Magic Blue Smoke Suppression Circuit

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  • January 12, 2018 at 10:10 PM #18506
    occamman
    Participant

      The OSSC is a wonderful piece of engineering, our family’s been enjoying it tremendously — it’s amazing to see games looking so good on a big screen.

      However…

      As you probably know, using a common barrel connector for power has the drawback that the mechanical size is common, but the output – voltage, AC/DC, polarity, is not standard. Indeed, one of our family members accidentally plugged our OSSC into a 12v supply with the same-sized plug: while the mishap didn’t actually produce any magic blue smoke, it did kill our OSSC, which is being returned for repair. (Leaving it unpowered for some time did not lead to a resurrection, unfortunately.)

      As an electrical engineer and product developer myself, I thought I’d throw out a few thoughts on relatively straightforward hardware fixes to prevent this from happening in the future — these may have already been considered, but just in case:

      1. Add a clamping circuit and fuse between the 5v in and the rest of the circuitry – there are a number of schemes for doing this e.g., http://www.instructables.com/id/Voltage-Clamp-for-Arduino-Using-Zener-Diode-PTC-an/. I suspect that this would add well under $1.00 to the manufactured cost of the unit.

      2. Use a USB micro jack for power – this could supply up to 1.8 A (IIRC) at 5v. I understand there could be some concerns around voltage drops if an owner uses a poor USB cable, but from a quick (perhaps too-quick?) look at the schematic it seems that not much current is needed at close to true 5v within the circuit, so a simple/cheap boost or buck/boost circuit could handle this – I’m guessing this would add less than $1.00 to the manufactured cost of the unit, but it would likely be offset by the ability to use USB power adapters that are very inexpensive – in total, it might actually reduce your costs. Perhaps a little bit of velcro could be added at the board edge for a strain relief, if there’s concern about the plug pulling out. Another possibility would be to have add a simple circuit that lights an LED green if USB voltage is sufficient, or off if not.

      Thanks for your consideration!

      January 13, 2018 at 5:39 PM #18515
      Harrumph
      Participant

        Considering the amount of reports coming in, I do agree Marqs & Bucko should consider this for the next production run.

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