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Type of resistor for heatbed?

tim12

Hi to all,

 

I have almost finished building my 3D printer... But a major problem arises...

 

Unfortunately, no resistor came with my Sainsmart mk2B heatbed. After some browsing online, I found the reprap wiki had something to say:

 

resistance between 1.0-1.2 ohm (12V) or 3-3.4 ohm (24V) (Sainsmart board came in at 1.8 ohm @ 12V/3.6 ohm @ 24V)

Since I've bought the Sainsmart heatbed (12V), should I get the 1.8 ohm resistor, despite the large difference between 1.2 ohms and 1.8 ohms? Thank you

 

Furthermore, what kind of resistor should I get, I found loads of them online:

  • ceramic cased (this is the one I was going to choose)
  • carbon film
  • wirewound

 

Thank you in advance

 

Best wishes,

Tim Timmy

  • Hello Timmy

    You will not need to purchase any resistors.  The statement "resistance between 1.0-1.2 ohm (12V) or 3-3.4 ohm (24V) (Sainsmart board came in at 1.8 ohm @ 12V/3.6 ohm @ 24V)" is talking about the internal resistance of the pcb.  Depending on your power supply voltage you will have different connections.  They will be labeled on the hotbed.  Hope this clarifies things.

     

    Nate

  • in reply to Nate1616

    Aha! I see now, I was quite confused too why there weren't any results for "heatbed resistors". Well, thanks for telling me about this mistake! I wonder what would have happened if you hadn't told me...

  • in reply to tim12

    Just a follow up question Tim.  How is your 3d printer project going that you were working on a while ago.  I haven't heard anything from you in a while.  Have you trademarked or patented anything?

     

    Nate

  • in reply to Nate1616

    Hi Nate,

     

    I'm sorry that I haven't been able to reply to your message for six days since I'm currently on holiday - actually right now, I'm in Frankfurt Airport. Then, when I get back to the UK, I will only have two days to prepare an entire new office, do some gardening(!!) and notably, finish my 3D printer. And then, I'll have to fly to Canada. And then, I will start sleepwalking.image

     

    Anyway, thanks for your interest! I've been working on the company magazine, contacting a patent holder, finding intelligent (well, at least interested) employees and much much more. I am also due to see a marketing expert in Canada to review the company work. Indeed, I hope to (if I have the time) to create in the next few days a thread detailing important features of the product and a poll (I hope) to find out the demand for the product in preparation for the guy in Canada.

    thumbs_work-joke-01.jpg

    Heh heh...thumbs_work-joke-04.jpg

     

    I must really stop wasting my time finding funny picsimage

     

    Kind regards,

    Timmy Timothy Timmy Timothy Timmy Tim Timmy

  • in reply to tim12

    Tim,

    I look forward to seeing what you have in store.

     

    Nate

  • in reply to tim12

    The resistor would have got quite hot and the bed would only heat up at about half the rate it would without the resistor. Ceramic resistors are fine for most applications. Also, LOL to your pictures. I am posting this from on holiday in Switzerland.

  • in reply to Nate1616

    Hi Tim -
    wow - 1.8 ohm @ 12V - that will draw a lot of amperes - likewise 6.6   - and has so,  80 watts of power ... I suggest a  separate powerdevice to feed that 'beast  - and - additionally a PWM 'regulation  - (oh ideas  - arduino' small, the tiny 8 pin one, with programmed 1 PWM output and 2 ADC in. (six  in all, universal in-out)  One, for perfect regulation the feedback of actual temperature, and the other, via  'Poti -  to set the desired temperature  measured via LM 32, 10mV /°C,    usable - if the  bead temperature  will not exeed  150°C) and a PWM signal, amplified by a transistor to drive the gate of the PowMOSFet, to drive' the heat mat... )

    https://www.youtube.com/watch?v=30rPt802n1k   (8-pin ATtiny chip, the how' to use, how to  programm, via Arduino ISP !  image
    http://www.ti.com/lit/ds/symlink/lm35.pdf

    my 'two cents'  to it.. 

    nice regards, Oliver