Hello

Hi guys. Im in need of some help.


Im working on a down hole tool. one of the sensors failed and it is stuck down hole. I cannot find a way to reset it to go home, its waiting on that sensor to go hot before it begins the home sequence.

Is there a way to just force on the home sequence?

Obviously there are all sorts of safety things we don't know about and so advice is given free of any responsibility. Rather than fiddle with software couldn't you just simulate the sensor closing on the terminal rail.

as already stated, way to many unknowns for anyone to answer.
your best bet is to get with maintenance and the operators and discuss the sequence of events for the machine. then trip the sensor on the terminal block or my preference is to go online with the program and see where the sensor is used and track the program to its home state before attempting to do anything else. put the machine in manual and lock it out to keep from getting hurt.

james

Thanks guys.. I will try to simulate the sensor

I just found it weird that i couldn't find a return home sequence for a power loss or an estop situation.

Relace the sensor?

Thats the plan.. But the sensor is down hole

Safety issues resolved, add a branch around the sensor address or alias tag and insert a XIC to bypass it. Then when you can lockout and replace the sensor. I use timers in a case like this if there are no alarms for other problems, i.e., high current, high temp, etc, because something broke. That way after about 30 seconds the timer takes over for the sensor and returns the equipment to the starting position. Hope this helps.

Agentbill008,
bypassing the sensor may not always be possible.
on the machinery I program, all sensors have a failsafe timer.
for example, an air cylinder cannot be extended and retracted at the same time. likewise, a part sensor cannot be made when the machine is in the home position and there is no part on the fixture.
the machine will fault, exit the automatic cycle, and the display tells the operator what the issue is so he can fix the problem.
this method keeps the machine from operating due to false signals causing damage AND keeps the operator safe by faulting out before the next cycle starts.

this may be an over kill, but when downtime costs are $300/minute at my last plant, $1200 / minute where I am now, to $10,000 for an automotive supplier after 15 minutes, downtime is a big issue
regards,
james

Thanks for all the feed back.

James Mcquade,

I get that time costs money and downtime can cost thousands of dollars per minute. I also get that safety problems can cost a lot more very quickly. I'm not saying make any programming changes hastily or carelessly. I work in a steel mill where we process over a hundred tons of molten steel per hour. One has to be wise and careful when bypassing any logic that is part of the normal process, especially when operators are involved.

My three main rules are:
1) Know what you're doing.
2) Know where you're doing it.
3) Know who you're doing it to.

They are more complicated than that, but that's the jyst of it.

I used to work in a plant that among other parts made the floorboards for Dodge Durangos and Jeep Cherokees, so I know where you're coming from.

Regards,
Agentbill008

If it was me I would not put an or around the logic or put a force on (if that is possible), It takes time to send an update via the program or force. The best way is to blip the plc input with the supply i.e. link sensor supply to the input for a fraction of a second. blip the solenoid manually or contactor if motor driven (other possibility turn power off wind motor back) . This gives some sort of control most sequences i.e. send down probe until at bottom, bottom sensed do what ever... probe at bottom sensed send it back up. this way just holding the input on for as long as it takes to start that part of the sequence. after all a human is a better judge of when to let go!. I must iterate that trying to cover a sensor inside a machine with power on is a no no. Normally I would not short anything out unless there was no option but I would rather hold a wire on a terminal that I have control over than use a PC to download a fix.
I have seen people mod a program on-line & do quite a bit of damage during the time it takes to remove the mod, and seen some close shaves people have had frigging a sensor with a screwdriver and nearly taking their arm off.
I have been involved for over 45 years in machine control and by following my own simple rules (as above post) and still got all my fingers:teacher:

Agentbill008,

I did not mean to slam you in any way. I was trying to point out things that may be programmed into the plc and other issues. I admit, momentarily powering the input with a jumper wire, bypassing the sensor, forcing the input, or manually control the machine until the machine finishes its cycle will have to be done so you can fix the issue.
james