Position signals

  1. Hood

    Hood If it walks like a duck....

    Messages:
    11,666
    Location:
    Carnoustie, Scotland
    As can be seen I know very little about electronics but I think that as long as the Gnds are tied it should be fine but if not then please let me know.
     
  2. awemawson Forum Supporter

    If the 12 volt rated input devices on the relay board are getting 24 volts stuffed up them, they may well be breaking down and going into avalanche

    :sheep::sheep::sheep:
     
  3. Hood

    Hood If it walks like a duck....

    Messages:
    11,666
    Location:
    Carnoustie, Scotland
    Ok just tested out my theory regarding 0v tied and it works fine.
    Connected the bench supply up to VCC on the relay board, connected the 0v from supply to Gnd on relay and also took the 0v from Controller to that pin. Put the output to the relays input and when I activate the output from the CNC the relay works fine. So to me it looks like it is the L7812 that is the problem and as has been said it is likely that the caps missing are the fault.
     
    WorkshopChris likes this.
  4. eSCHEn

    eSCHEn Bit Wrangler Staff Member

    Messages:
    5,906
    Location:
    SW Scotland
    You want some caps sending up mate? I have 100nF and 330nF in ceramic here which should be okay (please correct me if SWK knows better :) ).
     
  5. Hood

    Hood If it walks like a duck....

    Messages:
    11,666
    Location:
    Carnoustie, Scotland

    Very kind but I think my best course of action is to just get a 24v relay board as it will simplify things greatly.
    If you however fancy a 12v relay board you can have one as I can't see me ever using it :D
     
  6. daedalusminos Member

    Messages:
    894
    Location:
    Norwich
    They aren't since the CNC controller output is open collector meaning that it can pull down but you need a resistor to pull up - you can connect the resistor to any supply (within reason) lower than 24V and it will work fine - you can even connect to voltages higher than 24V though you need to be careful you don't exceed the output transistor breakdown voltage.
     
  7. Hood

    Hood If it walks like a duck....

    Messages:
    11,666
    Location:
    Carnoustie, Scotland
    Here is my bench supply test, look away now if you are of a nervous disposition when it comes to twisted together wiring connections :D

     
    daedalusminos likes this.
  8. Hood

    Hood If it walks like a duck....

    Messages:
    11,666
    Location:
    Carnoustie, Scotland
    Right now that is cleared up can anyone confirm whether my thoughts on the VFD connections are correct. Below is a pic from the Yaskawa manual showing the Inputs and what they are calling Sink mode. To me it looks like Source but I suspect that they are calling it Sink because it requires a Sinking output to be connected to them for operation, is that the case?

    ScreenHunter_2371 Jan. 27 19.51.jpg


    Now the next image is from the control, they are sinking Outputs so I am thinking that all that is required is for me to tie the 0v of the control and the VFD together and connect the outputs of the control to the Inputs of the VFD and all should be happy. Is that correct?

    ScreenHunter_2369 Jan. 27 19.49.jpg
     
  9. MattH

    MattH Member

    Messages:
    3,894
    Location:
    Bristol
    Both those diagrams are ambiguous, I don't understand why they are showing external transistors on the VFD inputs.
    And the output from the CNC shows no ground.

    On the VFD if the inputs are switched to Sink then the output on the CNC controller needs to take a floating pin to ground when activated.
    If in source mode then the CNC controller needs to output 24v on the output pin when activated.

    On the CNC controller diagram the output is run through an inverting buffer cct (which is confusing on the diagram). Therefore when activated the buffer output will go to ground (which is confusingly not shown).

    So with the VFD in sink mode and connected directly to the CNC output pin you should be good to go.
     
    Hood likes this.
  10. Hood

    Hood If it walks like a duck....

    Messages:
    11,666
    Location:
    Carnoustie, Scotland
    Yes it confuses the heck out of me especially them calling it sink when to me they are sourcing.
    Same with the CNC diagram, couldn't get my head around that at first either but it does seem they sink when active.

    I could go with relays to control the VFD inputs but if they are not required then it is just added wiring and complexity. I will have to use relays for the servo drive inputs as they are sinking and can not be configured otherwise, outputs on the servos are sourcing so will also require relays, the axis drives will be fine as all I will need is a fault output from the drive and the drives have a relay output that can be configured for that. The servo drive that works my turret will need relays though as there are a few outputs I need.
     
  11. daedalusminos Member

    Messages:
    894
    Location:
    Norwich
    The VFD manual mode source/sink is referring to the device driving it, in this case your CNC.

    The CNC has a ULN2803 driver onboard and this is an open collector NPN darlington i.e. it's a sink. So set the VFD to SINK

    You need to connect the grounds, do not connect the 24V from CNC since the VFD has it's own 24V which is connected to the opto couplers via the sink switch position.
     
    Hood likes this.
  12. Hood

    Hood If it walks like a duck....

    Messages:
    11,666
    Location:
    Carnoustie, Scotland

    Great, that's how I thought it would be but two confirmations make me happier :)
     
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