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C2 Power capacity

Discussion in 'Mods and Upgrades' started by OutsourcedGuru, Sep 8, 2017.

  1. mark tomlinson

    mark tomlinson ༼ つ ◕_ ◕ ༽つ
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    Although, in my case it meant some rewiring with connectors to match what the hotend assembly for the C2/R2 uses. That was a bit of a pain, but not horrid. I really needed to get the correct connectors eventually and now I have them and a crimping tool :)

    Still very valid point ... I bought none of that from Robo directly. I couldn't either since they had no stock of spares at that point.
     
  2. OutsourcedGuru

    OutsourcedGuru Active Member

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    That's a respectable-enough answer. It could cost $100 and it wouldn't matter to me. I care mostly about suitability and having the perfect height-match against T0 to its left. Although sourcing a near-match would have worked out in the end, I didn't feel like troubleshooting the load difference which—although small—would always have been an unknown in the big scheme of things. I now have two perfectly-matched hotends for this project. Did I pay more? I don't know because I didn't even look at the price tag, tbh. I value my troubleshooting hours later at a fair rate and to me, it's a big savings to just jump to apples/apples and remove that from the equation.

    Somewhere out of our hands is a spec sheet for this puppy. I don't have it. You'd think there would be values in there to indicate max power, rated voltage and such. In the real world outside of 3D printing, it seems like engineers actually go through the motions of working a part until failure and documenting the process to come up with these ratings. In what likely happens, they just produce a part by copying what the last guy did and just xerox'ing the specs from the last one.

    Half the time, the rated specs on a transistor will assume that it's heatsink'd even if they didn't ship with that. The next person might then copy that transistor design, add a heatsink and double the current rating. (Oops.) And now your transistor blows out under load. If I'm online, I try to use places like digikey which at least talk the talk. I don't design for the market at-large; I am the market I design for and my time is money.
     
  3. OutsourcedGuru

    OutsourcedGuru Active Member

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    I didn't see that you 24'd your C2. One of these days when you pull that project back onto your benchtop it would be good to do a side-by-side comparison of the resistance of T0/T1 on that. If they're the same and applying the same voltage to both produces the same temperature curve then you've got a reasonable match, ignoring the height or any other physical differences.

    Another unknown is the throat size. You can't see inside that.

    On the re-wiring, I think I have a plan for that. I'll let you know later.
     
  4. mark tomlinson

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    I just used the 24v heater core. It is running at 19v :)
    There is no reason you couldn't swap the C2 to 24v given that the R2 runs those same boards at 24v. I suspect there my be a jumper on the control board...

    IIRC they are NOT the same resistance, and they are certainly not quite the same heat up time either.
    However I am not convinced that they sourced 19v heater cores.... Either they used 24 and derated them or the used 12v and over rated them.
     
  5. OutsourcedGuru

    OutsourcedGuru Active Member

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    Braydon confidently suggested I could drop in a 24V brick, "no problem". I went to confirm this with Allen (within three minutes of walking out the door, his eyes bugged a little and even though he was due within a couple minutes of participating in a new video with Braydon), he took a few seconds to reasonably suggest that this wouldn't necessarily be advisable given the configuration changes and he ended with "you'll want different hotends if you want to do that". Now granted, he was forced to communicate something in under two minutes which you'd want more time to talk about, but he seems to think that there's more to this than the label on the ziplock bag.

    Allen's slight panic moment there seems to suggest that it's indeed a 12V-rated hotend and they're pushing the limits. In designing the R2 they probably bricked it at 24V and fried some of the earlier hotends, maybe. Couldn't tell you.

    And yet, I haven't put a meter on this. They could be clamping the voltage for all we know in the C2. With innovative cooling, you could double the power on almost anything electronic.
     
  6. mark tomlinson

    mark tomlinson ༼ つ ◕_ ◕ ༽つ
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    well I can confirm this much ... the power to the heater core is 19v on the C2. I measured it on mine.

    When we were doing the dual extruder mod I had a conversation with Braydon and he mentioned that it was 19v -- actually he seemed surprised that I had found 19v heater cores* (I had not even looked at the brick and assumed it was all 12v) ... I panicked a bit until I ordered in some 24v** heater cores.

    So in summary, I strongly suspect they are using 24v cores...

    *he seemed certain that using 12v ones would be bad...in that it would draw too much current for their control board.

    **because nobody I could find sold 19v ones...
     
    #26 mark tomlinson, Sep 16, 2017
    Last edited: Sep 16, 2017
  7. mark tomlinson

    mark tomlinson ༼ つ ◕_ ◕ ༽つ
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    lastly, totally anecdotal (but I have tested it repeatedly) the second extruder with the 24v core does heat just a bit slower than the other. You can see the graph in OctoPrint and the curve is slower for that second extruder.

    Why they would opt to double the amount of spare bits they need to stock for the savings in the P/S brick cost -- I do not know. The cost savings between the 19v brick and the 24v brick is probably significant simply based on the extra current the R2 needs for a second extruder and a heated bed.
     
  8. WheresWaldo

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    I had in the past researched these heaters and like anything else If you are willing to order 100000+ per month you can get a lot of stuff built to your specs, You want 19V heater cartridges you can get cartridges labeled 19V. If you really want to make sure they are 19V you have to have a full-time agent at the supplier to make sure you get what you spec. If you are only willing to buy 10000 per month then you get what most manufacturers make. This is true in nearly every industry where you are trying to drive the cost of manufacture to the bare minimum. I would be very surprised, no, I would be amazed if Robo with their limited volumes had custom made 19V heater cores.

    Now I can believe 12V cores overvolted to 19V, or 24V undervolted to 19V and I also can believe a mix of 12V and 24V depending on the current supplier demands (again why you need a full-time agent on your payroll when dealing with Chinese manufacture).

    Anyway this could pretty much be put to rest by measuring the resistance of the heater core. Facts:
    V = I * R -> Volts = Amps * Ohms
    W = I * V -> Watts = Amps * Volts​

    Typical 12V and 24V cores have resistance levels that can be calculated with very simple math. If you use 40 watts as an example. 12V @ 40W will draw about 3.3A so it must have a resistance of 3.6 Ohms.
     
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  9. mark tomlinson

    mark tomlinson ༼ つ ◕_ ◕ ༽つ
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    That sounds spot-on for the 12v 40w units we use. I have not had a chance to run a test on the C2 ones, yet...
     
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  10. OutsourcedGuru

    OutsourcedGuru Active Member

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    At least we have a litmus test. When I get further along on this I'll do a current measurement on the second hotend at its hottest setting. And then a resistance across that out-of-circuit.

    Allen confirmed my guess about the layout and types of the green connectors on the Robo board.

    digikey
     
  11. WheresWaldo

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    Those power connectors are pretty standard in the RAMPS boards and clones. There really is nothing special about Robo's board other than the fact that they decided they wanted their own form factor. It is electrically and programmatically identical to a RAMPS 1.4 board, even using the same pin assignments. They obfuscated the type of board it is in their firmware source by creating pin files for both the C2 and R2 called pins_ROBOC2.h and pins_ROBOMB.h, they could have just used a single file as the only difference are the pins used for the heated bed and are undefined in the C2. To be 100% accurate they could easily have used the RAMPS pin file since there are no differences in those assignments. Since you can enable or disable the bed heater in Configuration.h, this was, simply put, a waste of coding resources.

    I have compiled their code, with all the code they thought unworthy stripped out and a Generic Marlin and when you compare the compiled code sizes and amount of space available for data, they only differ by a few bytes.
     
    #31 WheresWaldo, Sep 16, 2017
    Last edited: Sep 16, 2017
  12. OutsourcedGuru

    OutsourcedGuru Active Member

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    Somebody there's probably thinking of the "next big thing" so even though the C2/R2 are the same, essentially, they have enough uncertainty that they'd put a layer in there, just in case. Nice group of people. Busy. A little rushed. Fairly quiet around the office except for fulfillment in the back. Probably no time to think. They knew us all by username, pretty much.
     
  13. WheresWaldo

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    Just running the numbers, I highly doubt that Robo is overvolting a 12V ceramic heater cartridge. If they did it would draw 4 AMPS and be equivalent to a 75 WATT heater. It just isn't that fast heating up (this all supposes a 30W 12V cartridge).

    A 30W 24V cartridge would run at 1 AMP draw and produce about 19.2 WATTS of heat.

    Please note that nothing on this planet has 100% efficiency so please do not look at these equations as the hard and fast rule. If you measure ohms and are close then you should have a good idea what parts were speced.

    Also note these were 'back of napkin' calculations.
     
    #33 WheresWaldo, Sep 18, 2017
    Last edited: Sep 18, 2017
  14. mark tomlinson

    mark tomlinson ༼ つ ◕_ ◕ ༽つ
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    I am with you, I doubt they are doing that. Initially we used a 12v one on the second extruder and it worked... so it is possible, but again Jerry was fairly certain that was a bad move :) I'd more readily believe that they are using a 24v one, but then ... having two versions in stock doesn't seem to make sense.

    All supposition on my part.
     
  15. Geof

    Geof Volunteer Moderator
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    foxcon sells them two instead of one :D great idea lol. one 19V (24V) and one 24V (24V) :D pow pow!
     
  16. OutsourcedGuru

    OutsourcedGuru Active Member

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    There you go: straight from the horse's mouth (connectors in the Robo board). If you create an account you can even download the STL, in theory.

    I'll see if I can pull a Foxconn P/N from one of these cable assemblies to see if it's just their stock parts.
     

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