing the expansion I/O communication problem? The fault was "unable to communicate with expansion I/O. Unable to determine which one."

Not supplying the power from the same source as the native PLC's was a huge blunder on my part and I will correct that Monday morning.

Wirtgen planers are generally half tracked , so whatever they sit on would be bonded to the planer by contact , if I recall , the hood of the drum also sits on the ground during transit , and of course the thing would be chained down , so unless the low loader is building up a charge , then I don't think static would be the cause - My money is on the common power supply . I suppose a simple charge relay ( or nick a feed off the charge lamp) could be used to prevent the PLC from powering up until the start has completed , and the alternator has come up - I'd still be careful , the charging circuit is not the most stable thing , and I would prefer a more stable power source.

Will setting the S1/8 bit reset this fault on power up? Under what circumstances would I want to set the S1/12 bit (On power up go into run)? When I cleared the fault in RSLogix it went right into run after I selected it. I sure hope S1/8 will reset this particular fault. Does anyone know for sure?