LED circuit indicator

Discussion in 'OnBoard Electronics & Controls' started by bcervelo, Sep 13, 2013.

  1. bcervelo
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    bcervelo Junior Member

    I want to make a small switch panel with 9 switches for various items on a RIB eg nav lights, vhf.

    I want a way to illuminate the lables for the switches, red when the switch is off/open and green when on/closed.
    I will drill a hole where the label will be placed but no bigger than the label, the hole will be covered by the label and filled with clear epoxy which will also hold the LED in place.
     
  2. CDK
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    CDK retired engineer

    That would mean with all devices turned off, you have 9 red leds, each drawing a few milliamps. Is that what you want?
     
  3. bcervelo
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    bcervelo Junior Member

    Yes, when the boat is used at night switches can be easily identified.

    LED's will be off when main battery isolator is switched off.
     
  4. bcervelo
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    bcervelo Junior Member

  5. CDK
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    CDK retired engineer

    With a 3-wire bi-color led this is the simplest circuit I can come up with.
    All resistors are 1K, .25 watt, the transistor can be any plastic small signal NPN.

    Current through the leds is approx 9 mA, enough to make them clearly visible, but if you want more light, use 560, 680 or 820 Ohms.
     

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  6. bcervelo
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    bcervelo Junior Member

    CDK could you explain the function of the transistor in the circuit is it some form of a switch?
     
  7. bcervelo
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    bcervelo Junior Member

  8. CDK
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    CDK retired engineer

    When the switch is closed the Tr goes in a conductive state and lowers the voltage over the red led below the working threshold. Without it, both leds would light.
     
  9. BertKu
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    BertKu Senior Member

    No, first at all they are extreemly expensive and most likely draw too much current x 9 .

    You see, CDK has another solution for you also.

    If I would be you, use circuit diagram no C, just 2 LED's and 2 resistors. If you are going to fiddle around with epoxy, you may as well solder the 2 resistors onto the 2 LED's and then encase them in epoxy.

    here are the type numbers you should use.
    9 x BG12WH 17.000 mcd 520 nMeter green, 5 mm @ 0.15 English pounds each
    9 x 14C0594 12.000 mcd red , 5 mm @ 0.2 English pound each.

    2 resistors , one of 18 KOhm , 1/4 watt 5% in series with the red LED, does not matter on which side and one of 56 KOhm in series with the green LED.

    If the circuit is closed by you , let say, port light. The red LED goes off and the green comes on. Should you switch the port light off, the green light goes off and the Red light goes on. If your port light is blown, both LED goes off, or maybe very faintly, both come on and you have instantaneously an indication that you have a problem.

    You must just make sure that your plus side of the LED, regardless whether a resistor is soldered to it or not, is connected to the plus. The same applies for the green LED.

    If you are unsure, I gladly airmail post you two LED's in the post with 2 resistors and you can experiment with it. Maybe I will even enclose some more resistors. Maybe even 2 LED holders.
    But to pay 10 pounds x 9 for something what is most likely not going to work, I would not buy it.
    Bert
     
  10. BertKu
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    BertKu Senior Member

    Indeed that is what is No D on thread No 11. I think we may have to help him by spelling it out, on how to do everything in detail. I am not even sure whether he is able to solder. He maybe very young and need some guidance in every step.
    Bert
     
  11. bcervelo
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    bcervelo Junior Member

    Bert i want to fix one LED in the hole behind the label, the hole will be less than 10mm dia.
    I have no problem soldering i just dont know anything about electronics.

    I must update my profile i am living in Somerset West at the moment.;)
     
  12. BertKu
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    BertKu Senior Member

    Go to Mantech Electronics, just at the back of the Grand West Casino and at the back of the Posoffice distribution Center in Epping Industria. Ask for Gordon and he will help you with pleasure. 2 Led's of 5 mm is also 10 mm. Just difficult to drill the holes. You need to make a small mould from let say stainless steel, so that it drills properly in your console. Are you a member of Gordon's Bay Yacht Club? I could post it to them with a code name you could give me in my PM or to gqrsoftware@isat.co.za.
    Bert
     
  13. BertKu
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    BertKu Senior Member

    Not a problem of not knowing electronics. We will guide you. What you also can do is to grind some of the plastic of the 2 x 5 mm LED away. Then it will fit into a les than 10 mm hole. I have done that often to grind either from the side or the top, some plastic away. You just have to be careful not to take too much and damage the chip.
    Bert
     
  14. BertKu
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    BertKu Senior Member

    I looked at the LED through the magnifying glass and you can easy grind 1 mm away at both sides of each of the LED's and then it will be only 6 mm in total. The same as off you have a LED holder, but then 10 times cheaper.
    Bert
     

  15. CDK
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    CDK retired engineer

    What happened to Ohm's law Bert?
    18K over a 9V drop gives only .5 mA....:?:
     
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