Converted to Split 12V/24V - No Communication HELP



  • Hi All,

    This being my first post to this forum, I have to say how helpful the information I have found here and in the wiki has been. The culmination of all of this knowledge and lessons learned has been beyond valuable.

    I converted my RostockMax V2 to the Duet Wifi with a PanelDUE, an E3D V6, JohnSL FSR auto leveling, a Zesty Nimble extruder and just about every part Trick Laser sells in July, I have been overwhelmed by the performance of my machine with all of the upgrades except for the heated bed which left much to be desired. So, I recently purchased a 24V kapton bed heater from Ultibots and built a 12V/24V power supply from two ATX supplies and went for the install.

    I ran the board and all other components off of the 12V supply exactly the way I had it configured before, but ran 24V to one side of the bed heater and connected the other side of the bed heater to the switched ground side of the bed heater control connection of the Duet as suggested for people converting from a RAMPS system in the wiki.

    When I first switched on the new system, everything worked great. However, after the first power cycle, there was no connection to my PanelDUE or the web interface over Wifi. I also noticed that the DIAG light was on and I had never seen it on before. I immediately became terrified that I fried my board somehow, even though I thought I had followed the instructions for wiring a system such as that very carefully.

    I started to try diagnosing the problem by removing the 24V connection and checking the voltages from the supply at the board, and everything checked out which made sense considering that the 12V, 5V, and 3.3V LEDs were lit on the board. I then tried unplugging one connection at a time and re-powering the board to see if I could connect to the board with the PanelDUE or the web interface, but no dice all the way to the board completely disconnected from the printer.

    I then tried to connect to a Windows7 PC with several USB cables (one of which was a Motorola cable labeled with "data cable") and several USB ports, but I could not connect to Pronterface and no COM port shows up in the device manager. I have installed SAM-BA and tried the erase-reset method, but SAM-BA cannot connect to the board and I never see the Bossa port in the device manager. I then pulled the SD card and verified that all of the files on the card look correct and are not corrupted, but everything looked fine.

    I am at my whits end with this and would really love to get my printer running again, so any help would be greatly appreciated…

    Thanks ahead of time!!


  • administrators

    I'm sorry you are having problems getting your Duet to work again. If you have already followed all the steps at https://duet3d.com/wiki/What_to_do_if_your_Duet_or_Duet_WiFi_won%27t_respond then please ask your supplier to replace your Duet under warranty.



  • Thanks dc42, I have gone through all of those steps repeatedly, so I guess I'll just throw in the towel…

    To clarify though, it is acceptable to run 12V to the main power and 24V through the bed heater to the switched negative (and only the switched negative), correct?

    I am wondering if it is possible to run 24V to the main input and only run the fans and extruder on 12V. That way I get the benefit of the 24V on the bed heater and the steppers without worrying about having to replace my heater cartridge, fans, and other 12V components.

    Let me know your thoughts!

    -Cheers


  • administrators

    Yes it is acceptable to connect the bed heater between +24V from your PSU and the BedHeater- terminal, and to connect the negative output terminals of both PSUs to the negative VIN terminal.

    To run the Duet from 24V but use 12V heater cartridge and fans, you would need to:

    1. Connect the extruder heater between +12V and E0-. Caution: the E0 heater pins (and E1 heater pins) are labelled the wrong way round on most board revisions. However, heater cartridges are cheap so I suggest fitting a 24V cartridge instead.

    2. Remove the fan voltage selection jumper and feed +12V into the centre pin of that 3-pin jumper block.



  • Thanks for the info! I'll be sure to check the E0 pins for the correct ground pin when I get the new board.



  • I didn't know about the e0/e1 header pins being labelled wrong way around explains why my smarteffector heater LED didn't work until I swapped the pins around. Funny how you can joins the dots so many moths later.



  • So, after the comments about pins being possibly reversed, I was curious about what could be going on with my board. I got out my multimeter and everything seemed on the level until I got to the bed heater terminals. Something is seriously amiss here.

    Here is the voltage between the positive and ground input terminals (12.5V):
    https://photos.app.goo.gl/gsT9W8UVNJWJA3Np1

    And here is the voltage between the negative terminal of the bead heater connection and the ground of the input block (10.9V):
    https://photos.app.goo.gl/30Z4hog0OJyQvreX2

    Considering that there is nothing connected at the bed heater block, that has to be a telltale sign of a problem.

    Is there an obvious thing that could cause that? If so, is there a fix that I can try before sending the board off?

    Thanks ahead of time for the advice!


  • administrators

    There is an LED and resistor connected to the heater output, that's why you can measure VIN less the voltage drop of the LED at the heater output pin.



  • The bed heat LED is off on your first photo but lights on on second one. Maybe this is a cue?



  • That was my thought as well. I am unsure why connecting the grounds of the bed heater control and the VIN should allow current to flow between the two.

    I have no bed heater connected in these photos, so in my mind there should be no reason for the voltage to get from the bed heat + to the bed heat - unless something has gone wrong.



  • @wwmotorsports:

    That was my thought as well. I am unsure why connecting the grounds of the bed heater control and the VIN should allow current to flow between the two.

    Because your multimeter doesn't have infinite resistance.

    @wwmotorsports:

    I have no bed heater connected in these photos, so in my mind there should be no reason for the voltage to get from the bed heat + to the bed heat - unless something has gone wrong.

    As David says, with the bed heater off you should see the ground of the bed heater at (Vin - LED voltage drop), because the LED is connected between the + and - terminals of the bed heater terminal strip.

    With the bed heater off, the positive terminal will show Vin and the negative terminal will be floating, pulled up to Vin (less the forward drop of the LED) by the bed heat LED and its resistor.



  • If the multimeter is in good shape it would have input resistance in order of mega-ohms so it can't provide an essential current to light LED and to make such a big voltage drop across LED. I suspect that heater's nMOS switch is partly fried.



  • @zov:

    If the multimeter is in good shape it would have input resistance in order of mega-ohms so it can't provide an essential current to light LED and to make such a big voltage drop across LED. I suspect that heater's nMOS switch is partly fried.

    Nope, I have a perfectly functioning Fluke 179, it provides enough current to light the LED enough to be visible.



  • Look at the spec's of my multimeter (Fluke 289), input impedance 10MOhm < 100pF so the current through LED is about 12 uA in our case. Don't think this current is able to fire up any perceivable glow in LED. To speak frankly I don't check it by myself so can be mistaken and contemporary LEDs might be such effective.



  • zov: I think what elmoret is talking about is the "diode test" mode, available on most multimeters. In this mode the multimeter provides typically 3V on the probes, and limits the current to 2-3mA. If you put your probes onto an LED in this mode, the LED will light up dimly - but it will definitely emit light! This mode can be used to measure the forward & reverse bias voltage of diodes (and light-emitting diodes of course).



  • If you look at photos of OP you see he is measuring voltage between 2 terminals not diode test.
    ADD: And I have mistaken in the post above: the current through LED should be about 1.2 uA not 12 uA. So it makes the multimeter much more unlike as a shunt to lights LED on.



  • @resam:

    zov: I think what elmoret is talking about is the "diode test" mode, available on most multimeters. In this mode the multimeter provides typically 3V on the probes, and limits the current to 2-3mA. If you put your probes onto an LED in this mode, the LED will light up dimly - but it will definitely emit light! This mode can be used to measure the forward & reverse bias voltage of diodes (and light-emitting diodes of course).

    No, wasn't talking about diode test mode. Regular DC voltage mode.



  • @zov:

    If you look at photos of OP you see he is measuring voltage between 2 terminals not diode test.
    ADD: And I have mistaken in the post above: the current through LED should be about 1.2 uA not 12 uA. So it makes the multimeter much more unlike as a shunt to lights LED on.

    My multimeter also has a 10Mohm input resistance, and it is enough to light the LED, faintly. You can see an LED's light output at as little as one microamp.

    http://forum.arduino.cc/index.php?topic=183526.0



  • Won't argue with you as I don't have any practical experience of using LEDs with such low currents. Anyway thanks for a new knowledge you gave me.


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