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Solved New heated bed issues

Discussion in 'Troubleshooting' started by Fraser Simpson, Sep 23, 2018.

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  1. Fraser Simpson

    Fraser Simpson New Member

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    Hi all,

    I think I know the issue here, but not sure how to go about resolving it.

    I had an issue with my original Robo heated bed playing up since it had the wiring under the bed and I wanted to upgrade to the cabling coming out of the rear via a ribbon type cable such as the later + model has, but I waited and waited as requested by Robo tech support then contacted them back to get fobbed off with some wishy washy..... "I'm not really sure when we can actually help you, you might want to look into doing something else" answer which I thought was pretty unprofessional...……..

    Anyhow moving on...…….. I decided to purchase a new heated element to replace the existing one and have installed it etc and it seems to work OK to a certain degree in that it warms up the bed OK, but then I think something on the Arduino can't cope and shuts power off to the heated bed and it starts to cool down. Feels like one of the MOSFETs is getting really hot. I've got a fan cooling the Arduino, but I think it's not enough.

    The unit is a Keenovo 300W 12V unit. Picture attached. I guess that this heater is drawing too much current ? Pretty sure the power supply is up to the task, but not sure exactly how everything is setup with the Robo, I just wired the new heater into the existing points on the Arduino...…..

    Any suggestions ?
     

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  2. WheresWaldo

    WheresWaldo Volunteer ( ͠° ͟ʖ ͡°)
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    Your solution would be to provide power directly to the bed heater from the power supply not from the RAMPS board. The RAMPS was designed to handle a maximum of 11A of power for the bed heater, a 300W heater at 12V draws as much as 25A. You need something like this:

    Heat Bed Power Module Add-on (not endorsing this model, just the first one that comes up when searching Amazon Prime).
    [​IMG]

    There are numerous thread about how to wire this up already on the forums.
     
  3. Fraser Simpson

    Fraser Simpson New Member

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    Yeah OK cool, I kinda thought as much...…… I also assumed something like a simple relay would work where the current RAMPS board just switched the relay and then the power would be provided straight from the PSU...….but thanks very much as you just confirmed what I had thought...…….. so I wasn't going to be chasing a pink elephant ! :D
     
  4. mark tomlinson

    mark tomlinson ༼ つ ◕_ ◕ ༽つ
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    The relay will work too, that is essentially the same job that MOSFET is doing. I tend to prefer the MOSFET over a mechanical relay myself, but either one is fine.
     
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  5. Fraser Simpson

    Fraser Simpson New Member

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    Thanks very much to you both, you've been very helpful. Ordered a MOSFET upgrade similar to the one mentioned so I can get it working, will report back here with results just in case others find it useful.
     
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  6. Fraser Simpson

    Fraser Simpson New Member

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    Got the unit wired up today and it works like a dream. This heater can get much higher temps than the one that came with it and more consistent temp across the whole pad.

    I've never been able to get much success with ABS due to the heated bed not being able to get hot enough so now I think I'll have no hassles at all...……..

    Thanks very much for the advice, it was so easy to resolve in the end.
     
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  7. WheresWaldo

    WheresWaldo Volunteer ( ͠° ͟ʖ ͡°)
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    No problems, glad we could help.
     
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