Hi guys,
Seeing as the FMC project is now on hold awaiting the tactile switches I have started looking at replacing the cards in the OH. I have successfully traced all the 'switches' / inputs to their respective wires on the ribbon cables and now need to do this with the LED's/outputs. My plan was to simply stick the voltage down the wire and see which LED lit up but:
a) Do OC master cards always output 5v?
b) If they do I am going to need to know what voltage the LED's will take to work out what resistors I need (and also when I am testing them to see which is which) so is it possible to work out what voltage a LED will be as I do not know as they are already in place and I can only see the soldered legs so I do not even know what colours they are?
Foolishly I already played with sticking 5v down 1 wire :idiot: - it lit up! Then fizzed and went off in a puff of smoke so I do not want to repeat this and have to replace all the LED's!!!
It's a learning curve!
Cheers
Mike
I think that if you test with 2 AA batteries in serie (3V) for a few secs nothing bad should happen.
JP
Hi Mike
I use one of these
http://hobbyistcentral.com/electronics/2009/05/kemo-led-tester-review/ (http://hobbyistcentral.com/electronics/2009/05/kemo-led-tester-review/)
It's easier than trying to figure out how to connect two AA in series, (kidding!)
Ralph
Good point:
For this side of the pond: http://www.allelectronics.com/make-a-store/item/LT-100/LED-TESTER/-/1.html (http://www.allelectronics.com/make-a-store/item/LT-100/LED-TESTER/-/1.html) ($8)
what oh mikey........
most common LED's will be 2.2v forward voltage, so if you are using 5vdc to test, simply solder a 330ohm resistor in you positive lead. then your LED's won't 'pop'.
and if you don't have any, give me mail and i'll send you some.
good luck..... ian
Thanks again chaps!
I obviously had a stupid moment and just stuck 5v down the wire - just as I did so I remembered about the resistors (they dont use them with the fsbus cards for some reason)...
I thought I read somewhere that different colours may use different voltages - is that likely to be the case - in the OH there are green, blue and amber...
I'll give it a try with a 330...
Thanks again
Mike
hi mike.......
depends on the exact LED. u can get LED's 1.7v thru 2.7v, but me and Mr Ohm sort of worked out that 330ohm was a good safe value. i actually use as low as 220ohm if the LED seems a bit dim. i have been known to go down to a 180 (i'm a little devil aren't i).
good luck matey....
regards ... ian
Quote from: ian@737ng.co.uk on February 18, 2010, 09:14:02 AM
i have been known to go down to a 180 ... ian
(https://www.cockpitbuilders.com/proxy.php?request=http%3A%2F%2Fi24.photobucket.com%2Falbums%2Fc29%2Fjackpilot%2Fian2.jpg&hash=ef35ad493dd03ec35c340095db9aaa69e91b0c0f)
:D always living life on the edge Mr S!
Will give it a try - few little presents have been arriving in the post:
new glue gun
some connectors for the ribbon cables
and an AFT OH from Jakub in Poland - quick turn around on that one and he was on the ball for checking I received it ok (typically the UK couriers tried to deliver and took it back to the depot but never left a card >:(
One of these days I will fly this thing!!!
Cheers
Mike