OK, I did the cardinal sin and took it off-line. Here's what happened. I should have known better. BTW rbbalaji, contract programming starts at $125/Hr!
Hi Jay,
The PLC was luckily able to have 120V AC outputss.
Jay I need another favor from you. I need to write a
program for a fixture. It has two touchbuttons, four
sensors for clip presence on clip holders, two
cylinders to lock or clamp the part. and two cyliders
to insert four clips on the part. I have two outputs,
one direct valve connected through tees to the two
locking or clamping cylinders and another direct valve
connected through tees to the two cyliders used for
clip attachment. Now I want the program to be written
in such a way:
1. When you press two touchbuttons, the locking
cylinder locks the part if the four clips are present
on the clipholder.
2. once the part is locked the clip attachment cylider
attaches the clip on the part.
3.If by chance there is any clip left on the
clipholder dont release the locking cylider, so that
the operator cannot take a faulty part. then operator
presses touchbuttons for 3 seconds for reset.
4. If everything is fine release the lock and end
cycle.
I had a similar program and I am using that with some
modifications since I did not have the time or
experience to write another program. But this program
is really very long. Can you help me out. If you want
I can mail you the program I am currently using.
Bye, and wish you a very happy and joyous newy year.
Balaji.
Man, didn't you learn anything from this one!!!!!
September 26th, 2002 09:40 PM
rbbalaji
actually i am using the plc for pneumatics. and i use part sensors and when part is detected i wnat to clamp the part when two touch buttons are pressed. then i check for clips. once the clips are put then i want to release the clamp again when the touch buttons are pressed. but this occurs only once. in the sense that once the clamp is released i want it to continue so that when the next part is put it is clamped again. can anyone help me. the program i have written works only for one cycle. the program is as follows(omron plc)
LD 00006 touchbutton1
TIM 005
#5
LD 00007 touchbutton2
TIM 006
#5
LD 00006
AND 00007
AND 00001 partsensor1
AND 00004 partsensor2
AND NOT TIM 005
AND NOT TIM 006
OR 200
AND NOT 300
OUT 200 clamppart
LD 200
OUT 10.01
OUT 1100
LD 00000 clipsensor1
AND 00001
AND 00002 clipsensor2
AND 00003 clipsensor3
AND 00004
AND 00005 clipsensor4
AND 00006
AND 00007
AND NOT TIM 005
AND NOT TIM 006
OR 300
OUT 300 clippresent
END
September 27th, 2002 05:31 AM
Jay Anthony
This is a classic alternate action or flip-flop circuit where the first press of an input turns an output on and the second press turns it off. Two things are different:
1. There are two inputs instead of one
2. There are permissives in the On side of the circuit and the Off side of the circuit.
Let's see what we can salvage out of the original circuit.
LD 00006 touchbutton1
TIM 005
#5
LD 00007 touchbutton2
TIM 006
#5
This sets up the beginning of an anti-tiedown operator pushbutton circuit.
Now re-arrange your common input conditions to drive a DIFU (one-shot for you AB programmers.)
LD 00006
AND 00007
AND 00001 partsensor1
AND 00004 partsensor2
AND NOT TIM 005
AND NOT TIM 006
DIFU 300
Now use the DIFU 300 to drive the coil to a SET 200.
LD 300
AND NOT 200
SET 200
Finally use the DIFU 300 and all of your release permissives to drive the coil to a RST 200.
LD 300
AND 200
AND 00000 clipsensor1
AND 00002 clipsensor2
AND 00003 clipsensor3
AND 00005 clipsensor4
RST 200
Keep the original circuit that actually controls the clamp.
LD 200
OUT 10.01
OUT 1100
The key to this arrangement is the DIFU 300 (one-shot) which only gives a one scan pulse when PB1 and PB2 and Part1 and Part2 are energized and then released.
September 27th, 2002 09:13 AM
rbbalaji
thanks for your help. i have another doubt. i am using this plc in my fixture wherin i have two sensors. one sensor has a clip detector and when a clip is detected one cylider is fired and it keeps the part. and the part is cut using a cutter on application of a pushbutton. when the cutter cuts the part, the other sensor senses the cut the cylider should go back so that the part can be removed. the sensor that senses the cutter senses it only for a few seconds.
ow should i program the omron plc
LD 00.00 clip sensor
AND NOT 00.01 cutter sensor
OUT 10.00 cylinder
September 30th, 2002 05:15 PM
Jay Anthony
Did the circuit above solve your original problem? Is this the same machine? If it is, then you are not saying the same sequence as above. Make a step by step sequence of operations.
__________________
September 30th, 2002 08:19 PM
rbbalaji
yes that solced the problem. and this is not the same circuit. this is for another fixture. the step by step sequence is as follows:
1. the operator places metal clip.
2. the operator inserts plastic tube into the metal clip and the other end of the tube goes t the cutter.
3. the operator presses pushbutton one. this locks his plastic tube using a cylinder that is directly connected to the puhshbutton(no plc action). but ther is another cylinder lets call it cylinder1 that has to fire when he pushes pushbutton1 depeding on sensor1 that detects the metal clip.
4. the operator presses another pushbutton2 which fires the cutter again without the help of plc(direct switch).
5. when sensor2 detects cutter which is only for a fraction of a second this cylinder1 one should go back.
please help me with this.
Thank You in advance.
October 1st, 2002 05:25 AM
Jay Anthony
(Quote
1. The operator places metal clip.
2. The operator inserts plastic tube into the metal clip and the other end of the tube goes to the cutter.
3. The operator presses Pushbutton one. This locks his plastic tube using a cylinder that is directly connected to the Pushbutton 1(no plc action).
If I understand you correctly, up to this point, none of the above pushbuttons and cylinders are hooked to the PLC.
(Quote
But there is another cylinder (let's call it cylinder 1) that has to fire when he pushes Pushbutton 1 depending on Sensor 1 that detects the metal clip.
4. The operator presses another Pushbutton 2 which fires the cutter again without the help of plc(direct switch).
5. When Sensor 2 detects cutter which is only for a fraction of a second, this Cylinder 1 one should go back.
Try this out:
LD 00.00 ClipSensor1
SET 10.00 Cylinder1
LD 00.01 CutterSensor2
RST 10.00 Cylinder1
Let us know what happens.
October 1st, 2002 07:03 PM
rbbalaji
Hi everyone!
Thanks for everyone who has helped me in this site. I have another doubt. I hope you will be able to guide me as before. I am actually modifying someoneelse's program. Let me explaing the operation.
This is a fixture wherein the steps are as follows:
1. Operator places two metal clips on clip holders. Two sesors are used for this purpose and are inputs to Omron PLC 000 and 001.
2. Operator places two parts on the nest which is on top of clip holder.
3. Operator presses pu8shbutton. Input to PLC 002.
4. Two cylinders press the part from the top. Outputs 10.00 and 10.02.
5. Two cylinders pushes the clip from the bottom. Only one direct valve for both cylinders and output is 10.01.
6. The bottom cylinders for the clip holders is released.
7. The top cylinder is released.
Now this program is working very well. But I altered this program due to new demands. Since the operators were putting parts that already have clips on the nest and as a result the clipholder was damaged we had to find a solution. As a solution this was decided:
1.we put two more sensors to see to it that the part placed on the nest doesnt have clips alreay attached. We used inputs 007 and 008 for thses two sensors.
2. I clip already attached then dont clamp the part,
The program for this is as follows:
LD 007
OR 008
OUT 500
LD 001
AND 002
OUT 200
LD 200
AND NOT 500
OUT 10.00
But this gave rise tom a new problem.
1. Once the part without clip is placed and the clipholder cylinder is activated and the part clamp cylinder is activated it senses the new clip to be attached and then resets the part clamp and clipholder cylinders as a result of which the clip is not attached.
CAN ANYBODY HELP ME WITH THIS PLEASE
October 8th, 2002 08:23 PM
Jay Anthony
(Quote
1. Once the part without clip is placed and the clipholder cylinder is activated and the part clamp cylinder is activated, it senses the new clip to be attached and then resets the part clamp and clipholder cylinders as a result of which the clip is not attached.
This is a case of permissives for a start circuit becoming the early stoppage of the start circuit. The only thing you are concerned about is that the clips are not present before you push the start clamp button.
Let's see what we can salvage from your circuit:
LD 007
OR 008
OUT 500
LD 001 (should this be 000?)
AND 002 (should this be 001?)
OUT 200
This is all OK. Now we need to remember that the clips were not present before you pushed the start clamp pushbutton. Use an open contact of 10.00 to latch the circuit:
LD 200
AND NOT 500
OR 10.00
AND NOT 201
OUT 10.00
Now you need a way to unlatch the circuit. Use the bottom cylinder output to drive a DIFD (trailing edge one-shot for you AB programmers.)
LD 10.01
DIFD 201