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EEVblog #1035 – Flaming DIY Power Supply

Smoke in the EEVblog Lab! What component failed and caught alight in the RD Tech ...

  • tlhIngan

    Most likely if you just power it up, nothing will happen. It’s a remote diagnosis box.

    The traditional thing for this is you plug it into your phone line, into power and it sits there. At an appropriate time, ,you lift the cover, and press a button or something where the modem will dial the hospital and establish a modem data connection. You then speak with the doctor and go through the various checks. If the doctor wants you to do an ECG, he’ll have you put on the wrist straps and then he’ll click on his end a button on the screen to do a remote measurement, which tells the box to do an ECG measurement. The box does it, gathers the data, then uploads it over the data link to the doctor.

    If the doctor wants to see the pacemaker results, he’ll do the same – he’ll instruct the patient to put the sensor over the pacemaker, then the doctor will click another button to gather the pacemaker information, which powers up the loop and talks to the pacemaker, where again the data is gathered and sent over the data link.

    So for the most part, those measurement tools are off until requested.

    The pacemaker I’m guessing is probably a loop antenna to provide power to the pacemaker for the communications hardware, then the third one is actually an antenna to communicate with (the loop remains powered to provide power to the pacemaker). You have to remember they’re supposed to last for years on a battery, so communications is power hungry. The loop provides sufficient power to power the wireless communications module so the antenna can go and transfer information with the pacemaker and the pacemaker isn’t wasting precious battery power communicating.

  • Syd Jessop

    Interesting stuff, Dave, thanks. Nice to see some good design as
    required by medical regs. One slip of the tongue with your description
    at the sensor pad end was the transformer and optocoupler. Surely the
    transformer is giving isolated power to the sensor amplifier stage and
    the signal from that is coupled back to the main circuit across the
    optocoupler?

    What you mention might be a reg or reference to the
    left of the transformer looks like a MOSFET driver for the transformer
    given its proximity so there is basically DC-DC converter functionality.
    I guess they chose to do that discretely because of the isolation
    required?

  • eneuro

    “Most likely if you just power it up, nothing will happen.” – Dave forgot remove magnet from top case and put it close to this magnetic field sensor on board, so additionaly some kind of protection against open box might prevent any usefull mode in this device too 😉

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