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I How to change the color of an LED?

  1. Nov 7, 2018 #1
    An item I want to buy comes backlit blue and I need it to be GREEN. I contacted the seller and asked if I could change the bulb color with a green bulb condom and asked if it was currently a clear led, with a blue cover. THey said yes, but later they then wrote me back saying they made a mistake and the led inside doesn't have a cover, and an actual BLUE LED.

    If I put a yellow bulb cover overtop the blue led, would it make it green?


  2. jcsd
  3. Nov 7, 2018 #2


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    Welcome to the PF.

    It's not likely you can change the color of that display. White LEDs are more expensive than single-color LEDs, so it's unlikely they would use them in their display. Instead, just look for another display with the desired backlight color.
  4. Nov 7, 2018 #3
    I've looked everywhere for weeks and there are none like this in green. THis is the size and color I want. It's just a single led that's lighting the screen. What can I just put a rubber yellow bulb condom over it, or remove and put in a green one?

  5. Nov 7, 2018 #4
    EDIT, another pic added:

    Ok, the seller was able to show me a picture of the board.... The red circle are the leds. Crap, I wonder how hard to change to green led? s-l1600 (8).jpg

    s-l1600 (9).jpg
    Last edited: Nov 8, 2018
  6. Nov 7, 2018 #5
    Seems like standard 3mm through-hole LED mount. You need to take the soldering iron, take out the blue LED and replace with green one, without any cap.
  7. Nov 7, 2018 #6

    Charles Link

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    Note with an LED, there is a + lead and a minus lead. It will only light up if it is installed with the correct polarity.
  8. Nov 7, 2018 #7
    Thank you. I've soldered before, a few times, and by no means an expert at all. What do you mean "without any cap?"

    WHere would I buy green led's to fit this and wish I could send it to someone on here to help me if I can't do it.
  9. Nov 8, 2018 #8
    Typically that through-hole LEDs can be found in some home centers (for example, Royal Home stock them). Or on Digikey.
    Theoretically, i can fix it (have a large box filled with unused LEDs), but not sure the modification have any merit for you if you already do not have all necessary hardware - these thermometers are actually "cheap as dirt", and may be less money and time consuming to just buy the correct one.
    Search something like
    Pro LED DC 12V Digital Thermometer
    on ebay.
  10. Nov 8, 2018 #9
    Thanks. I actually saw that one, but it won't work as that one is C - celsius as most are, and i need the degress in F. This is being used in a car. Below are pics of the OLD SETUP.

    IMG-8225.JPG temp_721.jpg

    This is the old unit above, Worked for 10 years. Ran off 1 AAA battery, and a friend helped out and found a resistor to make it work off 12v... It has a green backlight (hard to see in this day pic) and everything is green backlit in the vehicle, dash, radio, volts, etc, and wants to stick with green theme. I found the same silver unit again, as shown above and bought 3 of them for backups but they don't work correctly, as the outside looks the same, but the inside circuit boards changed and the green backlight turns off after 5 seconds not matter what I try inside, which is pointless at night....

    SO, that's why I'm onto the new one I found, and I've looked for weeks for something that will fit in the hole I made out of the plastic veneer wood, but the blue will..... I'm not that smart to figure out how to get the old one to work as there are a few new capacitors on the board of the older silver unit, again where the green light only stays on for 5 sec. Before, I soldered two leads together and the light would stay on all the time constant, but these updated ones I bought... I can't stop the light from tuning off after 5 sec... Again, this is why I wanted to try a new solution, and the new blue one will fit, but I just need it GREEN.

    I appreciate all the replies and hope to get this working somehow. All i'm waiting for is the new blue led light, that's all I need as it's already a 12 v unit. Or I could ship it to you to inspect??? Thanks again.
    Last edited: Nov 8, 2018
  11. Nov 8, 2018 #10
    That's cool of you and thanks for helping out! THe one I found is in Kentucky. Meaning I can have it to me in 3-4 days. I'll have it ship to me first to make sure again it fits in that window, but it should.....
  12. Nov 8, 2018 #11


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    A little late, but I don't think just putting something yellow over / in front of a blue LED will work.
    LEDs have a pretty narrow spectrum.

    Filtering it through yellow will get you pretty close to ... black.
  13. Nov 13, 2018 #12
    Thanks. Wish it was as easy as adding a filter :)

    Just wanted to update. I got the unit and it fits in the old location that I posted above in the vehicle :) It fits perfect which in kinda unreal since that hole was custom sized with a file by me 10 years ago, got lucky I guess...

    Now just gotta figure out how to get it green led. Maybe someone knows what leds to buy or would anyone want to help me out with this project? I'm in PA.


    It was mentioned above that from the circuit board it might be a 3mm hole through led. Are these it?

    Last edited: Nov 13, 2018
  14. Nov 13, 2018 #13
    Yes, on photo is most common LED with 3mm lens.
  15. Nov 13, 2018 #14
    Ok. So. Confused again. As shown abovein my earlier post, the manufacturer sent pics of the circuit board before I ordered this and circled the leds supposedly on this board in red, see above posts. I just took the unit apart and I don’t see any leds on the board? I powered it up and they look like they are part of the lcd display and are embedded in the lcd? Am I right? Confused here. Below is pic of board and lcd I twisted off to the side.

  16. Nov 13, 2018 #15
    I see. This is the "LED backlight module" intended to reduce light losses of LED. It can still work with discrete LED, although with complications. You need to:
    1) Cut the existing LED clear from diffusor plate using knife or heavy-duty nail cutter.
    2) Either use "right angle" packaged LED, or bend leads of your LED to look sideways into diffusor panel
    3) Connect LED lens and diffusor plate with a drop of transparent acrylic or silicone adhesive (recommended)
  17. Nov 14, 2018 #16


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    NO! Do not use a nail cutter. The hard plastic of the diffuser will crack. Use a hobby knife such as an X-Acto, or similiar. Using the tip of the blade, make shallow cut strokes on the surface until you get thru the hard plastic. Carefully, like you are doing surgery on your finger.

  18. Nov 14, 2018 #17
    Well, you may have tried to cut used diffuser. I suspect some embrittlement by light happens. New one is more easy to handle, i had in one case even drilled 4mm mounting holes in diffuser. Although about knife you correct - my preferred tool for cutting materials like diffusers or rigid PVC is 30-degree cutter similar to X-Acto.
    Last edited: Nov 14, 2018
  19. Nov 14, 2018 #18
    @Turle and others. THANK YOU.... So, what the heck did the manufacturer send me above? They said this was where the led's were:


    Is that for a backup led? Could I disconnect those side leds and put one led in the red circle? Lol. Why on earth did they say that's where the leds go? And Tthere are two total leds in this, one at end end of the lcd glass...

    I'd like to try this myself but I'll probably destroy it. As my father would say "Custom items just cause problems" LOL, well, the original unit lasted 10 years with a resistor to converted to 12v so that was a good run. As mentioned I can still buy the original unit but the circuitry changed and not sure how to get that orignal backlight to stay lit but someone here could prob figure it out (the silver unit that I had originally)


    Also, a search revealed this... Same idea?

  20. Nov 14, 2018 #19
    Another update. I wrote the company again and they tell me the factory led is: 0603 LED light

    Is that wrong again?
  21. Nov 14, 2018 #20


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