Home Forums General Discussion Technical Questions Short toubleshooting quiz, anyone?

Here's a mildly interesting troubleshooting problem, "just" worth posting about. Maybe some of you have had it before.

MCE PHC 1000 control, submersible hydro, 3 stop.

Car on automatic, you put in a call, it comes to the floor, the doors open, then the dwell time expires, then the doors begin to close maybe an inch or so, then they snap back open. Process keeps repeating. I think it generates a fault after a bit, but I can't remember that detail now, but it's not germane, as it's unrelated to the cause.

All re-open inputs are clear, no i/r edge or s/e input, no DOB input, no car or hall call input. All contacts in door operator working correctly, and clean.

DOI, (Door Open Intent) software flag is low, during symptom.

As I'm writting this, I'm thinking "Someone has had this problem before, and will solve it immediately".

oil/motor thermal,load weigher fault?

i thought id try having never seen this equipment!!

Well, you're a courageous soul, to take a stab at it!

This has been up a couple of days, with no takers, so I'll spill it. But first, you should know that on Motion Control Engineering controllers, there is a software flag, know as Door Open Intent. (aka DOI) Basically, it just tells you if the program is calling for the doors to be open. For example, if some demand was established at that floor, or if any re-open device was actuated, or if there was a fault of some kind. None of those were the case.

Since DOI was not active, the controller program was not asking for the doors to be open, yet they would spring back open, immediately after beginning to close. No input device was telling the control to open the doors. Another way to say it, the doors were re-opening, on command from the controller, for a reason other than the control programming telling them to do so. If I say any more, I'll spill the beans..!

Before I tell you what it was, do you want to take a stab at it? It might harder for you, since you haven't seen how the equipment is built. No shame to pass on this one... 8^)

Side slide or C/O doors. What type of door operator...

These were side opening, with an MOD operator.

This problem could just as easily occur with c/o.

Just a guess, Door operator overtemp or overcurrent fault?

I have had this problem occur on GAL VVFR Operator recently with the MCE 2000/4000 series. The problem was they were using a 24 volt common to the operator inputs. These were insufficient to turn the optical input modules on fully thus creating the stuttering effect you speak of. The simple solution was to rewire the operator common to 2 bus. Another tricky input that causes problems is their use of the PTI input for monitoring the brake switch. PTI is usually used as an emergency power Power Transfer contact off of the emergency generator. MCE also uses this now for monitoring the brake switch.

Good ideas...

Nope!

Isn't this fun? 8^)

Interesting....

One time, I had a similar issue, where the bus voltage started at the operator, went back to the control through a long traveler for switching, (do, dc, nudg), and then back out through the traveler. By the time it got back to the operator, there wasn't enough voltage for the signals to be recognized. I installed "pull up" resistors, right on the operator, from the bus source, to each input. It just needed a few extra volts on the inputs, aiding the signal coming back from the controller, for the signal to be recognized. When the control would switch the input off, there was only a few volts idle on the inputs, not high enough to reach the switching threshold.

So here it is:

MCE, on their PHC 1000, used triacs to complete the path to ground, and this is how their "outputs" work.

The Door Close Front (DCF) triac brings in the Door Open Relay. If this triac is shorted, the doors will open normally, but then when the dwell timer expires, and the Door Close Relay comes in, the doors begin to close noramlly, but then as soon as the Door Open Limit changes states, the shorted DCF triac then brings in the Door Open Relay. Then the doors snap back open, they time out again, then try to close, and the process keeps repeating. The effect is that the doors just keep whacking off near full open. Changing the shorted DCF triac makes the problem go away.

Hope this was at least slightly intrigiung!

bugger not sure i would have picked up on a triac function short but SHOULD have picked up on coming off the open limit.

damn.

Whether you "get it" or not, talking about issues exercises your brain, and this is scientifically been proven to improve synaptic function . It's all good, as they say.

Not to be picky Vic, but I do believe you mean (DOF) triac , which is the door open front output and brings in the door open relay DO. DCF triac is the output to pick up the door close relay. talking about exercising the brain, I keep looking at a standard hmc100 print, and I still dont see how the door reopens, seems to me that DC, and DO will both be picked at the same time as soon as the door open limit makes and puts the 2 side of the line on terminal 36. if it is a mod operator, it should have blown the door fuse. both relays would have to be picked, since the cpu is outputting DCF to close the doors, then the door open limit makes and since DOF is shorted, DO would pick up, but, the cpu would not have any way of knowing that D0 relay was also picked, it can not tell that the DOF triac is shorted. Am I missing something here Vic,

oh, wow, didn't know you had responded to this!

Yes, you're right, I made a bad typo. I was trying to refer to the DOF triac, like you say.

I'll have to get back to you tomorrow on the sequence stuff. Wifey is calling me to bed. She must be tired...

Scott,
I've only got a traction print here with me, hope it's about the same...

"seems to me that DC, and DO will both be picked at the same time as soon as the door open limit makes and puts the 2 side of the line on terminal 36. both relays would have to be picked, since the cpu is outputting DCF to close the doors, then the door open limit makes and since DOF is shorted, DO would pick up, but, the cpu would not have any way of knowing that D0 relay was also picked, it can not tell that the DOF triac is shorted"

Hmm, lets' see....DOF triac is shorted, so any time the Door Open Limit is made, DO relay picks...ok...And on this print, DOX is in parallel with DOF, so you get that one in, too..

DOX n/c is in series with the DC relay coil, so when the doors start to close, as soon as the door open limit closes, DOF and DOX pick due to triac DOF being shorted, and DOX n/c opens, dropping the DC relay. So DC and DO aren't in at the same time

Do I get a star on my forehead?

Well Vic, I have only a few hydro and early model geared prints, none of them have a normally closed contact in front of the door relay circuit. Most of the older units would have a mechanical interlocking device to make sure that both door open, and door close relays could not be in at the same time. As I don't have every print that motion has made, i guess they finally got smart and incorporated an interlocking circuit to prevent the scenario i described. None the less, My early HMC1000 print clearly does not have an interlocking circuit incorporated into the DO and DC circuit. I guess I would have to say that we are both right, you do get a star, but does it have to be on your forehead!!!! I guess it depends on which print we are looking at. thanks for the reply. kind of makes you go Hmmmm Hmmmm Hmmmm

Here's an MCE print from 1999. This one has the DOX n/c contact in series with DC relay coil. I didn't know that others didn't have it, so I learned something! You can see it better in the Gallery.

right you are, I have quite a few old motion hydro prints, but none of them have a DOX relay, learn something new every day

Everytime I get really self-confident, and my head no longer fits through the door way, suddenly a huge problem hits me out of left-field, that I have no answer for, have no idea where to start, and am absolutely floored.

Humility returns!

I find it best to claim to know nothing. That way, I don't dissapoint people! 8^)

All MCE prints and manuals can be downloaded from the MCE site. As well as the triacs, the also use a universal serial bus to communitcate from I/O to processor. Hence only a couple of wires for comm from the I/O boards (CarCalls, etc) to the CPU..