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Power timer mod. Power down when print is finished

Discussion in 'Mods and Upgrades' started by tonycstech, Jan 17, 2014.

  1. Melody Bliss

    Melody Bliss New Member

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    If you are standing on the floor, you are grounded. Even if you are wearing shoes, you are probably still grounded. The resistance to ground is still very high, but a short through you at 110v to ground Is Not a Good Thing(tm)

    I think that SteveC just wants to make sure that we all stay safe. As fun as it is to work on the printer (or frustrating as in many cases) if we don't walk away from it safe and alive NONE of this matters.

    And all it takes is not thinking for one second. I'm an extra class ham and I'm used to working with very high voltages. But I know I've just had a momentary laps that later scares the *crap* out of me when I think about it.

    These same thoughts go with gun safety. All it takes is a momentary lapse and you have a tragic event. :(

    Please stay safe.
     
  2. tonycstech

    tonycstech Active Member

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    After weeks of printing i found out that bad relay can cause USB connectivity issues.
    1st obvious sign of a problem was my LCD blinks slightly.
    Print would start fine but it will not complete. After few layers, connection would get lost.
    Unplugging relay from the board fixes the problem.
    ALSO unplugging 110v with USB cable still attached makes the blinking go away.

    So far i tried 3 types of relay's shown below.
    The biggest one had the least problems but once in a while it would cause printer to fail (rarely but still there and will take much more print time before it does.)
    DSC06578.JPG

    Does anybody know any good relay that would not cause any connection issues ?
    I wonder why they cause those issues :(.
    I learned that tempering with LED's on thise relays has an effect on that because i tried to connect regular LED to the relay LED in order to have LED stick outside of the printer.
    Then i bought one on the left that has 2 small LED's. I remove them and wired into printer so i can see them from outside but this relay tends to screw up connection as soon as i plug in USB cord.

    All those problems are detected once printer is powered ON, USB connected and i go into LCD settings trying to tweak things. Then i see display slightly starts to blink. Then i know USB connection wont be stable.
    Again, unplugging the relay from the board solves the problem.

    Any ideas ?
     
  3. SteveC

    SteveC Well-Known Member

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    Tony,
    I am using the module on the right and have done 12 hour prints with no issue. It's schematics are similar to this:

    [​IMG]
    Did you modify the status LED on this module? If so, note that the status LED is inline with the opto isolator as part of the circuit and modifying it with another LED and extending the wiring may be causing your intermittent problem. The red PCB relay in the middle of your photo probably uses a similar scheme. The relay on the left of your photo has no opto isolator just a transistor to drive the relay coil.
     
  4. tonycstech

    tonycstech Active Member

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    Yes i remove the status LED and wired it to the small LED as the relay on the left has.
    I then bought the relay in the middle and used its LED and soldered it back on to the board on the right.
    Problem did not go away, connection would still get list once in a while.
    LED's look same, i assumed they would be same thing.


    Look at the relay in the middle. It has 1 LED (POWER) missing. Missing LED went back to the relay on the right :)

    I now have relay on the left installed.
    Why does it cause issues ? I have my wiring correct, there is only 3 wires, VCC,PS-ON and ground. Both LED's are lit on that relay. Relay also does work fine as i expected.

    Should i go buy another relay thats on the right ?
     
  5. Ziggy

    Ziggy Moderator
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    Where are you getting the 5v VCC supply from for the relay? Is the LCD getting its power from the same 5v source?

    If you are using the 5v from the Arduino board (USB Power) then it is possible that the relay and LCD will draw enough current to cause problems.
     
  6. SteveC

    SteveC Well-Known Member

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    Did you have any problems with long prints before you modified the right side relay?

    OK for the middle and right modules: The LEDs probably have the same characteristics. Are they both the same color? It is possible that the difference in LED voltage drop and could reduce the current that the opto isolator sees and make it too dim to be a reliable switch for the coil.

    For the left module: I don't have a schematic but it is probably a very simple transistor driver with a diode across the coil. Should work but something could be wrong with it.

    If you can get it into the state you mention with the LCD blinking then you can carefully measure some voltages to see what is going on:
    relay module input IN to relay GND. This should be less than around 1.5V DC.
    Relay module 120VAC in to out. This should have zero AC when the relay is closed. When open it should have 120VAC
     
  7. SteveC

    SteveC Well-Known Member

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    Hi Ziggy,
    I believe the USB cable is unplugged though all this but Tony should confirm. Both relay are LDC are supplied from the RAMPS board which gets it from the Arduino Mega's regulator.

    Correct me on this if I am wrong but I think the Arduino does not use the USB 5V supply if it has 12V(Vin) fed to it from the RAMPS (which comes from the Robo switching supply). So the only time the USB cable 5V supply matters is if the Robo's power switch is turned off. You normally never do this unless you are flashing the firmware.

    The USB supply is gated off by T2 here and 5V comes from the regulator IC2 from Vin:
    http://arduino.cc/en/uploads/Main/arduino-mega2560-schematic.pdf
     
  8. tonycstech

    tonycstech Active Member

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    I usually have USB pluged in at all times, but now that it gives me so much trouble i unplug it.
    I need to disconnect USB or the relay to stop LCD display flickering (indicating a problem)
    It does not start flickering right away, it takes few seconds or me going into menus etc, then i see it go.
    I have not noticed it for a long time with the relay on the right installed, but never the less problem existed, it just didnt show its self for days.

    It became more apparent when i started to temper with the LED. Then i changed 2 relays.
    Perhaps i did some damage to the board.
     
  9. SteveC

    SteveC Well-Known Member

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    Once I got the XXL LCD I stopped using the PC to control the printer. I'll have to sleep on this I have no ideas right now...
     
  10. Ziggy

    Ziggy Moderator
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    I would suggest you check this info out

    http://reprap.org/wiki/RAMPS_1.4#Power_Supply

    The Arduino/Ramps power supply arrangements have a number of options and limitations. It's important to understand where you are getting your power from.
     
  11. SteveC

    SteveC Well-Known Member

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    Thanks Ziggy,
    I checked that section out and everything I said above holds. D1 must be in place on our RAMPS boards otherwise it would not run without the PC. The only time the PC/USB supplies the Arduino is if the Robo's 12V supply is off. Please correct me if I'm out to lunch ;).
     
  12. Ziggy

    Ziggy Moderator
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    All good :) My thought was that the 5v power available from the regulator on the Arduino Mega is limited. The available 5v current is limited by power dissipation in the regulator (which is already quite high when the source voltage is 12v).

    In this case the Arduino Mega, Ramps, LCD plus the relay coil are drawing 5v power from the Arduino Mega board regulator. Could be too much?
     
  13. SteveC

    SteveC Well-Known Member

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    Yikes! good point. That relay coil is 71.4mA nominal at 5V. But I am having a hard time finding the XXL LCD power spec and it would be a pain to try to measure. I assume the robo3D uses a classic Taurino board. That Atmel part has a max current consumption of 200mA. Its regulator has a 7V drop. I think I will just measure +5V and see if it drops out at any point. I can probably figure out a way to log the minimum with my scope.. I also could put a thermocouple on the regulator but it is a bit hard to get to... I suspect that 71mA is not pushing it over the limit.

    relay:
    http://www.parallax.com/sites/default/files/downloads/27115-Single-Relay-Board-Datasheet.pdf
    Regulator:
    http://www.onsemi.com/pub_link/Collateral/MC33269-D.PDF
     

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