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Unresolved Bed heater doesn't work - Gen1

Discussion in 'Troubleshooting' started by Kodiak3d, Oct 25, 2015.

  1. Kodiak3d

    Kodiak3d New Member

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    I have a 1st generation Robo and the bed has stopped heating. It was an intermittent problem for a couple of days and then stopped entirely. The temp reading is 0, so I suspect it's not actually the heater but rather the temp sensor. I've checked the connections to the board and they seem solid (I reseated them all), and I took the bed off to look at the connections underneath and I don't see anything wrong with them .

    Any help is appreciated greatly. Thank you in advance.
     
    #1 Kodiak3d, Oct 25, 2015
  2. mark tomlinson

    mark tomlinson ༼ つ ◕_ ◕ ༽つ
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    If it is reading zero then it is either the wiring (bad connection) or a bad thermistor.
    (in rare cases it could be a defective RAMPS).

    There is often at least one connection in-line with the thermistor on the early generation Robo. You would need to unwrap the cable bundle to trace it.

    Me? I'd probably just replace the thermistor first :)
     
    #2 mark tomlinson, Oct 26, 2015
  3. Kodiak3d

    Kodiak3d New Member

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    First, thank you for jumping in to help, Mark. I appreciate that. The Robo forum is a great place for help.

    I should also note that I'm not completely useless when it comes to technical aspects of things, bu t I'm also no expert. I can build a computer from the ground up (given the right parts), but doing this kind of work on something like a Robo is new for me.

    I checked the wires and unwrapped them and there doesn't appear to be a connection in-line. The wires go straight from the bed to the board for the heater and thermistor. I checked all the connections and everything seems to be good. I would like to ask and make certain I have the thermistor jumper on the right pins. It goes on T1, right? I tried to put it back right where I found it, but I could have made a mistake I suppose. If that's not it, then the thermistor may be dead. If that's the case, I'll probably just get a whole new bed.
     
    #3 Kodiak3d, Oct 26, 2015
  4. mark tomlinson

    mark tomlinson ༼ つ ◕_ ◕ ༽つ
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    T1 should be the bed (T0 should be the extruder).

    It is likely a bad thermistor. (My original printer had two connections buried in the wire harness as well for the thermistors.)

    If you want to (just to prove it) swap T0 and T1 on the RAMPS just to see that the bed is now showing temperature (it will be showing the extruder temperature for the heated bed and vice-versa) -- that will prove that the electronics (RAMPS and Arduino) are fine.
     
    #4 mark tomlinson, Oct 27, 2015
  5. Kodiak3d

    Kodiak3d New Member

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    Yep, that sealed it. When I switched them, the extruder temp didn't work (hooked up to the bed sensor) .

    So...could you perhaps point me to where I can get a new thermistor and perhaps some easy-to-follow directions on changing it? I would just order a new bed (since I have the old, original model), but those are more $$$ and they're out of stock right now anyway.

    Also, thanks again, Mark, for the help. It is appreciated. This is a problem I've actually put aside for months now just because I was so frustrated I didn't feel like dealing with it.
     
    #5 Kodiak3d, Oct 27, 2015
  6. mark tomlinson

    mark tomlinson ༼ つ ◕_ ◕ ༽つ
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    You can get it anywhere really.
    Shop around. Here is one place (only as an example, not a promotion):

    http://www.reprapdiscount.com/electronics/78-reprap-100k-ohm-ntc-thermistor.html


    Whichever type you get make sure you check the firmware source (CONFIGURATION.H) that it is set to the correct type:
    You should know when you order it what TYPE it is (the seller should say) and then you make sure the firmware matches.

    Here is the snippet (note that the one I linked to is a "Semitec GT2-104" which would match type 55 so I changed the lines appropriately) :

    //// Temperature sensor settings:
    // -2 is thermocouple with MAX6675 (only for sensor 0)
    // -1 is thermocouple with AD595
    // 0 is not used
    // 1 is 100k thermistor - best choice for EPCOS 100k (4.7k pullup)
    // 2 is 200k thermistor - ATC Semitec 204GT-2 (4.7k pullup)
    // 3 is Mendel-parts thermistor (4.7k pullup)
    // 4 is 10k thermistor !! do not use it for a hotend. It gives bad resolution at high temp. !!
    // 5 is 100K thermistor - ATC Semitec 104GT-2 (Used in ParCan & J-Head) (4.7k pullup)
    // 6 is 100k EPCOS - Not as accurate as table 1 (created using a fluke thermocouple) (4.7k pullup)
    // 7 is 100k Honeywell thermistor 135-104LAG-J01 (4.7k pullup)
    // 71 is 100k Honeywell thermistor 135-104LAF-J01 (4.7k pullup)
    // 8 is 100k 0603 SMD Vishay NTCS0603E3104FXT (4.7k pullup)
    // 9 is 100k GE Sensing AL03006-58.2K-97-G1 (4.7k pullup)
    // 10 is 100k RS thermistor 198-961 (4.7k pullup)
    // 20 is the PT100 circuit found in the Ultimainboard V2.x
    // 60 is 100k Maker's Tool Works Kapton Bed Thermistor
    //
    // 1k ohm pullup tables - This is not normal, you would have to have changed out your 4.7k for 1k
    // (but gives greater accuracy and more stable PID)
    // 51 is 100k thermistor - EPCOS (1k pullup)
    // 52 is 200k thermistor - ATC Semitec 204GT-2 (1k pullup)
    // 55 is 100k thermistor - ATC Semitec 104GT-2 (Used in ParCan & J-Head) (1k pullup)
    //
    // 1047 is Pt1000 with 4k7 pullup
    // 1010 is Pt1000 with 1k pullup (non standard)
    // 147 is Pt100 with 4k7 pullup
    // 110 is Pt100 with 1k pullup (non standard)

    #define TEMP_SENSOR_0 1 //robo
    #define TEMP_SENSOR_1 0
    #define TEMP_SENSOR_2 0
    #define TEMP_SENSOR_BED 55 //robo
     
    #6 mark tomlinson, Oct 28, 2015
  7. mark tomlinson

    mark tomlinson ༼ つ ◕_ ◕ ༽つ
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    #7 mark tomlinson, Oct 28, 2015
  8. Kodiak3d

    Kodiak3d New Member

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    #8 Kodiak3d, Oct 28, 2015
  9. WheresWaldo

    WheresWaldo Volunteer ( ͠° ͟ʖ ͡°)
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    No it would not.
     
    #9 WheresWaldo, Oct 29, 2015
  10. Kodiak3d

    Kodiak3d New Member

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    Super. It's ordered. Thanks again for all the help.

    Are there any tricks or advice to taking the old one off or mounting the new one to the bed?
     
    #10 Kodiak3d, Oct 29, 2015
  11. WheresWaldo

    WheresWaldo Volunteer ( ͠° ͟ʖ ͡°)
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    Bed or hotend? You original post was about the hotend, just take the rubber cover off and pull it out of the hole through the rubber cover. Bed thermistor replacement requires much more work, I can't help you with that one.
     
    #11 WheresWaldo, Oct 29, 2015
  12. Kodiak3d

    Kodiak3d New Member

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    Must be some confusion. My original post is about the bed. Mark just mentioned switching the hotend thermistor and the bed thermistor so I could make certain it was the thermistor and not the RAMPS board that was the problem.

    Either way, it doesn't matter. You say the bed thermistor requires more work. Would you elaborate on that? I thought it would be pretty simple. The current one is just mounted to the bed with some rubber. I appreciate any suggestions.
     
    #12 Kodiak3d, Oct 30, 2015
    Last edited: Oct 30, 2015
  13. mark tomlinson

    mark tomlinson ༼ つ ◕_ ◕ ༽つ
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    Just mount it flush against the bed the way the current one is. Some high-temp RTV (or something similar) will be fine to hold it in place (high temp in this case is not 'that' high, but better safe).
     
    #13 mark tomlinson, Oct 30, 2015

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