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Nescafe Aeroccino, still fails with new Motor (red flashes only once)

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    Nescafe Aeroccino, still fails with new Motor (red flashes only once)

    Hi,

    i am asking for some Help.
    I have one of these Nescafe Aeroccino (Milk Frother) things with a bad motor.
    The Motor didn´t start anymore and internet is full of users just swapping the motor for a Mabuchi RF-500TB-12560.
    So i got a few of these from Banggood.

    I swapped the motor and now i have a new fault condition.

    In a working Frother you would press the start button, it will light red and work for a few minutes.
    If you press longer it will light blue and just mixup the milk.

    With the new Motor it just starts for a second (red blinks) and the stops, same with longer press.

    First i thought, the motor is faulty but with 2 other motors i have the same error.

    With no Motor the device works, with a short (instead of the motor) it works (but burncs BC817-25).

    There is a tiny Atmel, the motor driver is just the BC817-25 some Diodes for Motor and 9V.
    The BC817 is driven by the Atmel.

    I measured the old and new Motor, both are within the specs for a Motor with 0 RPM.

    The Diode and BC817 on the top left have been remove/checked and resoldered for testing.

    Can anyone think of other failure?

    I add a picture of the PCB.

    Thanks in advance

    Jürgen
    Attached Files
    Last edited by juergenb; 03-23-2021, 11:27 AM.

    #2
    Re: Nescafe Aeroccino, still fails with new Motor (red flashes only once)

    i dont know the motor voltage, but try replacing it with a lamp bulb as a load

    Comment


      #3
      Re: Nescafe Aeroccino, still fails with new Motor (red flashes only once)

      Why would you short the motor The BC817 can get damaged.

      It might be the power supply is sagging when the motor starts. Check the voltage holds up, that the electrolytic capacitors are OK.
      You could power the board with a 9VDC bench power supply and see if it works.
      This thing is pretty cheap, the secondary-side caps are small, C5 120uF 16V I would upsize it.
      I don't see a sense-resistor to monitor motor current.

      Comment


        #4
        Re: Nescafe Aeroccino, still fails with new Motor (red flashes only once)

        Can you give the circled cap and resistor a closer inspection
        Attached Files
        All donations to badcaps are welcome, click on this link to donate. Thanks to all supporters

        Comment


          #5
          Re: Nescafe Aeroccino, still fails with new Motor (red flashes only once)

          Does the original motor spin using a 9 volt battery?

          Comment


            #6
            Re: Nescafe Aeroccino, still fails with new Motor (red flashes only once)

            Thanks,
            the original Motor starts with 9v.
            I used a bench power supply with 9V and current limited to 1A.
            With a Scope and a China Motor connected i was able to trigger a measurent.

            The Voltage drops down to nearly 3V when pressing the start button.
            And i think there is a Current ressistor in the Power Rail for the Motor...

            I think these China Motor are crap and the startup current is way to much.
            I try to get some Origin Motors

            Comment


              #7
              Re: Nescafe Aeroccino, still fails with new Motor (red flashes only once)

              There is large inrush current until the motor is spinning. Nichbo RF-500TB-12560-R specification is 6V 2,700RPM max. 331mA locked rotor, around 192mA max power, no-load 20mA.

              If the motor's voltage sags down to 3V then the BC817 transistor or the power supply cannot keep up.

              Comment


                #8
                Re: Nescafe Aeroccino, still fails with new Motor (red flashes only once)

                I also suggest replacing those "CS"-branded electrolytic caps. They are some of the worst brands out there. If the device is more than 3-5 years old, it's very likely one or more could have gone bad.

                Also, I suggest to avoid cheap China motors. They are OK for hobby stuff / toys or applications where current consumption and RPM stability are not an issue. But for anything else, it may be best to avoid them (especially in audio equipment, like tape decks!)
                Last edited by momaka; 03-25-2021, 10:42 PM.

                Comment


                  #9
                  Re: Nescafe Aeroccino, still fails with new Motor (red flashes only once)

                  Hi,

                  i did a measurement today.
                  I used a benchtop Power supply, a 1 Ohm Shunt resistor and the old/new motor in series.
                  With a Scope i measured the voltage across the Shunt reistor at 9V/2Amps max at the PSU.

                  The Voltage spikes ramps up at 5-10us ...

                  The old motor had a Voltage Spike about 500mV at startup (0.5 Amps).
                  The new (China) motor had a Voltage about 13V at startup (13Amps).
                  Tested this several times...

                  The circiut itself has a shunt resistor with 0.27Ohms and the atmel seams to take this as a input.

                  So the board shuts down with these chines motors..

                  Comment


                    #10
                    Re: Nescafe Aeroccino, still fails with new Motor (red flashes only once)

                    You might have a high speed version of the motor? The low speed one needs more copper turns and china loves to use the minimum copper. So fans run fast even on low speed.
                    Maybe swap out the armature, assuming it's the brushes that wore out.

                    Comment


                      #11
                      Re: Nescafe Aeroccino, still fails with new Motor (red flashes only once)

                      probably the shit brushes that aren't really brushes no carbon to be seen .

                      Comment


                        #12
                        Re: Nescafe Aeroccino, still fails with new Motor (red flashes only once)

                        Originally posted by petehall347 View Post
                        probably the shit brushes that aren't really brushes no carbon to be seen .
                        I somehow doubt that's the problem.

                        I've seen cheap Chinese motors made with Carbon brushes as well as with cheaper Copper brushes. It's just down to model/design. Mabuchi, for example have many motors in the same case size, but with different brushes, depending on what application the motor is geared for (i.e. lots of On-time vs. infrequent use with much power-cycling, allowable noise, and etc.) Many of these same motors also offer various versions for different voltage/current/torque spec (and this has mostly to do with the rotor winding configuration and wire size.) See below.

                        Originally posted by redwire View Post
                        You might have a high speed version of the motor?
                        ^ This.

                        Sometimes, even two motors that appear "the same" on the outside can perform quite differently, and this indeed has to do with how the rotor is wound (as well as strength/type of the permanent magnet(s) used for the stator.) In fact, Mabuchi motors - a well-known and reputable Japanese electric motor brand - offers a good number of "the same" motor in different voltage/current/torque specs. Take, for example, a standard RS-540RH/SH found in many older-gen Ni-Cd cordless drills. Depending on if you got the 7516 or 5045 sub-model, one is specified for 2.4-4.5V range, while the other is specified for 4.5-12V, respectively. And accordingly, the 1st is specified for ~12 Amps (@ max efficiency), while the 2nd is specified for only ~6 Amps (again, @ max efficiency.) Both of these have the same 3-sided rotors and magnet sizes. So the only difference is in their rotors, with the 1st being wound with less turns of thicker wire and the 2nd using more turns of thinner wire.

                        So in the O/P's case, if he got the motor specified for lower voltage / higher current and/or higher speed, then that could well be why the inrush current is so high.

                        This is why I despise buying such things from AliExpress, Amazon, and eBay, because you never know which exact motor you're getting. Surely even the cheap Chinese motors should have datashets... but good luck finding a seller that ever includes this. Most listings just copy-pasta the same (and often brief) description about the item, and that's all you really get.

                        Originally posted by redwire View Post
                        The low speed one needs more copper turns and china loves to use the minimum copper.
                        Yup, lower speed motors do indeed require more turns... though it's usually thinner wire as well. So even for the "high speed" versions, they are still technically supposed to use the same amount of copper, but just fewer turns with thicker wire.

                        Thus, I think the problem with really cheap motors is that they just use fewer turns regardless of what voltage/current/speed spec they aimed for. And the even-cheaper ones may use weaker magnets too... which results in even higher no-load speed (on a DC motor, weak stator / permanent magnets = higher no-load speed)... that drops dramatically with tiniest of loads. As such, these motors tend to suffer from horrible efficiency numbers, too.

                        Another item of concern I find on cheap motors: lower quality bearings/bushings and/or more friction (for bushings / sleeve bearings) due to poor manufacturing tolerances and motor case construction. That surely also takes another ding in the motor's efficiency curve.

                        **EDIT**
                        I took a look at this picture again that the O/P provided in post #1, and from what I can tell, at least the logo on that motor does appear to be the same as a genuine Mabuchi motor... or perhaps just a very good fake??

                        Per the Mabuchi datasheet, the RF-500TB-12560 is rated as follows:
                        6V constant: 20 mA @ 2700 RPM no-load, 84 mA @ 2180 RPM @ max eff., and 350 mA with stalled rotor.
                        9V constant: 24 mA @ 4000 RPM no-load, 110 mA @ 3300 RPM @ max eff., and 520 mA with stalled rotor.

                        ... and that looks comparable to the Nichbo RF-500TB-12560-R spec @ 6V... so not sure how O/P is getting 13 Amp spikes from that tiny motor. If that really is the case, perhaps installing a small inductor (1-10 mH??) in series with the motor might alleviate the issue with the current spikes and allow the machine to work.
                        Last edited by momaka; 04-03-2021, 10:51 PM.

                        Comment


                          #13
                          Re: Nescafe Aeroccino, still fails with new Motor (red flashes only once)

                          Try this run the new motor in one direction for about a minute or so then run it in the opposite direction for a minute or so you might have to do that several times and see if the inrush current is less it could be that the brushes are not seating probably and this could be giving you this issue
                          9 PC LCD Monitor
                          6 LCD Flat Screen TV
                          30 Desk Top Switching Power Supply
                          10 Battery Charger Switching Power Supply for Power Tool
                          6 18v Lithium Battery Power Boards for Tool Battery Packs
                          1 XBox 360 Switching Power Supply and M Board
                          25 Servo Drives 220/460 3 Phase
                          6 De-soldering Station Switching Power Supply 1 Power Supply
                          1 Dell Mother Board
                          15 Computer Power Supply
                          1 HP Printer Supply & Control Board * lighting finished it *


                          These two repairs where found with a ESR meter...> Temp at 50*F then at 90*F the ESR reading more than 10%

                          1 Over Head Crane Current Sensing Board ( VFD Failure Five Years Later )
                          2 Hem Saw Computer Stack Board

                          All of these had CAPs POOF
                          All of the mosfet that are taken out by bad caps

                          Comment


                            #14
                            Re: Nescafe Aeroccino, still fails with new Motor (red flashes only once)

                            Yes the brushes might need to be broken in, to get the motor current down. It's usually a low speed (undervoltaged) run for many minutes.
                            But the inrush current seems to be more than the little PSU and BJT can handle.
                            OP can measure ohms for the two motor's windings to compare them.
                            I think I would swap the defective parts (brushes) and try to make a motor that works.
                            Or the mechanical load is too great, the pump is stiff? I've also seen cracked/crooked magnets (motor was dropped) cause high current and poor torque.

                            edit: another motor problem is carbon brush "mud" getting in the gaps between commutator contacts and shorting things out. You can clean the gaps to fix that.
                            Last edited by redwire; 04-04-2021, 02:43 PM.

                            Comment


                              #15
                              Re: Nescafe Aeroccino, still fails with new Motor (red flashes only once)

                              Thanks for all you help,

                              i replaced the BC817 and i got some NOS Original MABUCHI RF-500TB-12560 DC Motors from Aliexpress for 13$.

                              These Motor Type is working fine and had normal startup current.
                              So the Banggood ones are just fake one...

                              The NOS has even stamped MABUCHI on the plastic cases..

                              Jürgen

                              Comment


                                #16
                                Re: Nescafe Aeroccino, still fails with new Motor (red flashes only once)

                                It's good you plowed through the cheapness and found the problem.
                                I'll bet the original motor had no carbon brushes, just some copper leafs because not much air is pumped over the life of the machine.

                                Comment


                                  #17
                                  Re: Nescafe Aeroccino, still fails with new Motor (red flashes only once)

                                  Originally posted by redwire View Post
                                  It's good you plowed through the cheapness and found the problem.
                                  I'll bet the original motor had no carbon brushes, just some copper leafs because not much air is pumped over the life of the machine.
                                  case of no serviceable parts inside

                                  Comment


                                    #18
                                    Re: Nescafe Aeroccino, still fails with new Motor (red flashes only once)

                                    Thanks for coming back and updating us on the repair, juergenb!
                                    Also, always good to hear a success story.

                                    I guess it also goes to show how widespread the issue is with counterfeit parts. From the pictures you posted of the Banggood Mabuchi motor, the logo looked bang-on accurate (sorry for the pun ) for a Mabuchi motor. So I suppose one should always assume parts from Chinamarts (eBay, Aliexp., Amazon, and etc.) are counterfeit unless there is strong evidence to suggest otherwise.

                                    Originally posted by redwire View Post
                                    I'll bet the original motor had no carbon brushes, just some copper leafs because not much air is pumped over the life of the machine.


                                    See attached snapshot of the datasheet (upper-right corner tells the brush type)

                                    Indeed it is a "Precious" metal-brush motor. Not sure what that means exactly, though (perhaps gold-plated copper? or perhaps just regular copper?) Either way, the typical application is listed as CD Player / DVD player / VCR / Cassette Tape Player... which makes sense, since metal brushes tend to be more quiet than Carbon-type brushes. Thus, it should be a fairly durable motor, despite being a metal-brush type. Of course, it also all depends on the application too (i.e. at what voltage speed the motor was ran and how often / duty cycle.) I have had metal brush motors last a very long time in RC cars when I was a kid. One of them, in particular, I used to drive around after school every day for about 1-2 hours... and that went on for about 2 years, if not 2.5. Motor was an RE-280 type with metal brush. Not Mabuchi or other big name either, but probably a good enough Chinese clone (this was back in the early 2000's, so I imagine bad counterfeits weren't as widespread as they are today - at least not in electronics as much.) Eventually the motor's bushings (sleeve bearings) wore out before the metal brushes did, making the rotor harder to turn (or "vibrate" at high speed) and thus the motor ended up eating 2-4x the normal operating current. I remember I wanted to fix that RC really badly by either swapping the motor or cleaning the bearings... but there was a heat-pressed brass pinion gear on the motor shaft, preventing me from taking it apart.

                                    Anyways, point being is that metal brush motors can last a while too. But the best way to do that is to make sure any sparking/arcing on the brushes is minimized - so probably a good idea to install a big ceramic cap right across the motor terminals. It will also minimize RF/EM noise. In the case of the machine in this thread... if that is attempted, hopefully the controller doesn't trip from the low ESR of the ceramic cap (so I suppose don't go to extremes by picking a very large capacity.)
                                    Attached Files
                                    Last edited by momaka; 04-16-2021, 09:00 PM.

                                    Comment

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