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Old Nov 09, 2008, 11:02 PM
PLD
Magicsmoke maker
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Australia, QLD, Charters Towers
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Incase anyone is just jumping in here, wondering why on earth we'd bother making an electronic switch when there's already mechanical ones, it comes down to these things;

1) a lot of mechanical switches can cause a shorting of the battery during the insertion process (DC jacks however do generally avoid this, Audio jacks on the other hand don't)

2) reliability concerns of the resistance between the contacts. The mechanical switches are relying on their "normally closed" function, where two metal plates join together under spring-pressure to close the circuit. This joining can prove unreliable due to grime, oxidation and poor spring pressure.

The ESJs avoid both these problems by moving the switching of power to an internal MOSFET and using the jumper to activate the switch with an open circuit mode. That is, so long as nothing is shorting the jumper contacts, power will flow through the MOSFET.

As a small side effect, the resistance of the MOSFET is consistently lower than the metal plate contacts for anything beyond the first couple of insertions/removals (eg, once oxidation/grime starts building up).



.... now, back to the real problem, finding the most suitable connector to attach that can provide charging + on/off.
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Old Nov 09, 2008, 11:09 PM
Where'd The Wise Men Go?!?
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United States, NE, Bellevue
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i may have missed it early on in this thread; but do you have a schematic? I'd like to see how you are wiring these all up
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Old Nov 09, 2008, 11:14 PM
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Pensacola, FL, USA
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Paul,
Just dropped in and read the whole thread.
I cheer your effort and will be waiting for you to find the connector that will give me the same operational convenience of the mechanical switch/charge presently being used with no problems on several gliders.
Regards,
John255
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Old Nov 09, 2008, 11:27 PM
PLD
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Australia, QLD, Charters Towers
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Normally I'm not keen on releasing schematics - because there's a LOT of unabated outright copying from overseas competitors (at least with withholding schems they have to buy at least ONE unit ). Even my Open-source projects I'm somewhat hesistent.

Anyhow, here's the simplified schematic. Essentially it's just a low-side MOSFET switch with various biasing components and of course LED indicators.
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Old Nov 09, 2008, 11:28 PM
PLD
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John,

If you find anything yourself, let me know and I'll see if I can tie things together.

paul.
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Old Nov 09, 2008, 11:48 PM
PLD
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Australia, QLD, Charters Towers
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One connector I've strongly considered using is the simple mechanically polarized servo connector.

The + and - pins would supply charge power, and the Signal pin->GND would provide the 'short circuit' to disable the switch.

The trouble however I've found with servo connectors is that they can be prone to premature wear and give erratic charge results if the quality is poor.

Mounting would be a little bit tricky as there's no face-plate. You will have to cut a suitable slot in the fuselage and epoxy the connector.

Paul.
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