Espritmodel.com Telemetry Radio
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Old Jun 26, 2008, 01:16 PM
HyperFlight Support
Neil Stainton's Avatar
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Great new product Paul. I would certainly like to stock them at www.hyperflight.co.uk.

Some questions and suggestions:

1. What is the voltage drop across the switch? How does it compare with a mechanical stitch?

2. What is the current draw when on? If over a few mA I would prefer it without the LED, as I don't usually have any trouble knowing if my R/C is on or off!

3. I really think combining a BAC and an ESJ into a single unit, without flyleads, would be good. Less to go wrong, less mass, less volume, less cost.

4. I think that a good, bulletproof switch jack and charging socket solution would be very useful to many modellers. If you could come up with a better solution that a Y lead or unplugging the battery people would beat a path to your door!

Regards,

Neil.
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Old Jun 26, 2008, 05:48 PM
PLD
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G'day there Neil,

Quote:
1. What is the voltage drop across the switch? How does it compare with a mechanical stitch(sic)?
The voltage drop across the unit depends a lot on the current being drawn and the MOSFET used. In the current example, I'm using a model FDN337 MOSFET for the 1A class unit (I can also use the excellent PMV31XN)

The FDN337 has a 65mR on resistance, so using good ole ohms law, V = IR, we can deduce that at 1A of current it'll drop 0.065V (dissipating 65mW of heat)

For the 5A class, I'll probably use the FDS8874 which has about 7mR, so again, using V=IR, we can find at 5A that it drops 5A * 0.007R = 0.035V (while dissipating 175mW of heat)

Quote:
2. What is the current draw when on? If over a few mA I would prefer it without the LED, as I don't usually have any trouble knowing if my R/C is on or off!
The LED is only operational when the unit is active. When the unit is disarmed the draw is 7.7uA. The LED consumption varies but is usually between 5 and 10mA.

Quote:
3. I really think combining a BAC and an ESJ into a single unit, without flyleads, would be good. Less to go wrong, less mass, less volume, less cost.
What I am thinking of doing is offering a prewired combo of the BAC + ESJ, that is, already soldered up and secured. I have tried making up a single PCB with the facilities of the BAC + ESJ together but so far I'm having troubles with keeping the PCB size down to a sane level.

Quote:
4. I think that a good, bulletproof switch jack and charging socket solution would be very useful to many modellers. If you could come up with a better solution that a Y lead or unplugging the battery people would beat a path to your door!
Bullet proof is the crux. Working on it, certainly for the larger units that I was drawing up last night (30A constant, 300A peak - hah, that'd fry the copper off the board very quickly, charge path fused). For the smaller units it's going to be a case of a Y-lead somewhere. Either I solder it onto the board in parallel with the normal 3 pin input connector I use, or people push their balance connectors out through the fuselage. That's the other problem, picking a suitable second connector for the charging port... have been flipping through my catalogue for the last couple of days looking for a good one. A good connector will need to satisfy the following;

* installing using a drill/hole (square holes are evil )
* very low profile (we don't want our connector body protruding 10mm into the fuselage)
* mechanically polarized (no one wants to charge their packs backwards)

The closest connectors I came up with so far is a 4 pin TYRO Micromatch connector which has a very small physical footprint (it'd have to be soldered to the PCB), it's polarized but alas it needs a -square- hole, so that ruins that idea.

Lots of developments to come no doubt, I think this is just the start of another long line of variants

Thanks for your questions/suggestions, good to have these things to chew on.
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Old Jun 27, 2008, 04:18 AM
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cool , all we need now is this system availiable for all of us still using ni-mh packs in our slopers ..some of us dont like puffies..

cheers
doug
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Old Jun 27, 2008, 04:26 AM
PLD
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Flybaby/doug,

Good news - it works fine for NiMH 4 and 5 cell packs.

Paul.

PS, puffies provide an essential safety feature - it's like an airbag for the receiver
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Old Jun 27, 2008, 05:26 AM
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Hi Paul,

Thanks for your in-depth reply. All sounds good, though I still question the benefit of the LED (it could be increasing the R/C quiescent current by 25%), and hanker for an integrated device.

Regarding the TYRO Micromatch hole - couldn't you just drill an oversize round hole?

Regards,

Neil.
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Old Jun 27, 2008, 06:02 AM
PLD
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Neil,

Well, I suppose the easiest option is to provide some with... and some without LEDs - I don't mind splitting the product line (since it already looks like there'll be about half a dozen variants ).

As for the hole - yes, you could but my concern there is that since it'd be of the order of 5mm diameter one's starting to risk structural issues with some airframes (possibly).

*still flipping through the catalogues*
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Old Jun 27, 2008, 06:12 AM
PLD
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Well, I worked some of it out

I can add a 3rd pin - it makes the boards wider and heavier but it does solve a few problems.

The pin arrangement is as follows (at least so far)

(+) (ARM) (-)

The lead will have a short between ARM and - to turn off the unit and charge can be applied between (+) and (-).

Now the trouble is still the polarity - since you can easily install the charge circuit the wrong way around and *BOOM*, so I really need the mechanical polarity. I cannot put a diode in-line because that'll mess up the charging.

Paul.
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Old Jun 27, 2008, 06:16 AM
HyperFlight Support
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Paul: I think a 5mm hole is perfectly acceptable for most planes. Would a flashing LED use less energy?

Everybody: what do you think about the LED current (say 10mA), reducing the flight time allowable by maybe 15% for small planes? Is the LED a useful benefit or an unnecessary power drain?

Neil.
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Old Jun 27, 2008, 06:46 AM
PLD
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Neil,

In this case a flashing LED wouldn't really be an option due to the simplicity of the setup. Below 10mA LED brightness would start to become insufficient to be of any use during daylight.

The usefulness of a LED would tend to depend a lot on what is installed 'downstream'. If it's a BAC-MINI or BAC-LED, or maybe they have a LVA-NI/LI installed which has its own LED setup, then having a LED on the ESJ doesn't make a lot of real sense.

I think where a LED does come into use is when having a cursorary glance at the plane reveals that "ooops, I left it on!" (still, other indicators like servos chattering and the lack of an arming ribbon/flag/plug installed would help too).

Paul
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Old Jun 28, 2008, 04:12 PM
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cheap smoke machines too

c
Quote:
Originally Posted by pldaniels
Flybaby/doug,

Good news - it works fine for NiMH 4 and 5 cell packs.

Paul.

PS, puffies provide an essential safety feature - it's like an airbag for the receiver
they also provide a great smoke machine , and campfire to sit around when they burst . i had a lipo plane a few months ago that took out my best freinds car..

you can never be too safe , how about an inline lipo warning system that tells you that the cells are unstable like a lost model alarm..remember we are playing with detonators...seriously thats what they were until some guy relised they held a charge..

cheers
doug
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Old Jun 28, 2008, 07:37 PM
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Doug,

Other than the low-voltage-alarms which I do already have, there aren't too many other avenues to go down to determine if a lipo is unstable. Perhaps one such would be to monitor each individual cell's voltage, pack temperature and put strain gauges on the packaging to detect undue swelling.

Paul.
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Old Jun 30, 2008, 12:14 AM
PLD
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Well, this is certainly the 'boring' time during the development phase

Still looking around for a suitable charge jack connector. On anything bigger than a DLG then it doesn't really matter too much about size - but since this is originally focused at DLG/HLG I want to see if I can find the smallest thing possible. Right now I'm trying to track down a possible 2mm dia DC jack (similar to what you plug into your cellphones)
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Old Jun 30, 2008, 05:38 AM
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Like this? Plugs/Jacks


Go to connectors/audiovideo...2,5mm
/J
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Old Jun 30, 2008, 07:02 AM
PLD
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Oakman,

Audio jacks are a problem - because they will momentarily short as you insert/remove (not always, but it's a risk).

I did find some 1.3mm DC jacks today - though the cost is a bit high, about $3 for the plug and $3 for the socket

Paul.
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Old Jun 30, 2008, 06:44 PM
slope soarer
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I've been looking for a microswitch/charging jack for years, and currently use a telephone jack set-up that is OK, but is tricky for some eg me to solder. All the commercial offerings are way too large. This looks like a great solution. Most users will use NIMH not lipos, and like me many will not know what the PLD-BAC-001 is (please explain). Please display the completed setup up for a NIMH pack, with the connector in and out.
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