Part in motion indication

So I am fairly new to programming (1.5yrs). I’ve taught myself and have made some pretty good headway so far. I’ve programmed a couple of small conveyors and a few other small projects. On one of our conveyors we want to be able to shut the entire process down if a part is not seen as moving. I have an analog out laser sensor from Keyence (LR-TB5000C). How would I go about having a constantly changing analog input prove a part is moving. Example: a part falls from above on the conveyor at 36” from face of sensor. At 48” the sensor signals the next part to fall. The sensor has a NO output and an analog output. The sensor also offers a windowed output. It also offers two discreet outputs in lieu of the one discreet and one analog output. Any advice would be greatly appreciated.

Not quite sure what your setup is and why use an analog sensor, however to detect a moving part (falling or travelling) and assume if there is no part within a time span then alarm or stop system.
First AND a conveyor running signal with NOT part present signal (sensor) to start a timer slightly longer than the time between parts, if a part passes the sensor this will turn on part present signal and reset the timer before it times out, If conveyor running and no part then timer times out, taking the conveyor run signal off will also disable the timer so no alarm etc. However depending on your application you may need a more sophisticated logic.

parky said:

Not quite sure what your setup is and why use an analog sensor, however to detect a moving part (falling or travelling) and assume if there is no part within a time span then alarm or stop system.
First AND a conveyor running signal with NOT part present signal (sensor) to start a timer slightly longer than the time between parts, if a part passes the sensor this will turn on part present signal and reset the timer before it times out, If conveyor running and no part then timer times out, taking the conveyor run signal off will also disable the timer so no alarm etc. However depending on your application you may need a more sophisticated logic.

Click to expand...

The biggest thing we are trying to avoid are parts that get stuck in the process. The parts are added to the process individually but the last part on the conveyor pushes the part in front of it. So if any of the parts that are anywhere on the conveyor get stuck then the whole process is stopped. I’ve written it so that bars won’t just keep loading on top of each other BUT if the parts are not continuously moving then we will destroy other components in the system. I’m trying to add a safeguard that will shut down the conveyor AND an induction heater. I’m trying to give as much info as possible without giving out proprietary processes.

The reason for the analog: I was thinking a constantly ticking number (part moving in conveyor away from sensor until new part starts number over) can be used to identify the part moving.

Based on your explanation it would seem that an analog signal is necessary to ensure the product line keeps moving.

One way to approach it would be to use a self-resetting timer that continually checks the analog signal at the end of its duration and compares it to the value from the previous check. The absolute value of the difference between these two numbers should always be greater than zero--or some number close to zero to account for inaccuracies. (The absolute value may be necessary if the difference could end up negative, such as when a new widget is dropped in front of the sensor.) If the value doesn't change much, it indicates a potential clog.

kolyur said:

Based on your explanation it would seem that an analog signal is necessary to ensure the product line keeps moving.

One way to approach it would be to use a self-resetting timer that continually checks the analog signal at the end of its duration and compares it to the value from the previous check. The absolute value of the difference between these two numbers should always be greater than zero--or some number close to zero to account for inaccuracies. (The absolute value may be necessary if the difference could end up negative, such as when a new widget is dropped in front of the sensor.) If the value doesn't change much, it indicates a potential clog.

Click to expand...

Thanks, I was just needing an idea of a direction to go

What I do for detecting stall on a hoist encoder, which on some is a laser rangefinder to an analog input, is take the present value ADD 100 to it, SUB 100 from it and start a timer.


Since the analog input will fluctuate by a few values while stopped I compare the current value to the calculated values. GEQ - INPUT - Added_To_DINT, LEQ - INPUT - Subtracted_From_DINT and if either is true I reset the timer and recalculate new compare values. Depending on the speed of the conveyor you need to adjust the 100 and the timer preset.


If the timer ever gets DONE then there was a stall, set a fault or alarm.

Aabeck said:

What I do for detecting stall on a hoist encoder, which on some is a laser rangefinder to an analog input, is take the present value ADD 100 to it, SUB 100 from it and start a timer.


Since the analog input will fluctuate by a few values while stopped I compare the current value to the calculated values. GEQ - INPUT - Added_To_DINT, LEQ - INPUT - Subtracted_From_DINT and if either is true I reset the timer and recalculate new compare values. Depending on the speed of the conveyor you need to adjust the 100 and the timer preset.


If the timer ever gets DONE then there was a stall, set a fault or alarm.

Click to expand...

So I've finally gotten to the point of where I am programming this bit of code. The way I interpret your instructions doesn't seem to work. I wrote it as:

SCP I:1.0 to N7:0, ADD 100 to N7:0 Dest N7:1, SUB 100 from N7:0 Dest N7:2

N7:0 GEQ N7:1, N7:0 LEQ N7:2

Hopefully Im making a silly mistake, Any why you could verify? Im using RS500 if you couldnt tell. I zipped the file and attached it

disregard the last post. I figured it out. I ended up using the LIM instruction and the F8 data tables.