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Thread: Controlling Button LEDs

  1. #1
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    Controlling Button LEDs

    Calling any electrical whizzes...
    I'm more of a software guy myself so if any of this below is rubbish I'll be the first to agree with you...

    I want to hook up some illuminated buttons (say 6) to the internals of a keyboard. I've read that I need to run a couple of wires from each button to the tracks to simulate the ASCII key code that I am after. Fair enough.

    But, how do I go about powering the buttons LEDs?
    I'm not sure if I can power them off the feed for the Num Lock, Caps Lock and Scroll Lock keys or not?
    If this works I could probably run the leds in parallel to this source and they would light when the Num lock key is on or off (I can simulate this in software).

    What I really want is to have control over each individual LED but I don't think I can do this without a relay board or something.
    I have visions of being able to toggle each LED in turn to get a nice ripple effect....

    FYI - The LEDs I'm looking at are here :

    http://www.maplin.co.uk/products/mod...03&modulecode=

    Any help appreciated.
    Huge

  2. #2
    Variable Bitrate
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    Well, its all down to taste, but the first thing Id say is not to buy those ones from Maplin, but instead get them from Farnell (www.farnell.com). Farnell sell the ring illuminated version of these buttons which Maplin dont sell, and personally I think they look excellent. See this thread for a picture.

    you should be able to run the LED by soldering to where the LEDs in the keyboard used to connect, but that will only give you control of 3 of them. Try searching the board for serial and paralell controllers for relays.
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  3. #3
    Variable Bitrate peter3's Avatar
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    agry with phil.45
    don't know what you want but take a look at this:
    http://members.home.nl/lodio/audiovu.htm
    it's in dutch but the schamatics are clear.

  4. #4
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    I'd seen those buttons before - you're right they do look better but I hadn't realised that I could get them from Farnell. Think I'll go for them now...

    I've seen PC controlled (serial or parallel port) relay boards on the net and you are talking about 40 pounds (that's 6 million American dollars ) so it would seem a bit expensive just for doing that...

    Although if I wanted to power on my amp or turn on the screen as well when the PC boots then it might be an idea to go down that road...

  5. #5
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    The order codes for Farnell are: 3248896, 3248902, 3248914, 3248926.
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    (=========-) 99% complete
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    AMD K6/2 500 @ 450mhz to keep heat and power usage down, 64Mb, slim CDrom drive, 64mb USB pendrive for MP3 transfer, 10Gb 2.5" drive for MP3, USB>RS232
    All jammed in external CDROM drive case.
    Kenwood KVC-1000r In-Dash LCD. x-10 MouseRemote. Destinator V2 Gps. DC-DC with onboard Shutdown controller.
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  6. #6
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    Thanks for the Farnell codes but what's the difference in them?

    The first 2 are red and green leds as are the second two codes?

    Is there a difference?

  7. #7
    Variable Bitrate mp3hombre's Avatar
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    Try this link:
    Illuminated Keyboard

    The LEDs you want to use are rated at 1.6 volts, 2mA. So change the 15 ohm resistor shown in the schematics to 1800 ohms and you'll be OK.

  8. #8
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    Originally posted by Huge
    I'd seen those buttons before - you're right they do look better but I hadn't realised that I could get them from Farnell. Think I'll go for them now...

    I've seen PC controlled (serial or parallel port) relay boards on the net and you are talking about 40 pounds (that's 6 million American dollars ) so it would seem a bit expensive just for doing that...

    Although if I wanted to power on my amp or turn on the screen as well when the PC boots then it might be an idea to go down that road...
    40 UKP ~= 57 USD

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  9. #9
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    You can power small LED's right off the parallel port. All you need to do is wire the cathode(-) (the shorter lead on the LED) to ground on the parallel port (Any pin from 18-25), and wire the LED's anode(+) (longer lead) to one of the pins from 2 - 10 (a total of 8 LEDS can be controlled). Here's a diagram to help you out: http://www.diyha.co.uk/electronics/parallel.html. What exactly are you looking to accomplish here? Do you want explicit control over each LED, or do you want to have the LED's flash in a sequence, just for show? Let me know, I can write up a quick VB for you.

  10. #10
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    Originally posted by Huge
    Thanks for the Farnell codes but what's the difference in them?

    The first 2 are red and green leds as are the second two codes?

    Is there a difference?
    The first two are the red and green LED buttons that do what youd expect them to do, ie you push the button to make a contact, and there are seperate terminals to wire the LEDs. These are the ones I bought. The second pair are the same colour, but I have no idea why they are different. They have TERM in the manufacturers code, but I couldnt find any difference on the spec sheet. If in doubt, go for the top pair. Perhaps someone else knows?
    -------------------------------------------
    (=========-) 99% complete
    --------------------------------------------
    AMD K6/2 500 @ 450mhz to keep heat and power usage down, 64Mb, slim CDrom drive, 64mb USB pendrive for MP3 transfer, 10Gb 2.5" drive for MP3, USB>RS232
    All jammed in external CDROM drive case.
    Kenwood KVC-1000r In-Dash LCD. x-10 MouseRemote. Destinator V2 Gps. DC-DC with onboard Shutdown controller.
    ----------------------------------------------

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