EEVblog #330 - Medela Swing Teardown & Repair

[SeanB]

Just a voltage measurement, with a ohm sign. Not possible to read negative slope resistance without doing a sweep of the voltage or current to obtain the unknown and calculate the slope resistance

[IanJ]

Dave,

"The Ducks guts"......................hmmmm, much prefer "The Dogs Bollocks"........lets hear you using that one pls.

Ian.

[Monkeh]

Dave,

"The Ducks guts"......................hmmmm, much prefer "The Dogs Bollocks"........lets hear you using that one pls.

Ian.

Oh, but he might upset a poor delicate old lady somewhere!

[fcb]

Pretty certain that the second set of wires (black) is to a vacuum release solenoid - otherwise the unit would create a constant vacuum on the breast, rather than a suckling action. They are PWM'ing the solenoid as well.

I would also guess that there is no pressure sensor in the unit, or calibration required (they will have a vacuum test-jig as part of final test). The 24C01 may record cycle counts for service feedback, but it's main goal will probably be to remember the pressure settings since last time. Perhaps Dave can monitor the I2C packets with his MSO and see when the unit reads/writes to the memory.

The unit can be powered from an external mains adaptor, so the non-reset nature of the fuse is probably wise, also - it may a zener diode to protect against over-voltage (although I doubt it, I would design it withstand 15v and have a processor 'over-voltage' detection routine).

The black foam is probably a dust-filter for the vacuum release solenoid.
 

[amyk]

The mention of it being Swiss makes me think that MCU might be a custom part from EM Microelectronic. Oddly enough there are plenty of Chinese sellers saying they can sell you that part... with the exact part number (344-1.3M3) and package listed.

[EEVblog]

Oh, but he might upset a poor delicate old lady somewhere!

I think every time I make a video, a puppy dies!

Dave.

[Pat Pending]

The design patent for this particular unit is US8075516, other Medela patents describe the vacuum waveform shaping.
The vacuum signal is monitored for different user comfort programs.

[SeanB]

Dave, only in Shenzhen...................... Then it is eaten.

[fcb]

The design patent for this particular unit is US8075516, other Medela patents describe the vacuum waveform shaping.
The vacuum signal is monitored for different user comfort programs.

Where is the vacuum/pressure sensor? I can't see one - unless they sense pump motor current (which is possible).

[reagle]

This episode is in the today's Product Design And Development newsletter
"Dave does a teardown, troubleshooting, and repair of a Medela Swing Breast Pump.
View Video "
http://pddnet.com/video-eevblog-medela-swing-teardown-and-repair-080812/