Hall Effect power switch- Mtbr.com
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  1. #1
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    Hall Effect power switch

    Hi guys, not sure if this is of much use to the bike folk, I figured the diving folk would find it more useful...



    It's the white board. Basically U2 is a Hall Effect sensor and the board is obviously quite tiny. The square black 'thing' is a power FET that can handle at least 15A. On resistance of the FET is < 0.006 ohms. So, even at 10A, power dissipation is only around 0.6W.

    So, what's it good for??

    1) Can be use as a "power switch", connect battery to IN+/IN- (3V to 25V safe) and connect your load (direct drive LED or LED driver etc) to LED+ (common with IN+) and LED- (switched output power). Bring a magnet close to U2 and the board will switch power to the load on, remove magnet and power is removed. Quiescent with the board 'off' is around 60uA (so less than 0.05 amp.hour per month of parasitic drain).

    2) Can be used as a momentary switch with any of the flex drivers using the SW output (active low when magnet is close to U2).

    Obviously the idea is to use it as a fully water proof switch inside a housing with no external holes needed. More info on my website, the documentation is still a "work in progress".

    Anyhow, hopefully some of you folk may find a use for such a 'switch'.

    cheers,
    george.

  2. #2
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    Would a simple magentic reed switch do the same thing?

  3. #3
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    Quote Originally Posted by jmitchell13
    Would a simple magentic reed switch do the same thing?
    I have never seen a reed switch that could switch over a couple amps. This new module is said to be capable of 15A. Likely not much of an issue for many LED lights, but power levels seem to be moving upward all the time in the lumen race

    Might work for operation 2 in Georges post. My one experience with reed switches had some issues with contact bounce. I had to add some filtering logic to the control circuit to "debounce" the signal. I am not sure of what, if any, input filtering the flex drivers have.

  4. #4
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    As vankbiker says, reeds can't handle much current without risk of contact welding or contact damage. They are also somewhat fragile.

    The flex drivers have some level of software filtering by the nature of the sampling rate of the switch state.

    cheers,
    george.

  5. #5
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    I have used these tiny reed switches with Georges Flex drivers with no problems.

    If you are really keen you can sew a tiny rare earth magnet into the tip of your glove!

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