Re: [sudo-discuss] 3D Printer - needs new heating element

the new heating resistors came in - to anyone who's interested in replacing the heating element, i'll be doing it before next week's meeting unless someone is itching to handle it themselves before then. It does require kapton tape from what i've read - anyone have a few inches of that stuff lying around? Nov 2, 2013 09:58:15 AM, steveberl(a)gmail.com wrote: Is the tape wrapped around the hot end anything special? al lashers is great!  they don't stay open late enough for me to go there after work though, so i usually get this kind of stuff online. it is 12vdc so the LED warning is easily done.  for AC you could still just use one LED at just under 50% duty cycle and it'll block the reverse current. i don't know about all that empirical stuff - say you want 3V at the LED at 30mA, that's a 9V drop over the series resistor and R=V/I=9V/.03A = 300 ohm  resistor.  could also just slap a chunk of 12V led strip down and call it a day - definitely bright! i would be curious to know if the problem resulted from simply being left on or what.  the fan was not running iirc so that could have had alot to do with it, will have to check that as part of the repair - for now i'm just going to get these http://www.amazon.com/Resistor-Heating-Element-Printer-RepRap/dp/B00C44TBPA jake i'd be interested in learning more about how to tune the PID settings.  no idea about the temperature sensing status since it stayed at room temperature, didn't think to use body heat or anything to test it but that'll be an easy enough check.  i did not check the thermistor (or is it a thermocouple?) for continuity. cheers, hol Nov 1, 2013 05:45:36 PM, g2g-public01(a)att.net wrote:     Yo's-     And/or you can take the existing fried resistor to Al Lasher's     Electronics on University Ave in Berkeley and they'll find a     replacement, either exact-same or very close (the tolerances on     resistors used as heaters are pretty wide).  If it's a 3 to 5 watt     resistor it shouldn't cost more than a couple bucks.     Al Lasher's is an oldschool electronics shop that everyone in SR     ought to know about: their stock of raw component parts is     fantastic, and the folks who work there have been around forever     & know their stuff.  You'll probably find stuff there that     suggests new projects to do.     Chances are if you bring in the heat sink with the resistor glued     on, they'll also be able to tell you what kind of glue is needed,     and they probably have it in stock along with the resistor.      Re. putting an LED on the heating element:     Good idea and will need a dropping resistor ahead of the LED,     otherwise the LED will probably fry the first time it's turned on.      If the voltage used to run the heater resistor is AC, then wire two     LEDs together, one in reverse polarity with respect to the other,     and they'll both light up.      To estimate the value for the dropping resistor, measure the voltage     input to the heater resistor and the current it draws (after you     replace it with one that works), and compare with the specs for the     LEDs you're using.  If the dropping resistor or the LEDs get warm     when in use (aside from ambient heat from the heater resistor), or     the LEDs are excessively bright, substitute a higher value dropping     resistor.      If I was doing this, I'd just go empirical and use a large variable     resistor in series with the LEDs, and turn it down slowly while in     operation, until the LEDs light up to a sufficient degree (not dim     but not too bright), then measure the value of the setting on the     variable resistor and find a fixed resistor of similar or slightly     higher value.     Useful tools for these types of purposes:     A resistance decade box, and a capacitance decade box.  These let     you do empirical tests by switching-in progressively different     values of resistors and capacitors into circuits until you get the     desired result.  Lasher's probably has at least a resistance decade     box in stock.  The reason these are called "decade boxes" is because     the traditional version has selectors with ten positions each, and     the values of each selector increase by factors of 10 relative to     the next lower selector on the box.      The exception to the use of decade boxes is where a component     handles a large power level, such as a heater resistor, or an     electrolytic capacitor in a power supply.  I'm guessing that your     heater resistor handles from 3 - 5 watts, but it may be more.  The     resistors in decade boxes are typically rated at 1/4 watt to 1/2     watt and are designed for testing signal/control/audio circuits     rather than circuits that carry higher power levels.      -G     =====     On 13-11-01-Fri 5:20 PM, Jake wrote: >I retract my assertion that you hadn't put any text in       your email.       as for the printer, it seems clear that you and steve are right       that the resistor is burned out.  I wonder what caused this - i       haven't heard of it happening a lot bu        on Nov 01, 2013, Jake  wrote:               Hol,               you forgot to put any text in your post at all! please be         clear of how               you came to this conclusion.               The heating element is a resistor glued into a block of         metal on the end               of the extruder. It has two wires which go to a connector         a couple inches               from it, and they go back to the machine.               To test the heating element, one can unplug this connector         and use a               multimeter to measure its resistance. It should be         something like 8 ohms,               i don't know the exact value but 100 is too much and         indicates it's bad.               it was replaced a little while ago by a technician from         the corporation               that made it.               If the machine is acting up about heating, we need to know         whether the               problem is with the heating or the temperature sensing. If         the               temperature sensor is reporting ambient temperature, it's         probably               working.               if the temp sensor is working but the heating element         isn't making it heat               up, it could be the heating element (see test above) or it         could be the               connector near it, or the wires from there back to the         main board, or               where those wires connect to the brain.               can you give more information about what you tried and         what you observed?               -jake                 _______________________________________________ sudo-discuss mailing list sudo-discuss(a)lists.sudoroom.org http://lists.sudoroom.org/listinfo/sudo-discuss _______________________________________________ sudo-discuss mailing list sudo-discuss(a)lists.sudoroom.org http://lists.sudoroom.org/listinfo/sudo-discuss >-- >-steve