B777 cockpit outlet

[CONCOMBRE]

There are two outlets between the two cockpit jumpseats (:} for laptop????).
One is DC and the other is AC.
Does anyone knows the AC outlet frequency? :E :E (I guess voltage is 115 V)

Many thanks!

[ray cosmic]

Usually its indeed 115V 400Hz. Most usable for laptops!

[fendant]

400 Hz ???? This will kill your EFB or the Laptop!

Frank

[Watchdog]

It's fine for laptops and the frequency (400hz) will not be a problem as your laptop power supply converts the 115 AC to 18v DC...remember AC frequency is simply the number of cycles per second of AC polarity change - all nicely converted by the powersupply's rectifier :ok:

[27/09]

Watchdog

Have you actually tried using 115VAC 400Hz to drive the power supply for your lap top? You may get nasty surprise.

Yes, it is designed to work on AC power, BUT 400HZ is about 7 times the frequency that the power supply is designed to work with. This frequency difference is likely to have a dramatic effect on the impedance of the transformers that are probably used inside the power supply.

I'm not saying that it won't work, but I'd rather you tried your power supply first to see if it works OK, before I tried mine out.

[Denti]

We have the same outlets in the 733, at the moment our EFBs take that as usual source of power as do the flightdeck mobile-phones. Tested it on various noteboots as well without any problem, no matter if wintel or apple notebooks.

At the moment we try to certify a second 115v/400hz outlet so that both EFBs can run on power since their batteries run dry after just 2 to 3 hours and its a bloody nuisance to change them between pilots all the time.

[IRRenewal]

Your laptop power supply is in 99.99% of cases a switch mode unit.

In a low power switch mode power supply, the mains inlet is followed by a filter, then there is a rectifier to convert the AC to DC at high voltage. This is followed by the switching bit which transforms the DC to high frequency AC and a transformer to convert it to low voltage AC, which is then rectified again.

The input filter and rectifier are the only bits which get exposed to a frequency other than your mains frequency at home.

The filter is there to stop the power supply from polluting the mains supply with high frequency noise generated within it. It will typically be a low pass filter with a cut-off frequency well above 400 Hz.

The rectifier is typically just a diode bridge which will not suffer ill effects from being exposed to 400 Hz. I cannot think of any modern diodes used in these type of units which could handle 60 but not 400 Hz.

Bottom line is that as long as your power supply is specified for 115 V operation (most of them are 100 - 265 V) it will work just fine, as many people on here have reported before. No transformer will get exposed to a frequency it was not designed for.

Hope this helps.

Gerard (power supply tester for a computer manufacturer in a previous career)

[Watchdog]

27/09,
yes - I've been using mine (HP) in the 777s for over a year now - no problems and we still operate/charge the company EFBs (toshiba toughbooks) from them as normal practice, but these outlets are 60hz (not 400 as someone said). I haven't plugged mine into a 400 hz supply - I'll let someone else try that first) :O Imagine that the bridge would run hotter in the rectifier?
Can't grasp what impedence has to do with the primary windings of a power transformer??? (maybe I was asleep that day at electronics lectures) but pretty sure nowadays these are switch-mode supplies now anyway.
Impedence is more a concern with matching audio & R/F final stage output to eg. speakers & antenna systems. If you're a cone-head (EI&R) perhaps you could explain?

Edit: IRRenewal - we posted at the same time - good to have an explanation from some in the know - thanks :ok:

[CONCOMBRE]

:) Many thanks for comprehensive answers, folks. I plugged mine several times............so far so good! But I wondered what the details were :}

[AAIGUY]

Been using onboard outlets for a few years on different Boeings. Always works well, but battery seems not to hold the "full" charge after a few uses. Not that I mind (80% is ok, if I can use laptop ), but it does seem to damage the battery a bit.

[west lakes]

but battery seems not to hold the "full" charge after a few uses


Don't forget to let battery nearly flatten at least once a month (whatever the type)

[David Horn]

On the contrary, completely discahrging a Ni-Mh battery will damage it as some cells will begin to reverse-charge (I think that's the term, been a while since I touched on this). Little and often is best, but they seem to have a fixed number of charge cycles in my experience, whether you top them off from 90% or fill them up from 10%.

[Farrell]

Is that what it is there for though?

Or is it designed for other purposes?