Pallet Tracking at Conveyor

[drbitboy]

The line is as in the picture, ...

https://ibb.co/stRFDcX

That is a broken link, can you attach the image to a post in this thread?

 

[drbitboy]

I may not have understood what was meant by "false trigger."

Perhaps it is referring to"bounce" in the discrete input, that is a single pallet arriving at the sensor causes the severity input to change state several times.

For that you need a debounce circuit; see this link.

 

[Ronnie Sullivan]

From another thread, it's suggested this is school homework. Hmm.
I've done plenty of conveyor systems over the years, in fact I got a few jobs by recommendations from happy customers.
There is not any set way to do them but my description above is for a ' one item at a time' through the conveyors.
They naturally queue if there is a hold up and reset quickly if there is a false trigger.
Operatives do like to put their hands over a sensor as they walk past.

 

[parky]

I agree with Ronnie, I have also done many accumulator type conveyor systems / diverters, simple is best, power saving is another must now so yes if pallet assumed in-between sensors run for a pre-determined time, however, most systems I have done the conveyor is usually longer than the pallet so if a pallet is left due to a power failure there are options, retentive bits for pallet in transit and previous triggers both assume pallet will move, a jam alarm system i.e. if a pallet leaves a conveyor if after a time it does not reach the receiving conveyor stop & alarm. There are a number of possible requirements for example for speed of operation it might be that the customer wants the preceding conveyor to run if the conveyor in front is moving a pallet on, rather than wait until the conveyor is clear, use the sensors to "Measure" the pallet & use this to determine if a pallet is stuck i.e. sensor covered for more time than the length measure.

 

[Jim3846]

If pallet is in between sensors due to jam, power loss, or system stopped.
I always did a predetermined timer to run the conveyor to bring all pallets to front of conveyor. This timer was set to how long a pallet will travel from one end to other.
This ran the conveyor during a reset/restart of system. This part of logic is a typical feature of every pallet conveyor.

Pallet tracking is probably the hardest to do consistently due to the nature of pallets and their missing some board, so sensor placement is always a critical issue. Always detect the pallet not the product on the pallet.

 

[ganutenator]

a little something I wrote

(*R_Trigs*)
FBI_pulse_re (CLK := conv_pulse, Q => pulse_re);
FBI_Gate_re (CLK := entrance_pe_blocked, Q => gate_re);
FBI_sim_pulse_re (CLK := sim_pulse, Q => sim_pulse_re);

(*Increment a sequence number and load it into the tracking array at position 0 when the gate is blocked*)
IF gate_re AND conveyor_running THEN
	seq_num:= seq_num + 1;
	IF (seq_num > 100) OR (seq_num <=0) THEN
		seq_num:=1;
	END_IF;
	shift_table[0]:= seq_num;
END_IF;

IF ( NOT entrance_pe_blocked AND conveyor_running) THEN
	shift_table[0]:= 0;
END_IF;


(* This logic shifts the tracking table "shift_table" every time we see a pulse*)
IF ((pulse_re AND NOT sim_pulse_enable) OR (sim_pulse_re AND sim_pulse_enable)) AND conveyor_running THEN
pointer1:= 1999;
	WHILE (pointer1 >= 1) DO
		shift_table[(pointer1)] :=shift_table[(pointer1-1)];
		pointer1:= (pointer1 -1);
	END_WHILE;
END_IF;