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Thread: Heatermeter troubleshooting lcd display

  1. #1
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    Heatermeter troubleshooting lcd display

    Hey everyone,

    First post and just recently bought and soldered together a heatermeter (4.3)! Excited to get this thing working, but ran into a issue after booting up. I can connect via the web interface and it detects the device, but the LCD screen on the thing itself keeps scrolling through the menu options like someone if holding a button down (only after I plug in the thermocouple I might add.) Any ideas where I should start? Would it be an issue just with the LCD board or potentially the main board as well??

    thanks!

  2. #2
    TVWBB Wizard
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    Post good close up pictures of your boards, front and back. Check your button board for solder shorts. It's not the lcd. Also, check the main board for shorts.

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    Check connections and cannot find anything that seems to be a short, anyone have any ideas? Or seeing something I can't? Thanks!

  5. #5
    TVWBB Guru Steve_M's Avatar
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    A lot of your solder connections look like they didn't get enough heat and/or time to let the solder flow properly. If it were mine, I'd fire up the soldering iron again and redo a lot of the joints. You can especially see it on the shift register that communicates with the LCD and some of the LCD pins.

  6. #6
    TVWBB Honor Circle Bryan Mayland's Avatar
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    If the LCD is scrolling through the menus but working, that means there's something shorting the button pin OR your button pin is floating. Here's what how to troubleshoot that
    You want to check the voltage at the BTN pin on the bottom right of the LCD/Button board pin header. Since it is scrolling constantly, I'm guessing you're going to see a voltage there, when it should be 0V when no button is pressed. If you do see voltage, remove the LCD/Button board completely and check the same pin on the Base board side (flip the heatermeter over). If you see voltage still, it means the problem is on the base board. If there's no voltage now, it is on the button board or in the connectors.

    Base board: Check the 1k resistor right next to the pin header. One side should connect to the BTN pin on the pinheader, the other should be connected to ground. When I've heard of this before, it was that the ground pin wasn't soldered fully so it was floating. Check the continuity there. Also make sure the BTN pin doesn't have continuity to any other pin in that header.

    LCD Board: Check the the BTN pin doesn't have continuity to any other pin in that header. After that I'm not sure where to look. Maybe check the buttons themselves that they're open when not pressed (two legs are connected on both sides so check that one pair is not connected to the other pair when not pressed).
    I'm that HeaterMeter guy what ruins everybody's free time.

  7. #7
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    Thanks everyone, I ended up redoing all the joints and that fixed the problem then it started again! Although the second time was the LCD wasn't displaying and was just a case of having to clean off the flux to stop it from shorting....oops! Thanks again!

  8. #8
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    The base board works like a champ and connects to wifi but the LCD display displays rubbish.
    I had to do some desoldering so I reckon that's where I have to concentrate my efforts. Some of the joints look a bit ropey. I can't fault the instructions or the PCB labelling so most probably an RTFM problem.

  9. #9
    TVWBB Honor Circle Bryan Mayland's Avatar
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    The newer boards have labels on all the shift register pins to aid in troubleshooting. You'll want to check that 5V on the shift register connects to 5V on the LCD connects to 5V on the riser pin header, and the same with GND. Then check RS, E, D4, D5, D6, D7 from the shift register to the LCD while also making sure that each doesn't show continuity to any other one (i.e. E isn't showing as connected to RS or W or 5V or GND etc). If that's all good check MO, LCK, SCK to the riser pinheader and that they're also not connected to any other pins. Finally, check MO, LCK, SCK on the base board going from the riser pins to the microcontroller, as well as the Pi connector for MO and SCK.

    Most commonly, there's a bridge between two of the pins on the LCD or shift register with just a teeny wisp of solder connecting them. EDIT: Either that or if you damaged the PCB when desoldering. Almost always this can be worked around by just running a piece of wire directly to the component where the PCB is damaged.
    I'm that HeaterMeter guy what ruins everybody's free time.

  10. #10
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    Thanks for your reply Bryan.
    Here's the symptoms I had:
    • The LCD produced rubbish when the LCD and button board, base board and RPI were connected.
    • The baseboard connected to the RPI and was able to connect with WIFI
    • The LCD worked when I disconnected the RPI

    The fix was easier than I expected.
    I cleaned up the joints and stray bits of flux on the base board; no joy.
    I noticed that one of the header pins connecting the LCD to the button board was touching the metal casing around the USB ports on the RPI. I cut it off and all is working great now.


    Quote Originally Posted by PeterGiblin View Post
    The base board works like a champ and connects to wifi but the LCD display displays rubbish.
    I had to do some desoldering so I reckon that's where I have to concentrate my efforts. Some of the joints look a bit ropey. I can't fault the instructions or the PCB labelling so most probably an RTFM problem.
    Last edited by PeterGiblin; 12-02-2018 at 07:52 AM.

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