It’s alive! A real A320 Brake panel interfaced with Air Manager and FFA320

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JackZ
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Re: It’s alive! A real A320 Brake panel interfaced with Air Manager and FFA320

#21 Post by JackZ »

@jph As per your request, here's what I found (direct connection to the PSU, only one indicator powered at a time)
Surprising results:

Brake FAN pushbutton:
ON White 10.2mA only
HOT amber 28.6mA


TERR ON green 188mA

Gear down Green 197 mA

DECEL ON Blue 188mA

if the latter results are consistent with bulbs (i could partially open the korry and confirm these are white bulbs, but not to the point I could read the specs, sorry) ie: 90 to 100mAmps per bulbs, I am puzzled by the first two which coincidently are located on the same pushbutton and look much more like Leds. Maybe a mismatch, that even the casing is the same, the pushbutton is "latched" for the BRK FAN and the inner of this button doesn't show bulbs
My YouTube Chanel on the A320 (Real SOPs by an Airline Pilot IRL):
https://www.youtube.com/playlist?list=P ... 0Q6SBASRqJ

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jph
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Location: Somewhere over the rainbow..

Re: It’s alive! A real A320 Brake panel interfaced with Air Manager and FFA320

#22 Post by jph »

Hello Jacques.
Thanks for that.
Hmmmm. Interesting........ something wrong there it would appear.

Looking at colours in the datasheet, there isnt a white LED and there isnt an amber lamp... :shock:
If the top is removable without damaging it, then take a peak and see if they look like leds or bulbs - or shock horror - both :? :?:
From what I can see from the basic wiring, it looks as if the switch can have either a common 'gnd' or individual 'gnds' for the lamp blocks (where a block is the complete unit for one legend). Would you concur ?
The other figures for the lamps seem rather high also. too high for the F8 bulbs and too low for the F2... however..
How does the brightness level look to you compared to the actual aircraft ?

Re the led - presuming it is led - for the brake fan..... if you look on page 14 of the datasheet then it lists a Sunlight Readable Light Emitting Diode Capsule ... this only specifies a forward voltage and needs an external series resistor. The 5V low intensity led units have the resistor built in but are not sunlight readable which would tend to rule them out for use in an aircraft cockpit. A good check to see if it is the high intensity led unit in the brake fan is to measure the resistance from the rear connector to the lamp / led input on white and on amber and note the resistance. Something over 100 ohms may be noted, if so, then that switch is a different animal altogether. IF there is a series resistor we can then work out the required voltage.
There is nothing in the datasheet that says that a switch unit cannot have both incandescent and led in the same unit.. as far as I read it... and there is nothing to stop them putting a higher voltage rated unit in a certain switch although it seems quite illogical to me. For example, your amber unit, if T1 led, wouldnt be classed as sunlight readable so in theory 'should' be the sunlight readable type with external resistor (presuming led of course). The incandescent T1 versions are all sunlight readable though.
It is also confusing in that, if, there is an led in a switch unit, then the datasheet doesn't seem too clear on how many LEDs are in a legend. It actually reads as if the lamp equivalent, when in led format, has either 2 or 4 chip leds PER LAMP unit. - not per legend module. It seems that a legend module may well be 2 of these units and the complete switch 4 units - as per

The Series 582 uses four T-1, midget flange, based lamps for a light source, except for the sunlight readable LED light source
which uses integrally mounted LEDs in the capsule. T-1 lamps are the lowest replaceable unit when specified and are available in
incandescent, 2 chip LED and 4 chip LED configurations.


Sherlock Holmes would be fascinated :)
Joe. CISSP, MSc.

JackZ
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Joined: Mon Feb 22, 2016 1:02 pm

Re: It’s alive! A real A320 Brake panel interfaced with Air Manager and FFA320

#23 Post by JackZ »

As per comparisons with real aircraft configuration, it is hard to tell cause the cockpit is in an ever changing sunlight configuration.
Nonetheless I will not worry too much.
I just understand better why the BRK FAN amber and white lights were impacted the most in terms of luminosity drop when connected to the ULN if they were leds.

I will go on and multiply the number of ULN since they seem to be current limited at 500mA total, and that means that no more than 3 outputs can be used per ULN provided they are bulbs, and that I should pair the two BRK FAN output with one or two Bulb output
That means that I need at least 2 ULN with 4 output each (roughly 800mA per ULN), and one ULN with three bulbs output (600mA) plus one ULN with the two leds output (roughly 60mA) and two bulbs output (400mA for a 460 total).
The key here is trying to match the 4 annunciators that have bulbs so they are not likely to be lighted simultaneously (except for a brief lamp test), such as the AUTOBRAKE annunciators that cannot be LO, MED and MAX simultaneously.

Thanks all for the food for thoughts!
My YouTube Chanel on the A320 (Real SOPs by an Airline Pilot IRL):
https://www.youtube.com/playlist?list=P ... 0Q6SBASRqJ

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jph
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Location: Somewhere over the rainbow..

Re: It’s alive! A real A320 Brake panel interfaced with Air Manager and FFA320

#24 Post by jph »

No Problem at all.
Just something else that may be worth considering - when using the ULN, if you think you have a current limiting / V drop issue on a single pin, then you can combine pins to increase the current. For example, you can connect the arduino output to the driver input for pins 1 AND 2 (just wire the inputs together), and also connect the output stage - 1 and 2 together (again just wire them together) so they are in parallel hence increasing current capacity. This is perfectly acceptable and also a common practice and acceptable as per datasheet. So if you are ever using 4 pins or less per device, then use a pair of pins in parallel for each stage. If only using 2 pins on a ULN, then use 2 banks of 4 pins in parallel so nothing is wasted.
Great project, looking forwards to seeing it all come together.
Joe
Joe. CISSP, MSc.

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