Need Help With a Circuit

Discussion in 'General Electronics Chat' started by ChandlerW, Feb 23, 2011.

  1. ChandlerW

    Thread Starter Member

    Feb 15, 2011
    44
    0
    I'm sorry if I'm breaking a forum etiquette rule. I'm not able to change the original title of the thread I created and its not very descriptive. Its not my intention to start multiple threads for the same problem.

    I have a rather large saw. Its a Pehaka horizontal saw from the mid 80's I would guess. I do not have a schematic for the saw. I emailed the maker in Germany and they said they would send me a manual. Its been several months since they said they would send the documents.

    The wires for the solenoids are in a bit of a mess.
    I have a slight idea of how it operates.
    Turn on the hydraulic pump motor, hit the raise or lower switch for the solenoid and the saw arm would either raise or lower.
    If the saw arm went too high it would hit the limit switch and disengage the raise solenoid. Same thing with the lower solenoid, although the saw arm will lower under its own weight if the "lower" solenoid is engaged. If neither solenoid is engaged and the saw is in the raised position it will hold in place. The hydraulic pump can be on and neither solenoid engaged.

    I have created a diagram of the way it is wired up presently.
    The "saw motor on", "saw motor off", "hydraulic pump on", "hydraulic pump off" all work.
    The relays are all magnetic coil types activated by 24VDC that comes off a rectifier. The switches are marked NO and NC.
    Some wires I could not trace.

    I would appreciate any help I can get with this project. Its been 14 months since I got it and I would like to finish it.
     
  2. ChandlerW

    Thread Starter Member

    Feb 15, 2011
    44
    0
    Any takers on the circuit problem? I still haven't had any luck getting a schematic from Pehaka in Germany.
     
  3. Kermit2

    AAC Fanatic!

    Feb 5, 2010
    3,778
    932
    You need to tell us what the problem is. Does the saw not operate? Does it not move up and down?

    What exactly is wrong with it?
     
  4. ChandlerW

    Thread Starter Member

    Feb 15, 2011
    44
    0
    The switches to operate the solenoids do not work. The hydraulic motor works as layed out on the pdf file. The saw motor which turns the gear box works too. The solenoids are good. They are new and I have had some success with them.

    I would like to push the raise button and get the raise solenoid to engage.
    It should stay engaged until something disengages it. That something could be a limit switch or the push of another switch such as the lower switch. Maybe when I turn off the hydraulic motor the raise or lower solenoid should disengage as well? I don't know. I do know that pressing the buttons now does not engage either of the solenoids and I'm 98% sure it has to do with the way the switches are wired.
    Thanks for any help.
     
  5. ChandlerW

    Thread Starter Member

    Feb 15, 2011
    44
    0
    Looking at the attached diagram, when pushing the switch for the 7-8 path, there is no path to ground.

    The coil in the 7-8 relay which is supposed to engage the lower solenoid doesn't have a path to ground.

    I need help with this. Tell me if I'm understanding it right.

    The saw motor relay coil is jumpered to wire #4. There is no path to ground or the relay would be engaged.

    When I press the On (NO switch) it completes the circuit. I release the switch and the relay stays engaged because the path to ground now goes
    through the NC side of the Off switch. Pressing the Off switch breaks the
    circuit.

    If all that is true, then the same would apply for the raised and lower solenoids right? I just have to figure out how to wire them up
     
  6. Commander#1

    New Member

    Jan 22, 2011
    14
    0
    Chandler -
    I can get some of the circuit in your pdf. file to work by making a few assumptions, but, there's too many loose ends. I googled
    "Pehaka saws" and - oh, boy - there's plenty of hits out there. Would it be possible for you to provide a model # and motor plate
    info? I'd like to check some of the machinery distributors out here on the west coast for wiring diagrams. I think what you have
    is a horizontal BAND saw - you didn't describe your saw very well in your post. Thank you.
    .
    Phil Potter
    .
     
  7. ChandlerW

    Thread Starter Member

    Feb 15, 2011
    44
    0
    Hey thanks for the assist.
    I do not have a model number for it. It is very similar to a HS260 but the HS260 doesn't have all the controls.
    There are a lot of Pehaka hits on Google but 99% of them are people selling them. I haven't found anyone selling one like mine or close enough to it that a wiring diagram from the seller would help.
    Other Pehaka hits will be mine asking for help with the wiring.

    In my pdf I didn't add the motor wires (L1, L2 and L3). I added the control circuits for the motors which operates the relays. I did it that way because the controls for the motors are similar to the controls for the relays. I was hoping that someone would be able to determine how the switches and relays work for the motors and apply that to the switches and relays for the solenoids.

    I made the pdf to show how the solenoids are wired up. I didn't wire them up like this. The previous owner must have wired them up like this. It only had 1 solenoid when I got it so maybe they had something figured out for single solenoid operation.
    I check the mailbox every day waiting on the packet of information to arrive from Germany but so far nichts.
     
  8. Commander#1

    New Member

    Jan 22, 2011
    14
    0
    Just curious -
    Would you happen to be "shanghyd" in another forum? There's some neat pictures there.
    .
    :) Phil Potter :)
     
  9. ChandlerW

    Thread Starter Member

    Feb 15, 2011
    44
    0
    Yes. I'm active in lots of forums. CNC, machining, and welding are some of my most active.
     
  10. ChandlerW

    Thread Starter Member

    Feb 15, 2011
    44
    0
    I'm still stuck. Anyone have an idea how to approach the problem?
     
  11. ifixit

    Distinguished Member

    Nov 20, 2008
    638
    108
    Hi ChandlerW,

    I like to fix things, and I like a challenge. However, I have no direct experience with your peticular machine. Any advice someone gives you as how to proceed should be weighed carefully by you with regards to safety and/or causing damage to your equipment. After all, you are there, I am not.

    To get something working that is not working you need to eliminate all the possible reasons why it may not work, one by one. Start with the most likely cause first. Eventually, you will come to the reason... fix it and your done.

    If you could respond to each of the following items this would help me understand the problem.

    1. Is there a safety switch you are unaware of somewhere that can disable control by removing ground returns to the relays?
    2. Can you verify that the solenoids can operate the hydraulic valves by pushing with a tool? Try first with the hydraulic motor not running. Caution: the saw may move when you try this.
    3. Repeat (1) with hydraulic motor running.
    4. Repeat (1) with hydraulic motor running and applying 24V directly to the solenoid.
    5. Is it possible that the relay ground returns are through the frame of the relay and therefore there would be no wire needed?
    6. Raising or lowering the saw may require the operator to hold the button depressed and will stop when the button is released. (Safer)
    7. What controls the rate of descent when lowering? As the saw cuts through the material it applies pressure. Not too much or too little. How is this controlled? If this is done mechanically, then it is not likely part of the electrical circuits causing the problem.
    8. Can you verify that each of the relays are good and operate with voltage applied? No corroded contacts?
    Regards,
    Ifixit
     
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