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#130291 - 11/12/2002 11:40 Question about illuminated buttons
StigOE
addict

Registered: 27/10/2002
Posts: 568
I just received my first RioCar and ofcourse I can't leave it alone... I have to mod it with illuminated buttons...

I plan to use red leds, therefore I have a couple of questions. Since the white leds normally have Vf of about 3.5V and with 1kOhm resistor that should equal If of about 1.5mA. I guess I should be quite safe using a 2k2 resistorpack and low-current leds and not blow up the PIC? I could probably use 1kOhm as well since most PICs can sink 25mA...
The transistor for the knob is a PNP, isn't it?

And yes, I am able to solder the resistorpack...

Stig

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#130292 - 11/12/2002 13:01 Re: Question about illuminated buttons [Re: StigOE]
mtempsch
pooh-bah

Registered: 02/06/2000
Posts: 1996
Loc: Gothenburg, Sweden
If the supply voltage is 5V, subtract your LEDs Vf from that and then divide with wanted current to find the resistance. As long as you stay below or equal to the current Brians kits are drawing you should be OK. If your Vf is about 2V you should get about the same current if you use 2k or 2k2 resistors.

Have you considered using white LEDs and small pieces of filter material? That'd leave more options open for you in the future.

I believe, considering where the tranny is in the circuit, that it is a PNP - but I'm not 100% sure.

/Michael
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/Michael

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#130293 - 11/12/2002 16:36 Re: Question about illuminated buttons [Re: StigOE]
tfabris
carpal tunnel

Registered: 20/12/1999
Posts: 31594
Loc: Seattle, WA
StigOE, you do know about this project don't you?
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Tony Fabris

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#130294 - 11/12/2002 18:31 Re: Question about illuminated buttons [Re: tfabris]
StigOE
addict

Registered: 27/10/2002
Posts: 568
Ofcourse! Where do you think I found out how to put this together...?

And now I have red buttons... Well, grey buttons with a hole, like Brians first(?) mod of his buttons. Haven't got around to make the board for the knob yet, though...

Stig

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#130295 - 11/12/2002 20:58 Re: Question about illuminated buttons [Re: StigOE]
tfabris
carpal tunnel

Registered: 20/12/1999
Posts: 31594
Loc: Seattle, WA
Haven't got around to make the board for the knob yet, though...

Currently my knob lights are sans-board. I wired them carefully in a linear fashion at the correct distance from each other, then threaded the assembly into a piece of clear shrink-tubing. That tube now encircles the encoder shaft.
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Tony Fabris

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#130296 - 12/12/2002 03:47 Re: Question about illuminated buttons [Re: tfabris]
StigOE
addict

Registered: 27/10/2002
Posts: 568
I saw you mentioned that in a previous thread. Do you happen to have a picture how it looks? I can't seem to visualize how you did it...

Stig

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#130297 - 12/12/2002 11:18 Re: Question about illuminated buttons [Re: StigOE]
tfabris
carpal tunnel

Registered: 20/12/1999
Posts: 31594
Loc: Seattle, WA
Yes, right here.
_________________________
Tony Fabris

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