Need encoder advise on used machine.

[helluvawreck]

Hello, I'm helluvawreck and I hope that someone can help me with this problem or at least point me in the right direction. My company has purchased a used panel saw that is controlled by a computer that is non standard and the program cannot be read. The computer is 9 years old but seems to be working fine. The computer boots up and we have determined that the encoder which positions the pusher is defective. I had planned to convert the machine over to a PLC if I can't get the computer to work. For now it looks like this won't be necessary.

The problem is that the encoder is a magnetic strip type encoder that is made by Siko products, www.sikoproducts.com. If anyone cares to look at the data sheet for this encoder you can type into the search box at the top of the web page the following: as510/1 This will take you to the specs. The original SIKO encoder had a supply voltage of 10-30 vdc. However, now SIKO only manufactures it with a supply voltage of 24 vdc +/- 20%. The computer on the machine supplys the encoder with 12 vdc. They tell me the 10-30 vdc is no longer available. The machine technicians and the manufacturer said that the encoder still might work but naturally no guarantees. I have brought the encoder on in but it doesn't look like it will work. The power ld came on with the old encoder but no such luck with the new encoder (obviously it is only getting 1/2 it's required voltage).

I talked with an application engineer at a local supply company where I buy parts. He suggested that I use a 24vdc power supply to power the encoder by tying the two o vdc (plc supply and computer), dead end the 12vdc coming from the computer, supply the 24vdc from the supply to the encoder, and then feed the 3 signals back to the computer. The encoder operates with RS 422/TTL. He thought that this would not harm the computer, but would work. However, another technician said this could damage the computer. He said that I might be able to put a DC to DC converter to lower the voltage of the signals to the computer but he wasn't sure whether this would work either. He said it may just be necessary to just start over and upgrade to a new plc.

I would like some advice on what might be a good work around. Fortunately, we will not be operating this machine like someone would operate the panel saw. For example, a cabinet manufacturer might need to store 100's of programs. All we need to do with this machine is cut grooves in dentil moulding on a high production basis. All we would have to do is index it a set increment over and over to repeatedly cut the grooves. Naturally we would want to vary this set distance. However, this would not be a difficult task for a PLC conversion.

I'm not a trained technician. I have just been in this buisness for about 35 years and have had to teach myself electrical controls and machine work and I have built some special machines from the ground up and have done some plc programing on Mitsubishi PLC's. Again, I am no expertly trained technician. Any advise would be appreciated.

thanks

helluvawreck

[keithkyll]

I suspect the 24 DC is a raw supply. The unit will have it's own regulators for logic and RS422/TTL signals.

Connect 24DC as suggested and run it. You won't damage the computer.
Worst case, you would blow the RS422 interface card. The RS422 chips on this card are off-the-shelf items.
As an experiment, put a 9 volt transistor battery in series with your 12 volts. That should be enough to get it to run.

[rsdoran]

I did not look at the encoder specs BUT if the output is the same regardless of the supply voltage then you may be able to use another power supply OR modify the existing connetion.

As it is does the encoder get power from the computer power supply? If so you may be able to change the wiring to obtain 24vdc. Take a look at this for computer power supply details http://www.patchn.com/forum1/viewtop...e+power+supply

If your computer is standard and the encoder is recieving power from it then to obtain 12vdc it will be connected to Yellow +12v and Black 0v (common), to obtain 24vdc connect to the Blue -12v instead of the Black.

This "assumes" that the output from the encoder will be the same type signal regardless of input voltage, verify that, if so then you should be able to modify the existing supply or use another. Siko should be able to tell you if there is a difference in the encoders output signal.

PLEASE PLEASE verify before making changes, I do not want to see you hurt your computer or encoder.

[helluvawreck]

I certainly do appreciate the fast response; it is very much appreciated. I believe that I will start coming here more often. I'm always experimenting and trying to learn more about machinery and controls because of our manufacturing business. We just don't have many good techs in this area that can come quickly so we try to manage without. Thanks so much to the both of you.

helluvawreck