LED circuit indicator

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

  1. bcervelo
    Joined: Sep 2005
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    Location: Somerset West, SA

    bcervelo Junior Member

    Bert i will be attending the boat show too i work in the industry, why not leave it at the information desk at the show?
     
  2. BertKu
    Joined: May 2009
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    BertKu Senior Member

    Which information desk? There are normally a number of them. I have enclosed approx 100 resistors 9 -10 of each value, 2 photo resistors, 7 high bright LED's green and red, some 30 other low mcd green and red LED's and only 1 x 3 mm LED. I don't use them.
    Plus some solder, shrink wire, a used 3 volt Lithium battery to test the diodes for polarity, etc.
    If one comes into the main entrance hall, after one gets out of the garage, up the escalator, before the real entrance to the show. If there is a information desk, I will leave it there, except if you have better instructions. Look in your PM mailbox.
    Bert
     
  3. BertKu
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    BertKu Senior Member

    Yes, I will, but I am only going to the show on Saturday morning.
    If I were in your shoes, I would first experiment with the Philips photo-resistors (enclosed) and with 2 bright LED's with various resistors, until satisfies that it is dull enough at night when dark and bright enough during daytime. Don't forget the 120 Kilo Ohm resistor parallel over the photo resistor, otherwise the current through the LED's will be too low during dark. Daylight , it is not a problem as the resistance of the photo resistor is very low.

    I also would pot the 2 glued LED's green and red and see whether the values of the resistors in the shrink sleeve are the right values. At the end of the day, you have enough components to experiment first , before you mount everything into your panel. Bert

    As an after thought, If all switches are "on" it means that the LED resistors are 9 x paralleled and the photo resistors needs to be low enough to supply the correct current in the dark. If it is not satisfying, just use a zener diode and a double throw switch. I assume that all 9 switches will be switched on, when sailing in the dark.
    Bert
     

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  4. BertKu
    Joined: May 2009
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    BertKu Senior Member

    Hi bcervelo,

    I made a breadboard and replaced the 120 Kilo Ohm or 100 Kilo Ohm with a zener-diode. The photo-resistors ( 4 enclosed) act now as the switch. The curve of a zener-diode is quite flat and it does not matter whether you have 1 LED on or all 9 switched on, the difference is barely noticeable. With the resistor parallel over the photo-resistor you have the problem that the parallel switching of the either 1 or 3 or 9 LED circuits makes it fluctuating, not with the zenerdiode parallel to the photo-resistor. If daylight falls on the photo-resistor, the resistance is very low and if it is dark, the resistance is high and clipped by the zener-diode and it takes over. Just experiment with that little breadboard, if you feel the resistors should be changed. You have now the perfect circuit-diagram for your application.
    Bert
     
  5. BertKu
    Joined: May 2009
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    BertKu Senior Member

    Hi bcervelo, Here is the mock up, which you find in your envelope or parcel on Saturday morning.
    Unfortunately, it works well for me, but may not work as well for you.

    The reason being:
    a) I don’t know your load and had to adjust the value for the red LED resistor to a lower value by soldering a parallel resistor to it. Yes, I could have placed another value resistor to it, but I was too lazy.
    b) I don’t know how your potting is going to affect the diffused light from the LED’s after potting the LED’s in clear epoxy.
    c) I don’t know whether the Philips photo resistors will be mounted in bright sunshine or in some shadow place. If everything fails, use a double throw switch, or make it only work for dark condition.
    d) I don’t know whether your load may have another switch to switch on, like a radio. In that case, you have to match both LED’s brightness to your liking, as the load will be open circuit.

    Thus, you are on your own. But as seen from the photo’s, I made it easy for you. The white pieces of twin cables are 3 switches. The first circuit is complete, it has a load being a bulb from a automobile and you can play with it.

    The second circuit has only the LED’s , no load and no resistors. You have to gamble and use a few values to see what it does to your light intensity.

    The third circuit, you can place any of the LED’s finding in your parcel and match a resistor to it. But I must inform you, that the value of the resistor drops drastically with the low lcd type of LED’s. But you have more than 100 resistors in the envelope and I am convinced, something will fit. Even if you place resistors parallel.

    You mentioned that electronics is not your strongest point, I have therefore included an old 3 Volt lithium battery and as shown on the third photo, it shows you how to test the LED for polarity. If the led is on, it shows you what the plus side is of the LED and that has to be mounted always to the more positive voltage side of a circuit. The photo resistor can be mounted either way, so thus a resistor. The transistor you find in the envelope, is to experiment with a double LED with common cathode. (You can make a mock up by using two different LED's, whereby the cathodes are soldered together. ) The middle leg is the basis, the rest you must check and google on the Internet by typing the type number in.
    I have also included a 12 Volt relay to experiment with a relay instead of with a transistor.
    Bert
     

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    Last edited: Sep 29, 2013
  6. Pota de fusta
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    Pota de fusta Junior Member

  7. BertKu
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    BertKu Senior Member

    Hi Pota,
    You can use any NPN transistor, as long it has some gain.
    BC237B, BC237A, BC237C, BC237, BC337-16 BC337-25 BC337-40, BC337 and about a few thousand other NPN transistors. The trick lies in the maximum voltage you will be applying and then the VCE must be greater than the to be + Voltage . i.e. if you use 12 Volt, you can also use the BC238 , BC338 etc. A good gain like the BC337-40 means that you can drop the resistance of the resistor to be used. dual high mcd LED)
    2200 Ohm to RED LED, 1000 Ohm to the green LED, 27.000 Ohm to the base of the transistor BC238 or BC 237. or better said. Any resistor greater than 3 x the green LED resistor. i.e. if your green LED resistor is 1000 Ohm, the resistor to the base of the transistor should be at least 3300 Ohm. However you drive the transistor hard in that case.
    Bert
     
  8. Fanie
    Joined: Oct 2007
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    Fanie Fanie

    The most simple is probably to use a relay that switches on when the load is on and off when the load is off. The circuit is very robust and will handle a lot of spikes and power variations.

    The relay should have a single pole double throw contact - like the very common LZ relays - and the common feeds power to either of the normally open or normally close contacts which switches either the red LED or the green LED on.

    A 680R resitor would give you 12V / 680R = 17.65mA.

    Most power will be drawn when the relay is on, the relay draws ~30mA and the LED ~20mA, hence a total of 50mA (0,05A).
    If the relay is off and only the other led is on then ~20mA will be drawn (0.020A).

    (I fixed the drawing up to make it more clear)
     

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  9. BertKu
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    BertKu Senior Member

    Hi Fanie, Can I argue with a boer ?? Sorry I have a grin on my face. Hope you allow that.

    I don't know whether it is such a good idea to use a relay. Relays has its problems. Reed relays sticks quite often and a normal relay with contacts has a problem with carrying low currents and expect reliability. Already in thread No 11 is absolute the easiest . 2 resistors and 2 LED's that's all. A LED has a lifetime of 100.000 hours (not the organic one's) and then it should still produce 80% of its light. That is the standard. A resistor of good quality also last 25 years, so does a transistor. One can pot it in and make it waterproof, not with a relay, except if one goes for military specification. He should just stick to CDK design or my design in thread No 11, (G) which is basically the same. But C has the convenience of super high bright LED's, which you can then use with very low currents. As long the load is reasonable low and take at least some 100's of milliAmpere. 20 mA drain on a battery, when one leaves it for a long time means 0.02 x 24 Hours x 30 days = 14,4 Amperehour. We don't know what battery he is using or planning to use. It means he can only be away from his boat for less than a month, otherwise his battery is "pap" . I would personally have very low currents, so that the battery is not drained. Something like 0.5 mA at the most. Bert
     
  10. Pota de fusta
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    Pota de fusta Junior Member

    thanks for the information
     
  11. BertKu
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    BertKu Senior Member

    It was a pleasure to help you. If you like to get the best values for your project, let us know what the load is and what the battery voltage is. 12 Volt or 24 Volt.
    Bert
     
  12. Fanie
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    Fanie Fanie

    Hello Bertku,

    I'm sure it will be ok if we argue :D

    I allow grins too :D



    The LZ relay is probably the most used relay on the globe, all alarm systems use them. It is not a reed relay.

    I suggested the circuit because it is very easy for any novice to build and you don't even need a breadboard. You can simply glue your relays in a row and do the wiring from there.

    Anyway, it was just a suggestion.
     
  13. Pota de fusta
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    Pota de fusta Junior Member

    I would put a bicolor LED. Red and green. The battery is 12 volts. But when the engine is running, the alternator sends 14,9v (read on the digital voltmeter). Thank you for your offer: I need the resistance values ​​for the visible LED in to 12v. And not to produce excessive lumens in to 14,9v. (annoying at night). thanks
     
  14. Fanie
    Joined: Oct 2007
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    Fanie Fanie

    Pota, that can be resolved easily. You can use a micro with a LDR that senses the light and dim and bright as the environment light changes.

    If you are happy to settle for second best, you can use a constant current diode like the NSI45020T1G that would regulate the current to the on diode at 20mA. The LED's would still look dim in bright light and bright in the dark though.

    You can also supply the 12V through a variable voltage regulator like the 317 and adjust the brightness with a pot to what suits you.
     

  15. BertKu
    Joined: May 2009
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    BertKu Senior Member

    Pota, the only sensible advise I can give you is to experiment with a few values.
    Please bear in mind that red has a voltage drop over the LED of between 1.8 and 2 Volt, while green has between 2.8 and 3.5 Volt it depends which green light it radiates.
    Thus you need 2 different resistance values.
    For red the minimum resistance is 14.9 V - 2 volt divided by 0.02 (20mA which is normally the maximum current allowed for non organic LED's) = 750 Ohm
    I would start by 1 kilo Ohm/ 1/4 or 1/2 watt 5% (by us cost a resistor 0.1 USA dollar cent, thus a handful resistors does not make you a poor sailor) . If it is too bright you put 2.2 Kilo Ohm (2200 Ohm) 1/4 watt 5% , still not happy
    you go for 3.9 kilo Ohm etc. etc. until you are happy.
    The same applies for green LED 14.9 - 3 Volt / 0.02 = 680 Ohm (actual it is 595 Ohm, but one must not overdrive the LED) Again if you aren't happy use a higher value until satisfied.
    The standard resistor range is 1- 1,2 - 1,5 - 1,8 -2,2 - 2,7 - 3,3 - 3,9 - 4,7 - 5,6 - 6,8 - 8,2 this you can be multiplied by 1, or 10 or 100 or 1000 or 10.000 or 1 million. i.e. a 1,2 x 1000 = 1200 Ohm resistor. or 4,7 x 10.000 = 47 Kilo Ohm resistor.

    Look Pota, I probably cannot change your mind. But I personally would prefer
    you to use my C solution from thread no 11, I assume the load is very low.
    In that case you use high bright LED's with very high resistance and therefore low dimmed LED.
    example 17000 mcd green LED with a 22.000 Ohm (22 K Ohm) resistance and a RED led of 12.000 mcd with a 18.000 Ohm (18 KOhm) It depends whether you have the red on when the switch is open or a green LED when the switch is open, you just reverse it. You grind nearly 1/2 of both LED's away and glue them together. If you insist on one LED holder, yes you have to resort to a duo LED. If you are battling in getting resistors, give me an private mail and I will be in Jersey (UK Channel Islands) in December 10th and then I post them to you Poste restante Barcelona Central Main Postoffice, you must just give me a code name, which I can put on the envelope. Bert
     
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