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Old Nov 23, 2010, 08:15 PM
PLD
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Modular power distribution board with failsafes and electronic switchjack

After many requests for many people - and finally coming around to the idea, I've started work on a power distribution board for large models which includes fail safes and the electronic switchjack facilities.

The distribution board is also being designed with the option of a daughter-card to allow bolt-on regulator/optional boards. By providing this bolt on option it means that the one board can operate with many different input sources (Ni/A123/Li/...).

Attached is a preliminary design with 6 ganged channels and 4 separate power headers.

The switching facility incurs only a tiny 0.85milliohm resistance, which means at 20A of current it's still only dissipating 340mW of heat and a tiny 17mV of voltage drop.

The selected input schottky diodes for the dual input balancing can handle 10A constantly each and peak to over 100A for a few milliseconds.


Planned cost is ~$70 to start with for the baseboard and regulator daughter boards will be costed depending on their complexity.


Paul
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Old Nov 25, 2010, 12:51 AM
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Tony Finn's Avatar
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Paul

so this means that we can power our gear from multiple supplys, and if one fails the back up takes over and we can take away different supply voltages to power the camera, rx etc. ?

Tony
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Old Nov 25, 2010, 01:15 AM
PLD
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Tony,

I do need to expand on the explanation a bit more - sort of just threw it up here quickly yesterday.

The baseboard (motherboard), will accept two supply inputs, which ever has the greater voltage will be used (simple 2-diode input, you lose about 0.3~0.5V over this, but it's not all bad - more later ). So yes, if you have two NiMH packs, and one collapses, then the other will take over. Normally the packs will be drained fairly equally.

By default, without a daughter-board installed, what ever the supplied power is, will be fed through to the header distribution groups. What happens is that you bring your receiver channels over to the distribution board using leads with a servo connector on each end (or I might supply the boards with the leads presoldered - but that may be a problem for some people who have their receiver at different lengths away from what I've supplied). Once the receiver channels are fed into the distribution board, you can then plug in up to 3 or 4 servos into the ganged header, which will receive power from the distribution board but the signal from the receiver.

One thing I've not designed in yet is the ability to opto-isolate/buffer the signal, trying to decide if it's worth it or not since it will make the PCB larger and naturally cost more.

The entire power is turned on/off using the electronic-switch arrangement, which means that the switch you put on the side of the plane doesn't carry the high currents, only a tiny signalling current. As with all my other ESJ devices, it defaults to 'power on' for failsafe.

The whole board can cope with 10A constantly with peaks well into 100A, though I do not recommend that (I'd suggest no more than 25A peaks for less than 0.1 seconds).

Paul.
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Old Nov 27, 2010, 07:59 PM
PLD
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Attached is what I think is going to be the final board. I added a few little pieces, including a couple more caps here and there along with a set of 'charge' sockets on each battery pack input.

The daughterboard link plug/socket has been set as a 10 pin unit capable of ~17A constant, a rather major overkill but it was the most practical option in terms of parts supply.

Paul.
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Old Nov 29, 2010, 09:49 PM
PLD
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The design has been updated - I've added an optional servo signal buffer facility onto the board, for the situations where perhaps people feel their RX cannot generate a sufficient signal to drive 4 servos directly. In addition, the design will boost the smaller 2.3~2.7V signals (on modern 2.4GHz RX's) up to 3.3V, making them less prone to noise.
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Old Nov 29, 2010, 11:53 PM
PLD
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I think I've fiddled with the board design enough now - tonight I should submit it for production. 2~4 weeks later we should see the first live prototype.

Paul
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Old Nov 30, 2010, 06:18 AM
PLD
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Design has now been submitted
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Old Dec 08, 2010, 06:08 AM
Where did Steve go ?
Alexandra
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put me down for two.

cheers
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Old Dec 08, 2010, 05:57 PM
PLD
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The good news is that the boards have arrived in Australia... amusingly they're showing up in Alexandra

If things go well then tomorrow I'll have them, if they go bad, it'll be Monday.
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Old May 16, 2011, 11:28 PM
PLD
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Just a note that this product never has gone to production. The labour involved in making it along with the cost did not make it an effective product. A couple of units were built at moderate 1-off cost but they'll now stand as a trophy on the bench.
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